Need Diagnostic Help

[ellis8500]

Gentlemen, need some help diagnosing a problem. Had the 27T out for a drive and it was running great. Suddenly it would not run at idle. Had to stop and set idle screw to a higher rpm just to limp home. Check exhaust pipe temps today and cylinder 8 pipe near head is over 608F [max on my thermometer] when the rest are in the 520-530 range. Looked at carb nozzles and noticed the side ported to that cylinder was more erratic compared to the other side. I suspect it's a valve problem but wanted to get the opinion of the experts. I'll conduct a compression check to see if No. 8 has a burnt valve. Your comments please. Thanks.

 

[ellis8500]

Did compression check, engine warm, open throttle. 1-180#, 2-180#, 3-175#, 4-180#, 5-172#, 6-175#, 7-170#, 8-180#. So I guess it's not a burn valve problem.

 

[2old2fast]

Crap in the carb , sat all winter , right , pretty common...
dave
Or a vacuum leak ..you said 8 was hot , look at that port runner , vacuum cap ??

 

[ellis8500]

Thought it might be bad gas but I had that problem last week, filled with new gas and problem went away. Baffles me that it would show up again after 30 miles of good performance. Dumped in a bottle of HEET. Got it back together, let it run for a while and now problem has gone away. But, did find a leaking valve cover gasket. I have some on hand so that's next. Thanks Dave.