What factors determine pump gas compatability? My 355 has roughly 11:1 compression. It runs good on a mixture of 50/50 110 octane and 93 octane. I'm just trying to figure out how to adjust my timing to run on straight 93. Or what other things I might need to change in order to run only 93 octane.

Off the top of my head, timing, spark plug heat range, cyl. head material, comp. ratio, rpm's, jets and i'm sure a few more things but thats a start. Ralph

I don't remember exactly what I set the timing at, I'll have to check it tomorrow. The heads are aluminum Dart Pro 1's, the plugs are FR5LS, the CR is roughly 11:1, jet's are sec. 87 pri. 80. What do you mean by RPM's? Thanks!!

You first need to find your effective or dynamic compression ratio as it is called here.
This is determined primarily by where the intake valve closes & can be calculated on Pat Kelley's site by using his DCR calculator here:
Pat's site (http://cochise.uia.net/pkelley2/)

Next you need the correct tune up for your combo assuming cylinder pressure is not too high.
This includes the timing curve, mixture engine temp. etc.
Also, in most cases the tighter you can keep the quench the happier your engine will be.

Also, what will work in a 2800# nova will not work in a 4000# deal because of the load imposed on the engine.

Spark plugs have nothing to do with detonation unless they are the wrong ones & running too hot which will cause preignition which will lead to detonation when they become a "glow plug" & colder ones will not bandaid a bad tune-up.

In most cases, 11.0 is not my choice for a street engine on pump gas but is doable with the right heads,cam & tune-up.

Good luck in your quest for a happy pump gas engine :D

Here is a caveat......WE DON'T HAVE A CLUE WHAT WE ARE BUYING WHEN WE GO TO THE PUMP!

Think you do?
Ever see the truck that delivers the fuel?
Does it say Shell? Texaco? Chevron? Usually it bears the name of a trucking company. Remember the good old days!

Ever bother to find out what is really in that pump gas?

I have here in Oregon. All it takes is an email to the state fuels division....it is all regulated.

Does it contain alcohol? Is it oxyenated? Are you even close on jets?

My engine builder once said, do you really want to take a chance on your $6K engine with (at the time) $1.50/gallon fuel?

Build it with CR that will be safe even if you get a load of crap in the tank.

So we went with a 9:1 468 that only managed high tens. ALWAYS on pump gas....whatever it was.

Ron

Thanks for the added info Mike...i assumed he was looking for the easy to understand info but what you say is right on. thats what i meant about the plugs too. As far as RPM i was refering to how quickly it builds and what your max is as alot of stock distributers start to do odd things under acc. Ralph