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- - Engine RPM (https://67-72chevytrucks.com/vboard/showthread.php?t=265244)

extd56

11-05-2007 05:32 PM

Engine RPM

What is a good RPM for a 69 Chevy truck 4x4 with a 350/350 trans and a 6" lift and runnign 35" tires. It is going to be a heavy rig when I am done with it.

wibilly

11-05-2007 05:42 PM

Re: Engine RPM

your ? is pretty vague. are you talking cruse rpm? what is the truck being built for? what gears? what are you going to do to the engine? we need more info

cdowns

11-05-2007 06:00 PM

Re: Engine RPM

put some 5:13 gears in and wind it up to 6 or 7 thousand

mnunn454

11-05-2007 06:23 PM

Re: Engine RPM

If it's lugging at all with that huge torque and weight load and with all that wind resistance, you'll be burning even more gas than you would if it weren't lugging. So I'll venture a guess at around 2500 to 2800 RPMs when cruising on the highway. This should ensure the engine's not lugging and your manifold vacuum stays in a decent range.

extd56

11-05-2007 06:29 PM

Re: Engine RPM

I was thinking of the RPM at cruising speed of 65-70 if I can keep it at that speed as I tend to speed a little:metal: I will be running 35" tires on the truck and I figured that my cruising RPM would be about 2450-2500 at 65. I will be running a 91 350 with TBI and the truck will be used mostly for hauling me around, not too much towing or off road use.The truck is my crewcab 69 so I would think it will be pretty heavy and lots of wind resistance no matter what I do. I have a 4L80E and 241 transfer case that I could put in it but I think I am better off staying with the 350 trans and 205 transfer case. Thanks

Mudder

11-05-2007 07:37 PM

Re: Engine RPM

With 4.10's and 70 mph mine turns in the upper 20's on the highway.

68K20 x Drill

11-05-2007 10:49 PM

Re: Engine RPM

Mine weighs about 6000, and I get about 70 MPH out of 3000 RPM.
Ratio seems good all around, but not as good as more gears would be.
I would be inclined to ditch the TH350 unless it is seriously built.
Every time I drive on pavement, I try to shift to a higher gear that I don't have.

http://www.cartestsoftware.com/cartest2000/index.html
If you download and install the demo, this is a pretty good little program for figuring your performance with various engines, gears, weights, wheels, etc.
If you input is accurate, the results are pretty spot on.

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