From Jamie.L.Phillips@us.ul.com Tue Feb 15 22:46:21 2000
From: Jamie.L.Phillips@us.ul.com

After I had written:

>>> Early models with the higher outputs had the valve timing set for
maximum engine output. Unfortunately, this resulted in unburned fuel
escaping out the exhaust.  This in turn caused poor fuel economy and more
pollution.
<<<

Michael Baxter, MBaxter@Compuserve.com-OR-N7OVD@arrl.net wrote:

>The valve event timing for the 360 never changed from '71 to '91.
The compression ratio was a little bit more for '71-'73ish at 8.4 to 1.
8.25 to 1 after that. The 2150 is a slightly bigger carb. than the 2100 for
the 2bbls. Other than that, there is no rhyme or reason for Jeep's power
specs. being all over the graph.
<

I have to disagree with you Michael.  I had previously generalized because
most of the books I have read indicated that all the major auto makers
adjusted the valve timing of the engines by reducing the amount of
time/angle that the intake and outake valves were both open.

For more specific info I opened up my "Chiltons - Truck and Van Repair
Manual 1971-1978."  Though information on valve timing is limited in this
reference I believe it does indicate the general trend that I mentioned.

To keep things simple, I will just go over information on the 360 engine
you mentioned (2bbl) from '71 to '72.

In 1971 the 360 (2bbl) had its intake valves opening at 18 1/2 degrees.
In 1972 the 360 (2bbl) had its intake valves opening at 14 3/4 degrees.
This indicates that they were indeed adjusting valve timing during this
period.

In 1971 the 360 (2bbl) had an "advertised" compression ratio of 8.5:1.
In 1972 the 360 (2bbl) had an "advertised" compression ratio of 8.5:1.
No change, no effect.

In 1971 the 360 (2bbl) had an "advertised" horse power of 245@4400.
In 1972 the 360 (2bbl) had an "advertised" horse power of 175@4000.
A significant drop in horse power.

In 1971 the 360 (2bbl) had an "advertised" torque of 365@2600.
In 1972 the 360 (2bbl) had an "advertised" torque of 285@2400.
A significant drop in torque.

Unfortunately I do not know much about carburetors, I hope to correct that
soon. (that is start to correct it soon, it might take me awhile)

The other literature I have read though still seems to point to the valve
timing changes as the cause for the significant drop in performance.

If you have other information, send it on in.

Later,
Jamie Phillips

'73 J-4000
'77 F250