Compression/octane

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green1

green1

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Long one here. 70 340, 10.5, purple .484, 232 at .050. Not started for 20 years, then had to pull a head for stripped out threads, Found top of #6 piston missing at top land, found the last right bank factory piston remaining in the us. Pulled other head, all good.
Last driven in 87, ex-wife, who knows? regular gas?
My question is; what octane? pump hi? mix in race gas? Actual probably 9.5 compression? How much does that cam bleed off? 110 c/l, installed straight up. (x heads, 2.02, un touched.
Thanks, guys. Don't know whether to pull it and put in a 360 low compression. Which I don't want to do. Laid off. Oh, 4.88 4 link and manual reverse, 3000 stall. Don't think a low comp will work.
 
I'd start with the 92/93 for saftey. Only a gallon or 2. Then add a gallon of 87 when you get low and after it is tuned. If it pings, no worries, just add a bunch of 92/93 to it and let it idle a few minutes so the new gas gets into the lines and up to the carb.

Try again with 89.
 
Thanks rumble, that looked like detonation on that piston, but rest are fine, randomly checked bearing; even on that rod, no signs on upper shell. Maybe it was the piston's time? (used engine bought in 1978, never took it apart).
Another ?; been welding, so haven't hooked up the mallory hyfire 7 yet, but that engine will not idle under 18 degrees initial. Set it there, then changed dist, mech only for total 36. Sound ok for the octane?
 
You have a mech. distrib. now? 18* intail, 36* total?
 
I feel sure even if it's a honest 10.5 it will run on premium with that camshaft. That's a lot of duration compared to the factory stick. As usual, Rumblefish nailed it. Sounds like a good idea. Post a video. I wanna hear it. Bet it sounds good.
 
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