Right now im going to stick to a 350 block, ill but heads,cam and a mini ram on the car but im not sure weather to go with a 52 mm tb or 58mm tb? witch one would be better? TPIS says that it would be better if i just went to a 52mm since its only a 350 but what do you guys think i should do? thanks
Bobby

 

For a 350-355 the 52mm TB is plenty (750cfm). Price out the AS&M unit it's a nice piece of work, much better than the BBK.

 

Go with the 52mm, I am using a 50mm on a 350.

 

in my opinion unless you go radical, keep the 300 bucks. I am pretty sure the 48mm one flows in excess of 750cfm. The 52mm more than that.

 

just use the stock one w/ an air foil

 

If you have a 383 which one would you pick.

 

I have two cars. This tb question that im asking about is for the stock one. Im doing mods to it pritty soon. I just getting everything in order right now. I have a 58mm on the 386 that is in the other car.

 

I think you should say *** the throttle body and call up paxton for a supercharger!!!

 

how does a TB equal a supercharger??

 

ok a tb cost $300 a supercharger cost $3000, we arent talking about a supercharger we are talking about throttle bodies. Thanks for the help guys, im going to be building an engine and it will be getting the 58mmtb.

 

I would say go with a 58 mm throttle body if you're getting heads, cam, and miniram. They should all support the amount of air that the 58 can provide. With that setup, I don't think you will benefit with a 52 over a 58. Just my .02.

 

GM's ZZ502 is a 500 horsepower 500 cubic inch big block. They use a 48mm throttle body. 750cfm is a LOT of dry cfm. That's equalent to around an 850cfm carb. Think about the motor you need to make an 850 carb necessary.

 

Word, 48mm 4 Life!


Ill save my 300 bucks for Somthing that will actually Make a differance, Thanks.

 

The Crate 502 has a 48mm so I'd say you could stick with yours.

On a 383 I have a 48 also...

 

don't do it bob!! give me your 48mm and I will magically make it flow way too much for your engine.

 

thanks for all your imput guys, i really appriciate it but im going with the 58mm. I know it cost $300, but that is $300 i am willing to spend if i get more power. Think about it, even if it is to big the the engine then it wont do any harm. I mean i wont loss any power just gain. This 500hp 502 you guys are talking about, well just think of the power it could make if it have a bigger tb! What about LS1's running 80mm tb and 5.0's running 85mm tb? I think my 350 will benifit from a 58mm. Thanks guys

 

The LS1 & 5.0 are single butterfly, TPI, as you know are dual.

 

I do not believe you will feel any difference. It may make a few more HP but on the street most guys I have seen with them tell me," save your money."

 

Sure he'll feel a difference. When Tom Keliher slapped a 58 onto his 350 for a magazine spot, slowed down by a couple tenths in the 1/4.

EDIT: Edited for clarity.

 

i know those are single butterfly, but its still an 80mm tb. stock 4.6l come with that i think. here we are with 48mm tb.

 

also guys, this tb is not going on a stock engine. it will have a custom cam, afr 190cc heads, mini ram, ect....im not going to ceap a stock tb with these mods, that would be a wast.

 

Last year I tried a 52 mm and the stock one without airfoil for several passes each. On the whole I went .01 seconds quicker with the 52 mm and I have tonnes of mods to my 350.


***EDITED*** Please reduce size of your profile pics. Dial up users have a hard time viewing posts with pics of this size
Thanks
Kevin G
Moderator TPI

 

If your engine is pulling vacuum at peak power rpm you may need a bigger throttle - I think 0-1.5 in hg may be the target
0.02

 

Ok , I retract my earlier post, After a lot of research on port size
and air flow I have come to change my way of thinking on this.

I think all the adds for bigger TB's are BS lies to try to sell you
a product. Using some simple flow calculations shows the stock
TB should flow just over 750 cfm. Add an air foil to it and it will
go over 800 cfm. You would have to turn your 350 at 7000 rpm
to use up 650 cfm of air flow.

You would have to turn your engine at 8000 rpm to use up 725
cfm of air flow.

You would have to turn your engine at 9000 rmp to use up 800
cfm of air flow.

There is no reason for a bigger TB on a 350.
Unless you regularly turn 10,000 rpm.

Just my 2 cents.

 

Airfoils have been shown to increase airflow by a whole 12 cfm.

 

bob,

Let us assume that your 386 has 100% VE. We all know it does not, but your engine is special for this discussion.

so, your engine is a whopping .223 cubic feet, trust me. So you spin the engine to 6000 with that mini ram and you need 670cfm. So you get crazy and spin it to 6500 and you need 725 cfm. This is at 100% VE!!!! Actual numbers are much less than these!!

 

There are a few different airfoils out there and the TPIS foil is
the best. It will increase flow by a factor of about 6%. The stock
TB without the throttle plates and cross shafts calculate to about
810 cfm. Put the shafts and plates back in and you wind up at
like 760 cfm. Add 6% for the airfoil and it goes back up to 805 cfm.

 

swap, why do you call yourself the swapmaster and how did you calculate that? what pressure drop did you assume? or did you?

 

I do engine and tranny swaps, alot of them, for a living. Heavy
mechanical, the stuff sissy shops won't do no matter how much
you would try to pay them.

Hole size can be directly correlated into how much air will pass
through it with with a given vacuum or pressure.

The contour of the entrance into the hole has a significant impact
on the flow numbers. The stock TB has a fairly decent contour but
the area between the bores sucks. The airfoil keeps the air from
smashing into this center area thus reducing the drag on the air.

It does not matter what pressure drop you are using. The 6% is
a constant just as the hole size is.

 

Oh, the drop for the TB figures is 28".

 

Heavy mechanical?? In mass? or complexity?? like big semi engines??

 

Automotive, cars and standard trucks. I would do anything
though if I could get inside the shop.

 

can you put in a turbine in my car? I can get a used one out of a helicopter?

 

oh boy, think for a second, 80mm single blade.. 48mm twin blade, that means 48 x 2 (twin or dual blade) = 96mm total, hence the twin or dual part of the term..

 

dude (snake), edit your post before people make you look like a fool

 

As car guys we have this strange disease that tells us everything stock sucks, and must be replaces with something better. But it is possible that GM actually put something on our cars that will support higher horsepower. If our cars had come stock with 56mm TBs, there would be guys dropping $300 for a 60mm for their stock engine. If they had come with 40mm, everyone would run out and get 48mm. Just my theory. There are engines that need the bigger guys, and with the stuff you (bobs89irocz) have planned, just may be one of those guys. Here are some quickly calculations I made on single blade tbs vs. double square mm.

Single:
80mm - 5025 sq.mm.
85mm - 5675
Double: (total for both blades)
48mm - 3620 sq.mm.
52mm - 4250
58mm - 5285

I am sure you can't compare them directly, I think the dual design would be more efficient, but that's just a guess.

 

i know it is just a guess but why would you say a dual is more efficient??

 

You can compare them directly. Area is area whether it is 1, 2, 3
or 4 holes it don't matter.

Hell yea gofast, I'll put a turbine in your car. How much money
you got? That would make one hell of a project, wouldn't it?
Don't know anything about a turbine yet but if you got the money
I've got the time

Bring it on.

ROFLMFAO.

 

Well I knew something wasn't quite right. The area of the blade is not the only issue, the circumference would have a large factor too. The air doesn't flow through the blade, it flows past it. Anyway, again I am no engineer, so I will let you guys draw your own conclusions.

Circumference:
Double (total for both blades)
48mm - 301mm
52mm - 327mm
58mm - 365mm
Single
80mm - 251mm
85mm - 267mm

 

i fail to see how circumference matters.

 

Circumference does not factor in.

Hey gofaster, GM made turbine prototypes so it is possible.
Wa da ya say? $1000 a week plus parts?

 

hey, if you knew about turbines this could work.

 

If only.

 

I'm running the Holley 52mm. My stock T-body minimum air rate adjustment screw snapped off and I figured I might as well get something better. Personally I think GM went with the 48mm on the 502 because it increases their progit margin by using and off the shelf t-body versus R&Ding a new one. I would like to see a car mag test a larger t-body on the 502 just to end the argument.

 

Im glad you guys have replied as much as you have, reading all this info you guys are sending me is awsome, i appriciate it. I assume all this information is accurate. I belive it is and that is why im taking your advice (all of you) and im going to save $300 and not my an aftermarket tb, i was unsure about the cfm a stock one would bring in but now im not, i really appriciate your help guys in saving me some money. Later
Bob

 

I don't think you need a bigger one. If you really have nothing else to spend your money on then sure, but if you gained anything, it wouldn't be much.

On a stock engine you can lose a lot throttle response with a bigger TB.

At full throttle a single blade would be slightly more efficient. In a dual blade the shaft will take up a larger percentage of the space.

At part throttle it may be that the dual blade is more efficient because it spreads out the incoming air.

In lots of other cars, bigger throttle bodies are a cost effective way to make more power, so everyone thinks they need to sell bigger ones for fbodies too.

 

Hmmm, might just have something there! Yes agreed on a stock engine it's a waste.
However check out Car Craft May 2002-Fueling a Controversy:Carb vs. EFI.
It was a Demon carb, 825cfm on a BB. To match HP and TQ with the carb the EFI had to go with a prototype TB rated at 1250cfm.....
Check out the article for food for thought......

 

so they took a 825 cfm efi TB, determined it was too small and put on a 1250 cfm TB??? Or they just installed a 1250 to start with??? I think your info was misleading

 

No, in that article they had a 1000cfm t-body on and it was down about 10hp to the carb. So they used a prototype 1250 t-body and got the motor dead even with the carb. I forgot all about that.