Jim Muller writes;
> my $0.02 into the ring(*). My Spitfire has the 1976 9.5:1 compression
> ratio instead of the more common 7.0:1, and when it was rebuilt last
> year, we kept that "feature". It's gas spec originally called for 95
> octane (yeah, right!) but the best I can get now is Sunoco Ultra at 94,
> and sometimes I wonder if there is any difference between that any other
> gas except the macho price. This engine has always pinged a little under
> full throttle, maybe worse now. (Actually, the engine in the Naugahyde
Earlier this year I rebuilt a 1500 engine, and used 11:1 compression
pistons and shaved the head, so I guess the compression is now up
to 11.5:1. When I first started using the car I was disappointed because
the engine pinged like mad (expected), had little throttle response
and was generally a dog.
So I started using Sunoco 94, things got better, I fiddled with the
timing, things got even better, I started using 104+ octane booster,
wow there's power in this engine, I changed the jetting on the Weber
carb, fuel economy and power incra=eased. Finally I switched to
Champion N11Y plugs (these are colder than the standard plugs) and now
the pinging has been eliminated.
>From experience I found the first month after the rebuilt a pain,
because there are certain variable (gas, timing, plugs, mixture etc)
which you have to fiddle with until you get the combination right.
But once you have found the correct combination, the extra power
released from the engine makes it all worth while.
Ps - if I can not find a Sunoco gas station, I usually fill up with
a 93 octane fuel, and the engine pings ever so slightly on hard
acceleration. So I just drive easier until I have to fill up again.
I was surprised that a drop of 1 octane would be so noticable.
BTW I mix my own octane booster using a 12 ounce bottle with 33% 104+
and 66% Marvel Mystery Oil. I found this to be the best combination
for my engine.
Gerry
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