Highway RPM's

[AZ442]

My 1970 442 has 425 mild, B&W ST-10 trans and 12 bolt type 0 with 3.23.
14" SS-1 with 215-75-R14

The highway RPS's drive me nuts. turning 3200RPM @ 65 miles per hour. Interstate speed limit is 75mph in AZ.

Is this hard on the motor turning 3400 to 3600 RPM for extended periods???

Some day A 6 speed.

[mugzilla]

3200 @ 65 seems about right ...

[dan1s]

I would love to have that. Try having a 3.91 with CR M21 "Not a Highway car"

[Bobsw32]

Just some thoughts.....Borg Warner makes several different gear ratios.....2.64, 2.88, even a 3.42 first gear....... Couple one of these with a 2.78 or 2.56 rear gear and you can have the best of both worlds..... A 3.42 first gear and a 2.56 rear gear gives you and overall first gear of over 8 to 1......That is about the same as a 2.20 fiirst gear and a 3.91 rear gear......... and then cruise on down the road

[Bobsw32]

Secondly that rpm's seemed high so I went to one of the calculator web site and at 65 miles per hour you should be at 2600 -2700 rpm....maybe your tac is off....By going to a 2.56 you could get that down to close to 2000 - 2100 . Having a big block Olds with all that torque could easily get it down to 1700 - 1800 but that will take and Overdrive tranny

[442scotty]

I have 2 65's...one with 256's and an OD and the other stock with 323's...I get 1600 rpm at 65 miles per hour with the OD (built 455) and 3200 rpm at 65 miles per hour in the stock 65 (442 with AT)

[442scotty]

Im not crazy about driving my original 400 engine at higher rpms on the highway but they were made to handle it I believe. If you have a rare engine, like the 65 400, its not a bad idea to make sure its in perfect condtion to handle the repeated use. Mine only has 54K on it but after 45 years its coming out next spring for a complete overhaul.
Dont want to risk losing her.

[Lady72nRob71]

With 225/70/14 tires, TH350 AT and 2.73 diff, Lady cruises 80 at 3000 rpm...

[bccan]

Just for comparison, 70 cutlass w/ 200-4R, 3.91, 26.5" tire runs 2400 rpm @ 70mph. I think it is actually 72 as my speedo reads 1-2 miles per hour slower than car is going, according to those radar speed signs around town.

[Lady72nRob71]

Originally Posted by 442scotty

Mine only has 54K on it but after 45 years its coming out next spring for a complete overhaul. .

Gee - that engine's just now broke in! It has a long way to go...

Do report it's condition when you rebuild it - If cared for reasonably, I suspect just the gaskets and seals need renewing...

[Nilsson]

Your RPM'S struck me as high as well. I have a 4 speed with a 4:33 gear and I turn 3500 @ 65mph. That is also with stock wheels and tire sizes (rubber bands)

Needless to say I try to avoid long distance highway trips.

[mugzilla]

Originally Posted by Bobsw32

Secondly that rpm's seemed high so I went to one of the calculator web site and at 65 miles per hour you should be at 2600 -2700 rpm....maybe your tac is off....By going to a 2.56 you could get that down to close to 2000 - 2100 . Having a big block Olds with all that torque could easily get it down to 1700 - 1800 but that will take and Overdrive tranny

The local highway patrol should be able to direct you to a shop that can calibrate your speedo/tac ...

[dan1s]

Here are two sites to help you out.

http://www.csgnetwork.com/multirpmcalc.html

http://www.miata.net/garage/tirecalc.html

[wmachine]

Originally Posted by Bobsw32

Secondly that rpm's seemed high so I went to one of the calculator web site and at 65 miles per hour you should be at 2600 -2700 rpm....maybe your tac is off....

Originally Posted by Nilsson

Your RPM'S struck me as high as well. I have a 4 speed with a 4:33 gear and I turn 3500 @ 65mph. That is also with stock wheels and tire sizes (rubber bands)
Needless to say I try to avoid long distance highway trips.

X3. I'd look into it. IIRC, I'm about 3200 rpm with 3.90s in a stock '67 442.

[dan1s]

Does any one know the tire height for a

F70x14 standard
7.75x14 optional
205 R14 Radial ply optional

These were tires that could have come on my car

[Aron Nance]

This has absolutely nothing to do w/your situation, but as I recall, our '92 Custom Cruiser (5.7/700) is turning about 1500 @ 65 miles per hour.

[442scotty]

What kind of mileage are you getting Aron? I have not checked mine yet

[redvettemike]

I have a '71 442 with th400 and a/c. I think the rear end is something like a 3.23 (I think the a/c cars all came with the same rear end ratio). I am at about 3000rpm at 70mph. Too much for me. I am going to get a 700R4 or 2004R or perhaps a GearVendor overdrive unit. The GV unit reduces the rpm's by about 28%. I have a '69 Camaro with a 700r4 and it runs at about 2300 at 70.
My tach was also not correct. There is an adjustment on the back of the tach that lets you adjust the instrument. We adjusted to be in line with a dwell/rpm meter.

[agtw31]

i had 373's in my old 72 ragtop,that 462 loved cruising at 70 miles per hour heading to national trails every friday

it's just rpms,fellas.