Piston/valve clearance

ccoxva

ccoxva

Loafer
Joined
Apr 15, 2008
Messages
337
How many thous. tolerance should one have on factory engine. Hamilton cam but I think they are factory lift. I'm collapsing push rods and cant figure out why after new hg install.
 
Are both intake and exhaust pushrods collapsing or just one or the other?
 
Dude it might be a good idea to go ahead and pull the head, if your bending the push rods due to PTV contact you are definately going to end up with a broken valve. And that is extremely costly, I know personally.
 
This is my first time letting a guy work on any of my cummins' and now this is happening to me. I went to test drive it Monday after the mechanic said it was fixed. Drove it 1/2mile and it started pecking when it got warm. Something is puting so much pressure on those pushrods that its collapsing them right under were the rocker ball sits in the socket on the pushrod.(were the shaft starts). I'm thinking since this was a reman engine to start w/ that the block has been decked and .004 off the head combined with the standard gasket the company sent in the warranty package is causing the prob.
 
There's a lot of factors that it can be. Valve to head resestion, piston grade {protrution}, installed valve height. Did they deck the block? Dids the person that installed the cam get the gear off 1 tooth? It would be wise to pull the head and clay the cylinders to check clearance.
 
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Cam is correct the engine had zero valvetrain probs till the hg job.
 
ccoxva said:
This is my first time letting a guy work on any of my cummins' and now this is happening to me. I went to test drive it Monday after the mechanic said it was fixed. Drove it 1/2mile and it started pecking when it got warm. Something is puting so much pressure on those pushrods that its collapsing them right under were the rocker ball sits in the socket on the pushrod.(were the shaft starts). I'm thinking since this was a reman engine to start w/ that the block has been decked and .004 off the head combined with the standard gasket the company sent in the warranty package is causing the prob.
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X2. I would bet that is what is causing the problem. To know for sure though you would need to have a measurement on valve depth and piston protrusion, then the specs on the cam. I would start by making sure the valves are adjusted correctly. Is it bending all of the pushrods or only some?
 
Just for comparison, on my bone stock head, block, and gasket 95' junker drag truck, if I tighten down the lash adjuster 1.5 turns i can still bar the motor over without piston to valve contact on cylinder #1. If I go 1.75 turns, there is contact. I did this test at or near top dead center so it takes the came completely out of play, just checking to see how far the valve has to protrude into the cylinder before it makes contact.

On my 98 12 valve, at 1.75 turns, there is barely contact, so little in fact that if I'm not really careful it will still rotate through the contact so either the push rod flexes a little or possibly the carbon deposit on the head squishes down a hair or something. At 2 turns, I have obvious piston to valve contact.

If I were you, I'd get the motor about 20-30* past TDC try tightening the #1 intake valve 1.5 turns past 0 lash and see if you can still bar the motor over in reverse with the alternator nut. If you can't, you obviously have less piston to valve clearance than my two trucks. It seems like my buddies 96' 12 valve was the same 1.5 turns no contact, 1.75 turns, there was contact.
 
Sounds like maybe the head gasket was replaced with a thinnner version.

To check piston to valve at tdc put a dial indicator on the valve retainer and start adjusting the lash adjuster until the valve touches the piston. Read the indicator for the amount of clearance. You can do this at tdc 5 btdc and 5 atdc for a complete picture of clearances. If you need help with identifying the issue, p.m. me and I will get you hooked up.

Zach
 
Thanks guys for the help so far, the thing is I cant really do anyting to the truck because I let a shop do the job, and you see were that got me dont ya. I am telling the mechanic that the pistons and v's are coming in contact and he acts like he dont give a **** to check to see.
 
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