HELP!!

[Tx Jim]

I know but if you take some out and you put back what they taken off with a gasket then you end up at the same point you started from.

Resurfacing a flat diesel head & setting valve seats too far into head surface are too different machining operations. Valve seats setting too deep in cylinder head lowers compression ratio.

 

[M59]

Hey guys just got my head resurfaced on a long 460 and now my push rods are too long. Any advice? I've heard of this happening before but never experienced it personally and it's VERY time sensitive to getting it back running thanks.

klc336,

I agree with TX Jim's response. Something doesn't make sense. If head milled to bring into a planar surface to correct for warpage then MAX I would expect to see removed is 0.100 and more likely 0.050 ( 50 thousandths).

Are you sure you got back the head you sent in?

The volume contained within the head, for a diesel, is usually quit small. Removing significant amounts of thickness of the head changes many things: Reduces volume, raises compression, puts valves closes to piston, changes swirl within the space, and could place a sharp edge inside the circumference of the cylinder leading to hot spots.

Pic of a yanmar 3 cyl diesel. Notice how thin the head volume is at one edge of the cylinder for each cylinder.

 

[skipmarcy]

Have seen it many times from lesser quality machine shops in automotive - they don't grind the valve stems down after grinding the valves & seats and/or improperly installed seats.

 

[Cougsfan]

I agree that the problem was not likely caused by milling the heads, but by the improper re-installation of valve related components. Let us know how you resolve it.

 

[ROUSTABOUT]

Thicker than specification head gasket will lower engine compression ratio causing engine to be more difficult to start operating.

But if the head has been milled, the volumetric efficiency has been increased already, so a shim or spacer will get things back to normal. If it's a flat surface, have to grind tips of valves. Make sure head bolts aren't too long. Check a few of the items that milling would change. I've seen the man here bolt the head to a plate and heat it to remove warpage. But even though I'm in a small town 100 miles from a big town, these folks were in hot rod magazine back in the 60's as a speed shop. I guess the heat would relax the stress of warpage. Most smaller engines set on 7 intake and 11 exhaust. But I rebuilt a D7 cat that had a 4 cylinder and it was 17 intake 34 exhaust. So it's best to check what the specs are for your particular engine.

 

[Tx Jim]

But if the head has been milled, the volumetric efficiency has been increased already, so a shim or spacer will get things back to normal. If it's a flat surface, have to grind tips of valves. Make su

What you state would be dependent on style of cylinder head. That will not apply to a totally flat cylinder head. I'll bet you won't find very many if any service manuals that state if cylinder head was milled incorrectly to add extra head gaskets or grind valve stem tips.

 

[ROUSTABOUT]

What you state would be dependent on style of cylinder head. That will not apply to a totally flat cylinder head. I'll bet you won't find very many if any service manuals that state if cylinder head was milled incorrectly to add extra head gaskets or grind valve stem tips.

If the engine was set up at the factory by grinding valves for proper clearance, that's the way to go. Since it doesn't seem to have adjustable push rods, or rocker arms, the valve length is all you can change. Milling the head would not make the valve too long, but if they ground the valve seats and re surfaced the valves, they may seem long. The valve stem tips will be the easiest way to remedy this, if no other adjustment area is there to be used. I mean, you probably can't just buy a new valve and chunk it in the engine. You would have to adjust the clearance somehow. And if he had individually adjusted valves and the shop took the head apart and put it all in one bucket...the individuality of each piece is now gone and must be re established.

 

[Jerry/MT]

Hey guys just got my head resurfaced on a long 460 and now my push rods are too long. Any advice? I've heard of this happening before but never experienced it personally and it's VERY time sensitive to getting it back running thanks.

If the valves were replaced, perhaps the stems need to be ground to adjust their length.

 

[arrow]

Honestly not sure how much was taken off. But hmm. I might could make some 1/4" shims. Previously I had full range of adjustment and now the rockers are adjusted all the way out and still need more. I would think a 1/4 inch shim on each tower should be plenty. Surely they didn't remove more than that.

Most heads milled for performance are around .30 thousandths. If your heads were just skimmed to resurface, your prolly less than that.
a quarter inch is 250 thousandths.

 

[pycoed]

I'm surprised that the rocker adjustment is not capable of accomodating a head skim without further work.

If you find out how many thou the head was skimmed, say 20 thou (.020"). If 20 thou was taken off then 20 thou needs putting back - simples!
Then get some 20 thou flat sheet & cut out the spacers for the rocker towers. Bolt down the towers & try to set the valve clearances. If you still have a problem, then something else is wrong (cam followers/ wrong push rods/valves etc).