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kRaSh
Dodge Dakota
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11/08/2003
02:08:35
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 Subject: Piston knock
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Message:
I just bought a 99 Dakota Sport 4x4 with the 318.
Whenever I accelerate I get piston knock. Now this is a brand new rebuilt engine from Chrysler with about 700 miles on it. Am I running the wrong octane gas or is there something else I should check? I am running 87 octane gas.
Thank you everybody for your comments!
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Matt
Dodge Dakota
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11/08/2003
08:36:58
|  RE: Piston knock
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The stock Magnum 5.2(318) had 9.0 to 1 compression ratio, I'm pretty sure. If this engine has been rebuilt, it may very well have been rebored .020 or .030. If it has, the larger bore diameter raises the compression ratio fractionally. You may need to run 89 octane to get rid of the knock.
The 4.7 in newer Daks has aluminum heads. That's why they can run on 87 octane in spite of 9.3 to 1 compression. Iron heads such as your 318 has, don't conduct heat as well as aluminum and therefore has higher combustion chamber temperatures. Try 89 octane and see if the knocking goes away.
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huh
Dodge Dakota
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11/08/2003
09:23:55
| RE: Piston knock
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First, DaimlerChrysler doesn't remanufacture engines, if you bought it through a Chrysler dealer it was out-sourced.
Second, do you mean spark-knock or piston slap? They're two completely different things. Spark knock requiresa higher octane gas to cure.
Piston slap means the cylinders were bored improperley.
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gen1dak
Dodge Dakota
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11/08/2003
18:09:19
| RE: Piston knock
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You got a rebuilt engine, but did you replace the belly pan gasket in the intake? If it's bad, the vacuum leak will cause a run lean condition, and this will cause ping as well. If you still ping with premium 92 octane, you need to fix that gasket.
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kRaSh
Dodge Dakota
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11/09/2003
11:53:18
|  RE: Piston knock
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I bought it and the engine blew 2 days later (bad oil pump) so the dealership intalled a Chrysler remanufactured long block. (according to the service ticket) And as far as the knock, I believe it is spark knock but I'm not sure. Like I said, I didn't rebuild it.
Thank you for your replies.
I'll try 89 and 93 octane to see if that fixes it. If not, I'm back to the dealership, still within 30 days of purchase ;)
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kRaSh
Dodge Dakota
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11/13/2003
02:14:03
| RE: Piston knock
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"huh", Well turns out we were both wrong. The dealership flashed the computer and it runs fine now. Who knew.
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Death flash
Dodge Dakota
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11/14/2003
16:23:54
| RE: Piston knock
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Too bad you didn't give higher octane a chance.
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for gen1dak
Dodge Dakota
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11/15/2003
06:47:40
| RE: Piston knock
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only an idiot would ever consider using a used gasket anywhere on a engine rebiuld, since you considered that someone would , that makes u an idiot.
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Nut
Dodge Dakota
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11/16/2003
01:41:23
| RE: Piston knock
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Matt
Are you sure that just by boring you increase the compression ratio, I thought it went down. But only if you keep the same type (shape) of pistons. By boring you increase the area the gas.air mix has to explose in. But if you go to a dome shape (from flat or dish) or shave the heads then you reduce that area of mix/explosion, therefore increasing the ratio?
Kinda new to the engine game and trying to keep the info correct.
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Kowalski
Dodge Dakota
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11/16/2003
10:40:05
| RE: Piston knock
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Message:
It should increase marginally. You'll be squeezing more air into about the same sized combustion chamber. That chamber could be very slightly larger if the piston sits lower than flush with the deck.
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