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Old 11-01-2002, 12:58 PM
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Post rod knock?

Been told I have rod knock in my 4.3 1989 s 10
added octane booster knock went away.drove truck from fl. to michigan with so called rod knock.
Have not been able to find reputable mechanic
here in michigan to verify is it possible to have rod knock and have octane booster reduce knock?
thanks in advance.

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if you have a lot of miles on that 4.3 you could have any number of things that would make a noise similar to a rod knock. 4.3's wear the pass front cylinder bad, they will then develop a piston knock when cold that usually goes away when warmed up, they also tend to wear the front rod journal more than normal because GM went and screwed up an oiling system that worked since 55 in the small blocks, they increased the pickup and screen size so now when you shut off the engine all the oil drains back into the pan, then creates an air lock when you fire it up cold and the front main and rod get no oil for a while, knock. then usually goes away, or you could have a piston pin knock, or just a case of low octane wrong ign timing etc. knock hard to tell over the computer! get it to a certified in engines mechanic with a few years under his belt and get the proper diagnosis, better than walking at three in the morning.
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Old 11-01-2002, 06:44 PM
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TRy this...Find a flat road that leads to a hill. Drive steady at the speed the knock is most noticeable. As you start up the hill, if the knock lessens or fades, it's probably a rod. They tend to quiet down under a load on the engine.
...This is "old" time rule of thumb stuff, NOT scientific certainy.
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Old 11-01-2002, 09:40 PM
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the "knock" you hear is likely detonation that`s gotten out of hand, the octane booster is what steers me to believe this, I`ve had a few cars come to me with "rod knock" and it was just detionation, I poured some water in a spray bottle, and sprayed it in the carb or injection butterflies while revving the engine with a occasional high rev and loads of black smoke would exit the exhaust, and the knock would disappear. High carbon build up on the pistons can raise the compression ratio enough and cause hot spots enough to make detionation loud enough to think it`s a rod knocking. it`s a suprise, but it`s true, and lastly, every vehicle I`ve did this way, the owner ran cheap gas and never floored the vehicle, so carbon would just build up all the more, my father, now a old timer, kicks his vehicles at least once a month to "blow the soot out" as he says, and none of his cars ever had this problem, try the water injection trick, if that doesn`t work, try some heavy duty top end engine cleaner. if neither works, then i`d say you do indeed have a rod knocking. but just doesn`t seem to logical to me octane booster would stop a rod knocking, once they start they don`t stop. good luck.
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Old 11-01-2002, 09:48 PM
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Water works great, there's also this stuff at NAPA called Sea-Foam De-carbonizer. It is like a tune-up in a can.....or almost anyway. Try it, even if it doesn't fix the problem, it will eliminate carbon as the problem.
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Old 11-01-2002, 09:59 PM
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An old school mechanic friend of mine does this to eliminate carbon/sludge buildup:
Just before an oil change he will add a quart of tranny fluid to the oil(if the oil is full he will drain out just enough to add the trans fluid)
Then he drives the car for a few miles(smokes like mad drunks)
Then he pulls it in the garage and changes the oil.After the oil change the smoking goes away within a couple of minutes and he claims no carbon/sludge.
Not sure if it works or not but he is a mechanic by trade and all of his cars are immaculant.
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