327 SB Chevy compression test results..help?
Thread Starter
Cruising
Joined: Feb 2011
Posts: 10
Likes: 0
From: Beloit WI
327 SB Chevy compression test results..help?
1972 Corvette engine issue
I just did a compression test on my 327 and came up with
F 1: 151 2: 0
R 3: 151 4: 164
O 5: 140 6: 160
N 7: 150 8: 145
T
The 327 is a 1968 and has around 60,000 since last rebuild, heads were rebuilt at the same time. This was back in 1975 though.
I did the compression test with the engine at running temp, then when I got the zero reading I did a wet test with oil in that cylinder. The wet test did not improve the compression so I know it's not rings. I found out I have a collapsed lifter on that cylinder, the other one for the same cylinder was feeling "soft" when I pushed on the rocker arm.
Any tips or advice you guys have would be appreciated...
I just did a compression test on my 327 and came up with
F 1: 151 2: 0
R 3: 151 4: 164
O 5: 140 6: 160
N 7: 150 8: 145
T
The 327 is a 1968 and has around 60,000 since last rebuild, heads were rebuilt at the same time. This was back in 1975 though.
I did the compression test with the engine at running temp, then when I got the zero reading I did a wet test with oil in that cylinder. The wet test did not improve the compression so I know it's not rings. I found out I have a collapsed lifter on that cylinder, the other one for the same cylinder was feeling "soft" when I pushed on the rocker arm.
Any tips or advice you guys have would be appreciated...
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
1972 Corvette engine issue
I just did a compression test on my 327 and came up with
F 1: 151 2: 0
R 3: 151 4: 164
O 5: 140 6: 160
N 7: 150 8: 145
T
The 327 is a 1968 and has around 60,000 since last rebuild, heads were rebuilt at the same time. This was back in 1975 though.
I did the compression test with the engine at running temp, then when I got the zero reading I did a wet test with oil in that cylinder. The wet test did not improve the compression so I know it's not rings. I found out I have a collapsed lifter on that cylinder, the other one for the same cylinder was feeling "soft" when I pushed on the rocker arm.
Any tips or advice you guys have would be appreciated...
I just did a compression test on my 327 and came up with
F 1: 151 2: 0
R 3: 151 4: 164
O 5: 140 6: 160
N 7: 150 8: 145
T
The 327 is a 1968 and has around 60,000 since last rebuild, heads were rebuilt at the same time. This was back in 1975 though.
I did the compression test with the engine at running temp, then when I got the zero reading I did a wet test with oil in that cylinder. The wet test did not improve the compression so I know it's not rings. I found out I have a collapsed lifter on that cylinder, the other one for the same cylinder was feeling "soft" when I pushed on the rocker arm.
Any tips or advice you guys have would be appreciated...
Le Mans Master
Joined: Dec 2006
Posts: 5,557
Likes: 9
From: Oquirrh Mountains
St. Jude Donor '09
Too much of a difference bet 8 and 5 as well. Try the oil trick in the others and see if you get different readings. If so, it's time for a leak down test. That will help you isolate the leak(s) better.
Without the benefit of that info, I would guess your exhaust seats are pounded out. That old of an engine doesn't have hardened exh seats. They don't like unleaded gas. It may be time for a new set of heads and valvetrain.
Without the benefit of that info, I would guess your exhaust seats are pounded out. That old of an engine doesn't have hardened exh seats. They don't like unleaded gas. It may be time for a new set of heads and valvetrain.
Thread Starter
Cruising
Joined: Feb 2011
Posts: 10
Likes: 0
From: Beloit WI
Too much of a difference bet 8 and 5 as well. Try the oil trick in the others and see if you get different readings. If so, it's time for a leak down test. That will help you isolate the leak(s) better.
Without the benefit of that info, I would guess your exhaust seats are pounded out. That old of an engine doesn't have hardened exh seats. They don't like unleaded gas. It may be time for a new set of heads and valvetrain.
Without the benefit of that info, I would guess your exhaust seats are pounded out. That old of an engine doesn't have hardened exh seats. They don't like unleaded gas. It may be time for a new set of heads and valvetrain.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
I have a new lunati cam part # 07102. I plan on getting my heads rebuilt as well as new lifters. The one lifter on the right side on front side #2 came apart when I took the rocker arm and pushrod pressure from it. That and the spring on that same lifter is broken in two places... I think I found the problem. Question I keep asking myself is why did both of those parts break on the same valve..
Last edited by 63mako; Feb 7, 2012 at 11:35 PM.
Le Mans Master
Joined: Dec 2006
Posts: 5,557
Likes: 9
From: Oquirrh Mountains
St. Jude Donor '09
I have a new lunati cam part # 07102. I plan on getting my heads rebuilt as well as new lifters. The one lifter on the right side on front side #2 came apart when I took the rocker arm and pushrod pressure from it. That and the spring on that same lifter is broken in two places... I think I found the problem. Question I keep asking myself is why did both of those parts break on the same valve..
With regards to your heads, consider a set of vortec heads instead of rebuilding yours. For about the same money, the vortecs will give you a lot better performance.
Thread Starter
Cruising
Joined: Feb 2011
Posts: 10
Likes: 0
From: Beloit WI
I am planning to replace the heads now, after pulling one off I realized that they were the smaller valve camel hump heads. The whole time I have had the car the previos owner had said they were the 2:02 &1:60 heads. So time for new heads and more performance for my small block. Will go well with the cam I have to put in it as well as the headees I had put on last fall..
