Valve tappet clearance

Billderr · Oct 20, 2009

I have a 240 black diamond motor 6 cylinder in a 1951 grain truck. It is out of a pickup truck of that era. Could someone tell me the intake and exhaust valve tappet clearance? Thanks.

shaun wallace · Oct 20, 2009

.025 hot strait thru. Timing 4 before.

Billderr · Oct 21, 2009

Thanks, Shaun. I appreciate it.

JerryCPP(WA) (PIC) · Oct 22, 2009

Those old International 6's had a problem with valve stretch. If you find you're having to adjust the valves because they are tightening up, more than likely the valve stem is stretching right where the head connects to the stem. Eventually the head will break off and you'll have a heck of a mess in that cylinder. I had a machine shop for many years, and that was a common problem on these engines. It was far more likely to be an exhaust valve.

Billderr · Oct 22, 2009

We have not had a valve head break yet. A mouse built a nest in the exhaust manifold and piled about 30 corn kernels in it. Some corn got in the cylinder and squirted out a spark plug hole when the plug was removed for diagnosis. It cracked the head (corn doesn't compress well) which was replaced. Would a new set of valves fix the stretch problem?

JerryCPP(WA) · Oct 22, 2009

Yes Bill, replacing the valves is the solution. Talking a farmer into replacing all six exhaust valves when only one is broken takes some salesmanship, for sure. When you see the price of those valves you'll see why. The exhaust are stellite faced, and on the big engines the exhaust are $odium filled - mucho dollars! When the valve head comes off it may only mess up the valve seat - that's good and easily fixed. When it knocks a hole in the piston, that's bad, but still repairable. When it takes out the cylinder wall, that's VERY bad, and requires sleeving the engine. Your mouse/corn story is a first for me, thanks for sharing it.

Billderr · Oct 22, 2009

The engine has already been sleeved. Wouldn't new valves be built differently (i.e. inexpensive and made out of better materials)? What on earth did sodium do inside a valve stem? We've put a tin can over the exhaust pipe when we winter the grain truck. Also, we have a 1947 truck with a lime bed on it. I'm not familiar with it as it hasn't been run in years...it probably has a whole clan of mice in it.

JerryCPP(WA) (PIC) · Oct 23, 2009

I've been away from the machine shop/parts business for 25 years, but when i was there we asked the same question. Answer? They already have the equipment to build the original valves, so why change? A sodium filled valve stem conducts heat away from the valve head far better than solid metal. Sodium filled valves were quite common in the big and industrial engines, and in many aircraft engines of the time.

Valve tappet clearance

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