Here in California you can walk into many 76 stations and buy 5 gallon
cans of 110 leaded racing gas because of detonation. The off road
motorcyclists use it. I used to mix it with pump gas for my Judson
powered 948 Sprite before I wised up and dropped a 1275 in it. I now use
only Chevron 91 octane with no problems. I expect no problems with my BN2
motor when it is installed being such a low compression engine.
Mike MacLean
56 BN2
60 Sprite
Bob Spidell
> re:
>
> "I'm not convinced that the fuels that are available today, particularly
> in
> CA I understand, are good enough to handle the amount of advance that the
> original distributors can produce. "
>
>
> 91 octane ((R+M)/2) is the best you can get in CA (unless you sneak a
> little avgas--
> 100 octane--in the tank ;). But 91 octane is 91 octane, in CA or any
> other state (the
> testing method is standardized), and I believe in the other CA (Canada) as
> well.
> I believe 91 octane ((R+M)/2) is equivalent to 95 octane using the "motor"
> ("M") method
> (or is it the "R" method?) alone, which I believe is what is used in
> Australia and GB
> (but I'm not positive).
>
> Question is, is 91 enough? I've run for 90K miles or so on mostly 91
> octane CA
> gas, with no problems that I know of, but my engine doesn't have
> particularly
> high compression (don't think I got a great ring seal on the last
> rebuild).
>
>
> bs
>
> --
> ***************************************************************
> Bob Spidell San Jose, CA bspidell@comcast.net
> '67 Austin-Healey 3000 '56 Austin-Healey 100M
> ***************************************************************
>
> -------------- Original message ----------------------
> From: "Michael Salter" <msalter@precisionsportscar.com>
>> Hi Ken,
>>
>> I would say, largely because of the way the pieces have broken off the
>> top
>> ring land, that there is little chance that that damage is attributable
>> to
>> anything but detonation. The other marks in the pistons are probably the
>> result of the broken off pieces hammering around before they went out
>> the
>> exhaust port.
>>
>> There appears to be a cracked piece just hanging on in this picture.
>>
>>
>>
>>
>>
>> I have seen similar damage several times particularly on MGBs and would
>> suggest that you check your distributor advance curve carefully both
>> before
>> and after you have the engine rebuilt.
>>
>> I'm not convinced that the fuels that are available today, particularly
>> in
>> CA I understand, are good enough to handle the amount of advance that
>> the
>> original distributors can produce.
>>
>> Detonation can be quite serious at highway speeds but completely
>> inaudible
>> to the driver. You can buy knock sensors which will turn on a light when
>> detonation is occurring; might be a good investment.
>>
>>
>>
>> Michael Salter
|