63mm Throttle body

[edram454]

it makes me wonder whey they didnt make them bigger seeing it was a dohc engine. my c5 z06 has a lsx 102mm throttle body and maf. quite a difference.

[XfireZ51]

One thing people may not realize is that you just don't slap on the 63mm TB. In order to take advantage of that, the plenum openings need to be port matched otherwise, what's the point?
Also, now that u have increased overall air intake, guess what? U need to tune the calibration to take full advantage of it.

[tpepmeie]

Originally Posted by secondchance

According to Marc, even bored, stroked to 378 with head porting and top end porting, may pick up 5 hp at high rev.

The only real way to determine whether it's a restriction is to put a vacuum sensor/gauge on the plenum at WOT. If you're pulling more than .5" Hg depression in the plenum, then you'd do well with a bigger TB.

My 427 w/ 63mm and oversize primary blade was over 1" depression at 7000 rpm. Too much restriction. Short of machining one from billet, there just really isn't any way to go bigger, although I am considering making an adapter plate to fit a big oval body to the front of the plenum.

I'd guess a stock displacement engine at 7000 rpm isn't pulling that much vacuum with a stock TB.

[edram454]

an obvious design flaw. there should have been a way to drastically increase the opening of the throttle body as they have done with all the ls engines. it is a very limiting factor.

[Hog]

Any serious GEN 3/4 SBC uses more than a single throttlebody anyways.

A design flaw? Less than 1% of LT5's would find the 63mm r-body sizing any sort of limitation.

[Hog]

Originally Posted by tpepmeie

The only real way to determine whether it's a restriction is to put a vacuum sensor/gauge on the plenum at WOT. If you're pulling more than .5" Hg depression in the plenum, then you'd do well with a bigger TB.

My 427 w/ 63mm and oversize primary blade was over 1" depression at 7000 rpm. Too much restriction. Short of machining one from billet, there just really isn't any way to go bigger, although I am considering making an adapter plate to fit a big oval body to the front of the plenum.

I'd guess a stock displacement engine at 7000 rpm isn't pulling that much vacuum with a stock TB.

On your 427 with the 63mm t-body, what was you MAP sensor indicating? Was it coinciding with the extra instrumentation you had added? Just curious.