I could've used this thread on may when I had my 302 built to 9.5:1 iron head comp 287th7.( mutha thumpr)
My dad is the veteran mechanic that has forgotten 10x more about engines than I will ever know. With that stated, I want to share some of what I have been able to pick up from him over my years of building engines with him. In the 90's we built a nice 350 SBC with swirl port (not vortec) center-bolt heads. We figured it to be right around 9.5:1 compression. I ran the **** out of that motor on pump gas and, it ran great. In an '86 Monte Carlo, I ran mid to low 14's et's on the 1/4 mile - all on pump gas. We then stepped it up and built a '76 Nova with a 454 BBC that we calculated to be slightly under 10.5:1 compression. When we drag raced it, we mixed in racing gas with some pump gas and cranked up the timing; we ran low 11's. When we were driving it on the street we ran pump gas and turned down the timing a bit. I couldn't tell the difference in engine sound. Although performance on the street wasn't measurable, I'm sure it would have only been a few tenths slower in a 1/4 mile if on pump gas only. It ran like a ****d ape no matter what. Most recently I've been running a stock '65 401 nailhead that is "estimated" to be at 10.25:1 compression. I have never ran anything other than pump gas in that engine and, it has always ran great. My point with all these obscure stories is rather simple. Unless you are going to be competing on the strip or routinely running your car on a ch***is dyno for self satisfaction, you are going to be happy as hell building whatever stock nostalgic motor you want to build - no matter the octane rating of fuel you choose to run. If your engine sounds a bit "pingy" on the road, put your timing light on your engine and adjust it accordingly. Ignition timing might just be the common man's golden hammer in a situation like yours. Just my two cents.
Yeh, FG, I remember reading about Crowers ideas, but, never heard anything since that article. Maybe with the new chamber designs it might work.
SO----Is there a chart to tall you what compression you have by measuring compression at the plugs with a compression gauge? AND what compression with fac timing will run safely on 93 octane pump gas?
I have looked at high compression pump gas motors for a while as well. Falcongeorge speaks well of the reasons. I have seen 12:1 on 93 octane run fine. Flame propagation/travel is key. Flat tops or even a dish, I have seen some run the pistons slightly out of the hole as well. Chamber design, cam grind,LSA every thing he says is right on. A couple friends went to several Vizard clinics and tried a few of these tricks with some success, with carburetors not fuel injection and electronic timing either. Its not rocket science but you do need to do your homework and cross your eyes and dot your ts because it truly is a complete package if you don't want catastophic failure.
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