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Originally Posted by Hex0rz
You're right, it does need to be pulled. But I'd rather be educated the fact so as not to repeat the same mistake again!
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ok, fair enough.
1.)low
2.)most stock small blocks like about 7-10* initial timing (assuming its still carbed), and that is with the vac advance disconnected and plugged.
3.)idle should be right about the 750 mark, though some say as low as 650.
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What do you mean wrong plugs? My brother bought the plugs so I dunno. I know they threaded into it just fine atleast... or are you talking about heat range?
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uneducated response, shooting in the dark. no way will a plug in the wrong heat range cause an engine to completely lose compression on a cylinder. i run plugs in my 86 305 that are 6 full heat ranges colder than stock, and have yet to have a problem out of it. still cranks around 170-180psi on all 8 holes, and it regularly gets heated up to 240+ when its running. we use it as a derby engine.
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If the compression ratio is 8-9:1 then why go higher octane than 87? Is'nt that the 87 octane range for CR? Because then would'nt that just be dependant on ignition timing?
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static compression ratio has very little to do with octane requirement, dynamic compression ratio is what really determines it. dynamic compression ratio actually measures the stroke of the crankshaft after the intake valve opens, and takes into account stroke length and rod length along with cam specs. i know plenty of guys running 10:1 on 87 octane. you just have to have a cam big enough to support it.
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I did time the engine to 8 degrees BTDC with vaccum advance disconnected. Thats when a week later it did this. I don't get it...
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well, you are dealing with a 30 year old engine, that if stock, has a) cast pistons, and b) crappy combustion chambers. you said it was pinging. the reason we use hypereutectic pistons and forged pistons now is that they are less prone to breakage from detonation (pinging). cast pistons are known for being especially weak under conditions where detonation is present. now take into account the combustion chambers, they're prone to hot spots, which will cause preignition which is another form of pinging, when the A/F mix is ignited before the piston reaches TDC, which is absolutely brutal on the piston, as the explosion is trying to force the piston back down the bore, and the rotating assembly is pushing it towards the top. then you get into carbon deposits over the last 30 years, which create more hot spots on the pistons or the combustion chamber, wherever the deposits happen to be.
judging by your blue and black smoke, i'd put money on pulling a head, and finding a nice big hole burned in the crown of the #3 piston. the blue smoke being the oil spray drawn through that hole, and the black being the uncompressed A/F mix that was intended for cyl #3, that is getting sucked out of the exhaust port as the valve opens.
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