My son and I found this while running the car, I can adjust the timing and gas mixture and it seems to cure this, is there something else going on here, like a leaking intake manifold. When I first bought the car, number four exhaust valve was stuck open. I can replace the gaskets on the manifolds, remove the head, possibly change the valves and springs to stainless valves. Is this a good plan?
Compression is around 35lbs in all cylinders, if I add oil, the pressure seems to go down a pound or two or hold the same.
I think your timing is a bit retarded - make it a bit earlier and then the gas mix would have time to burn until the exhaust valve opens.
The exhaust manifold will bend if you drive much as hot as in the picture.
The non improved compression with oil suggests you have slightly leaking valves, a valve job lies in your future
Hmm ... I thinking the spark is retarded too much, so the spark plugs are firing late when the piston is already going down in the cylinder. This can also happen when the air/gas mixture is too lean. That is the dash adjustment for the carburetor being set wrong ... or a leak in the intake manifold.
Lean mixture and/or late ignition timing can cause the overheating.
If it has the original two piece valves, then yes, it is a good idea to change them out. They have been known to come apart. There's a lot of T's out there running at 35 psi compression, but that's lower than I would like. Weird that adding oil brings it down. The fact it didn't bring it up makes it sound like your problem is in the valves. Plenty of folks would tell you you need to do a complete rebuild on an unknown engine. If it were mine, I would run it for a while and see how things go. But that's just me.
Dang. 3 of us typing at once.
Ha ... yup. :-)
Joseph, my son and I used a Wankel rotary engine in an old snowmobile for a number of years and the only time the exhaust pipe would turn cherry red was when the rubbing block on the points was wearing down and the timing was getting late. A pain until I figured it out.
Yep, timing and mixture. :-)
My 24 has had no red manifold issues yet and it's just plum wore completely out. Two of the cylinders are so bad they will not start the engine.
Yet, when it's running, they all pick them off perfectly. Two piece valves all around. Yes, in time replace those valves.
20 years on and yet he thinks he's 98 (28) years old.
Tough old bugger. Get what I'm saying Joseph? They can be a bit weak (or severely so) and still run like a million bucks!
OK, maybe a couple thousand bucks.
From the Junktard Mechanic, I personally wish you'd worry less about compression and worry more about the timer and the carb if the valves are half aXXed and doing their job.
You'll get it sorted out!
(Message edited by duey_c on December 03, 2017)
This is my old #4 exhaust valve. It broke apart one day and I shook the pieces out of my muffler. It got real hot like that too back then, 1995, but I can't remember if having to fix the valves made that problem go away. It still gets real hot if I forget to advance the spark.
If the manifold is getting that hot, your exhaust valves are running hot too! They will be burnt and warped. You need to do a valve job and re-set the spark and set your carburetor a little richer.