VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 1928 - Two Plugs Fouled / Two Perfect

Our 1927 Chevrolet Landau has a 1928 engine. The engine hasn't been running great recently, so I pulled the spark plugs and the two plugs at the front look perfect (electrodes greyish to brown), but the two plugs at the rear of the engine are very black and sooty. The difference between the front plugs and the rear plugs is night and day. I am thinking maybe this might be indicative of something with the valves or push rods etc., but would appreciate any thoughts on what might be causing the issue.

Here is a photo of the plugs from front to rear(firewall): [img]https://photos.google.com/u/0/album/AF1QipNSJ02KNf5uvOx5nSNkXcUWhtUFCy73yhhdCNO8[/img]

I would start with the point setting and an inspection of the inside of the cap. Next would be a compression check.

Black plugs are an indication of a rich charge from the carb. Normally it is all 4-6 plugs.

One other thing to check is valve clearance. If you have a valve that is not closing properly you will have both compression and combustions issues that will cause fouled plugs.

Be sure that the joint of the inlet manifold to the head does not allow "false air" to be drawn into the front inlet port.

Hi Chuck64
From what you have said, I would suspect a blown head gasket across the center of the head gasket between cylinders #3 & 4. The first thing I would do is compression check to see if cylinders 3 & 4 are a lot lower than the front 2 cylinders. The back 2 cylinders will be low and probably about the same pressure. This would cause fouling of the back 2 cylinder plugs because the cylinders do not have enough compression to fire efficiently like the front ones do.

If you find out this is the problem and need any engine gaskets, please check out our website www.marxparts.com
Regards Bob at Marx Parts