rags Posted May 2, 2010 Share Posted May 2, 2010 I agreed to look at motor for another Z guy who has been having oil consumption issues. Initial findings were some cracks in the head around the each of the valve guides. Figured this was a simple fix as I had a few good P90's and I'd just swap one on and everyone would be happy. Not so fast. I swap the head and although better, the oil burning continues. Since this is a fresh motor with about 1500 miles on it, I figured the oil that was coming down from the guides was enough to keep the rings from seating but before I ripped the motor completely apart, I wanted to rule out the turbo. So, I removed the turbo, pulled the intercooled and swapped in a new set of plugs. After running for 15 minutes, the cloud is back. Pull the PCV hose and see evidence of crank case pressure. Puffs of smoke from the PCV tube and valve cover breather. Gotta be the rings right? So I start with the motor removal. Get the motor out and begin breakdown. After getting the motor out and broken down to the short block on the engine stand, I stop and in deep thought about how this could be burning oil so bad, start to wipe the oil from the top of the pistons. While doing this I hear "clunk", "clunk", "clunk". WTF?! It's coming from the pistons moving horizontally in the bore on the wrist pin! From the naked eye, this seems very excessive. Quick measurement comes out to .038" movement in the bore Today I'm going to measure one of the pistons and the actual bore diameter to see what we have. So far it seems as if the pistons are too small for the bore which I am told is stock, never bored. This is turning into a total engine rebuild which I didn't want to do. I'm starting to feel for the owner as it seems all of the money he spent on the original headwork and the purchase of the custom pistons was a waste. I keep asking myself why did I get involved??? Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted May 2, 2010 Share Posted May 2, 2010 Yikes, that sounds like the machine shop that did all the work, did the owner dirty. Where did this rebuild happen? Quote Link to comment Share on other sites More sharing options...
rags Posted May 3, 2010 Author Share Posted May 3, 2010 Did some measuring today. Stock diameter L28 pistons. .030 overbore on the block! :lol: Now to find a stock bore block, clean it up, swap in the rotating assembly and see what happens. Joe Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted May 3, 2010 Share Posted May 3, 2010 I would have expected a decent shop to have noticed the loose fit in the bore! When I saw the title I was thinking someone was running their diesel on citronella oil. Quote Link to comment Share on other sites More sharing options...
teknomage Posted May 26, 2010 Share Posted May 26, 2010 I have been saving up about 2 gallons of filtered bacon oil, gonna fill my Z up with it just before going in for an emissions test at about 10:30-11 am just before lunch break. The looks on faces should be worth the $15 even if I do not pass... Quote Link to comment Share on other sites More sharing options...
kj280z Posted June 12, 2010 Share Posted June 12, 2010 I agreed to look at motor for another Z guy who has been having oil consumption issues. Initial findings were some cracks in the head around the each of the valve guides. Figured this was a simple fix as I had a few good P90's and I'd just swap one on and everyone would be happy. Not so fast. I swap the head and although better, the oil burning continues. Since this is a fresh motor with about 1500 miles on it, I figured the oil that was coming down from the guides was enough to keep the rings from seating but before I ripped the motor completely apart, I wanted to rule out the turbo. So, I removed the turbo, pulled the intercooled and swapped in a new set of plugs. After running for 15 minutes, the cloud is back. Pull the PCV hose and see evidence of crank case pressure. Puffs of smoke from the PCV tube and valve cover breather. Gotta be the rings right? So I start with the motor removal. Get the motor out and begin breakdown. After getting the motor out and broken down to the short block on the engine stand, I stop and in deep thought about how this could be burning oil so bad, start to wipe the oil from the top of the pistons. While doing this I hear "clunk", "clunk", "clunk". WTF?! It's coming from the pistons moving horizontally in the bore on the wrist pin! From the naked eye, this seems very excessive. Quick measurement comes out to .038" movement in the bore Today I'm going to measure one of the pistons and the actual bore diameter to see what we have. So far it seems as if the pistons are too small for the bore which I am told is stock, never bored. This is turning into a total engine rebuild which I didn't want to do. I'm starting to feel for the owner as it seems all of the money he spent on the original headwork and the purchase of the custom pistons was a waste. I keep asking myself why did I get involved??? Man I am hoping that once that motor is done that it is finally resolved - The owner has been jerked around for way too long and I know Joe is the right guy to get it right! I know it's a pain but hopefully another killer Z will be on the road soon! Quote Link to comment Share on other sites More sharing options...
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