Re: ihc-digest V6 #344

["John Stricker" <jstricke@domain.elided>]

I don't see a whole heck of a lot that you need straightening out on here
Hofs.

It used to be, that the ideal was considered to be "square" configuration.
That is, the bore dia and stroke were at or near the same.  Keep in mind
that this was many years ago and that the max rpm was well under 3,000 rpm,
and more likely 2,200.

If you make an engine "oversquare", that is the bore significantly larger
than the stroke, you shift the max toque point up in the rpm band.  While it
doesn't affect power output, you also increase the max rpm.  The max rpm is
completely related to stroke length and rpm that determines piston speed.
The higher the piston speed, in feet per second, the higher the loads on the
reciprocating assembly as the whole mass has to come to a halt twice each
revolution.

As you have a longer stroke and approach a "square" configuration, you lower
the total rpm range and (generally) compress the range of useful torque.
Not always, but generally.  Rod length has a lot to do with this as well.
You can shift the maximum torque range up and down the rpm band by changing
the rod length.

In the 345, in my Loadstars, if I can get it wound up to 3,000rpm, I can
pull most hills really well.  If I can't, I'll have a problem.  It seems to
me that the peak torque in my engines is right in that 2,900-3,000 rpm
range, regardless of what the charts say.

More specifically, with the 345 IHC, which I have two of in Loadstars, I'll
pose a question to the group.  Email me with the correct answer and I'll be
sure to herald your glorious achievement to one and all.  Two trucks.  Both
Loadstars.  They weigh within 400 pounds of each other empty.  (one weighs
right at 10,000, the other 10,300 or so)  Both have 4 speeds, same ratios,
with two speed rear ends.  Same rear end ratio.  Both have 345-2V.

OK, given an equal load, one truck seems to be perfectly geared.  Loaded, I
can cruise down the road 55-60 in 4th and under and almost never have to
shift.  The other truck, same weight, same speed, to maintain on hills
(shallow grade) I'm having to shift to 3rd and over.

Two last hints.  To keep you honest, both trucks have 9.00X20 tires, and
I've had them on the dyno because I couldn't figure out the difference.  One
had 112hp at the rear wheels, the other 116hp.

OK, I finally found, what I think, Is the difference.  Care to have a
guess??  I've had it confirmed by a couple of truck riggers.  Send me your
educated guesses at my email address.
:------------------------------
:
:Date: Tue, 8 Dec 98 12:47:52 -0700
:From: John Hofstetter <hofs@domain.elided>
:Subject: Horsepower and Torque
:
:>Ron:
:>
:>The 5.0 l Ford into IH might be cool. But it lacks the basic requirement
of
:>a Scout. That is torque. Part of what makes the IH motors unique besides
:>their massive size, is that they were designed as truck motors with longer
:>strokes than other manufacturer's engines of similar displacement. This
:>gave them a "leg up" in the torque department although they suffered in
the
:>high RPM/Horsepower area to say nothing of the deliterious effect the
:>longer stroke has on fuel economy.
:>
:>Tom H.
:
:Well said, Tom. You've stated exactly what I think is involved in IHC's
:truck motor vs. somebody else's car motor. John L. and I were talking on
:the phone the other day about why my 318 GC engine pulls a trailer so
:much easier than my Scout's 345. (There really is no comparison) Looking
:at the horsepower ratings, and the rpm where these horsepower ratings are
:achieved, of the two engines, it becomes very clear why although the
:345's long stroke makes it a vehicle that can climb almost straight up at
:an idle, on a long 8% grade the engine gets comfortable at about 2200
:rpm, and you can forget being able to keep going 60 mph as you pull your
:trailer on up the hill. My Travelall with the 5 speed tranny, at least in
:retrospect, dealt pretty well with this problem, but I suspect that if I
:still was towing with that Travelall, I'd not think it was the world's
:greatest tow vehicle as I did then.
:
:I realize that my Scout weighs half again as much as my GC, but this
:added weight isn't, in my opinion, a major factor. My best buddy when I
:was teaching worked on teaching-days off for his father-in-law who owned
:a corn chopping operation, that used a lot of large IHC trucks. His
:trucks all had 345's or 392's in them, and they were perfect for that
:job. These engines compare to car engines kind of like draft horses
:compare to Arabians.
:
:I love my Scout, and I'm not mean-mouthing it, It just kind of tickles me
:intellectually to explore the whole question. Straighten me out, John
:Stricker.
:
:Regards,
:John H.