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I'm faced with this dilema; while having my original L71 heads redone (guides, seals, etc) I thought it would be a good idea to have the cylinder walls inspected. At some point in time the block had been bored .030 which is why my mechanic believes the current condition exists. His assesment is that somehow when boring there was some sort of irregularity in the process because you can feel a circular depression (he estimates about .008) around the entire cylinder in almost all the bores. His suggestion is to pull the motor and bore (minimum amount)it out correctly. He also indicated that had he not seen this with his own eyes he wouldn't have believed it given how strong the car ran. I'm wondering what you all fell about boring this out further and suggestions as to how far I can go before I encounter further problems. Also since I'll be needing new pistons what's the consensus for brand of piston. The engine is powerful enough so I'm not looking to gain additional power. I suppose there will be enough gains just by the necessary corrective measures. Thanks in advance.
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Re: engine rebuild
find a engine builder with a dial bore gauge that reads in 1/10,000 of a inch to check the cylinders. engines with lots of miles will get a step at the top of the bore where the rings stop on the up stroke. this is called a ridge and this is maybe what he is feeling. -
Re: engine rebuild
Thanks for the quick rsponse Clem but I failed to indicate the depression appears midway in the cylinder. We're both aware of the ridge at the top of the cylinder, in fact you could hardly feel that. Previous owner told me the engine had been rebuilt in the early 80's and with the limited use some of these cars see it's no surprise the uppeer ridge wasn't there. In fact you can still see the cross hatch marks on the cylinder bores.Comment
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Re: engine rebuild
Gary:
If it were mine and the car ran good without smoking and I wasn't looking for maximum power, I would have to question the wisdom of spending another $1000-$2000 fixing something that isn't broken. After all, apparently it's been this way for twenty years. But, then, something must have been wrong or you wouldn't have pulled the heads, would you? This would make me question why the heads are being worked on. As you stated (limited miles) these engines don't get much use so why would you need to work on the heads.? Maybe someone mistook, for example exhaust smoke symptoms for bad guides, when it realy was your rings doing the hoochie coo in the cylinder walls.
If I didn't have the personal knowledge, I would definitly get a second party personal inspection as Clem suggested.
MikeComment
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