im really curious about this. i can read one thing that says you have to have a bigger throttle body and a bigger MAF sensor then i read another that says you dont need either. i seen a guy on the net putting 546 rwhp with the stock TB and MAF. anyways i guess my point is im building a 396 and if i need the upgrades i'll get them but if its not needed then i'll spend the money elsewhere. sorry so long thanks in advance.

 

I would definetely recommend keeping the stock MAF. As for the TB, it's really up to you. I'd probably go with a 52mm myself.

 

I just posted a messege about this!

this is the deal.

The stock 48 mm throttle body will feed a 500c.i. engine with a little room to spare. What happens is this.

Compare how much air gets through when the stock tb is open all the way.

What happens is the maximum amount of air that can get into your engine is getting in at less then 100% open blades in the TB. So your pedal will be down less then to the floor but your car is reading WOT. Some guys have added a 58mm and lost 10 HP throughout the range! It simply isn't needed. Make sure the stock TB is adjusted and closing all the way and clean it out but you don't need a bigger one. They don't even add any real HP. NOthing you will feel! I can think of many other things to spend $300.00 on! the GM 502 blocks come from the factory with a 48MM throttle body and it is fine!



Pointless mod

 

I heard that going from the stock TB to a 52mm is basicaly pointless and has no gains... and that if your going to do it go with the 58mm. I agree with that personly only because I trust Brents word. When I get mine I'm going with the 58mm Holley TB from T BYRNE.

Here, check out Brents page http://www.bfranker.badz28.com/96ss/58porting.htm

He has step by step proceedures on how to install it... might not be the exact same as your Camaro though.. don't know for sure

Trevor

 

I thought the 502 used twin 48mm tB's?? correct me if I'm wrong though.

CanadianZ

 

That is what we use also twin 48mm blades Each throttle blade is 48 and then the 52mm are twin 52's you get the idea.

 

A local shop did a compairsion on a engine dyno and yielded 7 flywheel HP on a heads and cam LT1... To the wheels, 4? I don't think its worth the money, that would pay for a nice chunk of head porting though

 

we did back to back dyno pulls and a 58 tb got 6-7 hp through out the entire pull

 

Yeah... and the stock factory air box with paper filter will feed a 500 c.i. engine as well but that doesn't mean that changing this out for a K&N FIPK won't help matters

With a fuel injected setup like we have with a large "surge volume" of air in the intake, I fail to see how a larger throttle body can actually HURT you. It doesn't make sense to me even though some have said they have a dyno run showing it. I wonder if something else factored into the dyno run because, like I said, it doesn't make sense that it can hurt performance... at least not to me. And on the flip side, I've also talked to a guy in Orlando who ported his intake to 58mm and stuck on a 58mm tb on an otherwise stock LT1 Camaro (94 I think) and picked up 10 rwhp on the dyno... go figure.

I have a stock throttle body, a 52mm throttle body, a 58mm throttle body, and a mono blade. I have wanted to do some testing with all these on a stock LT1, a highly modified N/A LT1, and a supercharged LT1. I've got the stuff and vehicles to do this... I just need to get off my *** and do this stuff to figure out this damn thing once and for all. When I do, I'm making up a web page with a ton of pics and data points and all that other crap to try and solve this age old debate once and for all

 

Now that would be a cool thing to see!

I'm with you on this Bret. If you actually crunch the numbers you can see where the 48 mm throttle body can become a restriction as the inlet velocity increases. I don't want to do the math right now but it was covered in another thread maybe a few months out.
Even a hot carbureted 350 making power to 7,000 will show gains with what most people would consider a "too large" 850 cfm carb. I've seen a change from 750 cfm to 850 cfm net ~20 hp and 15 lbs-ft of torque once properly tuned.
Here we're talking dry flow but the principle is the same. If the opening is a restriction then it's costing you power. If it's larger than optimal on a dry flow setup, then it's not going to cause you any problems as it doesn't need to atomize fuel.... just flow air.

-Mindgame

 

excellent idea some say bigger is better, some say the stocker is fine.... id love to see the results. i think it was last year or the year before where i had spoken with a certain well known shop to us fbod guys , asking about their 383, and they told me a 58mm tb was definitely needed. so... personally, i doubt id spend that much $$ on that unless there would be a decent gain.

 

Exactly... to me that is the actual debate... not if you'll gain power. With a completely stock engine you shouldn't see as much (if any) gain and with a 1000 hp engine you should see more. We are generally somewhere in between and the debate now becomes a cost vs benefit issue. Is it worth it to spend $400 on a new throttle body if it is worth only 2 hp? 5 hp? 10 hp? Most will agree a tb is not one of the better bang for the buck mods. However, if you've done most the other bolt ons and you have mod money burning a hole in your pocket, I don't see why it should hurt to try and reduce the intake restrictions a bit.

 

that is how i see it, and the motor can only take in soo much so if you go too big i dont see how it will hurt you

 

My 2 pennies...

I have actually had conversations with a couple of HP engine builders out here in CA. A couple of them have built NasCar motors & yet others have just built street strip motors. (Just incase you didn’t already know, NasCar motors have a single barrel 650cfm carburetor and they routinely make in excess of 600hp.) And I have mainly heard two things about the size of Throttle Bodies/Carburetors (whatever you choose to call them), in relation to HP & engine performance.

1) While a big motor can still make big power on a small TB/C do to the restriction it will take the engine longer to get there. (i.e. revs achieved per second under a given percent of throttle input) I realize this might not make a lot of sense but let me say it another way. The GM 502 will make the 500hp on a 48mm TB but it will make it quicker with a larger TB. If it makes any more HP, that is simply a matter of less restriction in the intake, but it would actually be more of a byproduct of efficiency, rather than more air. A 502 is going to be a 502, and a 350 will always be a 350, with the exception of forced induction & nitrous, the engine will only take in that much air, regardless of how big the intake on it is. Displacement is displacement, TB’s, CAI’s, Larger MAF’s, Air Foils, High flow filters, these are all about efficiency, not about making any power. The power was always there; it is just harder for the engine to make it through a restrictive intake, which lowers efficiency.
2) Outside of rev time, there is also another thing to look at. A 48mm TB will reach 100% efficiency sooner than a larger TB. What this means is that the 48 TB will be flowing its maximum amount of air before the engine has reached the desired point of shift/power. Put simply, a 48mm TB will have less response in the higher RPM’s vs. a larger TB, which might not (depending on the size of TB) have reach yet.

In a discussion with one in particular engine Guru, he explained to me that the stock 48mm TB is a well matched for the LT1 because the heads & exhaust on the STOCK LT1 are so restrictive, that the 48mm TB is well suited. The LT4 & the 502 are not quite the ideal engines for the 48mm TB, but he explains this by saying that GM doesn’t make a bigger TB. And they are not going to start any time soon. He said that to GM it makes about as much sense as an IRS in an F-body. HE went on to give me this breakdown.

283(L99) & 350 & 355 = 48mm to 52mm (good) 58mm = too much
383 & 396 = 52mm to 58mm (good) (depending on how well the heads flow)

This is just what I have heard and it makes sense to me. Take it for what you want.

One last thing, here are a few things that I think some times we forget. The LT5 made 405hp in 93 w/ a mono-blade 1000+cfm TB & 2 sets of fuel injectors. So sometimes bigger is better. And a 48mm TB is actually a 96mm TB and a 52mm is a 104. On any planet, that is a lot of air! Thanks hope this helps.

 

You can't just add the two bore sizes - a twin 52 mm TB has about the same throttle bore area as a single ~73mm TB!