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john charlton · 09-30-2020, 03:04 AM

I think RAY 64 has put me on the right track . The ONLY logical explanation is a sticky valve most likely the exhaust . At cranking speed the valve seats in time for good compression but at idle speed the sticking valve does not get time to seat . The fact I "cured" it by the last distributer swap was a coincidence . My starting and stopping heat cycling etc etc has freed it enough . The proof of the pudding will be an extended road test . Could be many engines have lazy valves but revolutions stay low enough that it does not show up . I will get some "sea foam" or similar and give it a dose. Thank you all very much for your suggestions .

John in sunny breezy morning Suffolk County England .

09-30-2020, 03:04 AM	#17
john charlton Senior Member Join Date: May 2010 Posts: 1,304	Re: Mystery missfire . I think RAY 64 has put me on the right track . The ONLY logical explanation is a sticky valve most likely the exhaust . At cranking speed the valve seats in time for good compression but at idle speed the sticking valve does not get time to seat . The fact I "cured" it by the last distributer swap was a coincidence . My starting and stopping heat cycling etc etc has freed it enough . The proof of the pudding will be an extended road test . Could be many engines have lazy valves but revolutions stay low enough that it does not show up . I will get some "sea foam" or similar and give it a dose. Thank you all very much for your suggestions . John in sunny breezy morning Suffolk County England .