Hink
Overkill Is Underrated
Aw, that's right! This also takes a solid lifter to do this, doesn't it?
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Another clearance question
- Thread starter Hink
- Start date
Aw, that's right! This also takes a solid lifter to do this, doesn't it?
Will L.
Well-Known Member
This is based on checked clearance is ok...
If you are using old springs, or even stock new springs, you are cutting it close because they are more likely to float than if you bump up to stiffer springs.
Also running close no timing chain, gears only.
If you are using old springs, or even stock new springs, you are cutting it close because they are more likely to float than if you bump up to stiffer springs.
Also running close no timing chain, gears only.
Hink
Overkill Is Underrated
Yup, Leroy's gears here.
Will L.
Well-Known Member
Yes solid lifter to playdoh for clearance. Someone (Nate maybe?) figured take one apart and flip the piston upside down.
Hink
Overkill Is Underrated
Well, I'm usually pretty good with puzzles but for the life of me, I can't see how a lifter can go together with the piston flipped and make it work.
Any suggestions?
Will L.
Well-Known Member
A military rebuilt 6.5
Now as far as build details go, I was able to mock it up and verify pushrod lengths and valve-to-piston clearance. My modded lifters that I tack welded to make solid didn't work. I had to keep the tacks small to make sure everything still cleared and using a MIG it just wasn't enough weld. If...
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Hink
Overkill Is Underrated
Hink
Overkill Is Underrated
nobby
Old Timey Diesel Guy
Lead wire for measuring clearance.
I seem to have lost my roll of 1/16 otherwise I'd pop some in the mail to you.
Cheers
Nobby
LEAD ROD-WIRE-WOOL | Non Ferrous Metals
Lead Wool is formed from finely extruded strands of pure lead. Properly packed, lead wool makes a tighter and more flexible joint than a cast joint. It can.
nfmetals.com
I seem to have lost my roll of 1/16 otherwise I'd pop some in the mail to you.
Cheers
Nobby
Hink
Overkill Is Underrated
Lead wire for measuring clearance.
LEAD ROD-WIRE-WOOL | Non Ferrous Metals
Lead Wool is formed from finely extruded strands of pure lead. Properly packed, lead wool makes a tighter and more flexible joint than a cast joint. It can.nfmetals.com
I seem to have lost my roll of 1/16 otherwise I'd pop some in the mail to you.
Cheers
Nobby
Excellent, thank you sir!
Hink
Overkill Is Underrated
Info from Cometic;
Good studs and a perfectly flat surface are crucial for multi layer gaskets.
They have a Viton coating on them that will not be damaged by copper coat, but copper coat will not allow the proper crush on the gasket.
Hink
Overkill Is Underrated
Ok, last little bit of info needed...
What is the preferred piston to valve clearance that we are looking for?
I see no specs in my books.
What is the preferred piston to valve clearance that we are looking for?
I see no specs in my books.
Hink
Overkill Is Underrated
Ok, I finally got a reply from my machine shop that answers this question...
Rather than having a piston to valve spec range like I've seen with other motors, the 6.5 has a negative spec (recessed) for the valve to head surface which is .034" - .048".
Then with your piston protrusion spec of .004" - .006", you have all you need.
When these two are in spec, then the distance from valve to piston is within stock clearances.
I ended up with a max piston protrusion of .016" and my heads were machined within stock spec for the valves (your valves should always be checked after milling the heads) so with .010" over gaskets (or Mahle .010" shaved pistons) I would end up with .006" protrusion so I'm good, right?
Well, I should be but I still had valve to piston contact. If you run into this, check that your timing chain (or my gears) are timed correct. I likely have the cam timing off a bit, when that is corrected, I should be fine. (I'll update when I know for sure)
I've not seen that much valve recession before... I can check records but it's more in the .026 - .030 area me thinks... but I will check, I wright this stuff down on each set of heads...
If their was that much clearance their wouldn't be so many valve imprints on pistons even with a wore chain..
If their was that much clearance their wouldn't be so many valve imprints on pistons even with a wore chain..
Found the info, I have it posted here in a different thread....
A little more info..
I checked valve depth from the head surface on a new 6.5 head with the p valves and vice versa the valves that were in the 6.5 head in the p head...
standard valve & standard head = .039" in .037" ex
p valve in p head head = .025" in .026" ex
What I found with these 2 heads was the P head valves are around .010" closer to the head surface..
A little more info..
I checked valve depth from the head surface on a new 6.5 head with the p valves and vice versa the valves that were in the 6.5 head in the p head...
standard valve & standard head = .039" in .037" ex
p valve in p head head = .025" in .026" ex
What I found with these 2 heads was the P head valves are around .010" closer to the head surface..
Hink
Overkill Is Underrated
Interesting. Again, I wonder why the difference?
Those numbers above came from the machine shop and I didn't double check them.
However, I just looked in my 1993 Chevy unit repair manual and the specs are:
.045" (1.143mm) for intake
.035" (.889mm) for exhaust
From the Hummer Manual (newer Optimizer):
.0013" (.034mm) for intake
.0018" (.048mm) for exhaust
I saw no spec in the military manual. I suspect because they don't machine, they replace.
So they pushed the valve recess way out on the newer engine.
My main concern is of course valve stikes, but I also want to consider using Harland Sharps later so the higher clearance is what I'm looking for.
At this point, it is what it is on these heads so I'll go check it and see where I actually am.
ak diesel driver
6.5 driver
I wonder if they pushed the valves out to leave more metal between the valves?
Doubtful, the extra material in the p400 heads is inside under the seat area... The valves in the p400 are thicker than the others.... Don't really know why the valves are closer but they are...
Hink
Overkill Is Underrated
I got some measurements on the passenger head and they were rather odd considering the numbers we saw as spec above.
2 - Intake - .059" Exhaust - .026"
4 - Intake - .045" Exhaust - .026"
6 - Intake - .055" Exhaust - .026"
8 - Intake - .053" Exhaust - .025"
This is an Optimizer head that was machined for flatness and the valves checked for recession but were not touched because they were considered in spec.
I used cylinder number four for my clay test since it is closest to the piston and had the highest (.006") piston protrusion and therefor the highest likelihood of valve strike. It looked fine but I still don't know what numbers that I'm looking for as clearance when measuring the clay.
2 - Intake - .059" Exhaust - .026"
4 - Intake - .045" Exhaust - .026"
6 - Intake - .055" Exhaust - .026"
8 - Intake - .053" Exhaust - .025"
This is an Optimizer head that was machined for flatness and the valves checked for recession but were not touched because they were considered in spec.
I used cylinder number four for my clay test since it is closest to the piston and had the highest (.006") piston protrusion and therefor the highest likelihood of valve strike. It looked fine but I still don't know what numbers that I'm looking for as clearance when measuring the clay.
What clearance did you have. Rule is .050" but these will be less. As far as i know their is no published spec.