burnt exhaust valve - 72' Cadillac Eldo

[orbitgyrl]

Just took my '72 Caddie Convertible in for it's spring tune up and my mechanic gave me some bad news. Says I have a burnt exhaust valve or seat causing one of the cylinders to misfire. Bought this car last summer and was told by the prior owner that the lead additive was not needed in this car, and I wouldn't have to add it when filling it up. SO. The car has been running on unleaded gas and they think the burnt valve/seat is due to this. The estimate is about $1100 to replace both sides and the head gasket. Anyone else out there run into the same problems? Sorry to sound like such a dummy, but in what year did they start making the hardened seats so you could just fill the car up with unleaded gas and it was fine?

Thanks!
Tracy

[Kevin5255]

i have a 71 eldorado and i read in the 1971 owner's manual that 1971 was the first year that all caddys were made to run on unleaded gas. so your 72 seems to be made to run on unleaded

[MagicRat]

Kevin is correct. Your mechanic is wrong.
There are MANY reasons why an engine will misfire on one cylinder, most of them are cheap to fix.

But the ONLY way to detect a burned exhaust valve is with a cylinder leak down test. I suggest your mechanic may be trying to stick you with a really expensive repair thats not required. Take it to another mechanic. Have them do a leak down test on all cylinders.
If they do find a leaking exhaust valve have them check the exhaust valve lash (clearance) for that valve before statring the repair. The lash might just be too tight, allowing that valve to hang open a bit.

Finally, why does your mechanic want to charge you for BOTH cylinder heads? If he says you have only ONE exhaust valve thats burned, its easy to identify that bad valve so you need to do only ONE cylinder head.
As I said, he is recommending unnecessary repairs.