Got head back on MH

David G · Nov 28, 2015

I went to Wisconsin with my brother this morning to get cheese curds. I got back and just wanted to get something done today, so I put the head back on. It was in the shop to get valve seals put on.

Janicholson · Nov 28, 2015

Is that a South Bend lurking in the background? They do not break. Looking good. The seals will also assist in maintaining manifold vacuum. And thus sensor accuracy, and fuel metering. Jim

David G · Nov 28, 2015

The lathe is a Logan, was my dads, the mill is a grizzly.

David G · Nov 28, 2015

I am contemplating the valve clearances.

The manual calls out .014 hot, but that does not seem right to me, I would think your would want .004 to .006 total hot clearance.

The push rods are 15" long, the thermal expansion of steel is .0000067, my calculations for a 100 degree change would be .010.

So do they really mean hot?

Janicholson · Nov 28, 2015

Cam engineering is the real issue. Cams for flat tappets (non-hydraulic) have a clearance "ramp" at the very beginning and trailing end of the lobe profile. This ramp is designed to take up the clearance over a set number of degrees of rotation. This ramp height is measured from the base circle (non-lifting part of the cam) to the exact point of the beginning of lift. The cold setting is wider because the valve stem, and pushrod length both increase with heat, as does the block and head. some of these decrease the clearance, (pushrod and valve) and others increase the clearance. The actual heat needed to set the valves is not full engine temp, but just warmed from running for 10 minutes or so. I would not second guess the cam engineering, as it is intended to create a quite and precise opening moment, as well as a crisp and smooth closing to clearance. Opening the clearance up to 16 or even 20 for startup would assure they wern't too tight before warming to be set "hot" Jim.

David G · Nov 28, 2015

I am trying to avoid setting them hot.

Does the .014 hot seem a little wide?

Janicholson · Nov 28, 2015

No, it is actually a common number for pushrod engines. Jim

kub6040 · Nov 28, 2015

I agree with Jim , I would set a little loose as loose will not burn valves and to tight will. Personal experience.

DLMKA · Nov 28, 2015

(quoted from post at 21:50:38 11/28/15) The lathe is a Logan, was my dads, the mill is a grizzly.

We have an old Logan like that with 3 speed leather belt drive. Dad paid $20 for it back when I was a kid. He never learned to use it and my curiosity got me to take a machining class in high school. Turned me to a mechanical engineer.

Dieseltech · Nov 29, 2015

Two things that SHOULD be done hot on that engine, re-torque the head, and reset the valves..

David G · Nov 29, 2015

I have no problem with resetting the valve clearance after hot. I am concerned with the head studs losing their seal if I muck with them after the sealer has set up.

Ozlander · Nov 29, 2015

(quoted from post at 10:37:46 11/29/15) I have no problem with resetting the valve clearance after hot. I am concerned with the head studs losing their seal if I muck with them after the sealer has set up.

Why would they loose their seal??
Studs shouldn't turn when you torque the nuts.

Got head back on MH

David G

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David G

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David G

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