ok so i has a 85 gt with a freshly rebuilt 2.8 in it that has been bored to 3.2l everything in it it brand new and it has a comp cam ive been told that the intake on our system is very restrictive and that a carb would help the comp cam reach its fool potential but ive also been reading and heard there are higher flowing intakes that work well too! but im thinking for that to work properly you would also need higher flowing injectors i want to know the advantages and disadvantages of both the carb and the performance intake the price that each setup would cost me ease of installation overall performance gains and fuel economy
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11:44 PM
PFF
System Bot
Nov 3rd, 2009
White Spyder Member
Posts: 1047 From: Gluckstadt USA Registered: Sep 2007
I can't answer the questions but do have an intake from an S-10 for sale with stock carb if you want it. I swapped to FI on my stroker. Comp cam, stroked and bored to 3.2L I have the big valve heads though.
[This message has been edited by White Spyder (edited 11-03-2009).]
Sure you can use a carb but they'll run you about $450.00 for the small 390cfm size. Then you'll need the hard to find and discontinued Edelbrock manifold. Figure another $250 for that. You will need a low pressure fuel pump, maybe $50.oo for that Then figure the result- lower gas mileage, higher emissions, a configuration that is far from emisson legal, decreased longevity and poorer drivability. I would take the time to learn about EFI. It's really not that complicated and you can use what was originally on the Fiero saving money and gaining benefits. May I ask, what is it that you don't like about modern self compensating electronic fuel injection?
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
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09:57 AM
rogergarrison Member
Posts: 49601 From: A Western Caribbean Island/ Columbus, Ohio Registered: Apr 99
I think it Orief who has a carbed 2.8. If your going to do it, there not that expensive. I bought a new AFB style 4 bbl from Jegs for $260. If you really want to play with being creative, ive seen hot rod 6 cyl Mopars running one or pair of 4 bbl carbs. Theres a guy with a Valiant that comes every year to the nats and runs a dual 4 bbl slant 6...think its around 400 hp on gas.
Sounds similar to mine. Carb'd and I get 27mpg. With all due respect, you don't want the S10 intake. It was designed for 110 hp. I have a full setup and my new engine will be a "better" carb'd 2.8. More performance goodies.
You will want the Edelbrock. One thing though, it is tall. You'll need a deck scoop for clearance.
The 2.8 is a little small for the available carbs. I use the Holley 390. It is reliable. If you want to get the info on how to modify it to run perfect on the engine, send me a PM.
If you have some time, look on Ebay for the Offenhauser intake. They come up once in a while. They don't go cheap, but, they are much lower profile and you can run them without a scoop. I paid under $300 with shipping
Expect about a 15 hp increase without other mods. If you port the heads, exhaust and Y expect about 30 hp increase at the wheels.
If you want a cheaper carb that will work just fine, get the Holley 2 barrel 350 cfm. They are about $100 less than the 390 and they are a closer match to the engine.
You'll need the vacuum advance distributor. Again Ebay will show an S10/Blazer unit for $75 on average.
Don't pull your fuel pump. Buy a bypass fuel regulator. The bypass regulator regulates the whole system down to as low as 4psi (I run 6 psi) and you won't believe how quiet the fuel pump runs at low pressure.
Good luck with the build.
Arn
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12:32 PM
drebinpk Member
Posts: 577 From: bridgeton mo Registered: Apr 2009
The 1981 to 1984 2.8L HO Z engine was 140HP and the short runners made it wind very nicely to 6500. You might have to mill the intake for the carb you want to you but it worked very well. You will lose a bit of low end torque but if you want to wind it up, that intake is very good. I believe the intake is the same as the 110HP X engine intake.
They can be found in the V6 Citation, Celebrity, Phoenix and Omega VIN X from 1980 to 1984 and 1981 to 1985 VIN Z.
[This message has been edited by TK (edited 11-03-2009).]
The 1981 to 1984 2.8L HO Z engine was 140HP and the short runners made it wind very nicely to 6500. You might have to mill the intake for the carb you want to you but it worked very well. You will lose a bit of low end torque but if you want to wind it up, that intake is very good. I believe the intake is the same as the 110HP X engine intake.
They can be found in the V6 Citation, Celebrity, Phoenix and Omega VIN X from 1980 to 1984 and 1981 to 1985 VIN Z.
The the carb'd intake for the 110 hp engine will not give you 140 hp. It may be that the Citation had a carb'd 140 hp engine but I don't recall that one and try to find one of those engines or the intake nowadays.
I do not recall a 140 carb'd 2.8 engine prior to the Fiero v6. Am I missing something? It sure would have been nice to find a worthy intake at the wreckers instead of paying Jegs.
Arn
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09:49 PM
PFF
System Bot
The_Stickman2 Member
Posts: 1030 From: Lehigh Valley Pa. Registered: Sep 2007
Actually if you read Chevy's Power book they tell you how to machine the Citation/S-10 intake. And they state that it has been used to around 200hp in different racing series.
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10:41 PM
drebinpk Member
Posts: 577 From: bridgeton mo Registered: Apr 2009
Originally posted by TK: They can be found in the V6 Citation, Celebrity, Phoenix and Omega VIN X from 1980 to 1984 and 1981 to 1985 VIN Z.
I've got one off an '85 4-speed Citation. What do I look for to see if this is the right intake? If this is the "good" one, I'll make someone a great deal on it.
if the 350 2b is better mated then why do you use the 390 4b?
It is a bit of a story, but, I started out with the 350 cfm carb. It worked fine. The car then started acting like it had a vacuum problem. It would run fine over 2000 rpm but stumble at idle and chug to get going. After consulting with some guys more knowledgable than myself, we couldn't solve the problem so I dumped the carb and got the 390. The 390 was a problem to control the accelerator pump but, after some research I found out how to handle that problem, and now it runs very well indeed.
However, that is not the whole story. The vacuum problem continued after the new carb was installed, so in desparation I removed the MSD 6L box and voila! No problem. It turns out the box was emulating a vacuum leak symptom. Needless to say that was the LAST MSD BOX MY CAR WILL EVER SEE.
As for the 350 cfm carb, it is likely the better choice for the engine however, the smaller primaries on the 390 do deliver a clean bottom end and the carb does take the engine up to red line and beyond with no problem. Either carb will work, but, you will need to do a little mod on the 390
I've got one off an '85 4-speed Citation. What do I look for to see if this is the right intake? If this is the "good" one, I'll make someone a great deal on it.
I looked in the ChevyV6 performance book and they don't mention a "good" one. They do mention putting on a converter flange to take a 500 cfm 2 barrel. I take it from that that the 2 barrel OE intake must flow better than what I've been told. It may well be that with some mild porting it will flow just fine for the engine. It might be worth an experiment.
The the carb'd intake for the 110 hp engine will not give you 140 hp. It may be that the Citation had a carb'd 140 hp engine but I don't recall that one and try to find one of those engines or the intake nowadays.
I do not recall a 140 carb'd 2.8 engine prior to the Fiero v6. Am I missing something? It sure would have been nice to find a worthy intake at the wreckers instead of paying Jegs.
Arn
Well there was. Search for the Citation X-11. LH7 VIN Z. We've discussed it here many times over the years. I owned three before I got into Fiero's. If I recall correctly, the LE2 and LH7 used the same intake. I can't speak to the S10/Camaro intake.
[This message has been edited by TK (edited 11-04-2009).]
has the full writeup. It looks like a 135 hp rating in stock form. That Citation intake may be a good match, however, it is also an emissions intake so it will likely need porting?
Arn
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11:30 AM
drebinpk Member
Posts: 577 From: bridgeton mo Registered: Apr 2009
I am not sure. My 390 is working very well and gives more flexibility for tuning options IMHO. The 350 was smooth and if I wanted reliability, simplicity, and economy I'd go with that one. I am, however, building a 175 hp 2.8 that could deliver more than planned. The extra cfm on the 390 is likely beneficial for future plans.
If I had not had the MSD problem I'd still be running the 350 and I expect I'd be happy. No, I traded it back in. BTW it pays to not get a used carb.
Here is the vital information on the accelerator pump ciruit from my old thread
In consultation with Scotty McLendon, I found the final answer to the bog. It completely solves the problem and the car now has a whole lot of snap from any rpm. The answer is reducing the shot. I took the orange accellerator pump cam but the white cam will do about as well. With the carb off the car, you remove the screw holding the cam in place. You then pivot the cam on the armiture so the #1 hole on the bracket is between the two holes on the cam. You then mark the cam with a magic marker and remove it. You then drill a hole the same size as the other holes through the spot you've marked. You then install the cam using the new hole on the #1 screw hole.
You then have to adjust the accellerator pump arm. If it is the metal one, you bend the tab until the arm returns to zero setting. If you have the plastic arm, you tighten the adjuster screw until there is some slack (very little) between the accellerator pump arm and the pump lever.
You will then have immediate throttle response with an overall shot of about 1/3 to 1/2 of the original cam. In my case, the new hole was about 40% of the distance between the two original holes. My shot is therefore reduced from 19cc to around 12cc.
Believe me when I say that this fix changes the response of the engine very noticably.
The plain secondaries spring that came on the carb seems to work well.
I have put the primary jetting back up to #512 (a true 51 thousanths)
The old thread takes you through, step by step, my difficulties, however it includes the blind alleys I went down before getting it right.
has the full writeup. It looks like a 135 hp rating in stock form. That Citation intake may be a good match, however, it is also an emissions intake so it will likely need porting?
Arn
It was 140HP in 1981 but they dropped it to 135 when they switched to the wrap-around crossover (vs the 1981's Y pipe). Jon Heinracy said they were really a bit over that.
I am not sure what the relationship is between porting and emissions but I would at least gasket match it. That intake was used in many wonky 2.8L off-road carb engines in the early 80's. It's a decent starting point if you can't get an AM intake.
If I didn't have an Offenhauser sitting on the new engine, I'd be interested in trying it myself. If GM recommended a 500 cfm carb could go on it, that means it flows pretty well and I expect the small valves and emissions stuff would mask the efficiency of it.
This is kind of interesting.
Arn
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04:03 PM
drebinpk Member
Posts: 577 From: bridgeton mo Registered: Apr 2009
I don't know but you should send the vendor a question. Ask him if it works with the Holley 7448. If he doesn't know, don't buy it.
As for the propane idea, I have an interest myself. Major outlay though. You have to install an approved tank and propane is not necessarily good for some climates. I wish I could look into it but $$ indicate I can't. Why don't you? and I'll learn from you
If I didn't have an Offenhauser sitting on the new engine, I'd be interested in trying it myself. If GM recommended a 500 cfm carb could go on it, that means it flows pretty well and I expect the small valves and emissions stuff would mask the efficiency of it.
This is kind of interesting.
Arn
I think the original Rochester Varijet M2SE used on the 2.8L V6 was 390 cfm. I can check my notes from back in the X11 days but that sticks in my head.
[This message has been edited by TK (edited 11-04-2009).]
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07:17 PM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
FYI ~ The Edlebrock intake manifolds are NOT discontinued as inaccurately reported earlier in this thread.
I believe that they may have been for a while but it looks like they have been brought back. So as of this date "discontinued" is incorrect info. Still with a near $200 investment (w shipping) for this manifold, a new carb ($400) and air filter ($35.00) and fuel pump (and or regulator $50) I don't see why the OEM Fuel injection system is not the more cost effective route. A simple chip reprogram and you're in business plus you don't need to cut the deck lid for clearance.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
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01:17 PM
drebinpk Member
Posts: 577 From: bridgeton mo Registered: Apr 2009
because the oem intake is the most restrictive part on the 2.8 engine and any performance upgrades you do with it wont have near the effect they should because of that
Well here we are. Back to the heart of the matter. The intake is not what I would call the worst restriction, but, behind the exhaust manifold/Y pipe it is close.
So, to step it up you have choices that are not cheap. The Trueleo intake, which will work well and is, by what I see worth the cost, and the Carb conversion, also not cheap but, works as well. And, oh yes, the carb gets just as good gas mileage and makes just as much power, and once it is set up (without an engine diagnostic electronic analysis ), it stays in tune and delivers good performance.
Arn
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03:40 PM
drebinpk Member
Posts: 577 From: bridgeton mo Registered: Apr 2009
the thing i like better about the carb is i can do the whole swap for $600 the trueleo its $600 for just the intake then i need higher flowing injectors and larger bore throttle body, plus the dyno time to tune it so that could easily reach 1k which i dont have right now
the thing i like better about the carb is i can do the whole swap for $600 the trueleo its $600 for just the intake then i need higher flowing injectors and larger bore throttle body, plus the dyno time to tune it so that could easily reach 1k which i dont have right now
You need dyno time for fuel injection but not carb??? Sure you can do a carb setup for $600? There's the fuel pump, manifold, carb...
Larger bore throttle body? Is it really a bottleneck? Injectors may not be needed. What's the current duty cycle? How much more air do you plan on flowing?
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04:31 PM
rogergarrison Member
Posts: 49601 From: A Western Caribbean Island/ Columbus, Ohio Registered: Apr 99
You need dyno time for fuel injection but not carb??? Sure you can do a carb setup for $600? There's the fuel pump, manifold, carb...
All my Edlebrock carbs were set and ready to run out of the box, no dyno needed. I didnt even have to adjust the idle speed. Carb $250+tax, fiber carb spacer $20, adjustable fuel pressure regulator $30, all from Jegs. Use stock fuel pump already there.
I had the 390 on mine and really liked it. There *is* however an issue with a carb, which is that the Holley 390 will starve on hard left turns. I think there's a kit that lets you convert to a center hung float which supposedly eliminates the problem, but it plagued me the entire time I ran it (I never tried the kit). I will say that the power difference between the Edelbrock and carb, and the stock intake (ported and gasket matched) with F/I was remarkable. There are a lot of naysayers who think the fuel injection is superior to a carb, but having run both, I'd say the carb will give great gains, plus it's a little unusual.
I picked up a couple of Holley/Webber 5200 2bbl carbs a few years ago. They're 270 CFM (if I recall correctly) They came on Pinto 2000cc motors, and are really cool carbs because they're progressive, having a primary and secondary. Basically a 2 barrel that thinks it's a 4 barrel. I was going to fabricate a custom intake to pair them up but never got around to it. II still think that would be a really cool setup.
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09:51 PM
Nov 6th, 2009
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
I picked up a couple of Holley/Webber 5200 2bbl carbs a few years ago. They're 270 CFM (if I recall correctly) They came on Pinto 2000cc motors, and are really cool carbs because they're progressive, having a primary and secondary. Basically a 2 barrel that thinks it's a 4 barrel. I was going to fabricate a custom intake to pair them up but never got around to it. II still think that would be a really cool setup.
If I recall the 1982/1983 Firebird SE with the high output V-6 (It was a 2.8L with the larger valved heads.) had the same style carb (like half a 4-bbl) and it has the same bolt pattern as the Holley 2-bbl.
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07:36 AM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
You need dyno time for fuel injection but not carb??? Sure you can do a carb setup for $600? There's the fuel pump, manifold, carb...
Larger bore throttle body? Is it really a bottleneck? Injectors may not be needed. What's the current duty cycle? How much more air do you plan on flowing?
The carb'd engine can be tuned easily without a dyno. My 3.4L with a carb was easily tuned 10 minutes after starting the engine for the first time. The 3.4L I built with the Trueleo, cam, 62mm TB, etc. Took the dyno shop about 1.5 hours to tune. You can tune a carb on a dyno, But after I tuned mine I later went to dyno the carb'd 3.4L to see what I really had, There wasn't much required in terms of tuning.
On a Fiero 2.8L the 52mm TB, the upper plenum, the exhaust manifolds, and the crossover pipe all have restrictive sections. While they are not too bad with a stock 2.8L, Once you modify the internals and need more flow the restrictions at all points become worse.
The issue is not the setup so far as I can see. Both the systems are relatively simple installs. The 390 carb needs some modification because it is metered for a 300 ci engine. After some enquiries that is doable with a $10 part.
The bigger issue to me is if the setup proves to be wrong. Where do you go? With a carb, you can tell if it is rich and you simply plug in a smaller jet or adjust your accelerator pump, however, with FI you really do need some sort of electronic analysis.
That is where it gets expensive. Of course a lot of guys enjoy playing with a laptop and there is a whole generation who don't realize that cars will run just fine without a computer. So the natural thing is to go to the computer for the answer.
My generation grew up with a wrench and a screwdriver. So my comfort zone is more mechanical than electronic. It still boils down to person preference IMHO. Both systems will work equally well.
The cost also for the basic setup is not very different. The bigger cost IMHO is servicing and whether it can be serviced with a screwdriver or software.
