Bad Cam????
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Junior User
Joined: May 2003
Posts: 59
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From: Monroe, WA
Bad Cam????
I installed a new lifter on the number one exhaust cylinder, and the truck ran fine for the first few days (put it all back together on saturday) and today, in the afternoon, the engine started running really rough, like one cylinder was out. I think the cam was ground down by the new lifter. Any other ideas???? Its a 79 351M. If I have to get a new cam, what else should I do, everything? Push rods, rockers, springs, timing gears, water pump??? Thanks in advance,
Junior User
Joined: May 2003
Posts: 91
Likes: 0
Bad Cam????
Hi,
Just my .02 here.
None of this may apply to your situation.
First:
Check for a broken push rod. If that is the case then look for the reason why and consider yourself lucky. Possibly a bad rocker arm caused it to break.
Second:
The lifter could just be bad and the plunger is stuck down giving the appearance it is ground off. You should be able to see this with visual inspection.
If it is ground off then it should have excessive lash beyond the preload. Meaning that the excessive lash is caused by the bottom of the lifter and or the cam lobe being ground off.
The bottom of the lifter may also be mushroomed enough that it will not easily be removed from the top. In the worst case scenario it may only be removed by going down. Meaning you got to disassemble the engine enough to drop it into the pan and fetch it there.
Now, assuming the lifter was ground off you will need a new cam and lifters. You better find the cause before spending more money and time. Otherwise you may be right back here again in a few days.
If it is missing bad enough to cause a dead cylinder as you describe then more than likely you have a mushroomed lifter, junk cam and significant metal in the oil. Many oil filters will go into bypass when the engine is cold and the oil is thick.
So all that metal may have just went through the bearings if you have started it cold after hearing that dead cylinder!!!
Now if this is the case then you got more things to think about and check.
IF the LIFTER is mushroomed and you have to remove it through the pan then you better look at the rod bearings while you are there. If you got metal in the bearings then it get ugly from there.
Time to get a new engine! Just changing the bearings won’t get it. You have to get all that metal throughout the rest of the engine cleaned out.
A little background:
With flat tappet cams, Lifters MUST spin. If they don’t then you got junk in minutes.
Worn out rocker arms will catch and bind causing excessive pressure on the lifter against the cam and prohibit the lifter from spinning.
Putting a new higher lift cam in with these stock sled rocker arms that have 50k plus miles may eat the cam and lifter set within minutes or days. The rocker arms are worn to the lift of the old cam. So, the higher lift binds as the rocket tries to move farther than the old lift did before. Just take a worn rocket arm with the hold down bolt and hold it in your hand. Pull down on the screw end of the bold putting pressure on the upper arm. Then rock it back and forth. You should be able to feel the worn edge catch as you go past the old max lift.
The Story:
A friend had a collapsed lifter on a 77 400. He replaced it. Then 2 days later it started to clack again. He had excessive lash. The lifter wouldn’t come up out of the galley. With some force it came up with out scoring the block.. The bottom was mushroomed off on one side. It apparently didn’t spin. He replaced the cam and lifters ( Oil & filter etc). 2 days later that same lifter was clacking again. This time he discovered the bad rocker arm. New cam and lifters were installed again. 4 days later number one rod started knocking. All of the bearings were full of metal. The crank was junk ( way past .030 ).
Anyway as I said just my .02
David
Just my .02 here.
None of this may apply to your situation.
First:
Check for a broken push rod. If that is the case then look for the reason why and consider yourself lucky. Possibly a bad rocker arm caused it to break.
Second:
The lifter could just be bad and the plunger is stuck down giving the appearance it is ground off. You should be able to see this with visual inspection.
If it is ground off then it should have excessive lash beyond the preload. Meaning that the excessive lash is caused by the bottom of the lifter and or the cam lobe being ground off.
The bottom of the lifter may also be mushroomed enough that it will not easily be removed from the top. In the worst case scenario it may only be removed by going down. Meaning you got to disassemble the engine enough to drop it into the pan and fetch it there.
Now, assuming the lifter was ground off you will need a new cam and lifters. You better find the cause before spending more money and time. Otherwise you may be right back here again in a few days.
If it is missing bad enough to cause a dead cylinder as you describe then more than likely you have a mushroomed lifter, junk cam and significant metal in the oil. Many oil filters will go into bypass when the engine is cold and the oil is thick.
So all that metal may have just went through the bearings if you have started it cold after hearing that dead cylinder!!!
Now if this is the case then you got more things to think about and check.
IF the LIFTER is mushroomed and you have to remove it through the pan then you better look at the rod bearings while you are there. If you got metal in the bearings then it get ugly from there.
Time to get a new engine! Just changing the bearings won’t get it. You have to get all that metal throughout the rest of the engine cleaned out.
A little background:
With flat tappet cams, Lifters MUST spin. If they don’t then you got junk in minutes.
Worn out rocker arms will catch and bind causing excessive pressure on the lifter against the cam and prohibit the lifter from spinning.
Putting a new higher lift cam in with these stock sled rocker arms that have 50k plus miles may eat the cam and lifter set within minutes or days. The rocker arms are worn to the lift of the old cam. So, the higher lift binds as the rocket tries to move farther than the old lift did before. Just take a worn rocket arm with the hold down bolt and hold it in your hand. Pull down on the screw end of the bold putting pressure on the upper arm. Then rock it back and forth. You should be able to feel the worn edge catch as you go past the old max lift.
The Story:
A friend had a collapsed lifter on a 77 400. He replaced it. Then 2 days later it started to clack again. He had excessive lash. The lifter wouldn’t come up out of the galley. With some force it came up with out scoring the block.. The bottom was mushroomed off on one side. It apparently didn’t spin. He replaced the cam and lifters ( Oil & filter etc). 2 days later that same lifter was clacking again. This time he discovered the bad rocker arm. New cam and lifters were installed again. 4 days later number one rod started knocking. All of the bearings were full of metal. The crank was junk ( way past .030 ).
Anyway as I said just my .02
David
