Pulley size for slightly higher compression

IllCobra

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So I just bought a Gen 2 VMP blower this past weekend and need help on what pulley size I should get. The guy included a pulley that he said was a 2.4, but I measured it and it had an 8 inch circumference. Which means it's actually an 2.55 pulley. I am not going to be using the pulley since I am pretty sure that is too much boost to run on pump gas and my the fact that I am running a little higher compression.
So I had a valve seat drop and damage pistons and cylinder walls a few years ago. I took the motor to a shop to get it put back together with some upgraded parts. To make a long story short, the motor now has Manley 11cc pistons which puts compression around 9-9.5:1 and it was bored .020 over.
My question is, what is the smallest pulley size I can safely run on this motor without pushing too much boost? Would I be okay with a 2.8 pulley? I am on a stock lower and will be on 93 pump gas until I go E85 next year. Oh, and I am running Mac Longtubes too.
Any help is appreciated.
 

MG0h3

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Most wont recommend anything over 18 on 93. Go on vmp and look at their boost charts to help you out. What’s your elevation?


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IllCobra

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How much boost would a 2.4 or 2.55 get you on that blower? 9.0-9.5 is still low compression.
~22lbs according to their chart.

upload_2019-2-6_19-19-38.png
 

IllCobra

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Most wont recommend anything over 18 on 93. Go on vmp and look at their boost charts to help you out. What’s your elevation?


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I'm in FL so sea level. I believe i might be right on the boarder of 18 lbs...I am hoping my longtubes are able to drop boost by a 1 or 2 lbs. VMP's chart is saying 19lbs with a 2.8 on a stock lower
 

MG0h3

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I'm in FL so sea level. I believe i might be right on the boarder of 18 lbs...I am hoping my longtubes are able to drop boost by a 1 or 2 lbs. VMP's chart is saying 19lbs with a 2.8 on a stock lower

Remember just because you drop boost in the intake (which is what your gauge is measuring) doesn't mean there is less air going into the cylinders. You may end up with a snappier car on a little less boost and more timing than the other way around.

If memory serves running something like a 2.8 at sea level is going to have you near 20 or something.
 

IllCobra

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Remember just because you drop boost in the intake (which is what your gauge is measuring) doesn't mean there is less air going into the cylinders. You may end up with a snappier car on a little less boost and more timing than the other way around.

If memory serves running something like a 2.8 at sea level is going to have you near 20 or something.
20?! Sounds like i might have to go with a 3.0 then.
 
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NateDogg

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Sounds awesome.

Why not hit the e85 right out the gates? Have you had a chance to break in the motor or is it still brand new?

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IllCobra

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Sounds awesome.

Why not hit the e85 right out the gates? Have you had a chance to break in the motor or is it still brand new?

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I have a "Cobra Fund" that I put into that i use for big mods. I wasn't even supposed to get the VMP blower until summer, but I found a good deal on this used one so I just decided to go for it. I'll probably end up going E85 November once they start offering deals on kits or something.
Yup, it's broken in. It's down in power though... when I took it to get it tuned I maxed out the stock maf (i brought my sct2600 but forgot the damn intake adapter) and ran into some other issues that prevented them for tuning it right. It's running rich under normal driving and turns off randomly at red lights or when i pull into gas stations; rarely, but it does happen. I am going to fix all that before I get the new blower on there and before the new tune.
 

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