Originally Posted by
shimniok
Thanks for the responses so far! The advice is VERY valuable.
The reason I didn't want to change anything but motor is I just spent $1800 on rebuilt, locked and regeared axles. Now I'm married and spending $ is... limited. :)
I wanted to keep hwy rpms to stock level. A mistake? Maybe. But get this...
A friend has an 87 GW, 33" tires, 4" lift, roof rack, very similar to me, but runs 3.31 gears and a 401 with 10:1 CR and mild/stock cam plus a Quadrajet which he just got dialed in a few weeks ago. He is now running 3/4 throttle in 3rd up that first big hill on 285 to keep up with traffic running 60-65. He runs most passes in 3rd. I've personally seen this truck PULL AWAY RAPIDLY from me on hills where I am foot to the floor to hold 55-60 in 3rd with only modest accel in 2nd. On Monarch Pass I was in 2nd where I could accelerate ok but he STILL pulled away quickly (I think he was in 2nd too). I've also seen him accelerate from 65 to 100 on nearly flat ground where I could barely make it to 80 in the same timeframe. Frankly it is jaw-dropping to see.
So, that is what is possible. Btw, Spitfire built his motor.
I've been playing with Desktop Dyno a lot (just ordered the 2000 vers). I modeled my motor and his as best I could. What I've found is my Comp Cams 260H is a horrible choice with stock CR and exhaust, weak on torque in just the rpm band I most use. He has like 100 lbs-ft on me with his combo.
In a 401 with 9.5:1 CR, small tube headers, the Edelbrock Performer cam puts out 430+ lbs-ft in 2000-3500 range, and with 320 hp @ 4000 (best of 260-ish cams). Factory Pontiac grind specs I found on the web puts out 440+ lbs-ft from 2000-3000 (447 @ 2500, 'only' 435 @ 3500 and 408 @ 4000) with slightly less hp @ 4000 (311 vs. 320). No other cam comes close to these two in torque. The next best are down 10-20 lbs-ft 2000-3000.
Seems the Pontiac grind puts peak torque @ my cruise rpm, most torque in the power band, and peaks hp @ 4000 suggesting good off-idle torque. I doubt 9 hp matters since it'll be 30 more than I have now. I think it's the best choice I've got. That's what I am leaning towards.
But this is all cloud pushing based on a lot of assumptions, book learning, and junk. What are your thoughts?
Also, EFI is planned too.
Michael
Reply With Quote
