Frustrated, discouraged and don't know what to do - The 1947 - Present Chevrolet & GMC Truck Message Board Network

formikaus · 03-09-2013, 10:06 AM

I just asked a buddy about this. He told me that when he installed the 6.0 in his he used the stock flywheel and wound up cracking it between the bolts, got another flywheel and warped it and eventually upgraded to a performance flywheel.............. HE SAIS he had the same noise and problem. It would sound fine when idling and reving in park, but once he put it under a load, same noise as yours..... did you use the stock flywheel?

hope this helps!

**derotoreut** · 03-09-2013, 10:32 AM

Quote:

Originally Posted by formikaus

I just asked a buddy about this. He told me that when he installed the 6.0 in his he used the stock flywheel and wound up cracking it between the bolts, got another flywheel and warped it and eventually upgraded to a performance flywheel.............. HE SAIS he had the same noise and problem. It would sound fine when idling and reving in park, but once he put it under a load, same noise as yours..... did you use the stock flywheel?

hope this helps!

Thanks. I have heard the same thing. However, my engine has a brand new SFI Precision flex plate. I also heard that loose torque converter bolts could cause this too. I'm pretty sure I can rule these out.

BADPURPLE70CHEVY · 03-09-2013, 11:08 AM

Man i know it's aggravating i have been in a similar spot before. I agree that maybe a fresh set of eyes and ears could give new perspective. Hang in there though and take a deep breath you will find it.

steves1967 · 03-09-2013, 11:28 AM

When they dyno'ed the engine did they use the same carb and distributor that you are using? I've had an MSD distributor with alot of shaft play and it was causing all kinds of noises. It finally just clearanced itself. I here a slight "whistle" noise- could it be a bad gasket on the carb?

**derotoreut** · 03-09-2013, 09:03 PM

Quote:

Originally Posted by steves1967

When they dyno'ed the engine did they use the same carb and distributor that you are using? I've had an MSD distributor with alot of shaft play and it was causing all kinds of noises. It finally just clearanced itself. I here a slight "whistle" noise- could it be a bad gasket on the carb?

Yes they used the actual carb and distributor for the dyno. The carb is a Quick Fuel 780 CFM, and distributor is GM Performance HEI. All new.

eightbanger · 03-09-2013, 12:34 PM

I installed a new damper on mine, and at the same time I renewed the timing chain cover and fitted a new chrome timing indicator also....on idle the engine was fine but when under load it made a similar noise to your's, turned out that the damper would rub on the timing indicator. I was really glad to find it because up until that point I could not understand what that dam noise was.....hope you pin it down.

budman k20 · 03-09-2013, 08:57 PM

I remember having to clearance my stock oil pan with a ballpeen hammer when I built my 383. There is not much rod bolt clearance right where the pan bolts to the block. This is just a guess...but I would bet the (thick) cast aluminum pan is being hit by the rod bolts.

**derotoreut** · 03-09-2013, 09:08 PM

Quote:

Originally Posted by budman k20

I remember having to clearance my stock oil pan with a ballpeen hammer when I built my 383. There is not much rod bolt clearance right where the pan bolts to the block. This is just a guess...but I would bet the (thick) cast aluminum pan is being hit by the rod bolts.

The cast aluminum pan is on my TH350 trans. The 383 has a painted steel 7-quart deep pan, so I don't believe there is an issue with the rod bolt clearance. You make a good point though. I have heard of this clearance issue in the past.

chipflyer · 03-09-2013, 09:45 PM

If you have someone "power break" it while you listen with the hood opened up can you hear it? If it does it you should be able to use an engine stethoscope or a piece of broom handle and get a pretty good idea exactly where its coming from or at least rule out areas.
I had a loose wheel weight once that made a terrible knock at only low speeds that was a pain to diagnose, might check those for fun.

Jeff

Lastson03 · 03-13-2013, 02:01 AM

Check your starter. I had one rebuilt once and the guy left out a return spring in the solenoid. It soul rattle like spark knock or rod knock under load. Even changed the engine before I figured it out. The starter would not fully disengage so under load when the flex plate would flex it would knock. There was hardly any noticeable damage to the flywheel.
Posted via Mobile Device

03-09-2013, 10:06 AM	#1
formikaus Registered User Join Date: Mar 2011 Location: Brunswick, GA Posts: 77	Re: Frustrated, discouraged and don't know what to do I just asked a buddy about this. He told me that when he installed the 6.0 in his he used the stock flywheel and wound up cracking it between the bolts, got another flywheel and warped it and eventually upgraded to a performance flywheel.............. HE SAIS he had the same noise and problem. It would sound fine when idling and reving in park, but once he put it under a load, same noise as yours..... did you use the stock flywheel? hope this helps!

03-09-2013, 11:08 AM	#3
BADPURPLE70CHEVY 406 Powered Join Date: Aug 2009 Location: waynesville,n.c. Posts: 877	Re: Frustrated, discouraged and don't know what to do Man i know it's aggravating i have been in a similar spot before. I agree that maybe a fresh set of eyes and ears could give new perspective. Hang in there though and take a deep breath you will find it. __________________ 70 GMC 68 c10 2002 silverado 72 4x4

03-09-2013, 11:28 AM	#4
steves1967 Registered User Join Date: Dec 2001 Location: Manteca, Ca USA Posts: 307	Re: Frustrated, discouraged and don't know what to do When they dyno'ed the engine did they use the same carb and distributor that you are using? I've had an MSD distributor with alot of shaft play and it was causing all kinds of noises. It finally just clearanced itself. I here a slight "whistle" noise- could it be a bad gasket on the carb? __________________ '71 Chevy 3/4 Ton Longbed '22 Chevy Tahoe RST '67 Firebird- 8 sec street car '24 GMC CC 4x4 Duramax Dually

03-09-2013, 12:34 PM	#6
eightbanger 454 MAKES IT ROAR Join Date: Jan 2008 Location: Essex, U.K Posts: 2,701	Re: Frustrated, discouraged and don't know what to do I installed a new damper on mine, and at the same time I renewed the timing chain cover and fitted a new chrome timing indicator also....on idle the engine was fine but when under load it made a similar noise to your's, turned out that the damper would rub on the timing indicator. I was really glad to find it because up until that point I could not understand what that dam noise was.....hope you pin it down. __________________ Nigel. An American living in a British body. 1971 Chevy Cheyenne 10 454 "In a time of universal deceit, telling the truth becomes a revolutionary act." - George Orwell "When injustice becomes law, resistance becomes duty" - Thomas Jefferson No more pain. 03.12.60 -- 12.28.10 http://www.youtube.com/Eightbanger

03-09-2013, 08:57 PM	#7
budman k20 1972 K20 Join Date: Apr 2008 Location: Greenfield MN Posts: 360	Re: Frustrated, discouraged and don't know what to do I remember having to clearance my stock oil pan with a ballpeen hammer when I built my 383. There is not much rod bolt clearance right where the pan bolts to the block. This is just a guess...but I would bet the (thick) cast aluminum pan is being hit by the rod bolts.

03-09-2013, 09:45 PM	#9
chipflyer Registered User Join Date: May 2004 Location: Topeka, Ks Posts: 2,293	Re: Frustrated, discouraged and don't know what to do If you have someone "power break" it while you listen with the hood opened up can you hear it? If it does it you should be able to use an engine stethoscope or a piece of broom handle and get a pretty good idea exactly where its coming from or at least rule out areas. I had a loose wheel weight once that made a terrible knock at only low speeds that was a pain to diagnose, might check those for fun. Jeff __________________ I'm not a pessimist, I'm just optimistic that bad things are going to happen. 1971 Cheyenne Super K10 - tilt, cruise, air, am/fm, tow hooks, factory buckets! 1986 Jeep J10 pickup, - 5.3L Vortec with 4L60e and NP241.

03-13-2013, 02:01 AM	#10
Lastson03 Registered User Join Date: Jan 2008 Location: Asheboro, NC Posts: 7	Re: Frustrated, discouraged and don't know what to do Check your starter. I had one rebuilt once and the guy left out a return spring in the solenoid. It soul rattle like spark knock or rod knock under load. Even changed the engine before I figured it out. The starter would not fully disengage so under load when the flex plate would flex it would knock. There was hardly any noticeable damage to the flywheel. Posted via Mobile Device



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