Bad knock in 460

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Nov 16, 2001 | 02:35 AM

the law

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From: Billings, MT

Bad knock in 460

My '89 EFI 460 knocks really bad under high load when set at 10 degrees btdc. Not knowing what to do, I tried 89 and 92 octane gas, with little effect. With timing a 12, it knocks just pulling out of the drive way, and I have to retard the timing to 5 degrees just to drive without concern for my pistons. Of course, now I get crappy fuel economy (8ish, I'm used to 10, even with my lead foot) and I can't accelerate worth a darn. I put in new plugs, and made sure to gap them properly (0.044"), but beyond that, I'm not sure what to try. Am I pulling a stupid and is the answer right under my nose, or is this indication of something like a bad electronic advance system?

The Law

Nov 16, 2001 | 06:45 AM

DeenHylton

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From: Crooked River Ranch, OR

Bad knock in 460

When my 89 EFI 460 "knocked" last year I found all eight rod bearings hammered (93,000 miles). I did a total rebuild with top quality parts. There is a difference between a light "ping" or light "rattle" for detonation, and a heavier dull knock which can indicate a number of more serious mechanical problems. Get a "Motors Manual" or "Chiltons Manual" and go thru their trouble-shooting steps.

Nov 16, 2001 | 09:20 PM

the law

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From: Billings, MT

Bad knock in 460

it's not a rattle, but it's not a quiet knock like I get on the 3.0 windstar I drive for work. It sounds like extremely loud cracking. I assumed that it was louder 'cause of such a large engine. I've had the truck about 8 months, and I got the knock only once in the first 4 months, but then almost overnight it showed up. I know its not a mechanical wear problem because it changes depending on where I set the timing.

The Law

Nov 17, 2001 | 07:09 AM

DeenHylton

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From: Crooked River Ranch, OR

Bad knock in 460

Try setting the timing where it knocks or rattles the most then add a tank of premium (or premium with octane booster) to see if the noise goes away...if it doesn't go away its probably not detonation.

Nov 17, 2001 | 07:14 AM

DeenHylton

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From: Crooked River Ranch, OR

Bad knock in 460

OOps, just reread your first post and realized you've already tried premium. Put a timing light on it and see how much advance your getting at 3000-4000 RPM, could be something is wrong with your distributor allowing you to get too much advance and thus ping.

Nov 18, 2001 | 12:09 AM

Mil1ion

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Bad knock in 460

Nov 22, 2001 | 06:47 PM

the law

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From: Billings, MT

Bad knock in 460

Now this sounds wierd to me, but replaced my temperature sender 2 days ago because my guage read my truck as never being warm. Now suddenly, it idles alot more smoothly (less surging), and I can't get her to knock, even in situations where it was horrible before. Is there some sensor in the whole EFI/Electronic Advance system that sets a different time for a cold engine? Is it possible the computer never thought that the engine was warm? I'd be pleased if my knocking is solved with a seven dollar part, but it seems too easy. What do you think?