Clunking/knocking on turnover.. bearings? - Ford Muscle Forums : Ford Muscle Cars Tech Forum
 
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post #1 of 14 (permalink) Old 07-09-2005, 11:47 AM Thread Starter
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Clunking/knocking on turnover.. bearings?

I have a stock bottom end 351 W in a 67 stang. When it hasn't been cranked in a while, it makes a clunking/knocking at startup which goes away when it fires off. I have a HV oil pump with about 25-30 psi at idle and about 50 hot running. Should I be really concerned since there is no noise while engine is running, or should I pull it and tear it down? I want to do a forged 408 stroker kit eventually, but I really can't afford it now and would like to drive my car in the meantime. I figured I'd go ahead and pull the pan just to visually inspect everything, but I dont think I could tell if a bearing was out without pulling the rod caps.
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post #2 of 14 (permalink) Old 07-09-2005, 12:24 PM
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Clunking/knocking on turnover.. bearings?

Change your oil, and use a good filter like a wix. Sounds like your oil filter is old, and the anti drainback valve isnt working.

Those that say it cant be done should say so quietly, so as not to disturb those who are doing it.
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post #3 of 14 (permalink) Old 07-09-2005, 01:18 PM Thread Starter
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Clunking/knocking on turnover.. bearings?

Im confused. Are you suggesting that the noise is coming from dry bearings because of no check valve? I have a new Fram on there now, and I wasn't aware that it had a check valve. Thanks for any help.
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post #4 of 14 (permalink) Old 07-09-2005, 01:20 PM
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Clunking/knocking on turnover.. bearings?

Do you have oil dripping around the oil pan? If so it could be the rear main bearing. Worn or loose main bearings deffinatly will cause this noise..
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post #5 of 14 (permalink) Old 07-09-2005, 01:30 PM Thread Starter
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Clunking/knocking on turnover.. bearings?

What would oil dripping around the oil pan have to do with a worn out bearing?
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post #6 of 14 (permalink) Old 07-09-2005, 01:33 PM
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Clunking/knocking on turnover.. bearings?

If the oil is fresh, try a different filter. I've had this problem several times with Frams. I prefer Wix.

Those that say it cant be done should say so quietly, so as not to disturb those who are doing it.
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post #7 of 14 (permalink) Old 07-09-2005, 01:40 PM Thread Starter
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Clunking/knocking on turnover.. bearings?

Just to clarify, I don't have an oil leak. I have a clunking bottom end only when the motor is being turned over before firing off. Im not sure how much diference a new filter would make. Maybe Im just not understanding all this correctly.
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post #8 of 14 (permalink) Old 07-09-2005, 01:55 PM
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Clunking/knocking on turnover.. bearings?

I think what they are tryiny to say is that a rear seal tends to leak when the main bearing are loose/bad. The loose bearings can be the cause of the noise and the seal leak is a symptom of loose bearings.
In other words, if the rear seal leaks, its a good possibility the main bearings are the problem.
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post #9 of 14 (permalink) Old 07-09-2005, 03:37 PM
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Clunking/knocking on turnover.. bearings?

What Im saying is with a bad oil filter, the entire engine empties its oil back into the pan. The pump loses its prime. It doesnt get its prime back till the engine fires and the RPMS climb to a point where the oil pump can work past the air in the pickup tube.

Those that say it cant be done should say so quietly, so as not to disturb those who are doing it.
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post #10 of 14 (permalink) Old 07-09-2005, 05:57 PM
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Clunking/knocking on turnover.. bearings?

Thanks scottford351. I have never seen a rear main bearing go out without the seal going too.
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post #11 of 14 (permalink) Old 07-09-2005, 08:48 PM Thread Starter
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Clunking/knocking on turnover.. bearings?

If it was a rod bearing would the knocking continue while the engine is running?
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post #12 of 14 (permalink) Old 07-09-2005, 10:13 PM
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Clunking/knocking on turnover.. bearings?

my friend had a 460 in a cube van and he used it only on occasion and the engine made a lot of clunking noise when first started he had an in car bering job then a head overhaul still clunking so we put a diesel in the van and took the 460 apart we found the camshaft was bouncing backward and forward,when it was running as soon as oil pressure came up and the cam berings got lubed the clunking stopped, the other thing happening with this engine was from time to time it would shear off the distributor gear,happened 3 or 4 times over several years. I had a 351 cleveland made similar noises years ago the engine only had 8k but never found out why but when pressure came up it was fine drove it for over a year everyday
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post #13 of 14 (permalink) Old 07-09-2005, 11:54 PM
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Clunking/knocking on turnover.. bearings?

Is it an automatic?

Maybe torque converter is loose? for that matter, maybe the starter is?
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post #14 of 14 (permalink) Old 07-11-2005, 12:17 AM
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Clunking/knocking on turnover.. bearings?

Take that POS Fram and throw it as far as you can. But first cut open that POS and take a look at the construction of the filter with the little amount of element being glued to your mounting plate. Use a good filter always! like a Wix (NAPA), Bosch, or even a Wall Mart $2.00 filter is made better than the fram and will filter out smaller micron particles. P.S. Wal-Marts are made by the same company that makes Mobile One and Bosch
My .02

[ This Message was edited by: Rattpac on 7/11/05 12:18pm ]
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