I just had my engine rebuilt by a local shop. They are still working out some boost problems but the vacuum at idle looks low to me. I am showing 11 in-hg at 850rpm and 13 in-hg at 1000rpm. Comparing previous posts I was expecting atleast 14-16 in-hg at 850rpm. My motor is not street ported. Mod's include modified stock airbox, DP, CB, injectors and M2 ECU.

Am I off on the vacuum numbers I'm expecting? I am going to have the shop run a compression check. What compression numbers should I see on a rebuild?

 

U might want to check your pressure chamber, the one below the alternator. I use to see 16-17 around 900 rpm and my pressure chamber nipple were broke off but I had fixed it and I still see 16-17. However over the years with alot of heat it might loose it's plastic weld seal together, I happan to have an extra pressure chamber and I compare it with the other pressure chamber that I removed from my car and it look like it's suck in like, otherwords it like someone took a pliers and squees it together. Anyway I change it to the extra pressure chamber and now I have 19 vaccum @ 900 rpm.

 

A rebuild will show slightly lower numbers than normal until it's "broken in". Those numbers are too low for a stock-ported motor though. You either have a vacuum leak or it's a ****-poor rebuild. Who's the shop/rebuilder?