I am currently making a Dual Throttle Body Intake for my 3.4 swap. I've done a bit of research on these and it seems like the people who have used a similar setup have been pleased with it. If they work so well how come there are only a few floating around? The ones I have seen look fairly simple to make and the one I'm making hasn't been Too hard. Most of the time is spent in the porting.

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1987 Pontiac Fiero GT - 3.4 OHV Bored .30 flat tops, Stage 2 cam, Double Roller, 1.6 Roller tips - Some suspension upgrades as well.
1965 Ford Mustang Coupe - 302 HO 600 cfm carb, headers, aluminum intake C4 trans with shift kit and 2400 stall

if you make one let me know. ill be interested.

quote Originally posted by Jennings03: I am currently making a Dual Throttle Body Intake for my 3.4 swap. I've done a bit of research on these and it seems like the people who have used a similar setup have been pleased with it. If they work so well how come there are only a few floating around? The ones I have seen look fairly simple to make and the one I'm making hasn't been Too hard. Most of the time is spent in the porting.

Because people that install the 3.4L generally aren't inclined to spend alot of extra money / time on the build, just a quick cheap swap with little modifications. The guys that are more crafty and have the money / time to spend on the car generally just install a bigger / stronger engine right from the get go.

The dual Tb's looks really cool though, theres a picture of a red one kicking around that is just beautiful.

That is true. But I'm sure there are some people who are like me and did a 3.4 swap because it was one of the cheapest and simplest swaps and now are looking to make a little more power later on. I think I know the red one your talking about its all polished and it looks sweet. I'm planning to make mine with the throttle body closest to the firewall facing the opposit direction, relocating the batter and have each filter running down each side of the car, haven't seen one like that yet.

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1987 Pontiac Fiero GT - 3.4 OHV Bored .30 flat tops, Stage 2 cam, Double Roller, 1.6 Roller tips - Some suspension upgrades as well.
1965 Ford Mustang Coupe - 302 HO 600 cfm carb, headers, aluminum intake C4 trans with shift kit and 2400 stall

quote Originally posted by Custom2M4: Because people that install the 3.4L generally aren't inclined to spend alot of extra money / time on the build, just a quick cheap swap with little modifications. The guys that are more crafty and have the money / time to spend on the car generally just install a bigger / stronger engine right from the get go. The dual Tb's looks really cool though, theres a picture of a red one kicking around that is just beautiful.

Very true


Most (not all) 3.4 swaps come around because the onwer of the car blew up the existing 2.8 that the car came with, The 3.4 is in the books the easiest swap that can be done unless your doing a 2.8 for another 2.8. its an added 20HP a better oil pump system and a newer motor. Also being the fact that the only thing you have to modify is the starter location its the ideal and smartest swap someone can do in place of the 2.8. As custom2m4 said a lot of people who do them are doing them to get back on the road. there are some who build them for preformance though. From what i have read the P/R3.4 is a great car to do a turbo set up in. it will easily put you into the 13 second bracket. Also a lot of the guys who turbo these seem to like to use the duel TB intake setup. The most common way to do this is to use 2 Fiero TB's linked onto the throttle cable to open at the same time. I've also seen a single TB at the end of a Y type setup that is ideal for a turbo system. There is one guy I know who is not on this forum that if you can get past the useless bullsh*t that pours out of his mouth has some info on the duel TB intake. I'll let someone else chime in on it because most of the members on here know who I'm talking about.
I'm also sure there are a lot of members on here that will chime in with some great info as well. Welcome to the forum by the way.

[This message has been edited by pontiackid86 (edited 02-22-2011).]

Thanks for the welcome. Yea that was basically why I did the swap, except the simple swap turned into a $2000 rebuilt 3.4 lol. And I would love to go turbo if and when I can come up with the parts and money. I wanted to switch it up and run twin turbos, one on each side of the engine and one per throttle body. This way the manifolds can be identical, everything exactly the same and you dont have a crossover pipe, just dual exhaust and each is already on the appropriate side for each pipe

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1987 Pontiac Fiero GT - 3.4 OHV Bored .30 flat tops, Stage 2 cam, Double Roller, 1.6 Roller tips - Some suspension upgrades as well.
1965 Ford Mustang Coupe - 302 HO 600 cfm carb, headers, aluminum intake C4 trans with shift kit and 2400 stall

quote Originally posted by Jennings03: ...$2000...

Is that all?
I had a big cam and and $800 worth of head work on top of that. Then the FOCOA headers and the Trueleo intake.
When I was done, it was as fast as my 4.9, but there are much easier ways, in retrospect.

Good luck with yours. You'll have fun, and will learn a lot.

And welcome to our obsession!

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Raydar
88 4.9 Formula IMSA Fastback

Read Nealz Nuze! Praise the Lowered!

Well the engine its self was 450 and the machine shop was higher than it was supposed to be like 750 so that was most of it right there. Did you have an issue with running a higher octane after your swap? Mine requires Premium or it pings under load

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1987 Pontiac Fiero GT - 3.4 OHV Bored .30 flat tops, Stage 2 cam, Double Roller, 1.6 Roller tips - Some suspension upgrades as well.
1965 Ford Mustang Coupe - 302 HO 600 cfm carb, headers, aluminum intake C4 trans with shift kit and 2400 stall

quote Originally posted by Jennings03: Well the engine its self was 450 and the machine shop was higher than it was supposed to be like 750 so that was most of it right there. Did you have an issue with running a higher octane after your swap? Mine requires Premium or it pings under load

What kind of ECU are you running. That motor should be able to burn regular all day without knocking it also could be a timing issue.

Just the stock ECM. The timing was set by ear so its possible it could be off. We set it a few times and its at the spot that feels like it has the most power and best idle. The company where I got the pistons from said it would raise the compression a little but I think the difference was only like .2 or .3.

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1987 Pontiac Fiero GT - 3.4 OHV Bored .30 flat tops, Stage 2 cam, Double Roller, 1.6 Roller tips - Some suspension upgrades as well.
1965 Ford Mustang Coupe - 302 HO 600 cfm carb, headers, aluminum intake C4 trans with shift kit and 2400 stall

quote Originally posted by Jennings03: I am currently making a Dual Throttle Body Intake for my 3.4 swap. I've done a bit of research on these and it seems like the people who have used a similar setup have been pleased with it. If they work so well how come there are only a few floating around?

One reason you see so few dual throttle body intake manifolds on Fieros is that unlike the (single throttle body) Trueleo intake manifold for engines like your pushrod 60^o 3.4L V6 ( http://www.trueleo.com/Fierointake.htm ), a dual throttle body intake for those engines never has been commercialized. Instead, they've all been created on a "one-off" basis, with the best-looking of them (IMHO) being this "one-off" creation:


I'd started a thread in December 2009 which asked the question, "Are There Any Dual-Plenum Intake Manifolds Being Manufactured for V6 Fieros?" ( https://www.fiero.nl/forum/Forum1/HTML/078871.html ).

I'd hoped that somebody would have been manufacturing these for sale by now. However, the short answer to my question about that in the aforementioned thread was "No" in 2009, and unfortunately, it still is.

That is by far the best one I have ever seen. And taking a closer look at it I don't think they even chopped off the top of the lower intake did they? Every other one Ive seen I think including mine has had the top chopped off. And as fas as vacuum lines I would think all you have to do is drill and tap a few holes for some brass fittings for lines. The throttle linkage is probably the hardest, but theres joining the two tb shafts like the picture above, or like a few other I've seen they have a cable attatched to each tb. I'd be willing to make another if the one I'm working on now turns out good.

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1987 Pontiac Fiero GT - 3.4 OHV Bored .30 flat tops, Stage 2 cam, Double Roller, 1.6 Roller tips - Some suspension upgrades as well.
1965 Ford Mustang Coupe - 302 HO 600 cfm carb, headers, aluminum intake C4 trans with shift kit and 2400 stall

quote Originally posted by Jennings03: I'd be willing to make another if the one I'm working on now turns out good.

I'd be interested in that. Can you make it all nice and shiny like the one in the above picture?

I had planned on it yes. I was working on polishing mine yesterday and I think it will turn out pretty good. I can't say it will be as perfect as the one above but I can post pictures when I get a little farther along. Any Ideas on anything to go in between the two runners? I was thinking a removable plate similar to the one above but with Fiero or maybe Fiero 3.4 engraved like on a stock manifold, not sure how possible and how complicated something like that is but I think it would look pretty good.

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1987 Pontiac Fiero GT - 3.4 OHV Bored .30 flat tops, Stage 2 cam, Double Roller, 1.6 Roller tips - Some suspension upgrades as well.
1965 Ford Mustang Coupe - 302 HO 600 cfm carb, headers, aluminum intake C4 trans with shift kit and 2400 stall

quote Originally posted by project34: I'd be interested in that. Can you make it all nice and shiny like the one in the above picture?

quote Originally posted by Jennings03: I had planned on it yes.

Excellent!

quote Originally posted by Jennings03: I was working on polishing mine yesterday and I think it will turn out pretty good. I can't say it will be as perfect as the one above but I can post pictures when I get a little farther along.

Good. I'd be interested in seeing those pictures.

By the way, will the dual plenums you're fabricating be made of aluminum, like all the sections of the stock Fiero V6 intake manifold are?

quote Originally posted by Jennings03: Any Ideas on anything to go in between the two runners? I was thinking a removable plate similar to the one above but with Fiero or maybe Fiero 3.4 engraved like on a stock manifold, not sure how possible and how complicated something like that is but I think it would look pretty good.

Yes, and I think we may be on a similar wavelength here, possibly because we both have 3.4L engine swaps.

Another, very similar alternative to that you mentioned is "Fiero 3.4L" (rather than "Fiero 3.4"). It could look like either the (more complicated) badge-shaped decals, or the (much simpler) stock-looking, small, banner-shaped decals for `85 and `86 V6 Fiero intake manifolds that fellow PFF member, Mailmule, once sold in The Mall section of this forum ( https://www.fiero.nl/forum/Forum4/HTML/044772.html ). Yet another option might instead be the words, "3.4L Edition" (which is what I'm getting on some custom floor mats I'm ordering).

Incidentally, I think the curved and finned engine cover in the above picture simply may have come from a different GM engine originally, but offhand, I don't know which one. If I find out which one, I'll post that info here since it could save considerable time and work. However, a curved plate without fins, and otherwise polished smooth --- except for some engraving or a 3.4L decal of some sort on it --- might look even better!

In any case, here's an example of the badge-shaped decal that I mentioned Mailmule sold:

quote Originally posted by Mailmule:

He made them in different colors as well, and the white backgoround is actually clear, not white. (The white color you see was just the removeable paper backing for the decal.)

I won't get a chance to work on it again until tomorrow evening so I will try to post a few pics maybe then. And yes I was going to use aluminum tubing for it and it's looking like they should be 2 1/4 in diameter? The length is what I am not yet sure on though because I know there is a difference in power with short vs long runners or at least a shift in peak power at a certain rpm. Any opinions here would be great. My particular 3.4 pulls all the way through 6k in 1st and almost the same in second but after that the power just isn't there by the time you hit 4k even. It tops out in 4th at 5500 roughly? But has a little more left in 5th till it quits pulling. Id like the runners to be tuned to give a balance between mid to high rpm power and I think from what I've read that shorter runners would be better for this.

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1987 Pontiac Fiero GT - 3.4 OHV Bored .30 flat tops, Stage 2 cam, Double Roller, 1.6 Roller tips - Some suspension upgrades as well.
1965 Ford Mustang Coupe - 302 HO 600 cfm carb, headers, aluminum intake C4 trans with shift kit and 2400 stall

hasnt anyone(sure they have) done a 1 larger throttlebody instead of the two holly smally's? just seems so much simpler to me to do as a do it yourselfer, as most of us are? there has got to be a NEAR bolt on swap from another car??

I think the issue with that solution would be that you would either have to have the intake to match the throttle body, or the stock intake bored, and also the IAC and TPS might not be the same or cause an issue. I could be wrong though. I personally like the look of the DTBs and as I said earlier I wanted to run them in opposite directions just to be different so that is my personal reasoning in the route as opposed to a bored throttle body or just a different one altogether. But everyone has different opinions and interests and I have heard of people using different TBs but I don't recall what was used. I'm also hoping that the intake sound from this is affected in a positive way but performance is the main goal in mind

quote Originally posted by Custom2M4: Because people that install the 3.4L generally aren't inclined to spend alot of extra money / time on the build, just a quick cheap swap with little modifications. The guys that are more crafty and have the money / time to spend on the car generally just install a bigger / stronger engine right from the get go. The dual Tb's looks really cool though, theres a picture of a red one kicking around that is just beautiful.

I spent more on my 3.4 install than most 3800sc's for one reason. I want a RELIABLE engine install that I know will go 200,000 miles. Yes I know the 3800sc can go for a lot of miles but a $800.00 junkyard engine is a crap-shoot and not guaranteed to go 2000 miles let alone 200,000.

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Best RV, Camper, and Trailer dealer in West Michigan. http://www.cliffstrailersales.com and he's a fiero owner too!

quote Originally posted by Jennings03: And yes I was going to use aluminum tubing for it and it's looking like they should be 2 1/4 in diameter?

I'd think the tubing's inside diameter for each plenum should match the size of each throttle body's opening. If you plan on using a stock Fiero V6 throttle body at one end of each plenum, the opening for a stock Fiero V6 throttle body is 52 mm. That works out to an inside tubing diameter of (52 mm / 25.4 mm per inch =) just a little over 2 inches. I assume you're instead quoting 2-1/4 inches because of the tubing's outside diameter, but if not, are you thinking of using even larger throttle bodies than 52 mm each?

quote Originally posted by Jennings03: The length is what I am not yet sure on though because I know there is a difference in power with short vs long runners or at least a shift in peak power at a certain rpm. Any opinions here would be great.....Id like the runners to be tuned to give a balance between mid to high rpm power and I think from what I've read that shorter runners would be better for this.

Yes, shorter runners favor top end power and longer runners favor low end power --- all other things being equal. However, I don't think all other things are being equal because with a dual plenum set-up, one is in effect getting rid of this nasty, choking obstruction in the neck of the stock Fiero intake intake manifold:

quote Originally posted by triker: After cutting one open, this is the worst restriction (57mm TB gasket0:

Aside from eliminating that choke-point, by employing a dual plenum set-up, one in effect already is shortening the runner system by not using the runner lengths in the uppermost (red) section of the Fiero's intake manifold:

quote Originally posted by $Rich$:

Because of eliminating the neck choke-point and the runners of the stock Fiero manifold's uppermost (red) section), I'd think that also eliminating part of the runners in Fiero intake manifold's middle (silver) section could be a bit of overkill.


I wonder if avoiding overkill was one reason this "one-off" dual plenum set-up appears to retain all of the Fiero intake manifold's middle (silver) section:

quote Originally posted by goatnipples2002: [/IMG]

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Source: All pictures in this post were sourced from the thread, Improving Stock Intake Plenum ( https://www.fiero.nl/forum/Forum2/HTML/069539.html ).

The center removeable plate is an idi cover from a 2.4 twin cam. The 96 up "quad 4"

Im not yet sure how to post pictures on here or I would, but there is a link to what Ive done as far as cutting the top of the intake off. Its not cut to the point of the one you have pictured, basically just the top flat part is cut off to the bottom of the bolt holes. If this setup proved to be too short, I was going to use longer tubing to make up for the difference, and as far as the diameter that is a good point so they may need to be 2 1/2 to be big enough.

quote Originally posted by kikinz24: The center removeable plate is an idi cover from a 2.4 twin cam. The 96 up "quad 4"

Thanks for posting that info, kikinz24.

However, what is meant by "idi" in the "idi cover" you referenced?

Well can you purchase aluminum tubing with the exact inside diameter of 52mm? And is the inside diameter being exactly that of the TB a big difference than it being slightly bigger as in 2 1/4 in?

The idi cover is the cover that the coil packs mount to on the 2.4 . I honestly don't know why its called an idi cover but that's what its called. I have like 4-5 of em here I was practicing my powdercoating , and polishing when I had my z.

The reason that few people do a dual TB is because it is a lot of work and is all for appearance - the flow offered by that sort of thing isn't needed nor can it be used by a 3.4

The easiest way to power on the 3.4 if you don't want to go Trueleo is to simply get the F body intake, and bore it out to whatever you think your engine will be able to use (I run a 62 mm, which is probably more than enough). The Camaro intake eliminates the gooseneck restriction of the stock Fiero (which looks nicer but flows worse).

No dual TB is going to get you any more power than that single TB mod, so do it only if you enjoy the machining/fabrication exercise, or just have to have the look.

My only concern with the trueleo is that it is out of my price range. It is a good upgrade though can't argue with that. I also would like to twin turbo this in the future and I have never seen anyone do it in the way that I plan to do it and it would require DTBs running opposite directions the way I described.

quote Originally posted by project34: I wonder if avoiding overkill was one reason this "one-off" dual plenum set-up appears to retain all of the Fiero intake manifold's middle (silver) section: quote Originally posted by goatnipples2002:

That is the intake I built for my 3.4L X-11 back in 1999-2000, before all of the forum discussions on the topic became popular. If you look at the picture again, you should be able to see that the middle intake portion was shortened considerably versus stock, so avoiding “overkill” was not a factor.

My baseline was a TBI setup, so I was not trying to design specifically around the Fiero upper plenum neck restrictions, but rather the iron head MPFI design deficiencies in general. My intake actually started out on a 2.8 Camaro, with the slightly different RWD plenum, but same middle intake.

My goals were to shorten the runner length, and eliminate the restriction where the upper plenum turns back around into the middle intake. For mine, I cut the middle intake perpendicular to the runners at the point where the port shape and curve upward begins. I wanted the runners to end up about ~1.5" longer, but the runner shape was more important to me than exact runner length. The end result is a straight shot from the plenums down into the intake ports. This design also allowed me to port the runners, adding some taper, and belmouth the runner transitions from the plenum.

If you are going through the hassle of fabricating a custom manifold, why not do it right? You may call it overkill, but I think of it as not compromising.

Marty

quote Originally posted by project34: ...I think the curved and finned engine cover in the above picture simply may have come from a different GM engine originally, but offhand, I don't know which one. If I find out which one, I'll post that info here since it could save considerable time and work.

quote Originally posted by kikinz24: The center removeable plate is an idi cover from a 2.4 twin cam. The 96 up "quad 4"

quote Originally posted by project34: Thanks for posting that info, kikinz24. However, what is meant by "idi" in the "idi cover" you referenced?

quote Originally posted by kikinz24: The idi cover is the cover that the coil packs mount to on the 2.4 . I honestly don't know why its called an idi cover but that's what its called.

Nonetheless, I appreciate your looking into this further, as well as your candor. I now also don't feel so bad about not knowing what "idi" meant.

quote Originally posted by project34: Nonetheless, I appreciate your looking into this further, as well as your candor. I now also don't feel so bad about not knowing what "idi" meant.

haha ive built alot of 2.4's i know the motor inside out i can put it together in my sleep. and i honestly dont know why its called that theyre very easy to come by beings 2.4's blow up easy! snap timing chains, number 3 bearing spins out. u know common gm issues lol. that setup that guy built is definitly nice tho. ive contemplated building a dual tb setup. but running a s/c on my 3.1 i dont want a y pipe to the tb's and im shootong for a stock look

quote Originally posted by Jennings03: Well can you purchase aluminum tubing with the exact inside diameter of 52mm? And is the inside diameter being exactly that of the TB a big difference than it being slightly bigger as in 2 1/4 in?

Essentially, yes, to both questions:

1. You can purchase aluminum pipe with an inside diameter of 52.5mm. For example, from this site ( http://www.speedymetals.cal...8370-round-pipe.aspx ), you could select aluminum pipe size 2. It has an outside diameter of 2.375" and a wall thickness of .154" which, in turn, equates to an inside diameter of (2.375" - .154" - .154" =) 2.067" or 52.5mm. The area of a circular opening 52.5mm in diameter (2165mm²) is only 2% larger than that of a opening 52mm in diameter (2124mm²).
   
   
2. In contrast, the area of a circular opening 2-1/4" (or 57.2mm) in diameter (2570mm²) is 21% larger than that of a circle 52mm in diameter (2124mm²). I'd think a difference of that magnitude would be enough to unnecessarily slow down air flow from the throttle bodies to the plenums, but I'll happily defer to an aerodynamicist on that issue because I'm not one.

quote Originally posted by timgray: I spent more on my 3.4 install than most 3800sc's for one reason. I want a RELIABLE engine install that I know will go 200,000 miles. Yes I know the 3800sc can go for a lot of miles but a $800.00 junkyard engine is a crap-shoot and not guaranteed to go 2000 miles let alone 200,000.

Damn few 3800's don't make 200K. 250K is easy with decent oil change intervals. Series 1 motors did that and the 2s and 3s are much better. Those in the yards are there for other reasons than the engines.

HUH..........
Is this thing for sale?




Figured it was worth trying.

quote Originally posted by unboundmo: HUH.......... Is this thing for sale? Figured it was worth trying.

Not at the moment. I am in the process of installing it on my Formula to see how well it runs on an otherwise stock 2.8. Once I am done playing around with it I would entertain the idea of selling it.

Marty

Here is what I have so far

[This message has been edited by Jennings03 (edited 02-24-2011).]

quote Originally posted by project34: I'd think the tubing's inside diameter for each plenum should match the size of each throttle body's opening. If you plan on using a stock Fiero V6 throttle body at one end of each plenum, the opening for a stock Fiero V6 throttle body is 52 mm.

I would think you'd need more plenum volume than that would provide...

I would think that any extra space in the intake would just mean that it takes longer for the air to travel through the intake, and the closer to the same size as the TB would create more vacuum. However I have absolutely no experience here so anyone with ideas or knowledge on this would be great. I probably won't actually order any tubing until this weekend and that link you posted project34 looks like the best option for the tubing.