Fast 90mm is a POS
I think you should keep the 90MM setup and check into changing your power ring. You can have a custom one made. The 78MM will be a bottleneck for that 422ci and you will have to go back up to the 90MM when a bigger power ring is available anyway. Also, if you go back down to the 78MM you might as well keep your LS6 intake and do a awesome ported TB. The gains from the 78MM over the LS6 Intake and ported TB is null. You should be able to take your power ring to any good fab shop and they can make you a new one to fit the 90MM. Thats what I would do while you wait on your motor.
TECH Senior Member
Joined: Nov 2001
Posts: 10,341
Likes: 1
No offense but it sounds like you ordered it without researching to see what else is involved. I wouldnt blame thunder for not accepting it either without a restocking fee/trade etc. It isnt their fault you didnt research your purchase!
TECH Senior Member
Joined: Jun 2003
Posts: 9,339
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From: NYC metro area
Originally Posted by Chris ARE 360
No offense but it sounds like you ordered it without researching to see what else is involved. I wouldnt blame thunder for not accepting it either without a restocking fee/trade etc. It isnt their fault you didnt research your purchase!
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
Posts: 4,983
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From: Texas
Sorry, can't fault Thunder for you not having your combo squared away. I'll give you $400 for the whole thing if you don't want it.
We have a 90MM intake and TB, and the car likes it 503/455. GM must agree since the new LS2 is 90MM.
One of the things with new parts is fabrication work is sometimes required, so you have the option of making a step-down/step-up adapter(s), or you have the option of fabbing a new ring which should be a piece of cake. As for the lid, you have the option of butchering up your old one, of making a new one. The MAF, you can either use an 85MM and live with it, or talk with ProM.
But, no it isn't a POS, just realize that in the aftermarket world, sometimes things are not just "bolt-on"...
We have a 90MM intake and TB, and the car likes it 503/455. GM must agree since the new LS2 is 90MM.
One of the things with new parts is fabrication work is sometimes required, so you have the option of making a step-down/step-up adapter(s), or you have the option of fabbing a new ring which should be a piece of cake. As for the lid, you have the option of butchering up your old one, of making a new one. The MAF, you can either use an 85MM and live with it, or talk with ProM.
But, no it isn't a POS, just realize that in the aftermarket world, sometimes things are not just "bolt-on"...
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TECH Fanatic
Joined: Aug 2002
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From: Alvin Texas
but one thing is for sure dont down grade to the 78mm you will be pissing in the wind its not much better than a ls6 out of the box intake you have now i promise you ....anyway i hope you have good luck and dont give up thats why its a hobby .......cause its a pain in the *** but its fun...... 
