Troubleshooting advice

Dewshan said:
Yes all valves are moving... compression test had it in 50s all cylinders but it wasnt super accurate my tester not the best for large spark plug holes. Was just checking for compression. I dont think this engine was broken in much after rebuild. New coil, changed condenser, have looked at it running in the dark and did not see arcing. In tdc on the timing gear i can not get a feeler gauge in either valve on cyl 4. Is this the problem?
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Yes, are you sure the lifter is on the heal of the cam lobe?
It may not be what is causing your problem right now but when the car gets
out on the road and the engine heats up you can burn a valve.
 
I know that Ed already mentioned it, but based on the symptoms you described I would double-check the points gap.
 
Bob C said:
Yes, are you sure the lifter is on the heal of the cam lobe?
It may not be what is causing your problem right now but when the car gets
out on the road and the engine heats up you can burn a valve.
Click to expand...

With the timing pin in its dimple, #1 is at TDC on compression stroke and #4 is at TDC on the exhaust stroke. At that position, both valves in #4 are just off their seats so it is correct that he can't get a feeler gauge in those valves.
 
Dewshan said:
Pulled spark plugs again.... #2 really rich, #4 perfectly clean. Dont think its firing. It is getting spark though.
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maybe it is #2 that isn't firing?? Have you checked to exhaust manifold to see which cylinder is cold?
 
Thats it for today. Put valve cover back on. Valves are moving. Took manifolds off again and checked intake with water. No leaks! It is sealed well against block copper gasket and gland rings, proper washers and torque values. Tried several times in the past to test for leaks with starter fluid. Never got it to race.

I think im going to get a new distributor with electronic ignition. I have electronic on my sportcoupe and has worked very well over the years. Ijust cant understand why #4 spark plug is so clean. Not sure what to make of that really.
 
Have you had an opportunity to try a known good distributor? And coil? When you do the test make sure you also borrow the high tension wire that runs from the coil to the distributor. There was another thread on the site where a miss was traced to a high tension wire that was not inserted completely.

I had the electronic distributor and didn't like it. The distributor I have now is the original one except it has the modern points and condenser. I think it performs better than the electronic one. Others have good results with the electronic distributor.
 
My 1931 Coupe was doing this last summer. I cleaned the screen filter in the carb , changed the points and condenser, and then changed the coil . Runs great now. My 31 is an early model with screen in the carb which was half clogged.
Good Luck
Dan
 
If #4 isn't providing any signs of power, after 12 years could have critters plugged intake opening into #4?
 
KR500 said:
If #4 isn't providing any signs of power, after 12 years could have critters plugged intake opening into #4?
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Yes i will check that out! It was stored inside but you never know! Im also going to try new gas before i throw more parts at it!
 
You might take the bottom half of the carburetor off and clean it out. Blow out all the jets. Who knows what might have crawled in there after all the years.
 
OK, back to the basics. 1-2-3 cylinders are firing as they should. The valves for # 4 are moving and there is compression. There is spark at #4. If 1-3 are firing as they should to me that eliminates the carb, the coil, the points. after all why would it work for those cylinders and not for # 4. A test for leak at the intake at #4 shows no result. That leaves a few items; the head gasket at # 4 would be one thing, but it has compression, so that eliminates that, a clogged intake runner to # 4 as mentioned is possible, critters build nests in strange places. The odd part is that there is no wetness from fuel shown on the #4 spark plug, why, the clogged intake runner is suspect? A thought to me is compression is a result of the piston moving up and down in the cylinder with the valves opening and closing at the proper time as defined by the action of the camshaft, that action creates a vacuum that draws in the fuel, yet there is no fuel entering the cylinder the plug is bone dry. Could the cam grind on # 4 be wrong, so as the crank is turning the cycle is wrong and not creating a vacuum? If it was me before I tore anything apart I would make an adapter where I could use a vacuum gauge to see if Vacuum is created at the #4 spark plug hole while the engine is turning over. This sure is one I would like to know the answer to.
 
everyone's having twopennyworth here so here's mine...what happens if you disconnect each plug lead in turn? have you tried squirting neat fresh fuel via the s/plug holes into the cylinders and quickly re-inserting and connecting the spark plug prior to firing up. If comp good .... I'm not fully convinced yet that this is a problem specific to one particluar cylinder... 90% of carb faults are electric! :)
 
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Try the old wax crayola crayon on the exhaust manifold to see if #4 is putting out hot gases. It should melt if Cylinder is firing.
 
heDONist said:
Try the old wax crayola crayon on the exhaust manifold to see if #4 is putting out hot gases. It should melt if Cylinder is firing.
Click to expand...

That's a clever trick I never thought of. I've used a spray bottle on the exhaust of motorcycles for the same purpose. If it turns instantly to steam I know I have a properly firing cylinder. If you get water droplets, it is not.

Ken
 
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