Re: Sticking #8 exhaust valve 359

Posted by Tim Cole On 2012/5/13 14:10:52

If the valves are sticking after being serviced the inside of the guides are corroded and varnish collects within pits which then creates little wedges that close off clearances once the motor cools.

On the subject of the cylinder head I think that is an interesting issue given that engineers were fully aware that the L-head motor is subject to pre-ignition. I assume because the compression stroke creates a front that is not evenly distributed and causes diesel type combustion. The L-head motor is much more suseptible to piston noise than OHV motors.

That these rebuilt motors do it more as they age points to hot spots in the aluminum cylinder head probably from corrosion. Or perhaps the carburetors are worn and the Economizers are closing off too much under moderate throttle. I drove a 359 once that had an NOS carburetor and it did not ping.

The 356 head swap is academic, but a better solution would be to use lower compression pistons. A good machinist can turn .060 off the top in a mill. All that is required is the right specification. .060 is about one compression unit for a cylinder head. Of course for a motor rebuild the piston specification could be had from the manufacturer.

I was dealing with one of these pinging things and heard all about distributor curves and what not from now deceased experts, but I never bought it. Fortunately for the case I was handling the detonation was from over heating. The owner agrued with me that if the gauge is no solidly on Hot the motor is not overheating, even though it was spewing coolant out the over flow in the shop.

So I just fitted a 160 thermostat with out telling him what I was doing. He came in and started yelling at me that I wasn't installing the thing the right way. The car didn't have seat belts and I told him to drive it a fast as he wanted.