Running on 7 &1/2

[Reds34]

I was also wondering if the higher octane fuel "ungummed" a valve.

Red

[tubman]

I know it's asking for trouble, but you could try using the 91 octane fuel again to see if the problem returns. I am just ruminating here, as I have always been a "If it ain't broke, don't fix it" type of guy.

[Ziggster]

I can’t imagine 95 octane solving any issues for these ultra low compression engines. The highest octane fuel we have here in Canada is 94, and it’s around CAN$2.00/L.

[Mickd]

Yeah Red. Might've "ungummed" a valve. But remember, the compression wasn't too bad. And I'm hearing you other boys about low octane & low compression engines and all that. AllI know is, it's running fine now 🤔

[38 coupe]

Classic symptom of a slow closing valve due to getting gummed up. Will have good compression when cranking on the starter but won't seal when running. At the slower cranking speeds there is enough time for the slow closing valve to land on the seat that you measure good compression. When running at several hundred rpm the valve doesn't seal and you get a miss. I run the cheapest swill available at the pump, but add marvel mystery oil to it occasionally to keep the valves happy.

[Mickd]

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That's a damn good point 38 Coupe. You might have hit the nail smack on the head!
Thanks for that

[aussie merc]

want to stop valves sticking add about 50mls of two stroke oil to a tank as modern fuels are dry [little to no oil residue] wont smoke but it helps them not to stick

[Mickd]

Well, the other thing I've been doing since using 95 is to add upper cylinder lube, primarily to protect the valve seats so it's all making sense.
I could probablg try going back to 91 and continue with the lube. Then again, I may just keep up with the lube & the 95.
Next time I pull the heads I might even replace the valve springs. A couple of them had a bit of a bow in them from what I recall.