The pushrod 3.4L V-6 engine I'm referring to in my `86 GT is normally aspirated, has a mild cam and some head porting, 9.2:1 compression, Sprint exhaust manifolds, an Ocelot exhaust, a freer-flowing Trueleo Y-pipe, and likely will have a Trueleo intake manifold added to it. Much of everything else is stock or near-stock design, including its 3-speed automatic transmission.

I've learned elsewhere on this forum that the stock 52mm diameter Fiero throttle body likely would be too small for this engine combination, but that using an aftermarket 62mm diameter throttle body on the Trueleo intake likely would represent a throttle body diameter larger than this normally aspirated engine combination would need.

I'm NOT going to turbo- or supercharge this engine, so for this normally aspirated, lightly modified, 3.4L daily driver engine that I've described above...

1. What would you suggest this engine combination's throttle body diameter should be?
2. For this engine, do you know where I can obtain a throttle body with that suggested diameter?

I'd appreciate your suggestions regarding one or both of these questions. Thanks.

Darrell Morse

if the upper fiero plenum is the most restrictive part, so dont waste your time with a TB untill the intake has been taken care of

Yup even a darel TB is basically wasted on a 3.4. If you think the stock intake stinks on 2.8, it's really a P.O.S. on a 3.4, even a ported out unit still leaves the engine gasping for air! Change the intake or Carb it or go forced induction. If you dont one of those 3 options; dont waste your money on other mods as they will be not be very cost effective at all. Not just biased here, seen it on the dyno.

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[IMG]



Trueleo.com/fiero.htm
RSpiderII@aol.com

I agree with you, $Rich$ and Francis T, but I AM going to have a Trueleo intake on the car, so given the combination I've outlined below (which includes a Trueleo intake), what do you suggest the throttle body diameter should be with this combination?

quote Originally posted by project34: The pushrod 3.4L V-6 engine I'm referring to in my `86 GT is normally aspirated, has a mild cam and some head porting, 9.2:1 compression, Sprint exhaust manifolds, an Ocelot exhaust, a freer-flowing Trueleo Y-pipe, and likely will have a Trueleo intake manifold added to it. Much of everything else is stock or near-stock design, including its 3-speed automatic transmission. I've learned elsewhere on this forum that the stock 52mm diameter Fiero throttle body likely would be too small for this engine combination, but that using an aftermarket 62mm diameter throttle body on the Trueleo intake likely would represent a throttle body diameter larger than this normally aspirated engine combination would need.

The one we built with around 230hp had the Trueleo intake with a 62mm TB and we upgraded to the Accel 19# injectors with a Holley adjustable fuel pressure regulator. This made tuning very easy and the car runs great.

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Happiness isn't around the corner...
Happiness IS the corner.
ZZ4 Powered !!

quote Originally posted by Oreif: The one we built with around 230hp had the Trueleo intake with a 62mm TB and we upgraded to the Accel 19# injectors with a Holley adjustable fuel pressure regulator. This made tuning very easy and the car runs great.

Oreif, the thread covering that 3.4L EFI build for a friend of yours and the build of a carburetored version for yourself was an interesting side-by-side experiment, and I'm glad you went through the trouble to document it. (For those interested, his thread was titled, "3.4L carb'd VS. 3.4L EFI Results" and has been archived on Pennock's here: https://www.fiero.nl/forum/A...060206-2-066575.html ).

The 3.4L EFI engine described in that thread seems somewhat similar to mine, but apparently had more cylinder head work, and a much more aggressive cam (Crane 272 versus my Crane 2030). That EFI car also was a 5-speed Getrag, whereas mine will remain a 3-speed TH125 automatic. Thus, while a 62mm throttle body was fine with your build-up of that 3.4L EFI engine, is a 62mm throttle body likely to be too large in diameter for mine?

What prompted the concern I raised in my opening post to the present thread actually arose from a comment you made in another thread (titled, "62mm TB ??" and also archived on Pennock's: https://www.fiero.nl/forum/A...070315-2-079017.html ):

"...the 62mm on the Trueleo intake will be more than the engine could possible use N/A...."

Incidentally, I'm NOT trying to play "Gotcha!" with Oreif or anybody else here. I'm merely trying to learn what my engine needs as a system, rather than just slapping the largest of everything on it. (I wish I had a buck for everyone I've ever seen with an "overcarbureted" car, or one with injectors that are way too large for an application. If I can avoid it, I don't want to be making a similar mistake by inadvertently selecting an overly large throttle body for my application.)

I've got Darrell Morse's TB (57mm?), a Trueleo intake, ported heads and lower intake, a 272 cam, 19# injectors and FOCOA headers. (Got them before the Trueleos were available, but they are quite similar.)
I'm quite happy with how it runs. If I were going to do anything else, it would be the 62mm TB and the Trueleo intake modified to accommodate it (or just a new Trueleo.)

It's hard to say since you're using the 2030. It's not as aggressive as the 272. I'm not sure how much air the engine can drink, using that cam.
Anybody?

Edit... One of the other folks on here (fierochild) has a 3.4 breathing through a Darrell Morse TB, and he's making right at 200 HP at the crank. He's using a setup similar to mine, except that his intake is a highly modified stocker (sectioned, gutted, welded, etc.) and his exhausts are... ported stockers?

[This message has been edited by Raydar (edited 06-03-2007).]

By request, I've provided a lot of intakes ready for a 62mm TB so it seems to to be a good combo as they are happy with the setup.

quote Originally posted by project34: The 3.4L EFI engine described in that thread seems somewhat similar to mine, but apparently had more cylinder head work, and a much more aggressive cam (Crane 272 versus my Crane 2030). That EFI car also was a 5-speed Getrag, whereas mine will remain a 3-speed TH125 automatic. Thus, while a 62mm throttle body was fine with your build-up of that 3.4L EFI engine, is a 62mm throttle body likely to be too large in diameter for mine? What prompted the concern I raised in my opening post to the present thread actually arose from a comment you made in another thread (titled, "62mm TB ??" and also archived on Pennock's: https://www.fiero.nl/forum/A...070315-2-079017.html ): "...the 62mm on the Trueleo intake will be more than the engine could possible use N/A...."

What I meant by the comment was that the intake will flow through out the entire RPM range (over 6500 rpm) without ever causing a restriction. EFI systems don't have the over-size problems like when putting too big a carb on an engine. The 3.4L needs 354 cfm at 6000 rpm. The 57mm TB only flows 335 cfm so somewhere around 5200-5300 rpm the TB will restrict air a little. Since you are not porting the heads and using the 2030 cam, You could get away with the 57mm TB.

Does anyone know which cars have the 62mm throttle body? I would like to know also as I plan a modified intake and turbo in the near future.

quote Originally posted by Hudini: Does anyone know which cars have the 62mm throttle body? I would like to know also as I plan a modified intake and turbo in the near future.

The one we used was bought from here:
http://www.pfyc.com/pc/GA30...w+Throttle+Body.html

(You can get it for $100 less if you grab a stock one off a Grand Am at the junkyard and send it in as a core.)

It should also be noted that the G/A stock one is 58mm in case someone wants to use just the stock one. (Maybe have the Trueleo ported for the 62mm and use the stock 58mm so that later they can upgrade to the 62mm TB???? )

quote Originally posted by Raydar: I've got Darrell Morse's TB (57mm?)

Raydar, I found out just this afternoon from a very helpful gentleman at "Minnesota Fieros Forever" that the Fiero intake manifold and throttle body I purchased from them in 2003 (no longer offered by them) has a "Darrell Morse throttle body," and that this throttle body is 57mm in diameter.

In short, depending upon where this thread leads, eventually we may both end up opting for something as large as a 62mm throttle body, but the "Darrell Morse throttle body" we (and many others) have is indeed a 57mm throttle body.

I used a Gran National ( 3.8 turbo) 59mm TB on mine, they can be opened up to 62-65mm.

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85 GT 3.4
14.9 @ 90 1.9 60' Old TH125/3.06
Unknown New 4T60/3.42

Here is what I found posted by (always helpful in my opinion) Oreif on an archived 2006 thread regarding other throttle body sizes for the V-6 Fiero ("What size is the stock V6 Throttle Body" at https://www.fiero.nl/forum/A...070315-2-077522.html ):

52mm = stock
55mm = Fiero Store
57mm = Darrell Morse

In the preceding post to the present thread, Lilchief reports having used a 59mm throttle body on his Fiero.

Francis T, have you any statistics on the percentages of your Trueleo intake customers who opted for these throttle body sizes versus the 62mm size you mentioned above?

Incidentally, for those V-6 owners interested in a 57mm throttle body, they are also advertised as being available (chromed or otherwise) from http://www.heartlandfieros.com

I mention this partly because from what I've seen elsewhere on Pennock's, while Darrell Morse's workmanship is widely acknowledged as excellent (and I have one of his 57mm throttle bodies myself), he may be difficult to reach, or no longer in that business. However, please feel free to correct that impression if you are one who RECENTLY has received one of his 57mm throttle bodies.

quote Originally posted by project34: Thank you Oreif, for correcting my erroneous interpretation of your 2006 statement on another thread: "...the 62mm on the Trueleo intake will be more than the engine could possible use N/A...." I'd erroneously concluded from your 2006 statement you were concerned about a throttle body 62mm in diameter being "too large." From your comments in the present thread, it appears a better interpretation on my part might have been: "Although more than adequate to the task with a Trueleo intake, a 62mm throttle body on a normally aspirated engine would NOT be too large." Incidentally, my car's cylinder heads which I mentioned earlier in this thread, ARE indeed ported (purchased from Race-Tech Automotive in Toronto in 2003), but perhaps not as extensively ported as those you used in your classic 2006 "carbureted-versus-EFI" 3.4L thread. Based on your comments in the present thread, it sounds like a 62mm throttle body on a Trueleo intake for my 3.4L "daily driver" engine should be fine, and that it would allow for an upgrade later, from the mild Crane 2030 cam I currently have, to the more aggressive Crane 272 cam you used in your 2006 "carbureted versus EFI" experiment. Is this interpretation correct, or not? (By the way, I easily can handle, without any weeping whatsoever on my part, being wrong.)

You are correct.
You can also upgrade to the H260 cam as well which is larger and more aggressive than the 2030 but smaller than the H272.
If you also want to get a little more flow without having to change the cam, You can use the 1.6 rockers which will give you a little more lift and flow. Combined with the mild port on the heads, The 62mm TB would give you restriction free flow and provide the most gains out of the mods you have.

from my experience, a 60mm tb on a blown 3800 setup is good up to well over 300 crank HP, but I would imagine that you could never have a TB too big for an NA car. If I was to match a perfect size for it I doubt i would pick the 62, but it doesnt seem that big for a 60degree 3.4, even more so with valvetrain mods, it should be sucking a significant larger amount of air over the 2.8.

quote Originally posted by darkhorizon: I would imagine that you could never have a TB too big for an NA car. If I was to match a perfect size for it I doubt i would pick the 62

Mine is not yet a "done deal" until I order the Trueleo Intake manifold, so I can still get any throttle body size that makes sense for my engine application.

Accordingly, if you DON'T recommend a 62mm throttle body for my 3.4L engine (specs outlined earlier in this thread), what size throttle body DO you recommend for it?

quote Originally posted by darkhorizon: from my experience, a 60mm tb on a blown 3800 setup is good up to well over 300 crank HP, but I would imagine that you could never have a TB too big for an NA car. If I was to match a perfect size for it I doubt i would pick the 62, but it doesnt seem that big for a 60degree 3.4, even more so with valvetrain mods, it should be sucking a significant larger amount of air over the 2.8.

Too big and I fear the throttle response would be more like a light switch than a rheostat?
But I could be wrong, I think I was once, a long time ago . . . . like yesterday? ;^)

Norm

quote Originally posted by darkhorizon: from my experience, a 60mm tb on a blown 3800 setup is good up to well over 300 crank HP, but I would imagine that you could never have a TB too big for an NA car. If I was to match a perfect size for it I doubt i would pick the 62, but it doesnt seem that big for a 60degree 3.4, even more so with valvetrain mods, it should be sucking a significant larger amount of air over the 2.8.

In a way yes, but too big a TB and too heavy/fast of a foot can = bogging. If you abruptly go to WOT with too big a TB you can lose most of your manifold pressure and the engine will fall flat on its face. It wont be near as bad as a carb whereas (not an injection carb) that may also lose fuel do to no air flow.

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[IMG]



Trueleo.com/fiero.htm
RSpiderII@aol.com

quote Originally posted by project34: Mine is not yet a "done deal" until I order the Trueleo Intake manifold, so I can still get any throttle body size that makes sense for my engine application. Accordingly, if you DON'T recommend a 62mm throttle body for my 3.4L engine (specs outlined earlier in this thread), what size throttle body DO you recommend for it?

Well if you go by air flow, The 3.4L requires 354cfm @ 6000rpm.
The stock Fiero TB is 308 cfm
57mm is 335 cfm
62mm is 410 cfm which allows the 3.4L to breathe all the way to 7000 rpm if you built up the valve train.

As a point of reference, Edelbrock recommends the 390cfm 4-bbl carb for a 2.8L with thier cam which is similar to the H260 Crane cam.

So although 62mm is slightly larger than what the engine could use normally aspirated, I would not consider it to be "over-sized".
The 2.4L ecotec engines used in the Grand Am's is 58mm TB and the 62mm TB is the bored version of it. So if a 2.4L with a 7000-8000 rpm redline runs great with a 62mm, The 3.4L at 6000 rpm will work just fine.

Yes there is a limit as to what size TB you can go to. I would guess anything over 500 cfm would cause problems.

Thank you for addressing my earlier question, Oreif:

quote Originally posted by Oreif: So although 62mm is slightly larger than what the engine could use normally aspirated, I would not consider it to be "over-sized".

Aside from the local junkyards (which I've no interest in fooling with), just HOW does one go about purchasing a 62mm throttle body for use with a Trueleo intake manifold on a pushrod 3.4L engine?

In a previous post on this thread, a site that was mentioned offered a 62mm throttle body, but clicking on that site immediately called up the following "Applications" restriction:

"1999-2002 Grand Am or Alero with the 2.4L Engine (you will re-use your stock gasket)"

Perhaps my question is a naive one, but is purchasing a 62mm throttle body for a pushrod 3.4L engine with a Trueleo intake like purchasing a 750 cfm Holley double pumper carburetor, where the MAKE of engine it's going on is irrelevant?

Help!

quote Originally posted by Oreif: Well if you go by air flow, The 3.4L requires 354cfm @ 6000rpm. The stock Fiero TB is 308 cfm 57mm is 335 cfm 62mm is 410 cfm which allows the 3.4L to breathe all the way to 7000 rpm if you built up the valve train. .......

is there some math for this - or maybe a table?
I have a 3.1, 272 cam & 57mm T/B, and want to work out what RPM this breathes to.

quote Originally posted by Pyrthian: iI have a 3.1, 272 cam & 57mm T/B, and want to work out what RPM this breathes to.

Pyrthian, my guess is that a critical issue that you likely first need to specify is whether you've a Fiero intake manifold (modified or not) versus, for example, an aftermarket intake manifold design like the Trueleo.

quote Originally posted by project34: Pyrthian, my guess is that a critical issue that you likely first need to specify is whether you've a Fiero intake manifold (modified or not) versus, for example, an aftermarket intake manifold design like the Trueleo.

of course - the stock intake will choke out no matter what TB I use.
I am in the process of gutting my stock intake - removing the runners & opening the neck.

quote Originally posted by Pyrthian: is there some math for this - or maybe a table? I have a 3.1, 272 cam & 57mm T/B, and want to work out what RPM this breathes to.

The formula for calculating what an engine requires for flow at a specific RPM is:

Cubic Inch Displacement * RPM /3456 * VE =cfm

(VE is NOT 100% on all engines. If I recall the Fiero 2.8L is around 90% but for comparison sake, I will do these at 100% since the TB flows are at the max value as well.)

So a 2.8L is 173ci * 6000 rpm /3456 * 1 = 300.34 cfm is needed at 6000rpm.

The 3.1L is 189ci so at 6000 rpm it needs 328 cfm and the 57mm TB is 335 cfm.
At 335 cfm the 3.1L would be spinning at 6126 rpm.

NOTE: These are max values. The rest of the intake, head flow, and cam size will reduce the VE of the engine and the throttle plate and shaft reduce the CFM's of the throttle body. The math above is to just get a general idea on flow and how to match components together to avoid restricting areas of flow. If you want actual values, The best way is to have each section ran across a flow bench.

The 3.4L is 207ci so at 6000 rpm it needs 359cfm. At 5600 rpm it is at 335cfm. So if everything was perfect for flow, you would be fine up to 5600 rpm. The problem is a normally aspirated production engine in not perfect so flow values are generally less which reduces the RPM at which power falls off. From past "real world" examples (dyno's), The 3.4L with a 57mm TB seems to fall off quickly in the 4800-5000 rpm range. The other thing to consider is as the CFM flow approaches the max it starts to restrict some of the air before max CFM is reached thus causing poor flow (turbulance, friction, etc.) which will also reduce power.

[This message has been edited by Oreif (edited 06-07-2007).]

thanks! I am working towards getting my 3.1 to a 6000 RPM shift point, and a 7000 RPM redline - so, it sounds like the 57mm TB will be just fine - maybe a bit small.

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1985 Fiero SE - Plain Red V6 Coupe
3.1 Crane272 MSD 4.10-4spd DarthChip WCF Long Tubes Borla
D.A.M.M. - Drunks Against Mad Mothers

quote Originally posted by Pyrthian: thanks! I am working towards getting my 3.1 to a 6000 RPM shift point, and a 7000 RPM redline - so, it sounds like the 57mm TB will be just fine - maybe a bit small.

At 7000 rpm you need 382 cfm. maybe the Trueleo with a 62mm TB would be better suited for you as well.

quote Originally posted by Oreif: At 7000 rpm you need 382 cfm. maybe the Trueleo with a 62mm TB would be better suited for you as well.

yes - 6000 shift point - 7000 redline. dont actually need to make more power past 6000 - and for my own good - better not too

Aside from fooling with a local junkyard, what and where specifically needs to be ordered to purchase a 62mm throttle body for a pushrod 3.4L V-6 engine?

http://www.60degreev6.com/s...iewProd&productId=23
Check them out

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85 GT 3.4
14.9 @ 90 1.9 60' Old TH125/3.06
Unknown New 4T60/3.42

Will the 62mm TB bolt on to the Fiero upper plenum (gasket matched) and function with the stock Fiero sensors?

quote Originally posted by Mister: Will the 62mm TB bolt on to the Fiero upper plenum (gasket matched) and function with the stock Fiero sensors?

yes, but the stock upper plenum has some things that need fixing first.
1st is the "hole" in the neck for the TB is roughly 55 mm. when we get our 57 mm TB's made, the neck is bored out too.
2nd is the EGR port. creates a nasty turbolant vortex.
3rd is the neck. specificlly where the neck meets the main body of the plenum. the cross section here has barely the area of the stock 52mm TB. this is the MAIN upper plenum restriction right here.
4th - lastly - the tight 135 degree bend, at the upper/lower plenum joint. endless smoothing & gasket matching needed to make this a nice transition.

I sense that I'm overlooking something very basic here.

Does the MAKE of the engine not matter if one is purchasing a 62mm throttle body?

An engine referenced in the first post above by Lilchief is a 3400 rather than a pushrod 3.4L engine, the latter being the engine swap I have.

Junkyards aside, how does one go about getting a 62mm throttle body for a pushrod 3.4L engine swap (i.e., 3.4L Camaro/Firebird engines produced between 1993 and 1995, inclusive)?

Bump.

There are no 62mm throttle bodies made specifically for the 3.4L Camaro/Firebird engine (that I have found). The stock one is the same 52mm as the Fiero throttle body. There is no way to bore it out larger than the 57mm that the Fiero one is bored. So I am in the same boat as you. Either buy a generic 62mm throttle body and add a compatible IAC and TPS, or get a junkyard 62mm with a compatible IAC and TPS and splice those wires to the Fiero wires. The upper intake will have to be modified to accept this larger TB too.

I'm betting I can find one at a pick-n-pull in Detroit from a GM car. Most GM TPS's and IAC's work the same, especially on the lower end cars where I'll likely find one. (I read only Toyotas have a bass-ackwards TPS which goes from 5v-0v instead of 0v-5v.)

[This message has been edited by Hudini (edited 06-09-2007).]

quote Originally posted by Hudini: There are no 62mm throttle bodies made specifically for the 3.4L Camaro/Firebird engine (that I have found). The stock one is the same 52mm as the Fiero throttle body. There is no way to bore it out larger than the 57mm that the Fiero one is bored. So I am in the same boat as you. Either buy a generic 62mm throttle body and add a compatible IAC and TPS, or get a junkyard 62mm with a compatible IAC and TPS and splice those wires to the Fiero wires. The upper intake will have to be modified to accept this larger TB too. I'm betting I can find one at a pick-n-pull in Detroit from a GM car. Most GM TPS's and IAC's work the same, especially on the lower end cars where I'll likely find one. (I read only Toyotas have a bass-ackwards TPS which goes from 5v-0v instead of 0v-5v.)

really? a Camaro 3.4 throttle body is 52mm also? that is surprising.
I thought the 3.4 DOHC motor would be the TB to look for
the TPS (throttle position sensor) is fairly generic - even across manufacturers.
and, the IAC is fairly easy to hook in, even if the new TB does not have provisions for it. it is just a "butterfly bypass". you can cut the IAC bypass off a stock Fiero TB, and keep using it.