I spotted one months ago but failed to write down where i saw it. I can go a bit smaller than 5 inch for max vacuum. I have a Moroso 3 vane pump.

During the winter, I called Aerospace components, they make a popular vacuum pump. They said the biggest they make for their crank mandrel was 5" (not 4")

Greg, have you tried Jones Racing Products?

Greg a buddy of mine ordered his 4.5” pulley from Butler Performance. I assume you’re referring to the pump pulley, and not the crank mandrel pulley.

https://butlerperformance.com/i-249...r-6-5-dia-v-belt-gz-vpp-401-402-404.html

Thanks guys, Wes, that was it! Ordered a 4.5. Best price too.

With a 3 vane you cant pull enough to hurt anything. Lots of old wives tales about vacuum for sure. Jones make a lot of pullies for accessories.

Al, care to elaborate on vacuum wives tails? This is uncharted teritory for me and i don't want to hurt my very costly new build!

A 3 vane pump simply will NOT pull enough vacuum to hurt anything. 11-12" is all they can pull generally. If someone says they get more from one in a BBM with a wet sump oiling system gonna have to show me with an accurate gauge that it happened. We never have regulated a 3 vane engine of any kindand never seen an issue.

I have NEVER seen an issues from "high" vacuum in anything I run or have been around. My Cuda routinely went 400+ passes between freshen ups. The pistons in that engine currently had 406 passes on them at freshen up, we coated and reused them and its still running them 7 years later. Never any issues with wrist pins and it pulls 16-18" every pass, or at least did. Literally a couple thousand runs on it before I sold it. Been running vacuum pumps for 15 years and never seen any issues of "pulling oil away from pins" in any of my junk. I have seen some Comp stuff that pulls 22-26" of vacuum with no signs of pin oiling issues. Wealso have not had any issues on the Vette running 18-20. It uses a 4 vane and no regulator.

We use a lot of 3-vane Moroso vacuum pumps with a regulator and have had over 16 " vacuum often. Check out our Facebook page for pictures and dyno sheets.

Thanks Pete. Hopefully i will get more than 12". My pulley ratio with the 4.5 will be right at or a touch above recommended punp rpm.