1G Compression and leakdown results

[Anthony Boni]

What's up guys.

I have a G4CS block with a 4G63 head. Compression tests came back 180 across the board. I just performed a leakdown test and I have about 15% on 3 cylinders, and closer to 20% on #1 cylinder. Used 100 PSI. All of the leak was crankcase. No intake, exhaust, or HG leaks. I did these tests cold. Would a warm engine cause less of a leak past the piston rings because they expand and seal better? Is 15-20% acceptable? I read an article on these forums that wrote 5-10% is good. 10-20% is ehh. Just wanted a second opinion.

The second concern is related but is a bit trickier. Because I have a G4CS block and a 4G63 head, the timing setup is a little wonky. I read that in order to correctly time the block to the head, you have to rotate the intake and exhaust cam gears half a tooth clockwise. I did so, and there's no contact between the piston and valves and everything rotates as it should. However, while performing the leakdown test today I came across something that I don't know how to explain. I had #3 cylinder at TDC and performed the leakdown test. No problem. Because #3 is at TDC, #2 is at TDC as well. I put the leakdown adapter into #2, and it all shot out of the intake. I was under the impression #2 and #3 both fired together. same thing with #1 and #4 cylinders. I had to rotate the engine a full cycle to go from #2 cylinder to #3. Am I just being stupid or?...


Any advice and explanation is appreciated. I'm not too concerned with the leakdown test. I'm more concerned with a potential timing issue. Thanks!

 

[Anthony Boni]

Anyone have any information? Or know where to find some?

 

[pauleyman]

What's up guys.

I have a G4CS block with a 4G63 head. Compression tests came back 180 across the board. I just performed a leakdown test and I have about 15% on 3 cylinders, and closer to 20% on #1 cylinder. Used 100 PSI. All of the leak was crankcase. No intake, exhaust, or HG leaks. I did these tests cold. Would a warm engine cause less of a leak past the piston rings because they expand and seal better? Is 15-20% acceptable? I read an article on these forums that wrote 5-10% is good. 10-20% is ehh. Just wanted a second opinion.

The second concern is related but is a bit trickier. Because I have a G4CS block and a 4G63 head, the timing setup is a little wonky. I read that in order to correctly time the block to the head, you have to rotate the intake and exhaust cam gears half a tooth clockwise. I did so, and there's no contact between the piston and valves and everything rotates as it should. However, while performing the leakdown test today I came across something that I don't know how to explain. I had #3 cylinder at TDC and performed the leakdown test. No problem. Because #3 is at TDC, #2 is at TDC as well. I put the leakdown adapter into #2, and it all shot out of the intake. I was under the impression #2 and #3 both fired together. same thing with #1 and #4 cylinders. I had to rotate the engine a full cycle to go from #2 cylinder to #3. Am I just being stupid or?...


Any advice and explanation is appreciated. I'm not too concerned with the leakdown test. I'm more concerned with a potential timing issue. Thanks!

No. They do not fire together. A look at the can profile shows you where they are. While both are at the top tjey aren t doing the same thing.

 

[Anthony Boni]

No. They do not fire together. A look at the can profile shows you where they are. While both are at the top tjey aren t doing the same thing.

That’s a relief. I thought my timing was slightly off and all of the pressurized air from the leakdown test was going out of the intake valves when they were all supposed to be closed.