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3.5" Pulley

RedGrandPrix

RedGrandPrix

New member
Hey guys. I know there has certainly been a lot said about changing the size of the M90 Eaton pulley, but you guys have had much more experience than me so I would value any input on the matter. I currently have a 99 Pontiac GP GTP. The current upgrades so far are:

AC DELCO 41-985 (iridium 1 range colder 0.055" gap)
K&N FIPK CAI
180* T-STAT
U-Bend DELETE
BRAND NEW Port and Polished high performance M90 Supercharger

I live in CA and give it the highest octane we have here (91). Do you think it is reasonable to go to a 3.5" pulley? I understand I should scan for KR no matter what.

Thanks for any and all responses.
 


I'm pretty sure K&N is the only one with a CARB exemption sticker. The emissions people here will fail a modified car outright without one the minute they pop the hood.
 
RedGrandPrix said:
Hey guys. I know there has certainly been a lot said about changing the size of the M90 Eaton pulley, but you guys have had much more experience than me so I would value any input on the matter. I currently have a 99 Pontiac GP GTP. The current upgrades so far are:

AC DELCO 41-985 (iridium 1 range colder 0.055" gap)
K&N FIPK CAI
180* T-STAT
U-Bend DELETE
BRAND NEW Port and Polished high performance M90 Supercharger

I live in CA and give it the highest octane we have here (91). Do you think it is reasonable to go to a 3.5" pulley? I understand I should scan for KR no matter what.

Thanks for any and all responses.
Click to expand...

ur kidding? u guys dont have 93 octane???
 
so is NC but every gas station (except the arabs) carry 87, 89, and 93... I think only shell stores carry the max of 92 octane
 


Yea you should be able to run a 3.5 with little Kr. As you already know and as i will repeat make sure you scan. If you drop and are still getting Kr you should be able to easily reduce it to safe levels with a downpipe. If you want to be extra safe a plog and a PCM will let you run the 3.5 with virtually no problems. That in mind every car is different but the above is usually true for most cars.
 


Thanks for your advice. I'll pick up a ZZP PCM 1.0 as well to be on the safe side.
I don't think its legal to swap ANYTHING before the cat here.
 
Why's that? In the main part of the forum is says the PCM is a recommended upgrade for a pulley swap. Something I'm missing?
 
The upgraded PCM isn't the problem. It's the fact that you have plans on purchasing a ZZP PCM thats the problem.


ZZP PCM's have caused way too many issues for too many people. It's pretty well known that when looking into buying a aftermarket PCM that you need to stay far..... away from the ZZP ones.
 
Street Wolf said:
Uh huh, sure.
Click to expand...

I know you missed the part where the only exhaust mod was a ubend delete. For a 3.5, at the very least a DP, needed to be added to his list. Still likely even with those mods, the only way to run KR free would be a PCM with a 10.6:1 AFR with reduced WOT timing. A combination of slow. I just don't get why after as much time as gone by and as much information available people are still recommending pulleys that are too small for the mods, instead of working the in order of optimum AFR>Timing and then go with the pulley that fits the build.

OP-go with an Overkill PCM :: Overkill Motorsports ::
 


^^^Listen to his advice, he knows what he's talking about. Fueling>Timing>Boost

I would highly doubt that you would be able to run a 3.5" with that mod list. If you are dead set on dropping pulley sizes, you should at least look into getting a front power log since the stock manifolds are ****. To be honest if I were you I would just go ahead and get some headers, since you will probably want them in the future anyways just save yourself some trouble and get them now (especially since the new ZZP headers are out and people are going to be selling their headers for cheap). If you get some headers you should be able to run a 3.4" no problem with your mods.

Oh and the reason why a PCM would be a bad idea with a 3.5" and your modlist is that an aftermarket PCM raises your timing and since you would probably be seeing KR anyway with the 3.5" it would result in even more KR.

There is a slight possibility that you can run that 3.5" without any KR, but you can never know for sure without scanning.
 
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You need to scan first. nobody can tell you what to do or what is best for you to do without scanning. So let that be your next mod.
 
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