I checked and set valve lash on my 2001 Dodge Cummins. I went .010” on intake valves 1-2-4 and .020” on exhaust valves 1-3-5 on the compression stroke TDC, and .010” on intake valves 3-5-6 and .020” on exhaust valves 2-4-6 on the exhaust stroke TDC, but I noticed that intake valve #5 was slightly loose on the compression stroke, .003” and intake valve #2 was slightly loose on the exhaust stroke, .003”. Shouldn’t these be tight? Or is there a slight overlap while at TDC compression/exhaust that would cause these to be loose? Or could it be push rods or some other wear. The truck starts and runs good. Thanks!

I think everything is normal. Since you were at TDC on the compression stroke #6 cylinder, that means the cylinder #5 (next in the firing order) would 120 degrees away from arriving at TDC compression stroke. That intake valve would not be full closed until after BDC, which could explain the .003 inches.

This hurts my brain. I think #2 cylinder is behaving the same way - just in the exhaust stroke.

• John

Thanks John!

This has me scratching my head, but I’m in agreeance with you. Although I don’t know enough about the valve train to be certain.

Remember there is a very wide allowance. Like exhaust is 0.015 to 0.030 or intake is 0.006 to 0.015 are conidered normal.

10 hours ago, Tractorman said:

That intake valve would not be full closed until after BDC, which could explain the .003 inches

I didn't say that quite right. The intake valve would be fully closed, but would not have reached the full .010 clearance yet.

• John

Mopar1973Man

Are you suggesting that I set those two valves at .006” and see if the play goes away? Thanks

5 hours ago, Mopar1973Man said:

Remember there is a very wide allowance. Like exhaust is 0.015 to 0.030 or intake is 0.006 to 0.015 are conidered normal.

No... Please don't do this! Excessive tight valve could cause a stalling issues.

The slach is the room it needs when the valve heats and starts to expand. Like myself I was playing with 0.008 and 0.018 for while but the excessive tightness was creating a stalling issue on hot summer days. I don't suggest going tight.

Still the spec is still 0.010 intake and 0.020 for exhaust.

Might check and measure total lift of each cam lobe and see how much possible wear there could be?

Edited March 21Mar 21 by Mopar1973Man

Thanks Mopar1973Man

I was wondering about wear on the cam.

On 3/20/2025 at 6:08 AM, TLar307 said:

Shouldn’t these be tight?

No, they shouldn't be tight. I think you are worrying about a potential problem that does not exist. Your explanation of your concern was well written, and I think accurate.

The two valves that you referenced were closed, but the #5 and #2 pistons were 120° on their approach to TDC. The cam lobes were still ramping down or up (depending which valve is being referenced) so the clearance was not the set clearance (because of the ramp). BUT, the clearance would be a normal clearance.

• John

On 3/22/2025 at 9:56 AM, Tractorman said:

I think you are worrying about a potential problem that does not exist.

Yeah, I think you’re right. I just wanted some clarification, because I wasn’t sure if it was a potential issue. Thanks!

On 3/21/2025 at 1:37 PM, Mopar1973Man said:

Might check and measure total lift of each cam lobe and see how much possible wear there could be?

I checked valve lift on intake valves 1-2-5 and they all measured @ .322”. I checked intake valve 1 for reference and valve 2 and 5 because they are the valves in question. Taking cam lift on a factory cam of .235” and multiplying by 1.36 rocker arm ratio, I get .3196”, so that’s just under 2-1/2 thousands out, on the positive side, so I’d say my cam is in good shape.