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Old 06-13-2004, 08:36 AM
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How to check pushrods?

Still and always looking for the knocking source of my 383 stroker.
The pushrods are standard length for SBC . I checked them rolling them one by one on a cast iron surface (my tablesaw) that looks straight...now I have found two or three that might show some unstraightness but so little that I wonder if it can affect on my engine. Pressing down one end of the pushrods there is some gap between the other end of the pushrod to the cast iron surface...now it is not much..maybe around 1/16 of an inch.

Is my method of checking them the right way and what do you think of such a small bend...enough to create knocking? I've just ran a compression test and it all came out at around 210 PSI with less than 10 pounds.

That darn knocking ,through the stetoscope, seems to be located on the lower end of the engine ....running the stetoscope along the side of the oil pan gives me a knocking..regular in strength wherever along the pan but not when the stetoscope is along the bottom of the pan...anyway so mostlikely the possible faulty pushrods sound like a farfetched possibility! I guess I am suffering of the shade tree mechanic's syndrome wich is to look at problems with rose sunglasses that bias the reality...

thank for the help..

Ronald.

Checking my post I need to precise that there was less than 10 pounds difference between cylinders compression wich ran around 210 PSI.

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Old 06-13-2004, 09:23 AM
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Good info on your pushrod question:

http://www.compcams.com/information/Products/Pushrods/
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Old 06-13-2004, 10:49 AM
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The slight bends in a few push rods will not cause a knock, how ever you should replace them with straight ones.

I check them the same way.

Troy

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Old 06-13-2004, 10:57 AM
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Pull the oil pan and start checking rod bearings first, sounds like your going to find one that is bad. Pushrods should be perfectly straight, a tolerance of 0.001" is about all I would accept.
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Old 06-13-2004, 11:01 AM
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Diagram "A" in that website sure does seem to be assbackwards as far as which way the rocker tip sweeps the top of the stem.
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Old 06-13-2004, 02:56 PM
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Thanks fellows...I'm becoming an expert pulling the pan...it will be my third time now! I've had checked four rod bearings and one main a while ago and since they all looked new (this is a fresh rebuilt) I decided to look elsewhere this is when I discovered the slightly bent pushrods...so I've closed the pan and ordered new pushrods thinking I had found my problem but by the answers I have here it looks that pushrods cannot knock that way. Well I'll pull that pan again ....
Ronald.
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Old 06-13-2004, 04:56 PM
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knocking

Does this motor have a mechanical fuel pump???

If so remove the pump ans have someone start the motor for you and see if the sound goes away.

keith
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Old 06-13-2004, 05:25 PM
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Keith,

It has an electrical pump and a blocking plate where the mechanical pump normally mounts and there is no noise from there when I put the scope on it....

thanks.
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Old 06-13-2004, 07:22 PM
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could you of not clearanced the block enough and the counter weight or maybe a rod bolt are hitting it??
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Old 06-14-2004, 09:51 AM
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Maybe a cracked flywheel? Ive heard it before and it will resemble a knocking noise.....just a thought
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Old 05-12-2007, 03:59 PM
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niose in the bottom end

i'm no engine expert but i have heard that when you use forged pistons they have a tendency to rattle a little when you start your engine as aposed to Hypereutectic pistons they fit a little tighter in the cylinder walls this is just what i have heard
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Old 05-12-2007, 04:33 PM
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Dropthe oil filter, cut it open and spread it out, if you've got a bearing going away it will show up, usually as small aluminum colored flakes.

You've had the pan off since the knock started?? Was there any debris in it??

How about the crank hitting the pan?? Just helped assemble a 383 with an internally balanced crank, the rear counterweight was slightly hitting the pan, just enough that it would have caused a noise but no damage, a couple smacks with a ball peen fixed it.
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Old 05-12-2007, 06:57 PM
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