People seem to agree that the whole intake system on the Fiero is very restrictive, and the only way to really open it up is to bore out the plenums and give it a larger throttle body. Enter carburation. (is that a word?) Edelbrock and other companies make intake manifolds that are very high flow. Heres what I found:

http://www.carshopinc.com/index.php/cPath/33_41/page/5

Its the 10th one down or so. An intake manifold for the Chevy 2.8l. I didn't have a lot of time to look around, but I know they also make fuel injection heads for people going from carb to FI. Would either of these manifolds work on the Fiero? I know some decklid modification would be in order, but otherwise it seems with some work it could. Would there be a noticible difference in engine response and performance with something like this?

I always wonder if one could use one of those manifolds and a Holley Pro-Jection system, it would give you the best of both worlds.

Flow is improved by almost 40% using the Edelbrock intake. I have a 3.4L with the set-up. It was engine dyno'd at 223hp/239torque.
You don't really have to modify the decklid if it's an 85-88 decklid (notchback or fastback) But you do if it's an 84. Do a search on "Oreif" and "carb" and you will find numerous threads on my engine.

If you really want to do this, I have all the info on what exactly needs to be done. There are already a few folks running a 2.8L with a carb and they are very happy with the gains.

There is no aftermarket manifold/intake designed for use on the 60* V-6's (well actually there is a company that will make a custom kinser type injection system but it very expensive)

The Holley Pro-Jection might work if you could find a smaller CFM throttle body. 600cfm is way too big for the 60* V-6 engines.

Here are some pics of the engine before it was installed back in September. The air cleaner on it will fit under the decklid.

And here it is in the car the day I first started it:

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Happiness isn't around the corner...
Happiness IS the corner.

[This message has been edited by Oreif (edited 12-13-2003).]

So then that one I found by Edelbrock doesn't fit? It says Chevy 2.8l engine. I assumed it was intended for the Firebird and S-10 guys, which is the same 2.8 as ours, but with different air intake. Is there a different 2.8 or something thats not 60*?

All I know about the 2.8 intakes is that the third generation/aluminum head intakes don't fit with the distributor. Other than that I thought that the blocks were the same for the S-10s, fieros, and the firebirds (non-3.4?).

Here's the next question for this thread though...

Some say that the intake manifold is the most restrictive part of the engine (airflow). If we had new intake manifolds, and the cylinder heads became the most restrictive part, how much work can be done to those to increase flow even further?

If we had new intake manifolds, and exhaust manifolds (the easy part), we could throw in a new camshaft, rocker arms, or various other valvetrain parts and really have the opportunity to build the top end up.

I didn't know anyone made intake manifolds for our engine, so now I'm really excited.

quote Originally posted by Fastback 86: So then that one I found by Edelbrock doesn't fit? It says Chevy 2.8l engine. I assumed it was intended for the Firebird and S-10 guys, which is the same 2.8 as ours, but with different air intake. Is there a different 2.8 or something thats not 60*?

The Edelbrock intake WILL fit any 60* V-6 with cast heads. (By "60* V-6" that means 2.8L, 3.1L and 3.4L engines)
So it will fit:

Citation
Camaro/Firebird's with the 2.8L or the mid 90's 3.4L (The mid 90's 3.4L engines have cast heads)
Early/mid 80's Cavalier Z-24's
Pontiac Fiero's
Early 90's mini vans with the 3.1L and cast heads
S-10/S-15 trucks
Celebrity/6000/Century's
(Basically any vehicle with a 2.8L and cast heads used in the 80's)

The Edelbrock will NOT fit any of the aluminum heads used on 60* V-6's

For flows:
The Fiero intake set-up ported and bored can flow enough air to support about 190hp normally aspirated.
The Edelbrock 4-bbl carb intake can flow enough to support 260hp.
The cast H.O. heads (like the ones on all Fiero 2.8L's) in stock form are good for about 175hp and can be ported to flow about 230hp.

[This message has been edited by Oreif (edited 12-13-2003).]

Alright, good deal. I don't think I'm going to do it, as my car has 150k miles on it and I hope to swap in a 350 V8 this summer, but if that falls through I'll look up this idea again.

BTW, engine looks great Oreif!

Is there any throttle body that will mate to these intakes? I really don't want to mess with a carburator but I've been looking for an intake for a while now.

Any suggestions would be appreciated.

quote Originally posted by iluvmacs: Is there any throttle body that will mate to these intakes? I really don't want to mess with a carburator but I've been looking for an intake for a while now. Any suggestions would be appreciated.

There are aftermarket adapters to add a throttle body injection. But you need to then have a scoop on the decklid. The adapter plate is 1/2" thick and the TBI's are about the same height (maybe slightly higher) as a carb. I've never looked into it, but a twin injector TBI from a 4.3L is what you use. You need to use an aftermarket injection computer to run the system and the 2-bbl riser with EGR port if you are required to pass emission testing. If using a 2.8L, you could alwasy get the intake and TBI from an 85-87 S-10 truck. The overall height is lower but I have no idea what the flow numbers are for the intake nor the TBI. The S-10 people have used the Edelbrock with TBI. They say it works good, but even with the S-10 trucks, the height requires the use of a scoop. Your best source of info on this set-up would be the S-10 forums.

[This message has been edited by Oreif (edited 12-14-2003).]

It seems to me that someone with a heliarc setup could, with some aluminum plate and tubes, piece together a a one-off manifold with the flow capabilities we are talking about here. Or beter yet weld up a "spacer" to fit between the upper and lower halves of the stock manifolds. Or has someone already tried that?

I don't think a spacer would fix the problem. The length is tuned, and already quite long. Short runners that are wider are what we need.

Orief, I don't have a problem putting a scoop through the decklid. Right now I have side scoops but no ducting to get to the TB. With all the necessary modifications to the edelbrock, it might be better to think of a new setup. Some guy named cooter got rid of the middle and upper intakes, and replaced them with a custom fabbed tube.

I don't think my questions are answered (in terms of finding some airflow for the 2.8), but thanks for helping.

iluvmacs,
**I don't think a spacer would fix the problem. The length is tuned, and already quite long. Short runners that are wider are what we need.**
I see what you mean. I've never disassembled a 2.8 before. I just looked at my Chilton's to see how the plenum and maifold go together. A spacer would only make the air track longer. So where is the restriction to flow? The plenum or the manifold? Or both?

quote Originally posted by Oreif: You need to use an aftermarket injection computer to run the system and the 2-bbl riser with EGR port if you are required to pass emission testing. If using a 2.8L, you could alwasy get the intake and TBI from an 85-87 S-10 truck. The overall height is lower but I have no idea what the flow numbers are for the intake nor the TBI. The S-10 people have used the Edelbrock with TBI. They say it works good, but even with the S-10 trucks, the height requires the use of a scoop. Your best source of info on this set-up would be the S-10 forums.

The best source of info would be the S10 forums.... However, you don't need an aftermarket controller. A reprogrammed factory computer will work just fine. You can get tuning advice from www.diy-efi.org

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'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

I have a 2.8 TBI manifold at home. I will post some pics of it later.

Where did you get your intake, did you fab it yourself? I don't know what length runners would be optimized for what flow/rpm, but since the optimum length is usually divided by 10 or more (the sonic wave goes back and forth 10 times) the length difference is probably pretty small.

I suppose that you could theoretically mate runners to a flange, and collect them at the throttle body, just like an exhaust. I guess that actual intakes are just like this except that the runners are hollowed from a cast piece, and the rest of the intake keeps the lifters and oil sealed.

Did you do any dyno testing before and after you installed the intake? Did you do any flow calculations for runner diameter or anything else?

I'm really interested in intake calculations, especially since I own a fiero and the intake sucks. Exhaust is much easier to modify on any car, and you can swap out camshafts too, but intakes aren't so easy.

The intake that I have is a factory TBI intake from a a late 80's S10.

This is NOT the modified edelbrock intake that I posted pics of earlier.

[This message has been edited by DanielKJenkins (edited 12-15-2003).]

quote Originally posted by DanielKJenkins: Do not assume that I am unfamiliar with intake manifold design. You have read the book... Have you actually altered an intake?

never, and I wasn't insinuating that you hadn't, I just post the question as my mind wonders/wanders. Since you have actually altered an intake, I have more questions for you, but not enough time to post them now.

Thanks.

Oops.

I may be a little thin skinned at the moment.

I need some play time!

Wondering if anyone else out there is using an intake manifold that is, well, not stock.

I'm really interested in this so if anyone has any product numbers or backyard mods they've done, I'd love to hear about them.

**DISCLAIMER**
**I have not run my engine with this setup**
**I am not sure if I have done the right thing or not**
**This will hurt idle and low end torque**
**I am aiming for a good strong 6500 rpm motor**

**Only the completed engine will tell the story**

I have a 5spd, no AC and no power accessories. I will be using a vacuum secondary holley 390 and a crane 272H (or maybe a crower that is somewhat hotter). With AC and/or an auto this intake would be undrivable due to low end power losses.

Orief is right on the money with the low end torque increases due to long thin runners. I owned a set of Edelbrock headers for about 2 days (sold em) and the tube lenghts/diameters are of different sizes on the header to match the intake.

It is possible to get the intake ports really close to equal size. If you cut off the bottom of the exhaust crossover, clean the area with a sandblaster, and apply some HI-TEMP epoxy to the underside of the manifold. The ports on the small side will still be slighlty smaller.

Here are some links to pics of my intake.
http://home.swbell.net/deannj/intake_plenum.jpg
http://home.swbell.net/deannj/intake_side.jpg http://home.swbell.net/deannj/intake_top.jpg

Keep in mind my previous disclaimer

I like what you've done, but I can't relate too well because I don't recognize the intake parts.

Seems odd that they'd have that bank separator on the plenum. Good job removing that. You mount a carb up to that, wonder how hard it would be to use a throttle body. I'd really like to refrain from learning anything about carbs.

Good port job on the upper and lower. Are the port holes on the lower manifold the same size as on the stock manifold? They look really really small.

Can you comment on the difference in engine response just due to the intake changes? I know that after the intake is opened up the most restrictive part of the engine is in the head, but I'll get to that later.

Did the torque peak shift, and if so, how far?

I do not know how far up the power band has shifted. The engine is not complete. should be this spring

I have opened the intake runners in the heads, opened the valve bowls, unshrouded both the intake and exhaust valves and opened the exhaust ports to ~1.2" form ~`1.1". I have some 3/8" flanges and I intend to build headers that are ~27" x 1.5" equal length. I will use the DOHC pistons to pick up compression that was lost during the unshrouding of the valves and the polishing of the combusion chambers.

I am shooting for strong power between 3500-6500 rpm. I may have overshot my intended RPM range. If I have I will start with narrowing the runners and/or replacing the lower portion of the plenum divider. The factory manifolds all seem to have close too equally sized runners.

It may also be that the TBI from the 4.3L Chevrolet is tunable enough to broaden the power band. If the unit can be made to ignore the unstble vacuum at idle.

quote Originally posted by DanielKJenkins: I have done about the same thing with a Mitsubishi 2.0. I can tell you that a friend of mine had a Toyota 22R (2.4L) that would stomp my mitsubishi before the intake and exhaust changes. After the changes I could really walk off and leave the Toyota. Hey Orief did you ever try the G-tech device? Would you recommend one for tuning purposes? I usally find a flat stretch and just compare speed to distance.

Opening up the intake on a straight (inline) engine like a 4-cyl or a straight 6 is different because you have different runner lengths due to the intake design. I am very interested in how your engine will run.

I used the G-tech with my original 2.8L and found the 0-60 times and 1/4 mile times to be OK. You need a very flat stretch. The horsepower readings are not very accurate, but if you use the same stretch of road to do your tuning on, you can see if you have a gain/loss with respect to your original run. So for tuning I think it's a good tool to use. I usually did 5-6 runs and averaged the readings. By doing the runs and averaging the times seem more accurate but the HP readings always seemed high. I will be doing the same thing with my 3.4L once it's fully broken in.

Orief

After our conversations on this subject I have looked at the possibility of a shortened divider and or narrowing the runners as a method of bringing back some low end power.

I will start with the intake as it is now and see if it meets my requirements. The plenum divider that I have made from 2" x 1/4" aluminum could be installed without removing the lower portion of the intake so that would probably come first.

The requirement that I can cruise at 70 in 5th gear without dowhifting for every small hill is the parameter that I am most concerned with.

I have 4 daughters and it is Christmas ($$$). Work on the Fiero is delayed. I have the engine coated in oil and covered. The heads are done the same way.

I will probably start with having a valve job and the Crane cams springs installed. BTW I compared the specs on the Crane springs Vs the Crowers and the crane springs are slightly stiffer. I have thought about the wildest hyd cam that Crower offers (maybe). The 272H cam falls between the 2 "level 4 street/strip" cams that Crower offers. Especially the duration @.05. The 272H should produce more vac at idle as it has a steeper lift rate on the intake side. Lift also falls between the 2 crower cams.

Solid lifters are just too noisy in my opinion.

Do you have your Edelbrock cam specs? Just curious as you have dyno results that would offer some valuable correlation data.

I'd really like to know if you overshot your RPM goals, because those are my goals. What intake did you start with, the edelbrock?

You mentioned idle vacuum problems. Could this be fixed by increasing the idle speed? I'm not really concerned with how the car sounds at a stoplight. Then again, as long as the computer didn't freak out, I can deal with a loping idle.

My original plan was to use solid lifters, but some people have warned me not to. Is there more to the story than noise? I don't want to be doing valve train repair every month.

I checked out the edelbrock site. I'd really like the car to peak around 5500 rpm, and pull to redline if possible. I thought the dyno chart was a little more for advertisement than for calculation.

I really really want to keep the MPFI system if at all possible. I don't care about noise, or idle (unless the computer does). I'll accept doing more maintenance, if it's worth it. I really would like the engine to have more horsepower than torque, and to pull all the way to the redline. Thanks for all the info.

Everything that I have posted so far is speculation based on my experience with other cars and other engines. This engine has not been assembled yet.

I assume that there will be a loss of idle quality because open plenums, longer duration cams and large runners tend to cause those sorts of problems on carbureted cars.

Solid lifters do require periodic maintenance (lash adjustments) and they are loud.

I have never played with F.I. My fiero started out as a 4cyl so I don't even have the pieces to assemble the FI.

thanks al or info and opinions am spending winter nights reading all! posts deciding what my spring upgrade is going to be... ..

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1986 Pontiac Fiero SE, 67k original miles, V6, Auto, AC, PB, PDrlks,Pwr windows, Sunroof, Silver body and black aero/gt trim, Factory Aero nose,Factory Wing and Alloy Wheels, 205-14-70, Optional Factory Guages. Mostly original stock. Remember those who serve our Country! currently under going minor repair/over winter project.

1984 2m4 RIP
1987 2m4 sold

[QUOTE]Originally posted by Oreif:

Flow is improved by almost 40% using the Edelbrock intake. I have a 3.4L with the set-up. It was engine dyno'd at 223hp/239torque.

ehhh.. why dont you guys just use a TBI unit from a 3.1L v6 from one of the GM minivans.. they dont use DIS, they have a distributor.. use the intake manifold from the 3.1 , and use the tbi unit off a 4.3L v6 it will bolt right up too/ you'll need the fuel sending unit, the ecm and the wiring harness too...thats what i did on my 2.8L V6 in my '85 chevy citation X-11.. the engine internals are completely stock, except for the inatke manifold and up, and i gained 35 hp and 45 ft lbs of torque by switching over.

quote Originally posted by DanielKJenkins: Solid lifters do require periodic maintenance (lash adjustments) and they are loud.

Just like a motorcycle, eh? I thought you had to do a lot more valve lash adjustment for all pushrod engines, because of the pushrod compression.

Now that I think about it, that might be pretty tough considering the placement of the engine with regards to the firewall...

quote Originally posted by aaronrus: [QUOTE] ehhh.. why dont you guys just use a TBI unit from a 3.1L v6 from one of the GM minivans.. they dont use DIS, they have a distributor..

I am looking at this as a future modification. Would I need the computer controled distributor? My dist is an early 80,s S-10 with no comp provisions.

What about tuning? The 2.8-3.1 TBI engines were never meant to make power in the upper RPM ranges.
Can the TBI system be tuned at home..I guess I wonder if I have to get a chip burned or is there a way to control this system from a laptop?

Is there a good book on the subject?

BTW do not underestimate the capabilities of a good carb. I have played with the webers and they are amazingly efficient. I suspect that the vac secondary holley is also quite efficient.

[This message has been edited by DanielKJenkins (edited 12-19-2003).]

quote Originally posted by DanielKJenkins: ...snip... 1.) Would I need the computer controled distributor? 2.)What about tuning? The 2.8-3.1 TBI engines were never meant to make power in the upper RPM ranges. 3.) Can the TBI system be tuned at home..I guess I wonder if I have to get a chip burned or is there a way to control this system from a laptop? 4.) BTW do not underestimate the capabilities of a good carb. I have played with the webers and they are amazingly efficient. I suspect that the vac secondary holley is also quite efficient.

1.) Yes. It is not that big of an issue having computer controlled timing. A knock sensor makes tuning the advance pretty easy compared to adjusting vac advance cans or swapping springs and weights in the mechanical advance.

2.) The intake will flow the air for more power, you will need the rest of the 'package' to get the best performance.

3.) I am running my Caddy v8 in the van with a TBI and Chevrolet truck ecm (a '747 from an '88) It is very tuneable with the available software. The stock truck program was pretty close on the fueling. Right out of the box, it ran good enough to drive it home from the shop. The program 'WinAldl' will really help on tuning the '747 ecm. My BLM's stay within the 120 to 136 ranges, all it took was time to edit the code, drive around the block, edit the code, drive around the block....

4.) I used to love my carb's, but now that I have a better understanding of how to wire, program and troubleshoot the EFI, I'd rather not mess with a carb. I have a great respect for people who can tune a carb and make it 'right' because I never had that much luck with them.

[This message has been edited by Cooter (edited 12-19-2003).]

Hmmm. So you have control over the mixture and the advance.

How about the retard on the knock sensor, can you control the degree of retard in response to detonation?

What about vacuum, can you disregard vacuum signals at idle to make up for camshaft timing overlap?

I guess the inputs to the system are air temp, eng temp, rpm, throttle pos, vacuum, the knock sensor and ??

I will look into the software you described.

I will start out with the carb (because I have more understanding of carbs). I will learn about FI in the mean time.

Thanks
Dan

[This message has been edited by DanielKJenkins (edited 12-19-2003).]

quote Originally posted by DanielKJenkins: Do you have your Edelbrock cam specs? Just curious as you have dyno results that would offer some valuable correlation data.

My cam specs are:
Intake lift: .461 (.467 with the 1.52 rockers)
Exhaust lift: .483 (.489 with the 1.52 rockers)
Intake duration: .274
Exhaust duration: .286
Lobe seperation: 112*
Timing advance: 36* @ 3400 rpm.

[This message has been edited by Oreif (edited 12-19-2003).]

Thanks Orief

I will start a new thread for TBI V6 questions. I lost my cheap digital camera so I cannot post pics of the factory TBI manifold. When I get the pics I will start the thread.

Dan