Problem after engine rebuild
Thread Starter
Melting Slicks
Joined: May 2005
Posts: 3,394
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From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Problem after engine rebuild
I know this is not a corvette engine but I'm in need of help. I figured an engine is an engine so somebody here may be able to help me out here. It's a 302 30 over flat top. Crank is turned 10, 10, under. All clearances seem good. Has excelent oil pressure. About 60 to 70 psi.Here is the problem, It seems to make a slight diesel noise. That is the best way I can describe it. It isn't near as loud as the actual diesel but it has that sound. It doesn't sound like a rod or a main knock. It's not something that you can hear while in the cab but if I have the hood up and rev it I can hear it. Hope somebody has an idea because I have no idea at all what would cause this. I have rebuilt many engines Ford and Chevy and never heard of this. Thanks, Marc
Drifting
Joined: Nov 2005
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From: Dallas Tx
flat top = higher compression. what CC heads are you running and what kind of gas? Might be getting detonating or getting a little octane ping.
More specs wouldnt hurt, what king of intake, injection, carb, whatever.
Shane
More specs wouldnt hurt, what king of intake, injection, carb, whatever.
Shane
Thread Starter
Melting Slicks
Joined: May 2005
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From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Originally Posted by Shane_S
flat top = higher compression. what CC heads are you running and what kind of gas? Might be getting detonating or getting a little octane ping.
More specs wouldnt hurt, what king of intake, injection, carb, whatever.
Shane
More specs wouldnt hurt, what king of intake, injection, carb, whatever.
Shane
Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Do you have headers?? If so, sometimes you will get some strange noises because of the thinn wall of the tubing that you dont hear on cast iron manifolds.
BC
BC
Thread Starter
Melting Slicks
Joined: May 2005
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From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Originally Posted by Bill Curlee
Do you have headers?? If so, sometimes you will get some strange noises because of the thinn wall of the tubing that you dont hear on cast iron manifolds.
BC
BC
Drifting
Joined: Oct 2003
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From: bloomfield nj
is the flywheel tight? if it's a automatic are you sure the flywheel is not cracked? also,how much crank end play do you have[this is dictated by the thrust bearing]? is it a double knock when you crack the throttle?if so,you have a piston pin problem.usually a loose or cracked flyweel will give you that low solid knock sound.try shutting the truck off and right before the motor stops,start it.if you hear your noise,the problem is with the flywheel[also a loose converter will do this]
Thread Starter
Melting Slicks
Joined: May 2005
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From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Originally Posted by dpd
is the flywheel tight? if it's a automatic are you sure the flywheel is not cracked? also,how much crank end play do you have[this is dictated by the thrust bearing]? is it a double knock when you crack the throttle?if so,you have a piston pin problem.usually a loose or cracked flyweel will give you that low solid knock sound.try shutting the truck off and right before the motor stops,start it.if you hear your noise,the problem is with the flywheel[also a loose converter will do this]
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Drifting
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From: bloomfield nj
you'll need a dial indicator and a magnetic block to do it the right way.
install the dial indicator with the stem of the indicator on the front center of the crank snout.with a screwdriver,push the flywheel towards the front of the car[you will feel the crank move].read your indicator,then move the crank back,look at the indicator,that's your endplay.you'll have to look up the spec but usually .003-.005 is normal.
loose main caps will give you your problem also.JMO
install the dial indicator with the stem of the indicator on the front center of the crank snout.with a screwdriver,push the flywheel towards the front of the car[you will feel the crank move].read your indicator,then move the crank back,look at the indicator,that's your endplay.you'll have to look up the spec but usually .003-.005 is normal.
loose main caps will give you your problem also.JMO
Racer
Joined: Apr 2002
Posts: 272
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From: Canton Georgia
What type of piston forged or hypereutectic? Wall to piston critacial and different for these types of pistons. Does noise become less when engine gets warm if so might want to talk to whomever machined block and see what he set wall to piston clearence at.
Thread Starter
Melting Slicks
Joined: May 2005
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From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Originally Posted by rodknock
What type of piston forged or hypereutectic? Wall to piston critacial and different for these types of pistons. Does noise become less when engine gets warm if so might want to talk to whomever machined block and see what he set wall to piston clearence at.
Melting Slicks
Joined: Sep 2005
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From: Watertown CT
I could be way off here, but I had a similiar problem, although it wasn't on a v8, it was on a Jetta. Had a kncocking diesel sound to it. Turned out that I had an accessory bolt loose and the big cast bracket was knocking against the block!! Tightened it up and it disapeared. The way I found the route of my noise was to disconnect all the accesories to then limit it to the engine and the clutch or torque converter. I always try to start with the smallest and easiest stuff, just pop a couple belts and start it up, see what happens. Hope it helps, Dan 
Thread Starter
Melting Slicks
Joined: May 2005
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From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Originally Posted by SpeedyD
I could be way off here, but I had a similiar problem, although it wasn't on a v8, it was on a Jetta. Had a kncocking diesel sound to it. Turned out that I had an accessory bolt loose and the big cast bracket was knocking against the block!! Tightened it up and it disapeared. The way I found the route of my noise was to disconnect all the accesories to then limit it to the engine and the clutch or torque converter. I always try to start with the smallest and easiest stuff, just pop a couple belts and start it up, see what happens. Hope it helps, Dan
