tapout911

Hope this falls under advanced, if not sorry. My vacuum pump kit came with an adjustable relief valve. It says Im supposed to check crankcase vacuum at 4k rpm. Where do I put the vacuum gauge to get this reading and whats suggested vacuum? Ive been told 10" to 15", just want some different opinions. The car doesnt see much street use, just the occasional drive because I can.

N20Dave

Not sure where to tell you to check it but I can tell you that it's not good to run much over 12" with a wet sump engine. It can pull oil away from the bearings and such.

96lt4vette

For the gauge, you can put it anywhere where it will be exposed to crankcase vacuum. Typically it's a boss in the valve cover. On mine, we just drilled and tapped a boss in the rear of one of my valve covers. Alternatively, if you have a hole left over from where your PCV valve or breather was, you can just use one of those with an adaptor to fit your relief valve.

On my dry sump, the builer and pump manufacturer told me between 10"-15". 15" was the max they both recommended for exactly the reasons that Dave mentions. Mine is more of a 50/50 street/race car, so it sits around 10".

mzgp5x

I did a GZMS VP103 pump mod to a 97ss D1-FI application. I also machined a pcv valve plug with a vac gage. Dialed the home-made regulator to about 12" Hg. vac (1/3 atm). Sort of shocked how good it works. B.