Compression Test Step by step

[jaskiewiczangus]

I recently did a (dry) compression test on my 93 N/A Slicktop and the results were very abnormal. I am seeking advice on the proper procedure. my results were as follows. (1) 120 (2) 120 (3) 140 (4) 145 (5) 125 (6) 135 . This was done with balance tube reattacthed and fuel pressure at standard 40-45 psi, also CAS was still active. Do i need to disconnect CAS or relieve fuel pressure?
* I currently have a leaking valve cover gasket at the passanger side downward cover as well as loud valve lifters. I am doing a compression test to justify new lifters and gaskets.

[itsa300zx]

Warmed engine, all plugs out, no cas plugged in, no fuel pressure, fully charged batt, crank with WOT.

[jaskiewiczangus]

thank you itsa300zx, Does the balance tube need to be off? or does that not matter?

[itsa300zx]

Shouldn't matter

[nissanfreak12]

Warmed engine, all plugs out, no cas plugged in, no fuel pressure, fully charged batt, crank with WOT.

Very important otherwise the numbers will be lower. Balance tube will not matter, and have a battery charger hooked up if you can. The more you crank it, it will drain battery making the last couple cylinders lower cause its not cranking as fast.

[t.mcginley.jr]

* I currently have a leaking valve cover gasket at the passanger side downward cover as well as loud valve lifters. I am doing a compression test to justify new lifters and gaskets.

If you do end up with fairly low numbers, you can get new head gaskets, but there's no need to get lifters, they don't affect compression at all

[bartZ32tt]

If you do end up with fairly low numbers, you can get new head gaskets, but there's no need to get lifters, they don't affect compression at all

I wouldn't consider a new head gasket unless an entire bank is much lower compression than the other. A compression test won't give the overall diagnostic - a cylinder leakdown test is a much better tool you can use to determine if it's a bad valve guide, cracked block, piston rings, etc.

leaking valve cover is not going to affect compression numbers, but you should re-seal it with rtv to prevent oil leaks anyways. that's a good time to buy the "half moon" plugs as well.

[t.mcginley.jr]

Yeah I was just saying that for his benefit, I was just assuming he wanted to replace the head gaskets just because. His numbers probably aren't even that bad he just has to redo the compression test