General TR Winter Blend Fuel

[RJS]

Hi All,

It's been a while since I've posted. Curious one this - last Saturday it got hot and really humid here in CT (85*F+). And the TR4A started running really bad - overly rich, missing. Especially when driving slow or sitting at a stop light. Or, idle was way up around 2,000RPM. Finally traced it back to still running on winter blend fuel. I had 1/8th of a tank left and per my notes, last time I filled 'er up was 11/29/2020. Winter blend fuel is sold here in CT from Sept 15 to June 1. They mix in butane to give it a higher vapor pressure to help with starting in cooler weather. Except, when it gets hot and it's used in a a carburetted car, it tends to boil at a much lower temp. I deduced I was getting heat soak off the exhaust manifold and the fuel was boiling in the float bowls - you could smell the heavy gas fumes too.

So, quick stop at Shell for a fresh tank of 93 octane and all was well. Plus, I normally add 3oz. of Marvel Mystery Oil every fill - which apparently has a side benefit of also lowering vapor pressure.

Bob
PS: I do not have heat shields and other than this instance with winter blend fuel, never had a problem.

 

[poolboy]

Every so often during these transitional months I found I had to do a little tweaking of my carbs' mixture adjustment.
I don't remember last year it being an issue, but this year there seemed to be something working it's way thru....I only use mid grade Chevron and Shell both 10% ethanol which is what I've been burning in the TR6's as far back as I can remember.