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Topic: cause of Detonation (Read 344 times)
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uwee440
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Iv'e been reading up on how to read plugs,mine look like I have detonation, Is it too much inital timing? running to rich?or too lean?I have not heard any sound that what i think detonation sounds like.A few of my plugs look like "pepper" on the porclin,and a few of the plugs the porclin turned brown.can someone explain in simple terms what causes detonation?
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Ray Barton Racing Engines
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65DartGT
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Detonation can be caused by too much timing, too much compression, wrong heat range plugs,too low octane fuel,lean fuel mixtures, and over heating.
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uwee440
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Thanks,now I can narrow it down.I don't think I have a good plug reading anyway,Last checked them after driving it on the street.
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Ray Barton Racing Engines
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Steve DeTar
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I have had alot of these same questions. Can you tell us about your engine if you could? Like what is the static compression ratio calucated, what cam, and whats the cranking pressure? My friend who has a 4x4 with a big block, has a small cam and 10 to 1 pistons. Once what he told what he had, I tryed to get him to run a colder plug. He constantly rejetted it thinking it was his carb. With his smallish cam, he was making 190psi on all eight cylinders, which was way too high for a cast iron head and cheapy pump gas. all he needed was a cam change to fix it. Let us know what you got.
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Engine by DeTar
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speedymopars
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Detonation is caused by too much heat in the cylinder on the compression stroke. That can come from the plugs being too hot, a bur or hot spot in the chamber, a fuel that is compressed too much (dynamic CR) for it's octane or temperature. If you have to much dynamic compression, you can get colder air or fuel in there to pull some heat out (if it is on the edge), or block the egr passage (to get some heat out), put more fuel or less timing in there (to get the heat out), retard the cam to lower the dynamic compression (which pulls out heat), or put in a cam with more overlap to bleed off the compression (bigger cam duration wise - the 1.6 rockers won't help you). If you have an oil leak on the intake, that will also cause it because oil is a really low octane fuel.
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70 Duster - Keith Black 526, 2 x 830 annulars/tunnel ram, big solid roller, 727 ProTrans, Strange 4.30s
77 440 Dodge van 12.96 @ 108 - 4800 lbs of love with a 2.72 peg leg and 1800 stall
74 cheyenne 452 stroker, 2x450's on a tunnel ram, 21 foot, Berkeley jet, place diverter
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speedymopars
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Also, try this dynamic compression ratio calculator to see if that is the problem. http://kb-silvolite.com/calc.phpIf you don't know what your cam card says - now is a good time to learn :-) |
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Logged
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70 Duster - Keith Black 526, 2 x 830 annulars/tunnel ram, big solid roller, 727 ProTrans, Strange 4.30s
77 440 Dodge van 12.96 @ 108 - 4800 lbs of love with a 2.72 peg leg and 1800 stall
74 cheyenne 452 stroker, 2x450's on a tunnel ram, 21 foot, Berkeley jet, place diverter
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