70 lp trouble

blinwmiaol.com · Oct 13, 2015

I picked up a non running complete 70 lp a few weeks ago. It was lightly set up but within an hour of some diesel in the cylinders and it was free. In trying to get it running I did a compression test and found one cylinder at 70# and the other at 0. When I took the head off, I found it had not to long ago been overhauled and had .45 over pistons with no ridge at the top of the cylinder. I popped the valves out and found one had visible pitting on the seat so took the head to an engine shop. On a visual inspection, he found cracks in both cylinders, on the raised brow above the intake valve. My question is, is this common, why in the world would it crack in both cylinders above a relatively cool valve, and what can be done about the cracks? Thanks in advance.

Mike M · Oct 13, 2015

Some places can pressure test to see if the cracks leak. Also if they do leak some places can repair them most commonly by pinning along the crack.
If you try and get another head that may be advertised as a rebuilt there is also a good chance it was cracked and repaired too.

tlock0331 · Oct 14, 2015

Mike,

Why would there be a good chance a rebuilt head had been cracked as well? Are 70 LP tractors "prone" to cracking the heads?

Ive rebuilt and rebuilt/sold a lot of heads that were not cracked, so that seems like quite a statement to make without some logic behind it.

Blin,

Since it was bored 45 over my guess is previous owner overhauled the block because it was water logged from the cracked head, spent a bunch of money on it, ran out before finding out the head was damaged, got ------ off, quit and sold it to you.

Mike M · Oct 14, 2015

Well you pay your money and take your chances. I prefer to have a cylinder head that was never cracked or repaired if I'm paying the same money for them ! I'm sure they are getting harder and harder to find the older these machines get. Worked on a model 50 for a fellow and he got exchange cylinder heads he didn't want repaired either. Went through 2 or 3 before we found one that looked good.

blinwmiaol.com · Oct 14, 2015

I don't believe it was overhauled because of water problems. This was
bought from a jockey who picked up a semi full from Iowa farms. There
are things that show this to be a very high hour tractor, like
steering shaft splines almost totally worn off and extreme wear in oil
slinger and carrier pin. Someone has put a good bit of money into it I
would guess in the last few years, besides being bored .45 over, the
flywheel side main housing has no paint leading me to think the crank
has been turned and new mains installed, all 4 valves are fairly new,
the manifold bolts came out easily and the orings in the bottom water
pipe were still totally round. Things like the clutch linkages have
all had bushings and new pins. The clutch arm has been replaced and
bushed and from the shape of the fork splines, it appears new also.
The drawbar hole on both ends is perfect so I suspect it's fairly new.
The ring gear, bendix and starter armature show no wear. New flywheel
bolts. Seems to have gone around the field a few times but someone has
put some money to tighten things up.

70 lp trouble

blinwmiaol.com

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Mike M

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tlock0331

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Mike M

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blinwmiaol.com

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