My custom ported FAST 85/85 - *PICS!*
anyone know if you were to get a FAST 78mm and a NW 90mm t/b if you could port the 78 to 90 and then the internals of the 78 and 90 t/b for a little more power? that sounds like the way to go, if it's possible...
Thread Starter
Joined: Apr 2006
Posts: 3,910
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From: Grand Rapids, Michigan
It's not possible. The 85MM TB is the largest you can put on a ported FAST 78MM because the outer ring of the O-ring groove is approximately 85MM. Porting it out any larger would eliminate the last area on the intake for the TB to seal to. Look at the pic of my intake after porting to see what I mean. Theoretically, you COULD grind it all the way out and epoxy it back up to work, but that's even more time and expense. My setup is truly cost effective since I only have about $500 in both the TB and the intake. Buying a NW 90MM TB would kind of kill the budget build focus of my project. You wouldn't really save enough money for it to be worth the effort it takes. Figure $400 minimum for a FAST 78 plus $400 for a TB, you're only $300 away from a 90/90 at that point, and that's if you can find a 78MM FAST that cheap. Most go for 500-550 that I have seen. You'd still have to deal with the fact that it would be difficult to get the TB to seal as well.
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Originally Posted by Tony Mamo @ AFR
Yep....welcome to the Internet....where accurate information is scarce and in-accurate information is plentiful.
General knowledge is weak on a subject oriented Internet.
Its few and far between that you will find an accurate depiction of whats really going on without someone being biased or skewed in the favor of their shop or products.
Some of the most obvious dirty dealings are the dyno numbers that can be played with.
12 Second Club
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From: Lafayette/West Lafayette, IN
I'm wondering now if I made the wrong choice with going with a ported TB/LS6... All I ever heard was the same "get an LS6 the 78 is a joke compared to the 90." Nobody seemed to think you could gain much at all over the LS6 with the 78. Basically they all said that Price/performance was the LS6 and you should only get the 90/90 if you wanted to pay a big premium for the extra 10rwhp (and only really needed it with a big cam)...
Are you going to be able to have any dyno numbers for this thing? I'm curious how much better it is than what I did for just a tad more money. And how it compares to a 90/90.
Are you going to be able to have any dyno numbers for this thing? I'm curious how much better it is than what I did for just a tad more money. And how it compares to a 90/90.
I bought the LS6/PP TB also, I wouldn't sweat it. This guy got a SMOKING deal on the 78, so for him it was truly pointless for the LS6. If you look at Tony M's matrix, you'll see that you're still paying over a G for the ported 78 combo. Not exactly cheap, and it's still the best hp/$ ratio, but LS6/PP TB setups are still running 400 combined, TOPS. I'll get another one later down the road when I have nothing left to blow money on 
-J
-J
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Joined: Apr 2004
Posts: 1,378
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From: Atlanta, GA Ft. Walton Beach, FL
Consider this in your search for "value" (I look at everything on a HP per dollar basis).
If you already have a good epoxied and ported 78 mm TB (like a Mark Shaner piece or something similar) score a 78 unit cheap and just consider having it ported. Even at the prices I charge to do a very neat and thorough job your return on investment is still better than buying a larger 85 mm TB and cutting up the snout which might close the gap in half between the 78 and the 90 netting you 2-3 HP. For an extra few hundred you would see an additional gain of 10 RWHP and a similar bump in TQ (my ported FAST 78 set-up went 20 RWHP and 15 RWTQ stronger than my former LS6/78 set-up as I previously mentioned).
For grins I just whipped up this spreadsheet....prices and performance may vary slightly but I think the general point I am making would still be intact.
Manifold.............Avg Retail $$...........Typical Gain.........Cost/HP
Stk FAST 78.............700........................8....... ............. $87
Stk FAST 90 (w/ TB)..1200......................13................. ...$92
FAST 78 w/ 85 mm.....900.......................11............... .....$82
Ported FAST 78.........1200......................18........... .........$67
Ported FAST 90/90.....1700......................23............... .....$74
The key is to understand that the snout doesn't represent the largest restriction in the FAST hence the smaller gains when messing with it. Reshaping and reconfiguring the ports are where the larger gains in airflow and power can be unlocked....
Tony
If you already have a good epoxied and ported 78 mm TB (like a Mark Shaner piece or something similar) score a 78 unit cheap and just consider having it ported. Even at the prices I charge to do a very neat and thorough job your return on investment is still better than buying a larger 85 mm TB and cutting up the snout which might close the gap in half between the 78 and the 90 netting you 2-3 HP. For an extra few hundred you would see an additional gain of 10 RWHP and a similar bump in TQ (my ported FAST 78 set-up went 20 RWHP and 15 RWTQ stronger than my former LS6/78 set-up as I previously mentioned).
For grins I just whipped up this spreadsheet....prices and performance may vary slightly but I think the general point I am making would still be intact.
Manifold.............Avg Retail $$...........Typical Gain.........Cost/HP
Stk FAST 78.............700........................8....... ............. $87
Stk FAST 90 (w/ TB)..1200......................13................. ...$92
FAST 78 w/ 85 mm.....900.......................11............... .....$82
Ported FAST 78.........1200......................18........... .........$67
Ported FAST 90/90.....1700......................23............... .....$74
The key is to understand that the snout doesn't represent the largest restriction in the FAST hence the smaller gains when messing with it. Reshaping and reconfiguring the ports are where the larger gains in airflow and power can be unlocked....
Tony
I would like to see one more choice (if it's any differnt from what you allready have
Ported FAST 78.........1200......................18........... .........$67
ported 78mm w/ported stock 75mm TB.
? for the Guru I choose the 78mm since I have stock heads was told that the 90mm would make the bottom power soft however you do gain a little up top?
True or false
?2. was also informed that the 90mm is spesifically designed for a larger cubic motor than 346CID?
True or false.
? I purchased my 78mm allready ported (for stock heads) the seller said someone from New York area did the porting.
in you're professional opion how do'es port job look?
Lastly when I get ported heads would you recomend port matching to the heads.
Thanks
Joined: Apr 2004
Posts: 1,378
Likes: 14
From: Atlanta, GA Ft. Walton Beach, FL
78mm larger image
I'm thinking the above chart #s are w/ stoch heads since the FAST is orginally designed as a bolt on.
my observations of this port job is there was'nt much material removed, I'm thinking it's more of a smooth out than a actuale port
I'm also thinking that porting really means port matching to what ever it's bolted to.
I'm thinking the above chart #s are w/ stoch heads since the FAST is orginally designed as a bolt on.
my observations of this port job is there was'nt much material removed, I'm thinking it's more of a smooth out than a actuale port
I'm also thinking that porting really means port matching to what ever it's bolted to.
Last edited by badmfkr; Nov 16, 2008 at 09:21 AM.
I have a few times, but all I ever see is "its not worth it just buy a FAST and NW TB"....well a ported LS6 and PP TB is A LOT cheaper! If it gives any gains at all its worth it.
If the 85mm MAF and 85mm lid help like people claim, then you'd think the 85mm TB on ANY intake would also help power production.
Anybody run this combo?
Actually a buddy of mine runs the 85 lid/maf/TB with a reducer plate and he definitely picked up some power, Im trying to talk him into doing this to his LS6 but hes scared.
TPIS had a 90mm version of the LS6 intake where an LS2 neck is installed onto the LS6 intake, but the mod costs a lot.
However, I have a home modified 85mm LS6 intake. In a thread named "Ported LS6 vs Ported Weiand....," or something like that, are the measured airflow results between the two.
EDIT: Just found it. The thread is called "My findings, Ported Weiand vs Ported LS6 intake.
Last edited by LS1-450; Nov 17, 2008 at 02:46 PM. Reason: Noted reference thread info.
