Piston to Valve clearance with performance cam

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06cumminstea

06cumminstea
Joined
Jan 3, 2014
Messages
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Anyone with a performance cam have any thoughts on the minimum ptv running on the intake valves? The exhaust valves have plenty of clearance. I have a 06 cummins 5.9 common rail and at the closest point(7.5 degrees after TDC) I am getting .087 thousandths of lift and at that point I push down on the valves by hand and get .019 thousandths before hitting the piston. Mind you this is all with the lite valve checking springs, zero lash at the crosshead, and me turning the engine over by hand with the degree wheel installed on the front of the crank. Any suggestions as to if this is too close? The cam has max lift of .308 at 195 degrees after TDC.
 
Yes its to close. Is that int or exh? What is the other one?
 
This is for the intake valves and is on the cylinder that had the highest piston protrusion. When you say "what is the other one", are you referring to the other cam that I have, or to what the exhaust PTV?
 
What was the exh? I wouldn't want anything under .040
 
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Exhaust was around .018 thousandths. Looks like I would need to fly cut the pistons to get it to work. I have the Marine version head gasket from Mumau Diesel. It is around .054 thousandths thick. I had my block decked because it was uneven (machine shop took off .007) I am using 12v rods which for some reason make my piston protrusion .003 to .005 thousandths more than the fractured stock rods. I had already spent about 800 getting those rods re-bushed, and machined for this build. So I did not want to go back with the fractured to save the 3-5 thousandths. Pistons were already coated on tops and skirts. So did not want to pull them back out and get what I paid for already machined off. Wednesday of last week, I:nail: had machine shop redo the head again to have valve seats cut down to get .045-.050 valve face depth as well. Just tired of spending to make this camshaft work. Just ready to get this build done. If it does not work, then it does not work. I have a regrind stocker that I was trying to avoid using for longevity and peace of mind, but I guess as long as I stay up on the oil changes every 4k and add zinc every change it will be fine.

If I do use the regrind, wonder if the 103# springs I bought for the Hamilton cam would be too much pressure on the lobes on the regrind and if I should just use brand new stock springs with the regrind?
 
What is your total piston protrusion, just out of curiosity?
 
Is it progressive? More protrustion as you move back to number 5?
 
It sounds like your block has been surfaced incorrectly. .010" variance can make the engi e sound sloppy due to compression differences

Another thing to note is that you have to factor lash into the equation to get correct piston to valve clearance. Also, light checking springs don't work as well on the 24v for clearance checking. Because one rocker operates both valves, light springs allow one valve to open before another which can skew timing events and clearance.

Good luck.
 
Since you had new bushings replaced in your rods, your center to center measurement might be off rod to rod.

And oem cams are not hardened throughout, they get progressively softer as you remove material.
 
In response to if protrusion on #5 getting progressively worse, then no, it always stays @.036 on that cylinder.

As far as deck being machined incorrectly, I guess it could be the case, but everything should be flat and true. I think maybe more along the lines of being a problem with the rods. I am not sure what the maximum allowance between cylinders as far as piston protrusion. I guess the only thing to do now is pull it back apart and take the rods back to the Machine shop. Any other ideas?
 
06cumminstea said:
In response to if protrusion on #5 getting progressively worse, then no, it always stays @.036 on that cylinder.
Click to expand...

I think Disturbed was asking if the protrusion increases progressively on cylinders 2, 3, and 4. What is the protrusion for each cylinder?
 
Striper said:
I think Disturbed was asking if the protrusion increases progressively on cylinders 2, 3, and 4. What is the protrusion for each cylinder?
Click to expand...

That is what I was wondering. If the decking machine was not true
 
Here's what I got:
Piston protrusion for each cylinder:

.028 on 1
.031 on 2
.028 on 3
.028 on 4
.036 on 5
.028 on 6

Valve face depth of .045 to .050 for intake and exhaust valves.

Head gasket thickness of .054 (Genuine Cummins Marine gasket)

This the highest in each particular cylinder. You know if you rock the piston in the cylinder a little it goes down 1 or 2 thousandths. Piston to Wall clearance is at 5 to 6 thousandths in each cylinder.

I got the regrind cam in the block now and am getting ready to degree it and check clearances if time allows tonight.

The reason I have the light checking springs to verify ptv clearance is because I did not want to rotate the engine by hand using the 103# valve springs and put wear on the cam lobes in case I need to sell this cam, springs, and new pushrods.

BTW, this is not the original block that came in the truck, the old block needed sleeves in each cylinder, so I brought this block from a company in Utah, that stated it hat never been decked, or sleeved. Come to find out after getting block decked by my machine shop #1 was sleeved and now I believe it had to be decked before. This is probably why my piston protrusion is so high. I have so much money in the block now, that it probably could have been setup for sled pulling. Not to rehash really bad and angry feelings over this horse $$$$ company that sold me the block, but won't take it back. So here I am, with a performance cam and not enough PTV clearance to be able to use it.

If anyone has any more thoughts, please feel free to chime in.
 
Just curious how you check the protrusion? Did you rock all the pistons to one side and then measure both sides of the pistons? That's a big difference between cylinders. You cant just measure one side because the rings may not move the same in the different pistons
 
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Jeremy,

Appreciate all the help. I not sure if I did what you mentioned in the previous post. I just finished checking intake centerline on the regrind and the intake centerline is nowhere near what it should be. Also found that ptv clearance is just about the same as Hamilton ' s cam. I will be taking the regrind out tomorrow and putting Hamiltons back in. But while cam is out, I will pull the head off and double check piston protrusion and let you all know. I may even contact machine shop that worked on rods and see what can be done.

One other thought before I do this is, I do have offset keys for cam. I could try installing and retard cam if this will help?
 
No degreeing the can won't help you. When you start moving the cam one or the other(int or exh) will get closer and the other will get farther away at the same time. Your stuck at this point because the cam is pretty much centered by your PTV clearance. Your just really close. Move it a couple degrees one way and the valves are going to hit on one and get farther away on the other.

When you check that protrution rock all the pistons to one side (towards the intake side of the block or the exh side) and measure them, then measure the other side with it still rocker over. Ad them together and divide by 2 and see if you get the same number as before.
 
Sorry to hear about our bum luck so far. Isolate the reason for #5 being high. Try a piston and rod from another cylinder. Once you get that figured out, feel free to send in the 188-220 and get it traded for something slightly smaller.

The 188-208 retarded 2 degrees would do fine or the 178-208 would drop in without issue.

Good luck,

Zach
 
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