No compression in 1 hole????
#1
No compression in 1 hole????
I kind of know my destiny with this, but thought maybe someone can give me hope? I bought a 68 400 motor complete that supposedly was rebuilt about 1 years ago, but never run. Afert gettin it home, I cleaned it up, put a drill into the oil pump drive and confirmerd oil pressure, and all seemed ok. Before I put it in, I decidedd to hook up a battery and test compression. Left side....all 150-160 lbs / right side....3 at 150 and one (#) had maybe 10-20 lbs. I put air into the spark plug hole and only when the valves are open, does air come out of the exhaust or intake. When both valves are closed, you can hear the air coming from oil pan area. My question is....is it possible one of the rings is just stuck in some kind of position that allows leakeage? I probably know the answer, that is more likely a broken ring and will require replacement and teardown. But, is there anything I can check for first?????
#7
Well, I pulled the intake and head off today. This definetly was never run after rebuild. Everything inside is new, and it all looks good. I did notice that the head gasket might not have seated against the water jacket. I think I see a residue of surface crud between the lower eg=dge of the cylinder and the water jacket. Can I be so lucky????? Can all it need is a new head gasket???? I am going to hope. I am goint to try a new gasket first, and take compression test again. hopefully, that will fix it. If not, out comes the piston. wish me luck...I need it.
By the way, when I took the intake off, it had the valley pan intake gasket. What do you all think about using the pan or regular gaskets. The motor does have the deflecter cover over the cam lobes. What gasket set up is recommended?
By the way, when I took the intake off, it had the valley pan intake gasket. What do you all think about using the pan or regular gaskets. The motor does have the deflecter cover over the cam lobes. What gasket set up is recommended?
Last edited by ctrain22; August 24th, 2009 at 02:44 PM.
#10
#11
Well...tried the head gasket.....not solution. So I took the piston out to inspect. Cylinder walls look good, nice hone, no scores, or cracks, that I can see anyway. The piston looks ok too. I am kind of miffed. No aha moment. No obvious problem. I was hoping to see the problem immediately. Broken ring, cracked piston, something. I am going to mic the cylinder and check for roundness, although it seems to be good.
#12
you may take the rings off and check the ring gap. maybe they put the wrong rings on one piston. i doubt that is it but at this point you have to check everything. what about a cracked head?
#13
Might have found problem...
Just kept looking for something that didn't look right. Inspecting cylinder walls, piston, rings, and then.....while my drop light was on the floor, next to the head, my eye caught light coming through the intake valve. I put the light directly over the valve, and looking into the intake chamber, I can see light around the valve. Not on the other cylinders, only the bad one. It evidently is not seating properly. I thought when I put air into the cylinder, that it only came out the intake when the valve was open, but maybe it closed enough not to really hear air, buy enough to have the compression escape out. I'm going to bring head to machine shop to do a leak test and hopefully, just reseat the valve.
Just kept looking for something that didn't look right. Inspecting cylinder walls, piston, rings, and then.....while my drop light was on the floor, next to the head, my eye caught light coming through the intake valve. I put the light directly over the valve, and looking into the intake chamber, I can see light around the valve. Not on the other cylinders, only the bad one. It evidently is not seating properly. I thought when I put air into the cylinder, that it only came out the intake when the valve was open, but maybe it closed enough not to really hear air, buy enough to have the compression escape out. I'm going to bring head to machine shop to do a leak test and hopefully, just reseat the valve.
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cts-v
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January 10th, 2009 04:55 PM