When you say stock, are you talking about an engine that has never been apart or had any significant work since it left the factory.  Or is it an engine that has been rebuilt, trying to keep it as close to stock specs as possible?  There can be significant differences, depending on who did the rebuild and the attention to detail.



Lawrenceville, GA

Mine has a dieseling effect when you power brake and try to rev a little but when going down the road and flooring it it diesels for a split second almost cant even notice it and then it gone.

That's interesting as the '56 LOM dual advance chamber (retard feature) was supposed to correct that.

I assume you still have mechanical points and base timing is set @ OEM or has it been bumped? Fuel quality also varies from pump to pump and area to area. How do your plugs read? Your first step may be to use premium fuel (if there is still such a thing). The advance feature within the DIST may also be worn and out of spec.

Make sure secondary IGN is in good shape. You could once put a carburetor car on a drip to break up carbon.

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I have wondered about this myself.  Most stock Y Blocks are not high compression engines.  My 1955 292 has been bored .060, squared, decked and align honed with flat top pistons and no valve reliefs. It's running stock 1957 G heads that have had the surfaces cleaned up with no excessive milling and composite FelPro head gaskets. I also have a 1957 distributor in this engine with 10 degrees advance on the crank and 38 degrees total timing.  I use 93 octane pump gasoline.  This engine runs great and does not run on or knock.   Should I use high test?

Question, what octane level are people running in their stock Y`s?

Mine has a dieseling effect when you power brake and try to rev a little but when going down the road and flooring it it diesels for a split second almost cant even notice it and then it gone.

Im wondering if the 87 octane regular I am running is just not up to par.

Either that or I need to back timing off some but I never had a too advance engine act like this one is so I am wary if this is the cause.

Only other option I could think of is maybe carbon build up from running the engine at idle over the years till I got to this point.

Anyways just curious what other people are running octane wise.  Might need to upgrade to middle grade on this old engine as that is 89 octane around here.


1956 Ford Fairlane Town Sedan - 292 Y8 - Ford-O-Matic - 155,000 mi