Re: [ihc] RE: Motoring along with Tom

[Tom Mandera <tsm1@xxxxxxxxx>]

Jim Grammer wrote:
> Great results on 85 octane, very impressive! I have long suspected that the
I *do* think altitude has a bit to do with it.. but then, as you drop in 
altitude, the "cheap stuff" goes up in Octane.. so as long as I don't 
fuel up with 50gal of 85 and then coast down into Death Valley, I should 
be alright. ;)


> > The GOOD news is that with this ~9.5:1 engine I'm running a points
> > distributor with a Pertronix Ignitor, and I set the static timing at
> More pertinent to this discussion, IMO, is the total timing @ 3000-3500RPM.
> Got any idea?
No, other than both vac. and mechanical advance works.  I neglected to 
wind it up to 3k or so and eye-ball the total timing.  I'll try to 
remember to do that sometime in the near future.


> You, more than most of us, could *really* use a cool air intake! Keep the
> TAC for winter-friendlyness, but maybe whack off the end of the horn and
> plumb some fresh air from ????
After seeing a 87-91 GM TBI air intake system adapted to an IH, I'm 
thinking that's the route I want to take.  It's designed for a TBI, 
which runs the same air horn as our 4bbls and 2300s.

The setup resembles a plastic "can" on top of the "carb" with a 3 or 4" 
pipe coming out the side to a cone filter.

I'm leaning towards either the easy "headlight" air, or maybe routing it 
down lower to the bumper area, since it's primarily a highway hauler.

I'm even pondering an air dam when I lift the truck and convert to 4x4 
(the lift being incidental to the 4x4 conversion).

I did consider cowl induction for a bit, but since I have the rear of 
the hood open for ventilation, the cowl induction doesn't seem like such 
a good idea.

I *could* close the hood correctly and louver the sides then chop the 
center for the cowl induction.. but it's a lot easier and cleaner to 
just leave the hood unmolested and opened for ventilation, with a 
cold-air intake to the front.

A re-routed intake has been on the list, just hasn't made it to the top. :D


> > chamber only), Isky 256/262 grind (12" of vacuum at idle.. <VBG>),
> That's a lower idle vac than I'd have expected. Is that grind adding a fair
> amount of valve overlap? 
Comer seemed like he expected my ~12" at idle.  I *do* have the idle a 
bit low, hovering between 650 and 700rpm.  Part of the equation is my 
altitude - we live between 4k and 5k, and I don't think I dropped below 
4k the entire trip (and if I did, I didn't think to check the idle vac.) 
 It IS a bit of a cam, too.

Motor pulls well, but REALLY pulls over 3000rpm.  If I start a hill just 
over 3k, it'll accelerate up it.  Just under 3k?  It's attrition.

Using DaveSr's actual head flow figures from *stock* 392 heads (vs. my 
ported heads), DesktopDyno has torque leveling off and dropping a touch 
from a 457lbs-ft peak at 2000rpm to 441 lbs-ft at 3k, but at 2500 it's 
at 214hp, while 3k is 252hp, 3500 283hp.  80% VE at 3500rpm.  Peak of 
300hp @ 4k.  Really likes 3k+

I *hope* my ported heads do a little better.  One of these days I need 
to take a bunch of stuff to my friend's chassis dyno..

Ironically, plugging in the stock IH grind STILL shows a big jump from 
2500 to 3000 to 3500.  208/246/274hp with torque 437/431/411 lbs-ft

> Any thoughts on whether blocking off the exhaust

> crossover helps or hurts at this point(cooler charge temp vs. even
> distribution)?
NO idea.  Seat-of-the-pants says the engine felt a lot stronger this 
year, vs. last year.  BUT.. I had 1000+ more miles on it before I left, 
I had the lifter assembled correctly (getting closer to the "right" 
valve lift and timing on #7 and making sure the valve closed fully), I 
dumped both stock mufflers and the rear-dump cast-iron manifolds and put 
on Stan's headers and dual Thrush Turbos.

So I changed enough in addition to the LPG intake gaskets that I don't 
have a good feeling for the difference.

I was just hoping to stop boiling the fuel out of the Edelbrock (yes, I 
run an insulating spacer).


> > Preliminary mileage figures fluctuate from 5mpg to 9mpg..
> Ouch.
Yes, Ouch.  But, in my happy, rose-tinted world, that's really 
10-18mpg.. since it was one truck burning gas for TWO. :D

When's the last time you saw 18mpg in your Scout?  :-)

I have a bad feeling that I'm going to find that the "slow" sections of 
road where I was on a 2-lane, or laboring over passes and around windy 
bends, or otherwise NOT hauling @$$ at 75mph will be closer to the 
9/10mpg mark, while the stretches where I was making time will lean more 
towards 5mpg.

I tried watching the vac gauge during the trip.. and sadly noted it 
hovering around 7" the majority of the time.. which, as I understand it, 
is right at the point where the secondaries open up on the 1405.

I still don't have my air/fuel gauge installed.  I'll try to get that 
taken care of before next year and watch the mixture a bit closer under 
real driving conditions so I can adjust the carb as needed.  I went 1 
stage rich on power and cruise before I left, since the plugs were 
white, and I refused to let my new 392 melt down. ;)

I managed 10mpg to the BinderBash at 75mph, but I wasn't towing 
anything.  That was also on the stock jettings, and with only 5deg advance.

I think my trail Scout was part of my problem - it just sits too high 
and blocks too much wind. :D

-Tom