95VertZ

Question guys, I finally found (using oil dye) that my intake is leaking on the back side. SO, I will be taking the intake off to put new gaskets,rtv,etc. My question is, I was considering going ahead and installing a new throttle body while Im at it but was wondering, will I need to do any other mods if I put on a bigger TB or can everything else stay stock for now? Also, which is better 52mm or 58mm? I plan to get a K&N CAI and LT1 inlet elbow to go along with this fix.

Thanks!

gaedbo

If you aren't familiar with the removal and install of the Intake, you may want to check out this website for some help or tips. Under items #6 and #7 Cam Removal and Cam Install there is the info on the Intake Removal and Install. I found it very helpful when I did mine. Especially the tip on using a couple of studs on heads to aid in the alignment so you don't smear the RTV.

4th Gen LT1 F-Body Tech Aids

http://shbox.com/ci/ci295.jpg

95VertZ

Thanks for the heads up, I have researched a lot on the process of R&R Intake manifold and feel like its definitely something I can take on. I'm just wondering if I can go ahead with my TB change now or if doing a TB change would cause me to have to do any other mods...

gaedbo

Others hopefully will jump in, but from what I remember from reading other threads/posts, going to a 58mm TB will not do you any good on a basically stock engine.

I believe the 52mm is more than adequate for moderately modifed engines, if I remember this correctly, the original TB is going to perform as well as the 52mm on a stock motor.

Hopefully someone else will jump in that has actually done the change. I am using the stock TB with CAI, and throttle body bypass, with Flow Master Exhaust and it runs great.

Injuneer

The stock bores in your intake are 52mm. So no changes required in that respect. You aren't going to notice any significant improvements going from stock 48mm to 52mm. Not on a stock engine.

To run a 58mm, you would need to have the intake bores machined to open them up to 58mm. 58mm would be total overkill, and throw the PCM's (auto trans) shift tables off. The shifts are programmed based on throttle position PERCENT vs trans output shaft speed. The PCM reads the TPS sensor voltage and translates that to percent throttle opening. Using a significantly larger throttle body throws off the calibration of throttle position percent to TPS volts. Would require PCM tune to correct.

We did extensive engine dyno testing on my 381 stroker. The shop showed me on the engine dyno that even approaching 500 HP at the crankshaft, my 58mm throttle body was only ~80% open, and opening it further did not increase air (mass) flow. Back calculating, a 52mm TB would have been adequate at 500 HP (normally aspirated). They still laugh at the 58mm TB.

Save your money and stick with the stock TB for now. And you already have an LT1 intake elbow. You want the "1LE” elbow. And there's no big gain. CAI is a definite power producer.

95VertZ

Yea i meant 1le elbow lol. Thanks for the replies guys, Injuneer, so you're saying that a 52mm is all the TB i will need and that if I wanted i could go ahead with it and be fine correct? I do plan on having head/cam work done at a later time so im just trying to save a step. I may do as you suggested and save on it for now. As my plan sits, im going to do intake fix, possible tb upgrade, cai, 1le elbow, lt headers w/ory to catbacks. Then wait a while to do my heads and cam.

Midnight_Z

We did extensive engine dyno testing on my 381 stroker. The shop showed me on the engine dyno that even approaching 500 HP at the crankshaft, my 58mm throttle body was only ~80% open, and opening it further did not increase air (mass) flow. Back calculating, a 52mm TB would have been adequate at 500 HP (normally aspirated). They still laugh at the 58mm TB.
THAT'S AWESOME INFO RIGHT THERE!!!!!!
You can get your stock 48mm TB bored out to 52mm also.

Injuneer

There's a fuel injected GM crate motor, the Ram Jet 502. 502 cubic inches, 502 HP, 568 lb-ft torque. Throttle body supplied with engine is dual 50mm.

https://ohiospeedshops.com/air-and-f...-throttle-body