crank diameter

blown5.0ho

Registered User
What is the diameter of the crank pulley on a super coupe?

I have an M90 from a SC and I'm tring to find the right diameter for my 5.0. Paxton and Vortech offer different crank pulleys for my application. I don't want to run 12lbs of boost, so pulley dia is very important.

Thank you,

Jason
 

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I assume your are doing some calcs on blower speed. On the supercoupe the supercharger is not driven directly off the crank, but rather through a jackshaft arrangement involving another pulley. The crank pulley diamater alone will not give you what you need.

I don't have the crank and jackshshaft pulley diameters, but this thread might have some information that will prove useful on supercharger drive ratios:

http://66.36.160.101/forums/showthread.php?s=&threadid=13117

Looks like quite a project you have going on there! Please keep us updated on your progress.
 
Thank you for the response. What is a jack shaft? Is it an idler pulley? My project will only have the crank, idler and blower pulley.

The formula was a little confusing. I do know that the blower pulley is around 3", the idler is a factory dia. and the crank....well that's my problem.

I found crank pulleys from Vortech and paxton, I just don't know which one to get.
 
The M90 pushes 90 CI per revolution. Your 5.0 (351) sucks in 175 CI per revolution. Just to keep up the blower will need to spin at 2x crank speed.

The boost pressure is completely dependant on how well your engine breaths. A well built 350 will outbreath a M90 without any problem, so boost pressure will not be a problem. You won't get 12 lbs of boost unless something is very wrong. The SC doesn't even get 12 lbs of boost when the heads and exhaust are done (yes, most are getting this but they are not using the stock pulleys).

When you know what overdrive ratio you want on the blower, multiply the SC pulley diameter by the overdrive ratio for the crank pulley diameter.

3x overdrive * 3" SC pulley = 9" crank pulley.
2.5x = 7.5" crank pulley

IMHO, look into a larger blower. The M90 is a little small to run a 351. If you can find a M112 use it, it will be much more efficient for your use. Otherwise make sure you get your M90 ported to flow as much as possible.

Aaron
 
I would also add that if you want the blower to flow you should get a raised top to help with the flow out of the blower.Anything you need to find just click on search in the upper right corner and type in the subject, scroll down and hit perform search.You should find all you will need.
 
Thanks for all the responses. I wished I had a 351 CID (5.8L), but I have a 5.0 (302 CID). The M90 Should be enough.
 
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