FAST 78mm: Keep or ditch?
Thread Starter
Le Mans Master
Joined: Jul 2007
Posts: 6,094
Likes: 3,467
From: Oswego IL
FAST 78mm: Keep or ditch?
Planning a 427" build over the winter, and will be adding some giggle juice as well. I currently have a FAST78 on the car with a ported stock throttle body. I would like to run a 90mm or larger t/b unit on the next build. Has anyone ever modded a FAST78? The snout is obviously made for the smaller t/b, but is there any way to open it up for a larger unit? I don't have a 90mm t/b here to compare flanges, etc. Time to sell it?
Melting Slicks
Joined: Nov 2009
Posts: 2,536
Likes: 15
Not what you want to hear but....IMHO the Fast 78 will not even come close to supporting the air flow requirements of a 427" motor. Let me say that again...NOT EVEN CLOSE.
I just have a 346 with some head work done to it and the manifold is about 40CFM down on flow compared to the head. And its a Fast 102 "ported".
About the TB, yes if I were you I'd be looking for the "biggest" TB you could afford.
Thanks.....PM Kevin "WKMCD" he has a lot of knowledge with a 427 "street car".
http://forums.corvetteforum.com/memb...137-wkmcd.html
I just have a 346 with some head work done to it and the manifold is about 40CFM down on flow compared to the head. And its a Fast 102 "ported".
About the TB, yes if I were you I'd be looking for the "biggest" TB you could afford.
Thanks.....PM Kevin "WKMCD" he has a lot of knowledge with a 427 "street car".
http://forums.corvetteforum.com/memb...137-wkmcd.html
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
The FAST 102 is a much better intake that the older style FAST. The 78mm is even too small for a medium sized 346 build IMHO. I run a FAST 102 opened up to 107mm with a Nick Williams 107mm TB. I run WCCH Stage 3 L92 heads that flow 380 CFM and they need all the air they can get.
My small cam "Gentlemanly" build make good power every where even with the BIG TB.
It's a very mild build but well optimized.
Here's a dyno graph: 403 vs 427
Nothing wrong with 400+ ft/lb of torque at 2K RPM.
My small cam "Gentlemanly" build make good power every where even with the BIG TB.
It's a very mild build but well optimized.Here's a dyno graph: 403 vs 427
Nothing wrong with 400+ ft/lb of torque at 2K RPM.
Thread Starter
Le Mans Master
Joined: Jul 2007
Posts: 6,094
Likes: 3,467
From: Oswego IL
Thanks, guys. I appreciate the info! At least the sale of the FAST78 will help offset the upgrade costs. I am running AFR205 heads which will be swapped for some TFS units as well. Thinking about selling the whole LS6 from top to bottom as a complete unit to make a quick sale.
