48mm TB Flow Capacity
#16
Well, let's see here... A stock throttle body with an airfoil will flow over 600cfm (from what I've read). This is good enough to feed a 350cid engine up to 6000rpm at 100% VE (volumetric efficiency). Plus, the ZZ502 (fuel injected version) makes over 500hp with a stock L98 throttle body.
With that being said, if you increase your displacement, rpms, or VE (heads, cam, exhaust, etc.), the bigger TB will benefit you. I have a book called "Small Block Chevy Performance" by Dave Emanuel that has a series of dyno tests on a Camaro LT1. They dynoed the engine with ported heads by CNC Cylinder Heads, CAI, and a stock 48mm TB. Everything else on the engine was stock. They bolted on a 52mm TB from TPIS; and gained 12hp and 6ft-lbs of torque. That's probably why you see so many people with bigger throttle bodies.
With that being said, if you increase your displacement, rpms, or VE (heads, cam, exhaust, etc.), the bigger TB will benefit you. I have a book called "Small Block Chevy Performance" by Dave Emanuel that has a series of dyno tests on a Camaro LT1. They dynoed the engine with ported heads by CNC Cylinder Heads, CAI, and a stock 48mm TB. Everything else on the engine was stock. They bolted on a 52mm TB from TPIS; and gained 12hp and 6ft-lbs of torque. That's probably why you see so many people with bigger throttle bodies.
#17
#18
Let me quote myself since this seems to have been overlooked:
That was just going from 48mm to 52mm on a STOCK 350 LT1 with a STOCK cam and a STOCK exhaust. You're talking about having a 383 with I'm assuming heads/cam/headers/exhaust/CAI, etc, and you think you'd only gain 5hp? Also, if you're patient, you shouldn't be spending $350 on a larger TB. You should be able to find one pretty easily for about the cost of a CAI kit, and I don't see many people around here saying those are a waste of $$$.
I have a book called "Small Block Chevy Performance" by Dave Emanuel that has a series of dyno tests on a Camaro LT1. They dynoed the engine with ported heads by CNC Cylinder Heads, CAI, and a stock 48mm TB. Everything else on the engine was stock. They bolted on a 52mm TB from TPIS; and gained 12hp and 6ft-lbs of torque.
#19
You will come to a day where 350$ for 10 HP will be well worth the money, like I am at now. Shorty headers and stock TB are what keep me out of the 11s (and bad launching). I am about to break down, but not yet. I want to break 11s w/ stock TB, fuel pump, shorty headers just for fun first.
#22
Let me quote myself since this seems to have been overlooked:
That was just going from 48mm to 52mm on a STOCK 350 LT1 with a STOCK cam and a STOCK exhaust. You're talking about having a 383 with I'm assuming heads/cam/headers/exhaust/CAI, etc, and you think you'd only gain 5hp? Also, if you're patient, you shouldn't be spending $350 on a larger TB. You should be able to find one pretty easily for about the cost of a CAI kit, and I don't see many people around here saying those are a waste of $$$.
That was just going from 48mm to 52mm on a STOCK 350 LT1 with a STOCK cam and a STOCK exhaust. You're talking about having a 383 with I'm assuming heads/cam/headers/exhaust/CAI, etc, and you think you'd only gain 5hp? Also, if you're patient, you shouldn't be spending $350 on a larger TB. You should be able to find one pretty easily for about the cost of a CAI kit, and I don't see many people around here saying those are a waste of $$$.
#23
You have a totally valid point but I personally would rather see results from an individual that has nothing to gain from the results. That book was made to be sold and you have to have interesting info to sell something. TPIS also probally donated the tb for advertising so even if it made no rwhp difference they are gonna put that it did anyways. I am not saying a that a bigger throttle body is not needed, I have no idea. I would just like to see some other results. Hopefully someone here has installed heads and cam on an engine with a stock TB and then bought a new one and installed it later. I really would like to keep mine stock if I can because I like the stock engine look and I plan to always stay with stock valve covers, heads and intake with porting to both (sleeper). I like doing the most possible with as little money invested as possible and $350 is a good chunk of change. I would rather spend $350 on gas driving my car around and enjoying it than gain 10-20 hp if thats all that can be had on a N/A motor.
and you can port the stock throttle body to keep that look you want, and it will cost you alot less. leaving your throttle body stock will cost you power, if you want to know how much injuneer has already broken that down very nicely for you
#24
I went back thorugh my archives, and found some dyno test data that I printed out 9 years ago. It was a series of dyno tests run by an indivdual named Markus Strobl, who had access to a dyno at Dynotech in Dallas, beginning in the summer of 1996. The results were on a website that no longer exists.... www.cyberramp.net/~mstrobl/96dynotest.htm. This appeared to be an individual who just wanted to test some of the popular mods of the day.... not a magazine, not a dealer, not a manufacturer. The documentation of the testing is fairly thorough.
The tests were run on a 96 Z28 with "Borla catback, Moroso airbox, Hypertech programmer plus, Homeported heads and 1.6:1 roller rockers".
Remove MAF screen: +1.1 HP, -0.4 lb-ft
Replace 48mm TB with stock TB bored to 52mm: +2.5 HP, +3.2 lb-ft
Add airfoil to 52mm TB: +1.1 HP, -1.9 lb-ft
MSD-6A: +3.5 HP, +4.7 lb-ft
Hypertech Power Program: +3.0 HP; +0.9 lb-ft
Cool down engine by spraying nitrous on intake: +7.0 HP, +11.1 lb-ft
The tests were run on a 96 Z28 with "Borla catback, Moroso airbox, Hypertech programmer plus, Homeported heads and 1.6:1 roller rockers".
Remove MAF screen: +1.1 HP, -0.4 lb-ft
Replace 48mm TB with stock TB bored to 52mm: +2.5 HP, +3.2 lb-ft
Add airfoil to 52mm TB: +1.1 HP, -1.9 lb-ft
MSD-6A: +3.5 HP, +4.7 lb-ft
Hypertech Power Program: +3.0 HP; +0.9 lb-ft
Cool down engine by spraying nitrous on intake: +7.0 HP, +11.1 lb-ft
#26
that does not make any sense, how are results from a dyno test on a throttle body gonna help him sell a book.
and you can port the stock throttle body to keep that look you want, and it will cost you alot less. leaving your throttle body stock will cost you power, if you want to know how much injuneer has already broken that down very nicely for you
and you can port the stock throttle body to keep that look you want, and it will cost you alot less. leaving your throttle body stock will cost you power, if you want to know how much injuneer has already broken that down very nicely for you
I also know that Injuneer has broken it down to me, 10rwhp. Thats why I stated 10-20hp gain....
Brad
#27
All technical details aside... here's my cold hard facts.
I consistently gained 1 MPH at the trap after installing my 58mm TB. That's all I care about.
Car's that need 'em, gain from it.. those that don't... well they wasted money.
I consistently gained 1 MPH at the trap after installing my 58mm TB. That's all I care about.
Car's that need 'em, gain from it.. those that don't... well they wasted money.
#28
You have a totally valid point but I personally would rather see results from an individual that has nothing to gain from the results. That book was made to be sold and you have to have interesting info to sell something. TPIS also probally donated the tb for advertising so even if it made no rwhp difference they are gonna put that it did anyways. I am not saying a that a bigger throttle body is not needed, I have no idea. I would just like to see some other results. Hopefully someone here has installed heads and cam on an engine with a stock TB and then bought a new one and installed it later. I really would like to keep mine stock if I can because I like the stock engine look and I plan to always stay with stock valve covers, heads and intake with porting to both (sleeper). I like doing the most possible with as little money invested as possible and $350 is a good chunk of change. I would rather spend $350 on gas driving my car around and enjoying it than gain 10-20 hp if thats all that can be had on a N/A motor.
I will completely agree on not trusting sponsored information and feel TPIS is one of the worst big vendors out there, they charge and arm and a leg for alomost no improvem,ent on a lot of their crap.
That said take a vacuum reading after it is together and try and get vacuum low see what it takes to get that. My money is you will endup needing a TB unless the heads are weak. If going 52mm a rebored stocker is THE way to go asves some of the hassles and issues guys have had with aftermarket units so you get your sleeper look.
Heads I would argue that for the overwhelming majority of applications ported stockers are the best choice not just the "sleeper" choice. If you thought using stock castings was just a "budget sleeper" idea as opposed to actually being a very good choice then you have not done enough research yet.
On the vacuum thing, the old rule with carburators was shoot for 1.5" or less vacuum at WOT with a street car, any more and the carb was a restriction. Using that rule let us know what you find.
Last edited by 96capricemgr; 03-29-2008 at 07:45 PM.
#29
No I wanted to use them because I am going the AI 200cc route. Might go the 185cc route if I dont need the 200's with a smaller cam and 355 cubes. I also know because you have some of the most realistic posts on the forum and you def push ported stockers.