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>> The M715 230 already has the harden seats and
>> positive rotators.
>> The civi 230 didn't and suffered the valve
>> recession.
>>
>
>Oh really, I never heard of this before...what is your
>source on this?
The 20 and 34 manuals mention harden seats not requiring much cleanup,
though 34P shows
the seats (exhaust) only as a separate replaceable part, but not the
material type.
When I purchased my M715, it had two broken exhaust valves, they were
snapped just below
the tulip. How it didn't damage the head, pistons or bore I'll call it
a miracle. All the other valves had a flaw, hairline crack, at the same point.
I swapped those valves from a set I had from a civilian head. That was 60,000
miles ago. The seats were all fine, didn't even need cleaning up. The
engine had
52,000 miles when I got it, speedometer cable was broken. Who knows
what the real milage was when I bought the truck.
Couldn't even turn it over, the starter was burned up on it.
I did lap the new valves in but that didn't make a dent in the exhaust
seats. The
valves seated very well with hardly any effort.
I found that the seats are not attracted to a magnetic, unlike the head
itself.
They also didn't scratch easily. So that, at least, ruled out the general
replacement cast iron seats that were also available back
before 1970.
My other source was a delightful conversation with an older engineer at
JEEP, Corp.
back in 1975. He sent me blueprints of the advance curves used on the civi
230 OHC.
These are the same as the M715 but no added vacuum advance for the mil
application.
This conversation was prompted by, you guessed it, valve burn up,
recession, on my
1963 Wagoneer. Oh yes, pinging as well.
He stated then that the main difference between the civi and mil 230 was
the hard exhaust seats, rotators, lower compression pistons, for the poorer
gas found overseas. Also stated that that was one of the reasons the civi
motor
was phased out after only 2 years, 62-63. The listed 8.5-1 ratio should
have been OK
for our regular leaded gas here at the time, BUT with the hemi-head
combustion chamber
and valve timing/duration, it acted like a 9.5-1 or better motor. Very
gutsy but
very susceptible to detonation. The mil version is 7.5 but it feels more
like 8.5.
I measured and calculated the ratio when the head was off. Its 7.5.
After all these years of use, M715, I'm looking at repowering it, and placing
the 715 motor into the 63 Wagoneer. With 1 ton less weight (Wagoneer), it will
fly. Go figure, I like the motor. I just keep in mine its differences.
Heck, my wifes 93 Sundance, with all its electronic control, knocks with
regular.
Timing is fine so she's been burning mid-grade since 1997. Motor is listed
as 8.5-1.
You'll like this, part of my learning process included throwing a rod on a
civi 230.
The rod separated just above the #1 bearing journal. Prolonged detonation.
Ignorance
on my part. Punched holes both side of the lower block and through the oil
pan.
Still have the motor, yup. Did I mention, I'm a pack rat to.
Wonder if a multifuel would fit the M715? (Only kidding)
Your thoughts Jon.
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