302 rebuilt is knocking

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Jun 25, 2010 | 11:49 PM

charon61285

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From: NW Illinois on 40 Acres

302 rebuilt is knocking

Engine Knock - Rebuilt 1980(?) 302 0.030 over on cylinders, 0.020 over on mains, and 0.010 over on rods. New oil pump and fuel pump. New values and rebuilt heads. All bearings have been plastigaged and checked out OK.
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Using a steel rod for sound amplification knock is low in the three and four cylinder area.
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Mistake was made when main bearings where installed (working too late into the night!). The top half of the number three bearing was installed on the top half of the number 4 main and engine was run for about 250 to 300 miles that way. Removed pan to locate knock and that is when error was found. Replaced the number 3 main and moved the top half that was on number three to number 4 (that may have been a mistake to do). The top half of the no.3 main bearing was hitting the counterweight when it was on the no. 4 main.
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Torqued everything back down and restarted engine. Knock is still there!
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Have not checked crankshaft end play.
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Have had numerous engine guys listen to it including a couple friends that run dragsters and they hear the knock but are unsure as to where it might be except that it is low in the “back” cylinders.
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We are planning on dropping the pan off again to take a second look around in a few days. Any ideas of what and where or how to look for the source of this persistent knock!
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Engine is in 1966 Mustang with manual Trans.
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Thanks

Jun 26, 2010 | 09:59 AM

Kemicalburns

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From: Bend,OR

how did the bearings look after you discovered the first knock? anything 0.010 over on a crank is to far in my opinion and alows the crank to deflect. your best to start with a fresh crank and standard bearings.

Jun 27, 2010 | 08:10 AM

charon61285

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From: NW Illinois on 40 Acres

Interesting comment as the knock was not there until after about three hours of run time.

I only looked at the bearinf from the 3rd and 4th main as that appeared to be the problem.

We will pull the pan (again) and look at ALL the bearings for possible cracks and other problems.

Thanks!

Ron and Ryan

Jun 28, 2010 | 10:26 AM

Kemicalburns

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From: Bend,OR

what oil are you using and what oil filter do you have on the motor? is the oil pump a standard, hi volume, hi pressure??

Jul 9, 2010 | 04:33 PM

charon61285

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From: NW Illinois on 40 Acres

Sorry about taking so long to get back but last Friday night my wife's sister and her husband where hit by a deer while riding their Harley with us , our son, and another couple. She is still in ICU but he is out.

Now about the engine, did have 10W30, trying 40SAE now, no change. standard oil pump (new) with standard output.

With everything else we have not had time to do anything else.

Still asking questions and scratching our heads.

Thanks,

Ron and Ryan

Jul 10, 2010 | 07:59 PM

BlueOvalRage

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From: Oxford, Indiana

Pull the pan and focus on checking the rod bearings. My experience has been that bad mains will cause low oil pressure and possibly a low rumble as the crank wriggles around if they are really bad, but more often than not, a knock is a rod. If you had some main bearing shells in the wrong place, it is very possible (likely, even) that the oil holes weren't in the right place and you starved a pair of rods and spun a bearing. Unfortunately, by the time it starts knocking, the rod is egg-shaped and the journal is beat up. Just throwing a new bearing at it isn't going to fix the problem. Plan on pulling it out and going back through it before it's over.

Mar 15, 2011 | 03:29 PM

charon61285

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From: NW Illinois on 40 Acres

The knock has been found!

A few days turned into a few months before we pulled the motor but all this time it was in storage but with spring starting to show some signs of life it was time to find the problem.

One of the 30 over pistons was a Standard size when we put a mic to it!
After pulling the engine out for the second time we finally saw that the piston in no. 4 was too sloppy. Pulled it and even though it was marked as a 30 over size and it came out of a new set of 30 over pistons it was for a standard bore of 4.005 not 4.035.
Luckly there was only minor damage to the cylinder wall and little honeing and everything is like new.

We have put in alot of new pistons in everything from lawn mowers to BIG Cat engines and never have we put a mic to a piston. We have checked and recheck all of the cylinders all the time but until now never a piston.

We should have it back together by the end of the weekend.

Thanks for your suggestions on this problem.