BBC TPI Style Throttle Body Advice Needed
Thread Starter
Drifting
Joined: Oct 2003
Posts: 1,426
Likes: 1
From: VetteMOD
St. Jude Donor '05-'07
BBC TPI Style Throttle Body Advice Needed
I posted this in the engine mods section but didn't get much of a response.
(A little background info) I am converting a 454 to port fuel injection with an Arizona Speed and Marine oval port, crossover style intake. 9.5:1 CR, hydraulic cam w/.510 lift. and unidentified exhaust (probably fairly quiet and restrictive). This is for a street driven car and I expect HP numbers around 450HP.
I have a couple of questions. I currently have a throttle body with dual 58mm bores. Someone told me that the GM 502 Ramjet uses a dual 52mm throttle body. The logic I guess is that driveability and tip in is better for the 52mm and the flow is adequate for a street car. Anyone have experience with this?
Also, if I replace the throttle body with the 52mm, what should I get. I have heard some bad things about BBK and Edelbrock makes them but I have not heard anything about them. Maybe get a GM 48mm and have it bored out?
Edit: The 502 Ramjet uses PN17113524 throttle body. This is listed as a replacement for a L98 motor. Wow, is it possible that the 502 uses 48mm throttle body? Can't find any specs on that trottle body at gM Performance. Thanks
(A little background info) I am converting a 454 to port fuel injection with an Arizona Speed and Marine oval port, crossover style intake. 9.5:1 CR, hydraulic cam w/.510 lift. and unidentified exhaust (probably fairly quiet and restrictive). This is for a street driven car and I expect HP numbers around 450HP.
I have a couple of questions. I currently have a throttle body with dual 58mm bores. Someone told me that the GM 502 Ramjet uses a dual 52mm throttle body. The logic I guess is that driveability and tip in is better for the 52mm and the flow is adequate for a street car. Anyone have experience with this?
Also, if I replace the throttle body with the 52mm, what should I get. I have heard some bad things about BBK and Edelbrock makes them but I have not heard anything about them. Maybe get a GM 48mm and have it bored out?
Edit: The 502 Ramjet uses PN17113524 throttle body. This is listed as a replacement for a L98 motor. Wow, is it possible that the 502 uses 48mm throttle body? Can't find any specs on that trottle body at gM Performance. Thanks
Drifting
Joined: Oct 2003
Posts: 1,486
Likes: 10
From: Big Pine Key FL
yep 502 ramjet uses THE L98 throttle body, the ZL1 Ramjet 454 uses the bigger unit.
The ramjet makes great torque with the small TB but starts feeing soft around 5200, though it pulls to 5800+ with reasonable authority.
I have a bigger TB, roller rockers and Bee Hive springs waiting for warmer weather
The ramjet makes great torque with the small TB but starts feeing soft around 5200, though it pulls to 5800+ with reasonable authority.
I have a bigger TB, roller rockers and Bee Hive springs waiting for warmer weather
Racer
Joined: Mar 2005
Posts: 263
Likes: 0
From: Creswell OR
I would go ahead and talk to the people at Arizona Speed and Marine.They could probably give you the best answers.They also make what might be the best throttle body out there.It is a beauty,but expensive.Holly also makes a throttle body,but I don't know anything about it.I have also heard that the BBK-Edelbrock throttle body is not the best.Good luck.....
Safety Car
Joined: Jul 2001
Posts: 3,921
Likes: 2
From: York PA
I am running a BBK 52MM Throttle body on my TPI 350. With a larger thottle body you will lose some of the precision at lower speeds, but that's not abig deal unless you go way too big. I probably won't buy another BBK when I get to the point that I want a 58MM. 
Drifting
Joined: Oct 2003
Posts: 1,486
Likes: 10
From: Big Pine Key FL
Originally Posted by BBShark
So to understand, the 502 uses the 48mm and the 454 uses the 52mm?
GM has only produced 200 all aluminum ZL1 engines, which is sure to make it a collectors item. The Ram Jet ZL1 is based on the
legendary all aluminum ZL1 first introduced in 1969 that was in a limited number of 1969 Camaros and Corvettes. The new Ram Jet ZL1 has some modern updates such as improved main webs and provisions for a roller cam. Original tooling that was used in 1969 was modified to update the block. Each ZL1 has a three digit serial number machined into the Ram Jet cast logo on the valve covers. The new ZL1 will produce 510 H.P @ 5750 rpm and 493 lbs of torque @ 4250 rpm. The ZL1 contains a 10.2 to 1 compression ratio with a 640/598 lift on a solid roller cam shaft using roller rocker arms with an 1.7 to 1 ratio that are held in place with 7/16 studs. The aluminum cylinder heads, that come on the ZL1, have stainless steel 2.25 intake and 1.88 exhaust valves with race quality springs. Valve lash settings are .016 for the intake and .018 for the exhaust. The air that is pulled through a 58mm throttle body should be mixed with 93 octane fuel due to the 10.2 to 1 compression ratio. An easy wiring harness and preprogrammed EMC computer are included with the ZL1.
Last edited by 84rzv500r; Feb 6, 2006 at 05:26 PM. Reason: correct the 52/58 thing
