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  #61  
Old 12-14-2020, 08:34 PM
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big gear head big gear head is offline
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I'm no engine expert, but in my experience when a cam goes bad the engine needs to be disassembled and cleaned out. I helped my brother with his LS6 after it had a cam go down and we just pulled the cam and replaced it. About 30 minutes after installing the new cam it was down again. The oil passages had filled with metal from the first cam and it caused the new cam to go bad quickly. The next time we disassembled the engine and completely cleaned the block. It didn't have any more cam failures after that.
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  #62  
Old 12-14-2020, 09:23 PM
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I concur with the above, although I've done it in the past and had success only because I caught it real early while lashing the valves and noticed that I had gained lash on one valve and the lock nut hadn't loosened up. Inspection of the cam lobe upon removal and it was minor and the lifter was flat, so I rolled the dice and installed a new cam and lifters and didn't have any problems, also I opened up the oil filter and it was clean.

On others that have ran on a rounded lobe and concaved the lifter the engine was full of metal, and you will usually find most of it on the knurls of the piston skirts.

Nowadays I wouldn't chance it, pull it and go through the engine, and while the engines at the machine shop that will give you plenty of time to clean and detail the engine compartment which usually snowballs to other things if you're not careful....
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  #63  
Old 12-18-2020, 03:04 PM
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Well, I was wrong. The cam and lifters are fine. After more disassembly and looking closer, with my glasses on, taking pic's with my cell phone I could enlarge, having others look and taking some pieces to the machinist to look at - everything is fine.
So I will re-set the valve adjustment using the method given on here, I took the time to mark the damper.
But then it will be back to the hunt for why the car has so little power.
I may need to try and see if there is still a lobe on the cam for the fuel pump - but there was/is no fine metal in the engine at all - so I doubt the fuel pump lobe is gone but will try to see.

Last edited by TomN; 12-31-2020 at 07:21 PM.
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  #64  
Old 12-18-2020, 03:42 PM
BLACKLS5 BLACKLS5 is offline
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Maybe I missed it but where are you located?
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70 Chevelle Cpe LS5 M22 58-58 756
70 Chevelle Vert L34 M21 28-A 791
70 Chevelle Cpe LS6 M40 14-14 756
70 Chevelle Cpe L?? M?? 926-99616 755
69 Chevelle Cpe L78 M21 71-B 756
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  #65  
Old 12-18-2020, 08:22 PM
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I'm near Knoxville, Tenn
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  #66  
Old 12-18-2020, 09:45 PM
BLACKLS5 BLACKLS5 is offline
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Tom, I thought if you were close I'd take a look. Knoxville is a bit of a poke for me.
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70 Chevelle Cpe LS5 M22 58-58 756
70 Chevelle Vert L34 M21 28-A 791
70 Chevelle Cpe LS6 M40 14-14 756
70 Chevelle Cpe L?? M?? 926-99616 755
69 Chevelle Cpe L78 M21 71-B 756
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  #67  
Old 12-19-2020, 12:11 AM
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Thanks, BLACKLS5 ..... I'm a little slow but I'll get it figured out.
I'm working now on getting the intake manifold back on the engine - but give me a few days. lol
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  #68  
Old 12-31-2020, 07:30 PM
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I did get the engine back together and running. But the valve lash problem is still there. Maybe a little worse this time since I went from .026 to .028 on the exhaust valves. Don't know for sure.
So since I don't know for sure what cam is in the engine, I'm thinking I will try setting the lash tighter - like a 'tight-lash' cam.
Wish me luck
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  #69  
Old 01-10-2021, 06:49 PM
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Well I got the valves all re-lashed, and I set them a little tighter this time..... I @ .020 and the Exh. @ .022
After I had set the valves I turned the engine through the 90* cycles a second time - rechecking my work as I went.
It may just be what someone on here said, that the set screws just weren't contacting the tops of the rocker studs correctly and needed to be tightened a few times until they did.
Anyway - for now the valve lash seems good - so I will try and find out where the power has gone
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  #70  
Old 01-21-2021, 10:15 PM
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Well, after trying all the wrong things first in my search for where the L-78's power had gone .... a different carburetor fixed the problem.
Of course now I will need to get everything adjusted and tuned - but the power is there, fish-tailing up the road proved that.
Still more to do but I'm hanging in there..... barely at times ... lol
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