As some of you may know, I bought these used with approx 850 hrs. I've been going through everything to bring them back up to spec. The final thing to do was to get a compression baseline. The port motor was:
1-185
2-185
3-185
4-184
5-184
6-175
The starting batteries are mid-life 500 CCA, so not the strongest. Cranking has always been "lazy" with them. With that in mind, I'm ok with these numbers.
The Stb motor was all over the place:
1-130
2-170
3-205
4-182
5-155
6-105
My mechanic went through the stb motor twice to verify. He is very experienced, and even he was scratching his head.
At first I thought, "Darn, I adjusted the valves wrong". But, the "shimmy" in that motor at idle has been there from day 1, long before I did the valves. It had been my hope that adjusting the valves would clean up the idle. Nothing that I have done.......from injectors, to Ringfree, to H/L filters, VST, plugs, the works.....has ever changed the "shimmy" at idle. I had begun to suspect bad compression numbers, and I was correct.
This motor runs out at 6000 rpm and is smooth through acceleration.
My mechanic said the rule of thumb is.....if compression is above 100, it'll run, so go run it with more Ringfree in the tank (not super-concentrated) for 50-60 miles. It could just be really gunked up. But, I have my doubts about that, because I've already run a fair amount of RF through it.
It would be one thing if all the cylinders were low, in the 110 range, give or take. That's a tired, nearly worn out motor. But this.....?!
So my initial question for you experts out there is.......what, in your experience could cause such wild swings? And supposing I wanted to fix it instead of run it, should the next step be a leak-down test?
1-185
2-185
3-185
4-184
5-184
6-175
The starting batteries are mid-life 500 CCA, so not the strongest. Cranking has always been "lazy" with them. With that in mind, I'm ok with these numbers.
The Stb motor was all over the place:
1-130
2-170
3-205
4-182
5-155
6-105
My mechanic went through the stb motor twice to verify. He is very experienced, and even he was scratching his head.
At first I thought, "Darn, I adjusted the valves wrong". But, the "shimmy" in that motor at idle has been there from day 1, long before I did the valves. It had been my hope that adjusting the valves would clean up the idle. Nothing that I have done.......from injectors, to Ringfree, to H/L filters, VST, plugs, the works.....has ever changed the "shimmy" at idle. I had begun to suspect bad compression numbers, and I was correct.
This motor runs out at 6000 rpm and is smooth through acceleration.
My mechanic said the rule of thumb is.....if compression is above 100, it'll run, so go run it with more Ringfree in the tank (not super-concentrated) for 50-60 miles. It could just be really gunked up. But, I have my doubts about that, because I've already run a fair amount of RF through it.
It would be one thing if all the cylinders were low, in the 110 range, give or take. That's a tired, nearly worn out motor. But this.....?!
So my initial question for you experts out there is.......what, in your experience could cause such wild swings? And supposing I wanted to fix it instead of run it, should the next step be a leak-down test?