Valve depth vs compression loss

TheSilverBullet

TheSilverBullet

All the correction factor
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Jan 30, 2012
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So I bought an I assembled engine for my 99 recently. All the machine work was already done by a reputable shop. The head looked like the valves were pretty deep so I took it to my local guy that’s done a lot of my work over the years.

Sure enough the valves are .0100 depth, factory max is .060. I guess my question is what will this hurt? He says we should plane it some depending on thickness of the head.

Pistons are 286210 non ic bowl
 
you would be surprised how much that will effect it by some quick math I would say you will be down 1-1.5 points of compression.
 
TheSilverBullet said:
So I bought an I assembled engine for my 99 recently. All the machine work was already done by a reputable shop. The head looked like the valves were pretty deep so I took it to my local guy that’s done a lot of my work over the years.

Sure enough the valves are .0100 depth, factory max is .060. I guess my question is what will this hurt? He says we should plane it some depending on thickness of the head.

Pistons are 286210 non ic bowl
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As a former engine machinist, I can tell you that I absolutely would NOT run it as-is. It'll run, but like crap. Also, what did they do to maintain valve spring seat pressure?
 
I wouldn’t be comfortable running it as it is.

The question I have when I see something like this is, if they can’t get valve recession right, are they going to be able to other, closer tolerances right?

Their “reputableness” goes downhill very quickly in my book when I see stuff like this.
 
The closer you can get the valves to the face of the head the better it will run. So protruding or flush is ideal .100 is going to run like chit and make no power. Compression loss is the least of your worries at this point. Are there relief in the Pistons? Stock cam?
 
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Stock cam no relief in the pistons. It’s a street setup, I bought this engine from a guy that was Not assembled and I’m glad because I thought this head looked like the valves were low.

I took it to my local guy that’s just a one man shop and is really good at this stuff. He says not to to run it and put seats in it. Just wanting to hear opinions
 
TheSilverBullet said:
I took it to my local guy that’s just a one man shop and is really good at this stuff. He says not to to run it and put seats in it. Just wanting to hear opinions
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I agree with the local guy.
Why not make it right while your looking at it?
Not like it's a major dollar amount for a valve job.
 
TheSilverBullet said:
Stock cam no relief in the pistons. It’s a street setup, I bought this engine from a guy that was Not assembled and I’m glad because I thought this head looked like the valves were low.

I took it to my local guy that’s just a one man shop and is really good at this stuff. He says not to to run it and put seats in it. Just wanting to hear opinions
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That's going to be the only way to fix it. You cant mill enough off the head to make it work the way it is. Only other option is to sell it to a kid that wants to blow smoke and not make any power. It would be ideal for that!!:hehe:

Would it be cheaper to just find a different head an stick on it? Anything special about it that makes it worth spending extra money in to make it right?
 
I’ve got a pile of cracked stock heads. Local guy called me and said he could safely take 30 thousand off the deck...still pretty low. I’m not stuck on this head but I figured it was my best bet.

My local guy I’ve taken 4 other heads and they’ve had cracks. I’m kinda running out of options, I don’t want a Chinese aftermarket castings.
 
TheSilverBullet said:
I’ve got a pile of cracked stock heads. Local guy called me and said he could safely take 30 thousand off the deck...still pretty low. I’m not stuck on this head but I figured it was my best bet.

My local guy I’ve taken 4 other heads and they’ve had cracks. I’m kinda running out of options, I don’t want a Chinese aftermarket castings.
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I’d have less qualms about running a Chinese head with correct valve geometry than that head as it is, or even milled 0.030”.

If you’re dead set against a Chinese head I’d say your stuck with putting seats, and possibly valves, in what you have.
 
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I have had good luck with Chinese castings .. I have ran 5-6 above 1000 hp with no issues ..most new Cummins heads are made in dcec plant in China
 
Rich dzl said:
I have had good luck with Chinese castings .. I have ran 5-6 above 1000 hp with no issues ..most new Cummins heads are made in dcec plant in China
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Yup. I just got some pushrods for an old NH220 and they're made in India.
 
At .100 down either the seats are shot or they ground the valves to thin or both, no way I'd run a head like that.
Spec is min .039 and max .060, cutting .030 off the head still leaves it .010 to low.
Pull to valves and check rim thickness, should be .031 min, if the valves are ok the seats need replaced.
Fix the head or replace it.
 
Personally wouldn't run it. Also keep in mind that the more you take off the head, the more the injector protrudes into the cylinder. Depending on the injector/piston combo, I've seen some hit the center of the piston
 
We’re putting seats in. I bought this head 2nd hand but it was fresh out of Waglers machine shop this way.....
 
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