FAST 78mm vs LS6 intake?
Here is my LS6 vs Ported Fast 85 (originally fast 78) + underdrive results. I'd have to say the fast was worth 20-25 rwhp over the LS6 through. About 20 ftlbs more through the entire curve. I sold my LS6 for $300 and paid $300 for a Fast 78. No brainer... All the info is in my signature link.
LS6 vs Fast85 + underdrive, low results are bolt on results to compare
LS6 vs Fast85 + underdrive, low results are bolt on results to compare
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yes, a fast 78 or fast 90 will give gains, if it's worth it depends on the price
plus later you could always look for a 90mm upper shell to put on the 78 as that is the only difference
plus later you could always look for a 90mm upper shell to put on the 78 as that is the only difference
depends on how much the 78 is...and you have to include the price of the throttle body into this calculation, especially for a car without cam and/or heads that isn't going to pick up as much
say you can get the 78mm for $300-400 or less and do a little easy port work and gain 10-15hp over the ls6...amazing deal
say the 90mm is $500-650 you do some of the same light porting and you still need a 90mm tb for $200+ to gain 15-20hp over the ls6...not as amazing
say you can get the 78mm for $300-400 or less and do a little easy port work and gain 10-15hp over the ls6...amazing deal
say the 90mm is $500-650 you do some of the same light porting and you still need a 90mm tb for $200+ to gain 15-20hp over the ls6...not as amazing
i have seen the fast 78 go for 400-500 never 300 someone would be stupid to sell one for the same price as an LS6.
and nobody has the upper shell anymore so if you buy a 78mm fast the most it will probally be is a ported 85mm
and nobody has the upper shell anymore so if you buy a 78mm fast the most it will probally be is a ported 85mm
The restriction on 440 rwhp car is not caused from 85mm throttle body I will tell you that right now. With the LS6 intake I would drop 4-5 kpa on the map reading above 3000 rpm. Now with my ported fast 85 the most drop I see is 0-1 kpa. So my barometric pressure is around 95 kpa and I had a 5 kpa drop with LS6 intake 95/90=1.055. This means I had the potential to gain 5.5% more power just from getting my kpa restriction out. My old setup made 411 rwhp so 411x5.5%=22.6hp, as you can see the math is very close. I do not think my car would gain anything with a 90mm setup, a fast 78 just sold a few weeks ago for $350 in the classifieds. The fast 78 and fast 90 use the same runners. I spent about 15 hours on my intake, radiusing all the entrances real nice, removing all the high spots, blending the runners and port matching the bottom shell to the heads. It takes time to do a nice job and you need to take it all the way apart.
Last edited by Nitroused383; Jul 30, 2010 at 02:56 PM.
I bought my FAST 78 for 250.00, incredible deal. The seller is member here and had hurt his motor, so he decided to sell off parts to fund his new motor. The FAST should be back from the porters next week and to sweeten things, I found a guy selling a 90 upper locally. I may buy that this weekend if it checks out.
