I have been looking at 3400 engines available in my area and most are going for $700 for a decent used motor. I do like the idea of getting the roller cam instead of the flat tappet cam.
Can the 3500 short block be bolted up with Fiero iron heads and top end, like the 3400 short block does? I am talking about the NON-VVT LX9 motor only.
The 3500, strangely, is cheaper ($450 with 83,000 miles) than the 3400.
[This message has been edited by masospaghetti (edited 02-15-2013).]
Can't the pistons be changed to increase the CR, similar to the 3400?
Yes, you'll have to replace them with the 3.6L DOHC pistons and get a thicker head gasket depending on the resulting compression ratio, if it yields ~12:1 static I'd just throw in a higher duration cam to bleed a little pressure off then tune and run with it.
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11:05 AM
masospaghetti Member
Posts: 2477 From: Charlotte, NC USA Registered: Dec 2009
You’re giving up over 60hp by replacing 200hp heads and intake with 140hp heads and intake.
Simply porting the iron heads and intake will not "make up" the 60hp difference. It is entirely unrealistic to expect a 30% gain in power from porting work. The improvements from the GEN III 60 degree motor from the GEN I are far greater than the roller cam and structural oil pan. -The newer heads have alloy aluminum construction that saves around 40lbs over the iron. -The combustion chamber has been designed to reduce valve shrouding and aid flame propagation ("quick burn") this allows a lower timing advance under load which will reduce the amount of negative work during the power cycle, of the 4 cycle process. -The ports have raised floors on the intake that increases the short turn radius, which is an impediment on flow. -The intake ports also feature tapered runners that aid in keeping the gas velocity high, giving charge motion a more uniform fuel air mixture. -The valves are canted, meaning they angle inward relative to the cylinder bore, lowering the shrouding around the valves, aiding in flow. -The exhaust ports are d-shaped, increasing flow along the port floor. -The intake has no neck to pinch to clear a distributer, the bend between the middle intake and plenum is more gradual, creating less turbulence in the runner, increasing overall flow.
Keep this as food for thought. A worked over iron headed motor makes around 175 HP at the wheels, while a worked over late model aluminum head motor makes around 275 HP at the wheels, both through manual transmissions. That is a 100hp difference.
So not only is the cost added to combine parts to give a streetable compression ratio to use 80's fuel injection technology on a 2000's technology long block. You have to crack apart a prefectly good let model engine, and open it up to the uncertaintys of a reassembled engine.
Why Fiero owners are so obsessed about keep the cool aluminum fins on the valve covers and intake with a Fiero sticker in the center has me baffled. I would take an extra 60hp over the red paint and brushed aluminum any day. I don’t stare at the engine when I drive the car, I feel power through the revs when I leave the stop lights.
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12:24 PM
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
I personally will never just drop a used engine into a car without hearing it run in the donor, so a rebuild is always mandatory for me. Hence cost of new pistons is just part of the rebuild costs and not an "extra" cost.
I'd go on Summit Racing and find "off the shelf" pistons that work. Otherwise get your machine shop to order new 3.6 pistons and have a little volume shaved off the top to get your compression ratio in line.
The iron heads only weigh 13 lbs a piece more than aluminum heads. Engine weights are 390 for the Fiero v6 and 370+ for the 3400/3500's in other words closer than you think since they naturally come with more hardware on them. Look up dynos on youtube of 3400 and 3500 motors and see what the real "at the wheels" power is before you believe the "leaving 60hp on the table" comment. IE do your own home work.
What I have found is that using an unrealistic meter such as a flowbench, you will get #'s that show iron heads flow 25+% less than aluminum heads, however, iron heads have a higher VE rating when it comes to actual performance. What's better to look at is the lift for the cam that you will run and don't look past those #'s on the flow bench.
When you take into account that your cam probably not going to lift that high, the numbers are even closer. When you take into account that you aren't going to spin your motor fast enough to hit that flow rate, you realized that heads don't matter at all. Also, someone else ported iron heads (properly) and got 163 CFM, so take "Fully Ported Iron Heads" with a grain of salt as some people think "ported is ported".
A 3.4L motor, be it a 3400 or a 3.4 at 100% VE is only pumping 360CFM at 6000rpm. Divide that by 6 and you'll see that 1 cylinder head port only needs to flow 60CFM...yet they can flow 150+ at the head... IE, the restriction has always been the intake neck which only flows 300CFM hence a 3.4 is choked at 4500 RPM on a stock Fiero intake. Heads are not the issue.
When you take into account that your cam probably not going to lift that high, the numbers are even closer. When you take into account that you aren't going to spin your motor fast enough to hit that flow rate, you realized that heads don't matter at all. Also, someone else ported iron heads (properly) and got 163 CFM, so take "Fully Ported Iron Heads" with a grain of salt as some people think "ported is ported".
A 3.4L motor, be it a 3400 or a 3.4 at 100% VE is only pumping 360CFM at 6000rpm. Divide that by 6 and you'll see that 1 cylinder head port only needs to flow 60CFM...yet they can flow 150+ at the head... IE, the restriction has always been the intake neck which only flows 300CFM hence a 3.4 is choked at 4500 RPM on a stock Fiero intake. Heads are not the issue.
158 CFM is not close to 200 CFM at all. 200 CFM is worlds apart.
3.5 litres at 100% VE is 370 CFM at 6000 RPM. 1 sixth of that is 61.8 CFM. However, that volume must get through an intake valve with about a 33% duty cycle (240 degrees out of 720 is exactly 33%), so it's only open 1/3 of the time the engine is running.
So to keep the engine fed at 100% VE, the AVERAGE flow rate while the valve is open must be at least 185 CFM.
Neither the iron heads nor the aluminum heads even come close to that, BUT the aluminum heads are a lot closer than the iron heads.
The 100 HP/L *RACE* engines are WAY more than the intake... The intake alone won't get there.
[This message has been edited by Will (edited 02-15-2013).]
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01:32 PM
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
158 CFM is not close to 200 CFM at all. 200 CFM is worlds apart.
3.5 litres at 100% VE is 370 CFM at 6000 RPM. 1 sixth of that is 61.8 CFM. However, that volume must get through an intake valve with about a 33% duty cycle (240 degrees out of 720 is exactly 33%), so it's only open 1/3 of the time the engine is running.
So to keep the engine fed at 100% VE, the AVERAGE flow rate while the valve is open must be at least 185 CFM.
Neither the iron heads nor the aluminum heads even come close to that, BUT the aluminum heads are a lot closer than the iron heads.
The 100 HP/L *RACE* engines are WAY more than the intake... The intake alone won't get there.
As for your 1/3 claim, you forget there is some power overlap with a v6 like a V8 and unlike an I4. I never claimed "intake alone" which is EXACTLY WHY I provided a link. With the sub-par port job that Falconer did they still flowed 300+HP worth of air. Infact the heads can support 410+ horsepower and yes, aluminum heads can support 550+ but what is the point of that if you are limited by CAM and RPM? FIero runners and also be ported to flow 150+CFM. The restriction boils down to the throttle body and intake neck. The stock 7/8" exhaust port openings on the iron head need to be opened up as well, but that's beyond simple.
This is no different an analogy than putting a big block behind a 2-speed transmission with the cam, valvetrain and connecting rods being the transmission. You simply can't spin a 3.4 or 3.5 fast enough to the point where the heads are the restriction...
When a naturally aspirated 3.4/3.5/3400/3500 can make 410hp, then I'll look at aluminum heads...
Speaking of VE:
Given two otherwise identical engines, the bottom line is as follows:
1) SAME compression ratio, one IRON heads, one ALUM heads: The Iron head engine will make more power,
2) One Iron head @ 9.5:1 CR, one Alum head @ 10.5:1 CR The two engines will make roughly the SAME power.
Why? In scenario #1 iron wins due to the better heat retention or insulating qualities of cast iron (higher thermal efficiency) Cast iron is a better insulator than aluminum or conversely aluminum is a better conductor than cast iron. In scenario #2, the two engines make roughly the same power because the difference in thermal efficiency (iron over alum) is balanced by the difference in static compression (10.5:1 over 9.5:1). Cylinder pressure at full operating temperature is very similar.
[This message has been edited by lou_dias (edited 02-15-2013).]
Your arguement still doesnt explain why someone would go through all the work to redesign an engine to use inferior componants, when it comes form the salvage yard already ahead of the game.
I will stand by my belief the the LX9 was one fo the best of the 60 degree design by GM. I have done plenty of homework on IC engines, fluent designed cylinder heads, unsteady flow, etc, I have by BSME to back me up. I get how they work, I dont feel like your fully grasping it. I know what will produce satisfactory figures, close is gud'nuf really doesnt.
To me it seems like you think ported iron heads are superior to the 3500 GM castings. You already have a running engine, and your happy with it, dont switch. I am only trying to give some guidance on a future engine build not by you.
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02:24 PM
masospaghetti Member
Posts: 2477 From: Charlotte, NC USA Registered: Dec 2009
Let's say I were to use a 3500 engine, the whole thing.
- Can the timing covers be swapped to keep my accessories? - Will the throttle cables line up? - The exhaust, I assume, will need to be custom fabricated, or can the stock Fiero exhaust be used? - The dogbone also doesn't fit without modification. - I would need some kind of adapter for the throttle body.
If I ran it using the 7730 - do I need the custom trigger wheel?
[This message has been edited by masospaghetti (edited 02-15-2013).]
As for your 1/3 claim, you forget there is some power overlap with a v6 like a V8 and unlike an I4. I never claimed "intake alone" which is EXACTLY WHY I provided a link. With the sub-par port job that Falconer did they still flowed 300+HP worth of air. Infact the heads can support 410+ horsepower and yes, aluminum heads can support 550+ but what is the point of that if you are limited by CAM and RPM? FIero runners and also be ported to flow 150+CFM. The restriction boils down to the throttle body and intake neck. The stock 7/8" exhaust port openings on the iron head need to be opened up as well, but that's beyond simple.
This is no different an analogy than putting a big block behind a 2-speed transmission with the cam, valvetrain and connecting rods being the transmission. You simply can't spin a 3.4 or 3.5 fast enough to the point where the heads are the restriction...
When a naturally aspirated 3.4/3.5/3400/3500 can make 410hp, then I'll look at aluminum heads...
Speaking of VE:
Given two otherwise identical engines, the bottom line is as follows:
1) SAME compression ratio, one IRON heads, one ALUM heads: The Iron head engine will make more power,
2) One Iron head @ 9.5:1 CR, one Alum head @ 10.5:1 CR The two engines will make roughly the SAME power.
Why? In scenario #1 iron wins due to the better heat retention or insulating qualities of cast iron (higher thermal efficiency) Cast iron is a better insulator than aluminum or conversely aluminum is a better conductor than cast iron. In scenario #2, the two engines make roughly the same power because the difference in thermal efficiency (iron over alum) is balanced by the difference in static compression (10.5:1 over 9.5:1). Cylinder pressure at full operating temperature is very similar.
Flow has as much to do with power as does charge motion and mid-lift performance.
Your heads do not flow as well at mid-lift as the newer heads do. That is where overlap occurs and induction/expulsion wave tuning. Your heads do not have the same quality of charge motion (i.e swirl/tumble) as the newer heads. Newer heads have the opportunity for greater ram tuning effects, and more complete mixture burning and flame front travel due to these advantages, allowing a higher VE. Not only do they make more power, they allow better fuel economy through efficiency. There is much more to engine tuning and operating than simple efficiency algebraic hand calcs, like what you are showing.
Also, Al is lighter than Fe, lighter more powerful cars are faster than heavier less powerfull cars. If you think all the advantages of a slower heat transfer rate in an engine, The ability of the Aluminum to pull heat from the combustion chamber can be countered with proper application of thermal barriers. Even so, tesst have been made for entirely ceramic engine, that had heat transfer slower than iron. The thermal effiency remained at near 30%. Guess where all the extra heat went? Out the exhaust.
You can be as happy as you want with your motor, I'm glad for you. But I was just trying to educate the forum on what GM benifits had to offer in it’s 3500 design over the past designs.
Let's say I were to use a 3500 engine, the whole thing.
- Can the timing covers be swapped to keep my accessories? - Will the throttle cables line up? - The exhaust, I assume, will need to be custom fabricated, or can the stock Fiero exhaust be used? - The dogbone also doesn't fit without modification.
If I ran it using the 7730 - do I need the custom trigger wheel?
I am not 100% on the timing cover, but It can be made to fit. No the throttle cable would need a different end. The exhaust would be different, but the fiero exhaust is not that good as a starting point anyways. (too small, and they-pipe and manifolds are pretty poor) The dogbone doesnt fit. If the motor is mounted well enough there is no need for a dogbone anymore. Running a 7730 would reqiure a trigger. But just run the 3500 ECU and get it programmed for use in a fiero, that would seem like a much simpler solution. (the 2006 OBDII unit is far better than one from 1988.)
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02:52 PM
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
As for your 1/3 claim, you forget there is some power overlap with a v6 like a V8 and unlike an I4.
I'm did not forget that. It's not relevant.
In the other thread, you essentially did claim that it was all intake, saying that Webers are street-legal while open exhaust is not... as if the discussion were about legality... or Webers.
[This message has been edited by Will (edited 02-15-2013).]
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03:12 PM
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
Flow has as much to do with power as does charge motion and mid-lift performance.
Your heads do not flow as well at mid-lift as the newer heads do. That is where overlap occurs and induction/expulsion wave tuning. Your heads do not have the same quality of charge motion (i.e swirl/tumble) as the newer heads. Newer heads have the opportunity for greater ram tuning effects, and more complete mixture burning and flame front travel due to these advantages, allowing a higher VE. Not only do they make more power, they allow better fuel economy through efficiency. There is much more to engine tuning and operating than simple efficiency algebraic hand calcs, like what you are showing.
Also, Al is lighter than Fe, lighter more powerful cars are faster than heavier less powerfull cars. If you think all the advantages of a slower heat transfer rate in an engine, The ability of the Aluminum to pull heat from the combustion chamber can be countered with proper application of thermal barriers. Even so, tesst have been made for entirely ceramic engine, that had heat transfer slower than iron. The thermal effiency remained at near 30%. Guess where all the extra heat went? Out the exhaust.
You can be as happy as you want with your motor, I'm glad for you. But I was just trying to educate the forum on what GM benifits had to offer in it’s 3500 design over the past designs.
Thanks for your well written response. If you look into TPI intake, you'll see that GM designed the original V8 TPI intake for the 305. It was perfect for the 305 and it achieved a very high VE on the 305. Their fault was they didn't [re]design it for the 350. Hence the 350 was "stuck" with a 305 intake. The same design was employed in the the Fiero 2.8 V6 and it's TPI-style intake. Hence they achieve very high VE until you put a 3.4L engine underneath it. Also, where the typical iron head motor has been crippled is the exhaust. You can look at 2.8 dynos (yes 2.8) where the intake mods were light but when coupled with a much bigger exhaust, they put down 150+ rwhp. My original 3.4 (3400 block+cam) has made more torque than ever 3.4 or 3400 I've seen. I've only seen a 3500 with higher compression make more torque but it had a cam, cubic inches and compression advantage.
I guess my point is "the theory of" all that improved head design and bigger ports is nice to talk about. Dynos as they say don't lie. I have a stock 3400 bottom end with a ported Fiero top end. If you will agree with me that my motor was crippled after 4500RPM because of the Fiero intake neck, can you please show me a dyno where a naturally aspirated 3400 with a stock cam, with any intake, with any exhaust short of open exhaust (I ran headers and a muffler) is making more power than I did to 4500 rpm? Once you can do that, I will bow down to the gods of aluminum.
Yes, aluminum heads are lighter by 13lbs a piece (or 26 lbs in total), however the intake is bigger and net weights show only a 20lbs difference if you look around the internet for listed weights. Those 20lbs could easily be made up somewhere else. We're talking 0.77% of a 2600lbs car.
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03:16 PM
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
Originally posted by Will: I'm did not forget that. It's not relevant.
In the other thread, you essentially did claim that it was all intake, saying that Webers are street-legal while open exhaust is not... as if the discussion were about legality... or Webers.
In a six-cylinder engine (other than odd-firing V6s), the next piston starts its power stroke 60° before the previous one finishes, which results in smoother delivery of power to the flywheel. How is that not relevant? This also means that the intake stroke overlaps 60°. I'd say that's extremely relevant.
As for your second paragraph, I don't understand your point. You claim the 3500 as a superior intake to the Fiero, and I agree. It doesn't mean that the stock Fiero intake can't be modified or replaced to achieve optimal flow for the engine running iron heads...so I don't see your point.
[This message has been edited by lou_dias (edited 02-15-2013).]
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03:36 PM
cerulean Member
Posts: 137 From: Shrewsbury, MA Registered: Jun 2008
Let's say I were to use a 3500 engine, the whole thing.
- Can the timing covers be swapped to keep my accessories? - Will the throttle cables line up? - The exhaust, I assume, will need to be custom fabricated, or can the stock Fiero exhaust be used? - The dogbone also doesn't fit without modification. - I would need some kind of adapter for the throttle body.
If I ran it using the 7730 - do I need the custom trigger wheel?
Take a look at this thread. It's comprehensive and should answer your questions. You can do some of the steps differently, but you'd need to do some searches here on and on google for "fiero 3500 swap" or "fiero lx9 swap".
In a six-cylinder engine (other than odd-firing V6s), the next piston starts its power stroke 60° before the previous one finishes, which results in smoother delivery of power to the flywheel. How is that not relevant? This also means that the intake stroke overlaps 60°. I'd say that's extremely relevant.
As for your second paragraph, I don't understand your point. You claim the 3500 as a superior intake to the Fiero, and I agree. It doesn't mean that the stock Fiero intake can't be modified or replaced to achieve optimal flow for the engine running iron heads...so I don't see your point.
quote
Originally posted by lou_dias:
A 3.4L motor, be it a 3400 or a 3.4 at 100% VE is only pumping 360CFM at 6000rpm. Divide that by 6 and you'll see that 1 cylinder head port only needs to flow 60CFM...yet they can flow 150+ at the head... IE, the restriction has always been the intake neck which only flows 300CFM hence a 3.4 is choked at 4500 RPM on a stock Fiero intake. Heads are not the issue.
A) I know what you're saying. It's not relevant to the flow demands--and thus port requirements--of a single cylinder. All I did was take your assertion (see quote above) about the 60 CFM demand of a 3400 and take it a step further by including the open time of the intake valve. Your assertion was that iron heads or aluminum heads can both feed the engine well enough to achieve 100% VE. Your conclusion is that the restriction is in the intake and aluminum heads won't make more power than iron heads. Neither the assertion nor the conclusion is correct. The assertion is incorrect because the intake valve is not open the entire time the engine is running. The constant flow rate does not apply because the cylinder can only draw air for ~1/3 or the engine's cycle. Your conclusion is incorrect because it's based on your incorrect assertion.
B) I claim the entire 3500 is a superior design to the 2.8. Your claim that the iron heads can supply 100 HP/L worth of air is based on the output of a race engine. The build of that race engine vice a street engine makes that comparison not viable. You seem to think that "race" or "street" just means intake manifold or open exhaust. I'm talking about the ENTIRE BUILD... from compression requiring 116 octane fuel, to solid lifters, cam profiles that push the limits of the flat tappet diameter, attention to internal windage... The race engines may have even been dry sumped. The comparison doesn't work. The race engine makes 300 HP under iron heads while the street engine makes 300 HP under aluminum heads seems like a remarkably clear victory for the aluminum heads to me.
[This message has been edited by Will (edited 02-15-2013).]
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03:58 PM
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
Your arguement still doesnt explain why someone would go through all the work to redesign an engine to use inferior componants, when it comes form the salvage yard already ahead of the game.
Using a 3500 just a matter of "dropping it in". You have to fabricate a new alternator mount, rewire, replumb. It's simpler to just pay a machinist $150 to modify your intake.
Well, he's running .540" of lift, an open exhaust, more cubes and I was choked at 4500 rpm. It doesn't take a genius to figure out where the 87hp difference came from.
quote
I will stand by my belief the the LX9 was one fo the best of the 60 degree design by GM. I have done plenty of homework on IC engines, fluent designed cylinder heads, unsteady flow, etc, I have by BSME to back me up. I get how they work, I dont feel like your fully grasping it. I know what will produce satisfactory figures, close is gud'nuf really doesnt.
That's all well and good but the OP asked about using the block only and he should be made aware of what else needs to be done to make the most of it. You tried to convice him to swap the whole motor and I showed him what can be done with what he's actually planning to do.
quote
To me it seems like you think ported iron heads are superior to the 3500 GM castings. You already have a running engine, and your happy with it, dont switch. I am only trying to give some guidance on a future engine build not by you.
The OP isn't looking to do a full swap. I think the aluminum heads would be great if it was a 4.3L motor. To me they are just overkill and not worth going to the trouble of a full swap. That's the difference.
[This message has been edited by lou_dias (edited 02-15-2013).]
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03:59 PM
PFF
System Bot
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
Originally posted by Will: A) I know what you're saying. It's not relevant to the flow demands--and thus port requirements--of a single cylinder. All I did was take your assertion (see quote above) about the 60 CFM demand of a 3400 and take it a step further by including the open time of the intake valve. Your assertion was that iron heads or aluminum heads can both feed the engine well enough to achieve 100% VE. Your conclusion is that the restriction is in the intake and aluminum heads won't make more power than iron heads. Neither the assertion nor the conclusion is correct. The assertion is incorrect because the intake valve is not open the entire time the engine is running. The constant flow rate does not apply because the cylinder can only draw air for ~1/3 or the engine's cycle. Your conclusion is incorrect because it's based on your incorrect assertion.
Why must you continue this arguement? The demand of the engine are based on RPM and displacement. Hence be it a 3.4 or 3400, the demand is the same. Show me a 3400 that made more power than me with stock cam and a muffler.
quote
B) I claim the entire 3500 is a superior design to the 2.8. Your claim that the iron heads can supply 100 HP/L worth of air is based on the output of a race engine. The build of that race engine vice a street engine makes that comparison not viable. You seem to think that "race" or "street" just means intake manifold or open exhaust. I'm talking about the ENTIRE BUILD... from compression requiring 116 octane fuel, to solid lifters, cam profiles that push the limits of the flat tappet diameter, attention to internal windage... The race engines may have even been dry sumped.
Newer motors come with windage trays stock. You are still missing the point that the heads flowed to meet the demand.
quote
The comparison doesn't work. The race engine makes 300 HP under iron heads while the street engine makes 300 HP under aluminum heads seems like a remarkably clear victory for the aluminum heads to me.
For those same assertions, I find it amusing that you compare my build having a known choke point at 4500 given the intake I was using to one with more cubic inches, .102" more life and open headers.
Using a 3500 just a matter of "dropping it in". You have to fabricate a new alternator mount, rewire, replumb. It's simpler to just pay a machinist $150 to modify your intake.
And get a reluctulator weel, new pistons, rings, and gaskets.
I was just trying to point out, that with a little bit of work, that isnt dimensionaly critical the whole motor can be swapped in, and will perform better than a hybrid, with less fabrication. a LX9 intake on a LX9 reqiures no modifications to perform to the motors potnential. The work to make a 200hp engine out of the LX9 is done. No porting, no intake cutting and welding, no exhaust grinding and rewelding. Sure you can put the stock fiero exhaust on an LX9 too, but it surely wont make 200hp anymore.
i have a question, why is there an arguement over 30 year old technology vs newer tech? theres no way in hell the iron head fiero topend can beat a junkyard LX9(or LZ1) topend, its been proven many times on 60V6 and v6z24.com over the years. im seeing alot of apples to oranges arguments here...
Why must you continue this arguement? The demand of the engine are based on RPM and displacement. Hence be it a 3.4 or 3400, the demand is the same. Show me a 3400 that made more power than me with stock cam and a muffler.
Because I'm right and you know it.
60 CFM of continuous flow per cylinder means 60 CFM of flow into that cylinder AVERAGED over the entire 720 degree cycle of the engine. At 6000 RPM, that's .01 CF per revolution. Each revolution takes .01 seconds and covers 360 degrees. However, the entire .02 CF for two revolutions has to enter the cylinder in the time the intake valve is open for one cycle. If we're talking about a 270 degree cam, the intake valve is open 270/360 * 0.01 = 0.0075 seconds. To get .02 CF through the intake valve in 0.0075 seconds takes a flow rate of 160 CFM *AVERAGE* through the entire period the intake valve is open. While peak flow may be in this neighborhood, the valve spends relatively little time at peak flow lift, so the average flow for the cylinder head across the lift curve is much lower than peak.
Both iron and aluminum heads fall short of the engine's flow needs, BUT iron heads fall a lot shorter.
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04:46 PM
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
Thanks for your well written response. If you look into TPI intake, you'll see that GM designed the original V8 TPI intake for the 305. It was perfect for the 305 and it achieved a very high VE on the 305. Their fault was they didn't [re]design it for the 350. Hence the 350 was "stuck" with a 305 intake. The same design was employed in the the Fiero 2.8 V6 and it's TPI-style intake. Hence they achieve very high VE until you put a 3.4L engine underneath it. Also, where the typical iron head motor has been crippled is the exhaust. You can look at 2.8 dynos (yes 2.8) where the intake mods were light but when coupled with a much bigger exhaust, they put down 150+ rwhp. My original 3.4 (3400 block+cam) has made more torque than ever 3.4 or 3400 I've seen. I've only seen a 3500 with higher compression make more torque but it had a cam, cubic inches and compression advantage.
I guess my point is "the theory of" all that improved head design and bigger ports is nice to talk about. Dynos as they say don't lie. I have a stock 3400 bottom end with a ported Fiero top end. If you will agree with me that my motor was crippled after 4500RPM because of the Fiero intake neck, can you please show me a dyno where a naturally aspirated 3400 with a stock cam, with any intake, with any exhaust short of open exhaust (I ran headers and a muffler) is making more power than I did to 4500 rpm? Once you can do that, I will bow down to the gods of aluminum.
Yes, aluminum heads are lighter by 13lbs a piece (or 26 lbs in total), however the intake is bigger and net weights show only a 20lbs difference if you look around the internet for listed weights. Those 20lbs could easily be made up somewhere else. We're talking 0.77% of a 2600lbs car.
The reason that you car is creating such good power below 4500RPM has to do with the same arguement that your TPI point brought about. Just like the fiero intake, the runners are long and skinny (wave tuning optimal for low engine revs). 1st gear pulls are great, then when someone shifts at 5500 or 6000rpm you will arive at 3800 or 4000 rpm and have 400-600 usable rpm band before the torque drops rapidly. It feels great when passing during cruising, or when on an on-ramp at reasonable speed. But when put through their passes, The intakes and heads cannot perfrom to airflow demands. The same effect is seen on 383 stroker TPI's very strong bottom end, with no usefull top-end. Porting helps, But I will still atest that teh late model 3400 and 3500 are just better all around performers, and can acheive fromer race iron head motor results with modest cams, low speed idle, and emissions complience. This arguement is valid for LSx to GEN 2 SBC's as well. The design is just so much further advanced.
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04:51 PM
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
60 CFM of continuous flow per cylinder means 60 CFM of flow into that cylinder AVERAGED over the entire 720 degree cycle of the engine. At 6000 RPM, that's .01 CF per revolution. Each revolution takes .01 seconds and covers 360 degrees. However, the entire .02 CF for two revolutions has to enter the cylinder in the time the intake valve is open for one cycle. If we're talking about a 270 degree cam, the intake valve is open 270/360 * 0.01 = 0.0075 seconds. To get .02 CF through the intake valve in 0.0075 seconds takes a flow rate of 160 CFM *AVERAGE* through the entire period the intake valve is open. While peak flow may be in this neighborhood, the valve spends relatively little time at peak flow lift, so the average flow for the cylinder head across the lift curve is much lower than peak.
Both iron and aluminum heads fall short of the engine's flow needs, BUT iron heads fall a lot shorter.
You have some funny math there. The intake stroke is 180 degrees. A cam with a 270 degree duration starts opening earlier than TDC so that the exhaust back pressure can help fill the combustion chamber prior to TDC. This is also why an exhaust of the right size is important. Too small or too big and it doesn't help the intake stroke prior to start of the actual intake stroke. So once the actual intake stroke starts, the cam is already partially lifted if not mostly, and in fact roller cams achieve full lift faster than non-roller ones. TPI intakes also emulate a mild supercharger effect because the closing of one intake valve increased pressure to the one that's opening up. This is how TPI intakes achieve such a high VE. Here, let a friend of yours explain it: http://www.fierofocus.com/T...old_and_fucntion.pdf The real world combustion cycle of an engine controlled by a cam is why I say the extra "flowbench-rated flow" of the Gen3+ heads is mostly useless.
You guys refuse to accept that because I was using a stock Fiero intake NECK that I was capped at 4500 rpm ... You actually should be scared once the collision center gives me my car back and I dyno it with the Trueleo intake and L98 twin 48mm throttle body. ;-)
PS, Your hero SuperDave is running a Weber-style intake:
Like I said before 275 = 275 hint hint and wink wink! :P
Did I just rest my case?
[This message has been edited by lou_dias (edited 02-15-2013).]
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06:20 PM
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
The reason that you car is creating such good power below 4500RPM has to do with the same arguement that your TPI point brought about. Just like the fiero intake, the runners are long and skinny (wave tuning optimal for low engine revs). 1st gear pulls are great, then when someone shifts at 5500 or 6000rpm you will arive at 3800 or 4000 rpm and have 400-600 usable rpm band before the torque drops rapidly. It feels great when passing during cruising, or when on an on-ramp at reasonable speed. But when put through their passes, The intakes and heads cannot perfrom to airflow demands. The same effect is seen on 383 stroker TPI's very strong bottom end, with no usefull top-end. Porting helps, But I will still atest that teh late model 3400 and 3500 are just better all around performers, and can acheive fromer race iron head motor results with modest cams, low speed idle, and emissions complience. This arguement is valid for LSx to GEN 2 SBC's as well. The design is just so much further advanced.
The reason I'm making good power below 4500 rpm is because I didn't hit the intake neck CFM limit yet.
I don't understand why you think that my motor only makes 187rwhp and 249Ft*lbs. That was when I was using the Fiero intake with the stock neck restriction of 300CFM, hence why I peaked at or just prior to 4500 rpm. I am now running the Trueleo intake with an L98 twin throttle body. Some time in May, I will post a new dyno. Perhaps then we can revisit this discussion? Skip to 13:35 to see me against a non-stock Ford Lightning, I actually babied it in the first race because I blew him off the line so bad, it had also just finished drizzling. In the second, I had a bad launch but still hung right with a 13s 1/4 mile truck in the outside lane: http://www.youtube.com/watch?v=rLidp-lIQpM ps, this is also the reason I don't currently have my car as you shall see.
Before I switched to wheels with less offset, too much body roll would cause my rear rubber to hit my spring...taking that into account watch me race a low 13s WRX with my bad launch: http://www.youtube.com/watch?v=LtpnQbRzMS0 ...obviously I took my foot off the gas after contact...
[This message has been edited by lou_dias (edited 02-15-2013).]
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06:27 PM
joshua riedl Member
Posts: 1426 From: watertown wi USA Registered: Jan 2004
Didn't you make less power with the trueleo intake?
In theory I did ... until I fixed my tune. I made 187rwhp with the Fiero intake and Fiero ECM. I switched to the Trueleo and '7730 and had lots of issues for a while. I was running 21-22 second laps with the bad tune and 19.x laps with the good tune. My "newest" dyno was with the bad tune.
To the OP, iron heads on a 3500 should be considered one of the seven (now 8) deadly sins. it can bolt in place of the 2.8 if you use the fiero timing cover and accessories.
crappy picture, but this is a stock Fiero front engine mount bolted to a 3500, all it took was minor clearancing on the cast oil pan.(which you would have to do either way)
a few pics of both heads...
They're lighter, they flow better, they have better combustion chambers, better rocker arms, better valve springs ect... putting fiero heads on a 3500 would be the equivalent of putting swirl port 305 TBI heads on a LT1 and throwing a carburetor on it... yes it's that backwards.
Lou, until you post a dynograph showing a FLAT torque curve from sub 2000 RPMs to over 6000 RPMs, I will not stop telling you that you're wrong, mark me red, I don't care, if you get me banned, so be it, but you're wrong,
This is at the wheels through a 282 getrag in a cavalier running a '7730 ecm.
From what I understand from my reading over at 60degreev6.com it isn't even possible to make the 2.8 heads work on a 3500 because of the bore size. I could be wrong though. For the amount of work to make a 2.8/3500 hybrid you could swap in a complete 3400 or 3500 into a Fiero and have more horsepower. That much I can say for sure.
The iron heads only weigh 13 lbs a piece more than aluminum heads. Engine weights are 390 for the Fiero v6 and 370+ for the 3400/3500's in other words closer than you think since they naturally come with more hardware on them. Look up dynos on youtube of 3400 and 3500 motors and see what the real "at the wheels" power is before you believe the "leaving 60hp on the table" comment. IE do your own home work.
I think there is some misinformation in the above statement. http://60degreev6.com/forum...highlight=lx9+weight In a Fiero a 34/3500 would not weigh over 370 pounds. Without AC, it woul be close to 350 pounds. With that weight savings, and the extra power, this is even more reason to swap the whole engine. Here's my dyno sheet from a while back. This was a completely stock 3400 5 speed running on a base tune.
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11:23 PM
ericjon262 Member
Posts: 3111 From: everywhere. Registered: Jan 2010
From what I understand from my reading over at 60degreev6.com it isn't even possible to make the 2.8 heads work on a 3500 because of the bore size. I could be wrong though. For the amount of work to make a 2.8/3500 hybrid you could swap in a complete 3400 or 3500 into a Fiero and have more horsepower. That much I can say for sure.
they will swap, but it's a bad idea.
------------------ we're in desperate need of a little more religion to nurse your god-like point of view...
PS, Your hero SuperDave is running a Weber-style intake:
superdave did the dyno posted above with a ported plenum, he just swapped to ITBs when he built the Camaro, and has since swapped back to a single throttle body plenum with a 75mm N* throttle body.
------------------ we're in desperate need of a little more religion to nurse your god-like point of view...
Originally posted by Bridgetown: I think there is some misinformation in the above statement. http://60degreev6.com/forum...highlight=lx9+weight In a Fiero a 34/3500 would not weigh over 370 pounds. Without AC, it woul be close to 350 pounds. With that weight savings, and the extra power, this is even more reason to swap the whole engine. Here's my dyno sheet from a while back. This was a completely stock 3400 5 speed running on a base tune.
Really?
quote
340lbs on the nose as pictured for a 3500 minus the alt, P/S and A/C.
Like really? Fiero can drop A/C too so that's a non-issue. You're also leaving a lot of information on the table, like exhaust setup which is obviously not stock 3400 in a Fiero....? Still you made less power than my restricted intake dyno...and at a lower rpm. What was that about mis-information again?
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02:06 AM
lou_dias Member
Posts: 5350 From: Warwick, RI Registered: Jun 2000
Originally posted by ericjon262: superdave did the dyno posted above with a ported plenum, he just swapped to ITBs when he built the Camaro, and has since swapped back to a single throttle body plenum with a 75mm N* throttle body.
Sorry, but his Camaro sounds exactly like the same motor he swapped into his Cavalier...note for note.
Sorry, but his Camaro sounds exactly like the same motor he swapped into his Cavalier...note for note.
it is, a few things have changed like the ITB and auto trans, different headers, etc. ITB's have been removed like ericjohn stated.
its ok to be dead set on 30 year old technology, no one can fault you for that. if all the same mods were done on a GEN III 660, it would deliver more performance than the old GEN I. i havent been at 60v6 forums for a bit, but have you made your case over there yet?
[This message has been edited by sleevePAPA (edited 02-16-2013).]
