[tyson199]

Would 68 mph at 2000 rpm's be to low for running a car with a\c and in o\d? The engine I plan on having is a 461.

[Grant Miller]

My 99 Jeep Wrangler turns about that in OD with the ac on with a 4.0 6 cylinder, so I'd say you're going to be fine. BTW, the jeep weighs about 4000 lbs and will have WAY worse aerodynamics than any Pontiac. The key here is to make sure that the torque converter is coupled at that speed unless you have a lockup converter. Of course a stick throws that all out the window.

[ericwy]

It will depend on the cam, compression ratio, and carb of your engine.

With all the torque on tap with a pontiac engine and it being a 461 assuming
a reasonable streetable cam I think 2000 at 68mph will easily work.

My 400 TA with an OD 700R4 & 3.08 & 27" tires cruises at the following RPM/Gears
3rd = ~2000 rpm at 50 mph with manifold vac 15" to 22"
4th = ~1800 rpm at 70 mph with manifold vac 10" to 15"

I will be changing gears to a 3.42 to bump my 70 mph cruise up to about 2k.

[tyson199]

Originally Posted by ericwy

It will depend on the cam, compression ratio, and carb of your engine.

With all the torque on tap with a pontiac engine and it being a 461 assuming
a reasonable streetable cam I think 2000 at 68mph will easily work.

My 400 TA with an OD 700R4 & 3.08 & 27" tires cruises at the following RPM/Gears
3rd = ~2000 rpm at 50 mph with manifold vac 15" to 22"
4th = ~1800 rpm at 70 mph with manifold vac 10" to 15"

I will be changing gears to a 3.42 to bump my 70 mph cruise up to about 2k.

What wouldnt be a streetable cam and why r u bumpin up ur rpms to 2k?

[ericwy]

Originally Posted by tyson199

What wouldnt be a streetable cam and why r u bumpin up ur rpms to 2k?

Your 461 will accept a fairly aggressive cam profile simply due to its size.
I am not cam expert, but I think a .47 - .50 lift with 235 - 245 duration @ 050
would be streetable in a 455 or larger. Choose the lower lift/dur if its a daily driver.

"streetable" is subjective, to me it means plenty of low-end and mid-range
torque down to 1200 rpm. Has good vacuum signal for good power brakes.
Overall well behaved in traffic including extreeme heat or cold conditions.
This means that the intake and carb need to complement the cam and be sized for
the intended use.

Two reasons I am changing gears to bump up the cruise rpm:
1. Improve performance, esp low end in the first 0-300 feet.
2. Engine seems happier at ~2000 vs ~1800. I know it doesnt sound like much
but, keeping the manifold vacuum in the 15" to 20" (on my engine) means less
throttle and better fuel atomization which means better gas mileage. Or at the
very least no loss of mileage but gains more cruise driveability.

[Overkillphil]

I'm predicting little or no change with the gear swap ( you already have a 3.06 first gear with that 700-R4) and more traction issues out of the hole.

Also, if you are changing the gears, why not put a limited slip in there while it is apart?

[ericwy]

Originally Posted by Overkillphil

I'm predicting little or no change with the gear swap ( you already have a 3.06 first gear with that 700-R4) and more traction issues out of the hole.

Also, if you are changing the gears, why not put a limited slip in there while it is apart?

Oh yeah! That goes without saying it!

Seriously, you think little to be gained in performance and adding traction problems to boot?

You are right about the 3.06 1st gear, its like a th350 w/ 3.74 gears. If I go with a set of 3.42s
it would be same as a th350 with 4.15 gears (at least in 1st gear). Does seem a little steep on
street radials without any other traction devices......I dont want to sit an spin