Fuel grade question

[nealf]

Am I doing any damage by using 89 octane in my car? The car is basically stock with the exception of a roto-faze distributor and I put a few gallons in and no pinging. Wondered how many of us use premium vs. other grades. Thanks

nealf
'70 2800CS
'73 2002
'73 2002Tii

 

[andrey]

I was about to say that 89 is fine for a USA 3.0 but then you have a 2800... that has higher compression pistions (like a European market engine) so I would try to use something higher like 91...

 

[corsachili]

I can't my CSL to run on 91 without serious detonation, but it does have the higher compression head (as yours should). I've had to retard the spark to 4 degrees BTDC with vacuum hose connected (should be about 7 BTDC) AND add octane boost. I'm going to try Toluene, but I think my car will get driven less than I'd originally planned as anything I add to the tank to raise the octane is going to also add seriously to the cost of running the thing.

 

[nealf]

my car may have a later head now that I think of it.

I need to check it out tonight. thanks.

 

[velocewest]

If it doesn't ping, you're not hurting anything. You will be able to run a little less retard on the timing if you run higher octane fuel.

For the record, all M30 heads up until the M30B35 starting in late 1988 use the same combustion chamber shape and volume. Compression is varied by piston top shape.