Throttle body options for 3.4?

[cardana24]

I am trying to find out if I can use a larger throttle body on the 3.4 SFI camaro engine. I am putting this engine in my jeep and before the engine goes in I would like to do a few little mods, and a bigger TB is one of them. Do any of the 4.3 throttle bodies work as plug and play units for this engine? I know I will need to port match the plenum, and I am fine with that I would just like to know if any larger TB will bolt up and will use the same sensors? Thanks for any info.

[IsaacHayes]

4.3 = 70mm TB. Stock 3.4l = 52mm. No way you can port out the stock plenum that big I bet. You'll run out of material. Besides, those motors are a gen1 iron head design which do not flow that great. You really don't need a bigger TB. If you want to make some good power with a mod, headers would be the easiest, followed by a cam. Other than that it's swapping heads/intakes, pistons etc for FWD parts which make more power but that's more involved and custom.

[cardana24]

Thanks for the info. Even if I cannot port the plenum that much is there still a bigger throttle body that would bolt up? I am just thinking of easy mods I can do now, plus I am going to make a junkyard run in a few days and would like to know what to look for. I understand the FWD heads and injection system would be another project but I am not looking to do that until I have the engine in and running well.

[IsaacHayes]

No idea what will bolt up without an adapter, but you won't gain much but quicker throttle response since you'll be flowing more air with less throttle opening.

[ForcedFirebird]

Issac is right, the TB is not your restriction right now.

[cardana24]

sounds like I will stick with the stock one. Is there any point in porting the stock TB at all or would the heads prevent any sort of gain in throttle response?

[ForcedFirebird]

sounds like I will stick with the stock one. Is there any point in porting the stock TB at all or would the heads prevent any sort of gain in throttle response?

According to the people who have ported 3.4 TB's say the butt-dyno proves positive results.

[BillS]

You can't just flail around looking for bigger this or bigger that. You have to look at what the bottlenecks in the engine may be.

That engine is limited by exhaust flow. First arrange some sort of free flow exhaust. I have used modified Fiero headers successfully, in combination with a 2.5" straight through system.

The engine is limited by porting and combustion chambers as well as by some areas of the intake tract. These need to be attended to. The details of how and where material needs to be removed are too complicated to explain here.

Then and only then does the throttle body become a limiting factor. But you are limited in how large you can go by the design of the upper plenum and size of the entry hole. I run a 62 mm TB which pushes it as far as you can go - a bit further, actually as machining the intake stem to match resulted in slight break through as the casting isn't of uniform thickness. Going any larger would be a complete waste of time unless you had flow bench results that indicated it would be of use, AND you replaced the upper plenum or arranged to substantially modify it.