TPI Throttle Body Size
Thread Starter
Drifting
Joined: Oct 2003
Posts: 1,426
Likes: 1
From: VetteMOD
St. Jude Donor '05-'07
TPI Throttle Body Size
I am building a 454 with a TPI style intake. This is similar to the RamJet 502 GM MPFI engine. The Ramjet 502 uses a 49mm throttle body from a 1990 Vette. I think this really needs to be a 52mm but I would like to know opinions from C4 guys.
Also, (if you tell me the 49mm is too small) should I get a ported GM unit or buy an aftermarket unit? They both seem to cost about $300, is one better than the other?
Also, (if you tell me the 49mm is too small) should I get a ported GM unit or buy an aftermarket unit? They both seem to cost about $300, is one better than the other?
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
Originally Posted by BBShark
I am building a 454 with a TPI style intake. This is similar to the RamJet 502 GM MPFI engine. The Ramjet 502 uses a 49mm throttle body from a 1990 Vette. I think this really needs to be a 52mm but I would like to know opinions from C4 guys.
Also, (if you tell me the 49mm is too small) should I get a ported GM unit or buy an aftermarket unit? They both seem to cost about $300, is one better than the other?
Also, (if you tell me the 49mm is too small) should I get a ported GM unit or buy an aftermarket unit? They both seem to cost about $300, is one better than the other?
Anyway. This is a huge debate. There really is no simple answer for you. I got some of my fastest times with a singleplane and a vortec/ls1 style monoblade. I experimented with 48, 52mm with absolutely no change. Ideally you'd like to get as close to 100% ve. I'd suggest trying the 48mm and see what your map readings are at WOT. If your not reaching atmosphere (whatever the map reading was prior to cranking), try a larger throttle body until you see no improvement or slow down.
-- Joe
