Hi,
I'm putting an engine together, here is the setup:

* L28 F54 flattop (std bore)
* L28 rods (std)
* L28 crank (std)
* E88 (shave 4mm) mild port/polish
* N47 valves
* Felpro gasket set (1mm head gasket)
* E88 intake (port matched)
* SU's w/SM needles
* MSA headers (port matched)
* 2.25 exhuast
* .460 Cam kit

1. Question is will my compression be too high to run on California 91 octane gas?

2. What's the highest compression I could run on 91 octane?

3. What should my compression be at with the above?

4. If I'm too high what are the tricks I could do to avoid pinging or am I out of luck?

Can I ask someone for a favor and calculate that for me. I don't have any other dimensions other then above otherwise I would just ask for the formula. It will be a daily driver along with some autocrossing.

Thanks A Lot,

 

From the sound of your set up, it looks like you might be running more compression than is streetable with 91 octane gas. (i'd have to find that formula to do the math for you). In Georgia on 93 octane, 10.8:1 is about the most we can get away with. If it turns out that you are indeed running too much compression, you can put on a thicker head gasket to lower the compression to a safe but performance minded level. With a big cam and high compression like you have, you might want to consider opening up the head more than just a mild port and polish, also running with maybe 2.5 inch piping instead of 2.25. You're trying to run alot of oxygen/gas through a SOHC with that big cam, using higher compression to increase the efficiency of your charge, but your head and exhaust my be holding you back. Opening it up a reasonable level will increase your volumetric efficiency and therefore hp-Taylor

 

Using the L engine program it gives a compression of 10.06, not taking into account the head shaving, which increases the comnpression a bit ( i think, it might decrease, not sure) So you could probably guesstimate a compression of 10.1 to 10.3

Alan, Australia