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Old 05-15-2014, 11:50 AM
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I have very similar pistons in a 383 . A bit more cam. The engine does not like a lot of timing under 3,000rpm. On the first test drive, had some pinging with "light" springs. Switched to the middle springs with about 10 degrees at idle with vacuum advance disconnected and it was much much better. Still some tuning to do when the tranny is back in.

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Old 10-25-2014, 08:49 AM
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From here it looks like you detonated it. A 10-1 motor needs 91 oct gas. Iron head motors do it worse. Aluminum heads will go about one point higher on compression, before det. You HAVE to limit the timing to a max of 34 degs @ 2500 RPM. No vac advance. If you don't have a timing light with a dial, get one! Looks like you hammered on it with 50-55 degs. Bummer.
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Old 12-10-2014, 01:15 AM
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"If you're inclined to push the limits do what the factories do, put a detonation sensor on the engine. It is not difficult to install one such that when it hears pinging it kills the ignition. ... will save the motor."

THANKS FOR THIS! I'm new to building engines and for all I've been reading, I never heard about such devices.

Just got a 455 block to replace a broken 428 after dropping a valve, which the builder said may have been caused/aggravated by detonation. I got a bit paranoid after learning detonation can occur and not be heard. I'd always heard to advance timing a couple degrees at a time until you hear knocking, then back off 2 degrees to be safe. All my old higher compression engines need to be retuned for today's gas.

Not sure if inaudible detonation would cause damage like the OP had (doubtful from responses), but any is going to ruin a breakin and/or take miles off an engine's life. I had "minor" detonation for a couple hundred miles (after replacing stock 1969 points distributor with an HEI from '76 400 GP, I could never get power at higher RPMs without knocking off the line). Anyway, the 428's stock cast pistons looked good (aside from busted one), but ~1" patch of all upper conn rod bearings was worn to copper.

Looked a bit on inet...
AutoSpeed - DIY Detonation Detection - Part 1
The article questioned how well an aftermarket knock sensor works with a particular engine, because of the frequency of the knock/proper sensor to use. An example was given of an LED system that flashed AFTER the driver could hear the knock... so author tells how to build a cheap audio setup. I'll do this - can test it on my 1988 GMC pickup which knocks during acceleration when cold with timing set to factory spec (will start a thread about this - original owner replaced a 305 with a 350 using 305's computer/TBI injector).
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Old 12-10-2014, 08:01 AM
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Read the first post guys, your answering a thread a few years old.
“She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself.”

— Han Solo
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