I'm having issues on my bracket motors (Two) getting above 5.0 inches of vacuum with a big GZ vacuum pump
The current motor is better than the one before it but not any where near 10+ inches, any things I should look for?
I bought the pump used several years ago and sent it back to GZ for repair or rebuilding as needed, they called yesterday and said it tested good
The current motor has a early Hamburger SS oil pan with the lower kick out in it with the drag link hole removed and covered up for more volume at a lower level. I put 11 quarts in it to get it on the tip of dip stick.
I'm sure it has a tiny pin hole in it some where as it will weep, seep, some oil onto the pan when it sits all winter, no weeping or seeping during the race season though

Respectfully, you have a leak larger than just a pin-hole. You should have no problem pulling OVER 10" at speed with that pump with NO TRICKS. Check the valley area for leaks. pressurize the crankcase 3 to 5psi max and bubble check via snoop.

So the way that I found my leak points was with a UE2000 ultrasonic leak detector. I borrowed it from work.

What I ultimately found was that I had a bad seal in the Indy valley tray. The vacuum pump had sucked in a portion of the RTV sealing the valley tray. Actually happened twice and I missed it with a visual inspection.

Cap your dip stick... they normally leak vac

It is plug off with a vacuum cap and sealed up tight with a screw on hose clamp
I'm going to look into trying to pressure test it and look for air leaks with soapy water

before i had a large electric vacuum pump, I had a old 1/4hp electric motor that used a long belt to drive the vacuum pump. I prefer to pull a vacuum to find a vacuum leak because i once had a relief valve that sealed great under pressure but would open up at 4in of vacuum. The owner said it was all sealed up because he had pressurized it and it didn't leak.


Joe

I run the same pump. It''ll makeover 5hg at idle. By adding air too the crank case (about 3psi) the biggest leak found was at the corners of the Indy valley tray/head gasket. I now add a little RTV at the top corners of the head gaskets during installation. Each side about a 1/4" down from the valley junction.
Doug

Ray Barton told me to silicone the harmonic balancer keyway.

Make sure the valve covers and any oil fillers are sealed with an o ring.

Mike

If you look at some of the old pictures of our engines built by best , you will see toe clamps from the head to the valley cover along each side. We had no luck until then . We even built 1/2 inch thick billet valley covers with no success. Pressurizing is a waste of time as the forces are reversed.

I do nothing special to my engines at all and pull 12 inches with the Star Standard pump. Mine Idles at 5 on alky.

Leak test? Anyone use a smoke machine?

I had issues with getting a lot of oil in the puke tank between runs, so I pressurized the crankcase with a smoke machine, it showed the rear main seal leaking and a small leak on the oil pan rail. And fixing those issues helped. But the bottom line was, how much engine blow by does the engine have? If you have more crankcase pressure from leaking rings, than the pump can handle, it will not pull any vacuum. I used a simple blowby tester that went into the valve cover , and it told the tale.

Smoke machine will work. The air test with soapy water works excellent. The only thing it may miss is if a shaft seal is being pulled back away under vacuum.
Doug

I have one of these:

https://www.amazon.com/AutoLine-Pro-Automotive-Diagnostic-SMK-1/dp/B06XHRBKTM/ref=sr_1_7?crid=368A71NJQ8X0Q&keywords=smoke+machine&qid=1582983126&s=automotive&sprefix=smoke+m%2Caps%2C182&sr=1-7

I have always been able to find all my vacuum leaks with it.

Good Luck!

Install the rear main and timing cover seals reversed. Use RightStuff sparingly on the sealing surfaces of the rear main seal cap. Fill the voids of the stock style seal cap with RightStuff. As stated seal the upper ends of the head gaskets with RightStuff. Seal the crank key. If the block has side bolted mains chamfer the holes and use an o-ring under the washer. Make sure the 0-ring fit for the distributor is tight. Pressure test with no more than 5psi and soapy water in a spray bottle. There are 2 nitrous motors out that we had to put vacuum regulators on that were sealed like this.

I smoked mine a couple of years ago and the smoke was pouring out of the rear main seal area. I took it apart and attempted to reseal it. It is better but I can still not make any vacuum. I have the star set up. I eventually removed it and put the pan evacs back on. I was sick of it blowing oil out of their fancy $400.00 catch can!