Compression test on 948
Posted: Sun Apr 20, 2014 7:30 pm
Greetings all,
So I attempted a compression test on my '59 948, and the results seem fairly dismal. This is the first time I've ever tried to do a compression test on anything, so there's the possibility the results are operator error some how.
Here's what I did: pulled all the plugs. They're all black around the edge, but the nose and the lead are tan. They all look similar and none are oily. Engine was cold. I put a brick on the throttle to hold it open. Then I put the tester in #1 and hand tightened it best I could. I turned it over a few times on the starter, and wrote down the result. Quick release the pressure and did it again. Then I put 2-3 squirts of 30wt oil in the cylinder and did it again. Repeat for each cylinder.
#1 dry: 110, with oil: 130
#2 dry: 105, with oil: 125
#3 dry: 100, with oil: 115
#4 dry 105, with oil: 120
I saw the thread on compression testing on a 1098. What about my 948? Should the results also be up in the 140+ range? They at least seem relatively consistent across the cylinders, but quite low. For what it's worth, I have a weird head. Casting number appears to be CAM4910, but could possibly be CAM4810, which I understand is from a 998 mini?
Last weekend I checked the valve clearances and cleaned up the points and distributor cap and the car seems to actually run decently, but is completely gutless on hills. But that might just be a 948 for you. I've no experience with any other car than this one, so I don't know what's "normal" to expect out of a 948.
So I attempted a compression test on my '59 948, and the results seem fairly dismal. This is the first time I've ever tried to do a compression test on anything, so there's the possibility the results are operator error some how.
Here's what I did: pulled all the plugs. They're all black around the edge, but the nose and the lead are tan. They all look similar and none are oily. Engine was cold. I put a brick on the throttle to hold it open. Then I put the tester in #1 and hand tightened it best I could. I turned it over a few times on the starter, and wrote down the result. Quick release the pressure and did it again. Then I put 2-3 squirts of 30wt oil in the cylinder and did it again. Repeat for each cylinder.
#1 dry: 110, with oil: 130
#2 dry: 105, with oil: 125
#3 dry: 100, with oil: 115
#4 dry 105, with oil: 120
I saw the thread on compression testing on a 1098. What about my 948? Should the results also be up in the 140+ range? They at least seem relatively consistent across the cylinders, but quite low. For what it's worth, I have a weird head. Casting number appears to be CAM4910, but could possibly be CAM4810, which I understand is from a 998 mini?
Last weekend I checked the valve clearances and cleaned up the points and distributor cap and the car seems to actually run decently, but is completely gutless on hills. But that might just be a 948 for you. I've no experience with any other car than this one, so I don't know what's "normal" to expect out of a 948.