Obtained a copy of Desktop Dyno 2000 and have been playing with it for a little bit.
I plugged in my combo (as close as I could get) and am curious what the racers and those that are building the Hi-power slants think of the results. The numbers are probably on the high side, but do not seem that far fetched...opinions?

Combo:

Cast crank 225 .080 over
10.07:1 compression (calculated)
1.70 intake, 1.50 exhaust (approximate--can't find my paperwork from the machine shop)--mild porting & gasket matching
Offy 4 bbl intake w/ Holley 390 cfm
Clifford 3x2 headers, true 2.5" duals w/ flowmasters
MSD 6AL ignition, Jacobs 8mm wires, NGK plugs gapped at .055
K&N 14"x3" open element
MP cam, .398 lift, 240 duration, 24 o/l, 106 centerline installed straight up (this tiny cam is killing me )

Desktop Dyno spits out 202 HP @ 4500 and 265 ft-lbs @ 3000. The torque curve is basically flat from 2000 (lowest rpm it shows) to 4500 (The torque numbers here jive well with where my slant starts to pull pretty hard, from about 2700 through 5000 rpm)

Running the numbers with Comp Cams 260H, DD spits out:

230 HP @ 5000
267 ft-lbs @ 3500
Torque curve is flat from 2000 to 5000 rpm.

Using the DD iterator I was not able to come up with much higher numbers using different 'custom' cams...am I approaching the N/A limit with no power adders?)

From what I have read about DD, I expect those numbers are high, but by how much? I eventually would like to hit the 250 HP and 300 ft-lb mark naturally aspirated and w/o nitrous. Am I dreaming or is there something I have neglected to address? FWIW--I am willing to sacrifice the HP goal for the torque goal, as ol' slanty is hauling a heavy truck around with the aerodynamics of a brick.

Opinions please..

-S/6

I'd say those numbers will depend A LOT on the head port flows. Those numbers are possible with those cams, but pretty hard to do. I'd say knock about 20-40 HP off for a near-stock head. Don't know enough about your head to tell.

Lou

_________________
Home of Slant6-powered fun machines since 1988

The head is original to the truck (87 smog head). Mild porting and gasket matching. 39 cc combustion chambers. O/S valves--I remember the machine shop telling me they had problems with getting Ford 300 valves, and that they used Ford 302 V8 valves...which I remember being similar in size to the 300 valves, but slightly different (hence the numbers I provided above.

One thing I noticed after my rebuild was a major seat-of-the-pants increase in low end grunt, but several changes occured at once during my rebuild: Increased compression from 8.5ish to 10:1, replaced supersix intake an Carter BBD with Offy 4 bbl and Holley 390, and the O/S valves and overbore.

If any of that helps.... I feel my head is better than stock, but am sure there is room for improvement. Unfortunatey I know of no (local) shop that has a flow bench, and even shipping to Anchorage would be prohibitive. Looks like I need to get my hands on a spare head and go nuts with a dremel...

-S/6

( sup bro catch me at hardy)


go buy a head and go to town on it. thats how i started learning, now im not anywhere near professional, but i kinda know what i am doing now. besides if its an extra head, what harm can you really do?
buy an old head, after 67 and before whatever you got.
Doctor Dodge has a pic of a cross section that shows just where to take metal off safely, mainly the "inside of the elbow" section, where the intake goes from near horizontal to vertical, the inside of that. that and widen behind the valves and polish everything untill its smooth.
If you wouldnt change a baby's diaper in there, its not smooth enough.
they dont call it "polishing" for nothin!

_________________
http://www.hardymotorcycles.com