Hi, does anyone know why the exhaust valve stem is machined down from .373" to .340" at the top of the valve for about 1/4" in length as this causes the valve stem seal to come out of engagement with the valve stem when the valve is fully open? This is on a 1975 350 engine. Any help would be greatly appreciated.
Hi Larry the engine came to England a few years ago having been overhauled at a shop in the US. The reason this had come to my attention was that I have removed the valve cover to replace the gasket when I noticed that on number one cylinder the exhaust and inlet valve springs were on the wrong valves, so although the engine had been running ok I thought it only right to put it back as it should be. This is when I saw the valve stem issue I described. I have now looked at the other exhaust valves and they are all fitted with stem seals, do you think I should remove the seals as Buick must have designed for some stem lubrication on the exhaust valve. Thanks
Correct, Buick DID NOT use seals on the exhaust valve guides. Reason was for lubrication of hotter running exhaust valve AND there is no vacuum draw on the guide as there would be for the intake valve, only pressure as the exhaust goes up and out. You CAN run seals on the exhaust side BUT you need to change the exhaust valves to ones with a smooth stem (no step) AND cut the guide down. The advantage to doing the above is it lessens the chance of oil burning in the exhaust system. I've done this on my Turbo Buick and my 350 GS with no issues
Hi Mark thanks for your comments it's only a stock motor so I guess the engine builder didn't know what he was doing when he fitted the stem seal on the exhaust valves and thought he was doing the right thing.
Sounds like the guy was assuming it was like a Chevy. I'd pull the pan and Plastigage the bearings just to be on the safe side
