Robotsan
Club Member
Hi all,
I'm looking at a 73 240z which had an engine rebuild a few years ago - inc a reconditioned N42 (I *think) head, but also chrome alloy piston rings were installed instead of the standard (cast iron?) ones. I spoke to the mechanic who looked after the car for several years (he didn't do the engine work though), and he said (I paraphrase) chrome alloy rings are intended for racing, and they are not seating 100% perfectly, which is allowing air through causing a very slight compression issue, so it runs a little rich and causes a little puff of smoke out the exhaust.
Does that make sense for anyone with the knowledge here?
He says its not a problem for the car now (apart from a little smoke and less MPG), but it does mean with these rings installed, the engine can't have webbers or any other triples installed, as the engine then wants too much air and the car can't run any richer. He knows because the previous owner got him to install webbers on it and it didn't play nicely so they were removed.
So if I was to purchase the car, I would likely have these changed and the engine thoroughly inspected. Question I have is what approx cost am I looking at to do that?
The mechanic I spoke to did refresh a lot of the rest of the engine bay - new alloy rad, all pipes replaced, water pump, brake master cylinder and almost everything else, and a machine shop did refresh the replacement head. He said the engine was running really well apart from the aforementioned issue, so hopefully there wouldn't be any nasty surprises if I did have it stripped down and rings replaced.
I'm looking at a 73 240z which had an engine rebuild a few years ago - inc a reconditioned N42 (I *think) head, but also chrome alloy piston rings were installed instead of the standard (cast iron?) ones. I spoke to the mechanic who looked after the car for several years (he didn't do the engine work though), and he said (I paraphrase) chrome alloy rings are intended for racing, and they are not seating 100% perfectly, which is allowing air through causing a very slight compression issue, so it runs a little rich and causes a little puff of smoke out the exhaust.
Does that make sense for anyone with the knowledge here?
He says its not a problem for the car now (apart from a little smoke and less MPG), but it does mean with these rings installed, the engine can't have webbers or any other triples installed, as the engine then wants too much air and the car can't run any richer. He knows because the previous owner got him to install webbers on it and it didn't play nicely so they were removed.
So if I was to purchase the car, I would likely have these changed and the engine thoroughly inspected. Question I have is what approx cost am I looking at to do that?
The mechanic I spoke to did refresh a lot of the rest of the engine bay - new alloy rad, all pipes replaced, water pump, brake master cylinder and almost everything else, and a machine shop did refresh the replacement head. He said the engine was running really well apart from the aforementioned issue, so hopefully there wouldn't be any nasty surprises if I did have it stripped down and rings replaced.