Lower than expected cold crank compression
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Joined: Jun 2006
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From: san antonio
20% and 30%, assuming the test was done properly and the data correct, is way too much. I would be rebuilding the top end with anything over 10%.
Last edited by djl; Mar 8, 2017 at 12:20 PM.
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From: Poolville
Sorry to hear of your issue man,
Definite problem there. Either the bore is off or the rings were not seated properly. How many miles on this build? I think you're gonna have to take it back down and have the pistons and bore's checked..... Earlier you stated you had to pull timing out to quiet it down. Is it possible it was running to Lean for break in and the rings got scored? Too much heat... can you post a pic of the plugs..... I believe MattVA had a very similar issue......
Definite problem there. Either the bore is off or the rings were not seated properly. How many miles on this build? I think you're gonna have to take it back down and have the pistons and bore's checked..... Earlier you stated you had to pull timing out to quiet it down. Is it possible it was running to Lean for break in and the rings got scored? Too much heat... can you post a pic of the plugs..... I believe MattVA had a very similar issue......
Last edited by 98hotrodfatboy; Mar 8, 2017 at 11:35 AM.
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From: WA State
Sorry to hear of your issue man,
Definite problem there. Either the bore is off or the rings were not seated properly. How many miles on this build? I think you're gonna have to take it back down and have the pistons and bore's checked..... Earlier you stated you had to pull timing out to quiet it down. Is it possible it was running to Lean for break in and the rings got scored? Too much heat... can you post a pic of the plugs..... I believe MattVA had a very similar issue......
Definite problem there. Either the bore is off or the rings were not seated properly. How many miles on this build? I think you're gonna have to take it back down and have the pistons and bore's checked..... Earlier you stated you had to pull timing out to quiet it down. Is it possible it was running to Lean for break in and the rings got scored? Too much heat... can you post a pic of the plugs..... I believe MattVA had a very similar issue......
Piston showed no signs of knocking at all. Knocking wasn't audible either while riding or on the dyno. It was something the ion sensor was picking up.
It's possible that I just didn't get a great break in for the rings.
Grabbed a set of take offs and getting them rebored, new pistons and rings.
Add some pictures. Those were new plugs installed for the dyno.
Last edited by ChickinOnaChain; Apr 8, 2017 at 03:24 PM.
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From: poway
Is that coolant on the piston?
Look at the valve relief, It's no longer an even radius.. Were the valves hitting the edge of the pocket? CP pistons and stock valves shouldn't hit. How much was milled off the heads..
As stated 20/30% leak is too much.. One plug don't look too hot.. I'd also made sure the valves are sealing. Could be leaking from more than one place.
Look at the valve relief, It's no longer an even radius.. Were the valves hitting the edge of the pocket? CP pistons and stock valves shouldn't hit. How much was milled off the heads..
As stated 20/30% leak is too much.. One plug don't look too hot.. I'd also made sure the valves are sealing. Could be leaking from more than one place.
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Joined: Jun 2006
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From: san antonio
I'm with Mr. Headflow on the possible valve to piston contact. Could be the photo but looks like the outside edge of the intake valve kissed the piston. Better mock everything up and check clearance when you put it back together.
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From: WA State
Coolant spilled when I removed the heads.
Not stock valves, 1.9 and 1.57.
When I get it put back together and check squish, I'll check valve clearance as well.
I zoomed in on my picture, I think it's just the flash that distorted the relief pocket.
Not stock valves, 1.9 and 1.57.
When I get it put back together and check squish, I'll check valve clearance as well.
I zoomed in on my picture, I think it's just the flash that distorted the relief pocket.
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From: poway
Not sure about the valve relief as a 1.9 should clear no problem but I would check it.
Sounds like you are going the right direction with cylinders and pistons plus having the porter check the heads..
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From: WA State
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From: poway
I think you are OK as far as clearance goes but there sure seems to be a lot of oil.. Can you see any leaking down the guides? That amount of oil and leads me to believe something was wrong it either the valve seals or rings. Maybe second rings in upside down?
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From: WA State
The exhaust ports show lots of oil getting through there as well.
For some reason or another the rings didn't set and oil was coming up from the crankcase.
That could also be source of the initial knocking that brought me to where I'm at today. Oil mixed in with fuel and air will affect resistance that the ion sensor is looking for.
New cylinders came in today so I'm rebuilding. Hope to have it done tonight and hit the road tomorrow for the break in.
Pistons and cylinders were matched so I shouldn't have any ring set issues.
For some reason or another the rings didn't set and oil was coming up from the crankcase.
That could also be source of the initial knocking that brought me to where I'm at today. Oil mixed in with fuel and air will affect resistance that the ion sensor is looking for.
New cylinders came in today so I'm rebuilding. Hope to have it done tonight and hit the road tomorrow for the break in.
Pistons and cylinders were matched so I shouldn't have any ring set issues.
Last edited by ChickinOnaChain; Apr 8, 2017 at 03:25 PM.