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Old 04-12-2019, 04:02 PM   #18
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Join Date: Jun 2009
Location: Swampscott, 01907

Originally Posted by klr142 View Post
Shoestring, just to confirm, no combustion chamber mods aside from shaving the head? And on the ignition tuning, is it less aggressive than stock at any point or would you be able to run stock ignition timing if you wanted? I’m trying to help a friend get his car faster and he’s worried about detonation with 2mm off a 405 head on pump gas.
You’ve run it before? What was the rest of the setup and what gas did you run?
No mods, shave only. 530 head. There is less overall ignition timing than the stock map in the -169 EZ116K we use. If you're using EZ116K, you could use the -3 or even -6 pinout grounding to achieve a similar result. If not, you probably have a distributor you can crank back? The key to all this is matching cam timing to static compression ratio to target a specific dynamic compression ratio. Dynamic compression ratio of 8.0 or thereabouts seems to ring a bell. Checking the stats on our race engine, we have a K cam in a 10.9:1 B230F and that's about 7.8:1 dynamic. We run that on pump 93 octane Shell.

B230Fs were not anywhere near the advertised 9.8:1. The couple I've measured were more like 9.1:1. I had to cut the head in my daily 0.040" just to get to 9.8:1, on a stock head gasket. Ran it for years on 87 pump Shell with an A cam with no problem. Dynamic compression on this is about 7.5:1. Recently switched to a V cam, still no problem. This is an EGR car, so that might be helping me out a little.
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