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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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Discussion Starter #21
That's what is so crazy. Bearings, everything under valve covers etc. is new, and that noise has not changed one iota. It's made that noise for 3 years, over the last 180 everything has been replace. No change at all, so what ever it is, it has not been replaced.
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #22
That's what is so crazy. Bearings, everything under valve covers etc. is new, and that noise has not changed one iota. It's made that noise for 3 years, over the last 180 everything has been replace. No change at all, so what ever it is, it has not been replaced.
Last 18 months.
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #23
I had the top-end off two weeks ago, replaces all the rocker arms and nylon plugs etc. Everything looked and felt fine bolting it all back in.Entire valve train has been replaced now. No difference in sound at all. The lower end bearings, oil pump etc. all new. Anthing directly related to crank and pistons is going to be at crank rpm, which would be twice the speed thatt the tao is now.
 

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1994 K2500 Suburban 6.5 turbo.
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Sound seems like it is in time with the bottom end. I have heard a sound like that on a different engine and it was piston slap or wrist pin. I have had bad main bering go in the past but usually they make noise on deceleration.
 

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Dang, that is a good tick there.... the first video it reminded me of my exhaust turbo side tick but from inside the cab it certainly sounds more mechanical (click/short/sharp) than an exhaust leak that usually has a more subtle start and finish to it.

Just spitballing here..... is it possible for a precup to become slightly loose and rattle in time with combustion?

-edit- looks like I am not the only guy under the redwoods!
 
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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #26
It is definitely a tap that is mechanical. Upper end doped. We checked the precups when the heads were out and nothing looked amiss. This is such a sharp tap. Not a rattle, slap, or knock. It sounds upper-end. It eminates from the entire engine. When the engine has been driven for 30 minutes, the tap is almost gone at idle.. be aware it was 40 degrees when I started it, so you are hearing it at its loudest. I'll warm it up good and record it then and post. Th
anks for all the thoughts folks, keep them coming and I'll keep digging.. Jim P
 

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1995 Chevrolet Silverado Z71 6.5 TD
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Maybe a lifter. the noise follows the engine speed increase. That's my 2 cents
 

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OP already replaced the lifters. I was thinking my 93 was knocking because of the lifters or the injectors. OP replaced both and still has the problem. At this point I am not going to do anything to fix mine. It looks like anything I could have thought of has already been tried. I highly doubt both of our 93s are making the same noise for different reasons. His sounds exactly the same as mine and the cold/warm behavior is exactly the same. I really hope he gets it figured out.
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #30
Dang, that is a good tick there.... the first video it reminded me of my exhaust turbo side tick but from inside the cab it certainly sounds more mechanical (click/short/sharp) than an exhaust leak that usually has a more subtle start and finish to it.

Just spitballing here..... is it possible for a precup to become slightly loose and rattle in time with combustion?

-edit- looks like I am not the only guy under the redwoods!
Saw your edit. Boulder Creek, Santa Cruz mountains. I'd give anything for a real garage and a cement floor! Carport and gravel....I can hope some day.
 

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1993 chevy silverado c3500 crew cab dually
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Timing chain?

The IP on the 93 is a loud MF'r could it just be the music of our people
 
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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #32
Timing chain?

The IP on the 93 is a loud MF'r could it just be the music of our people
The chain is new, but your comment on the mechanical pump has me thinking..... The pump, lines, injectors are all new, except for about a 2 inch thing on one of the lines. It looks like an extension to one line. It screws to the pump, and the line screws into the end of it. Anybody know what that is? It's old too... Not as old as me, but it's old. I'll check it out tomorrow. I spent 30 minutes today with the mech stethoscope as well, couple areas to check from that. One injector has a banging sound that sounds odd. I'll update when I can. Thanks all!
 

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Saw your edit. Boulder Creek, Santa Cruz mountains. I'd give anything for a real garage and a cement floor! Carport and gravel....I can hope some day.
Wow.... two 6.5s in one town?! Hah.... what are the odds? Anyways, maybe if I had time I could come have a listen but I hardly have enough time to work on my own stuff recently!

Your extension sounds like a line adapter. Used to convert old lines to new pumps. Also the fact it is only one reminds me, I have come across this in my reading, tip of my tongue but no firsthand experience so I cant say right now, plus its really late! I am sure someone will chime in as to what is up with the special line adapter... maybe a line no longer being made for the 93?
 

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Injectors are not all the same for 6.2 and 6.5. There are the long body coarse thread early 6.2 injectors, Long body fine thread mid/later 6.2 injectors and short body fine thread very late 6.2, 6.5 injectors. Long body uses different nozzles from short body. Also marine short body nozzle. Pop pressure varies for N/A, turbo, and Marine.

Yes, the lines are dependent on the IP ,heads, AND injector length.
Here it is.... so, you said you did the injector Pump,injector lines, and injectors.... did the line come like that? (not that I am feeling either way that this is your tick but just trying to get the details. Also triple check the lines are not touching anything!
 

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Does anyone know just how GM used this "Time Trac" sensor on the #1 inj. line to time the engine? Any kind of obtainable GM tools to use for this?
 

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1993 chevy silverado c3500 crew cab dually
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I have that same extension on mine. Mine clacks bad when I first start cold and only goes away under load. Your set up. Sounds similar to mine. 2x 6.5 and new Pistons in the 2nd motor. Same noise
 

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Will get the recording tomorrow, work rules on some days. And yes, I have a mech stethoscope. Anywhere on the engine it heatrs that loud, singular tap tap tap. Take off the intake plenum and that sound is like a bullhorn. ??????? I'll get the recording and go get some seafoam.
Did you do any work on the heads?
An inlet valve issue could cause one cylinder to allow blowback into the inlet manifold, and this will only happen every second rev during the compression/power strokes.
Have you done a compression test?
 

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1993 chevy silverado c3500 crew cab dually
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It kind of sounds like a valve slapping shut.

My 6.2 had a pushrod issue that started like that and went to hell after a bit.
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #40
Did you do any work on the heads?
An inlet valve issue could cause one cylinder to allow blowback into the inlet manifold, and this will only happen every second rev during the compression/power strokes.
Have you done a compression test?
New valves, seals, keepers. Have not done compression. Compression gauge kit will be here Monday.
 
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