Reply With QuoteThe compression ratios that are shown at Flatlander racing are not correct. Some are misprints..IE..they are showing some smaller chambers with lower(?) compression ratios.
Last catalog I have showing part # 2399F shows 8.73 to 1 with a 119cc head. They measure with a .0385 thick head gasket but do not mention deck height. Since they don't give me a dome CC, I can't calculate whether they are figuring the compression ratio at 0 deck or not. TRW used to use .020 in the hole for calculations but no mention in this catalog.
Since you are at sea level and want to use pump gas, I'd think you would want to lower the compression ratio. If you were at 4500 ft like I am, I'd say o.k. I would definately use some sort of octane booster.
Here's some ways you can do this. The piston dome of .095 is no doubt solid, so you could machine the dome off in a lathe. Since you would be lightening the pistons all equally, a slight overbalance(engine balance) would occur. You wouldn't need to rebalance your engine. Using a 4.350 bore size gasket .040 thick and assuming you have 0 deck would get you to 8.28 to 1. If you wanted to go lower (future use when you want to add more boost), then a .062 thick copper gasket (you have to O ring the block) at 4.500 bore size gasket will get you to 7.93 to 1. All these calcs assume 0 deck. If you are .020 in the hole, that's worth a drop of about 1/4 point in compression.
This is just food for thought. Many engine builders have many combinations, but my thought is to get a lower compression ratio due to todays junk gasoline and the fact you are at sea level, which means a lot. Plus the fact guys with blowers like the idea of being able to turn up the boost later on.
Infomaniac (unless he got blown away by a tornado) is sure to have more input and probably a whole lot more experience with gasoline. The number one reason I went to alcohol years ago is not to worry about octane or elevation.
