Highway RPM'S Seems To High

[atlbigboipimpin]

I have a 1986 cutlass which I just dropped in a 1971 350/350 combo in along the crappy 2:14 rear gears.My question is when I'm driving reasonable highway speeds(60-70) my rallye pac tach reads at like 3000 rpm's, whatz up with that. Someone please let me know if this is normal or not as I'm not trying to kill the motor!

 

[Blake442]

What motor was originally in the car?

 

[Longroof79]

3000 rpm's seems alittle high for that gear ratio. Are you sure they're not numerically higher? Are you running small diameter wheels and tires?
Is the tach reading accurately?

 

[dogsht]

Is your tach still set on 6 cylinder from the previous engine?

 

[atlbigboipimpin]

I have 14" rallye's and as far my gear goes my rpo codes says I have a 2:14 gear ratio and I doubt that it's been changed out and I also believe that my tachometer is reading correctly. The car originally came with a vin y 307. I'll be happy to give you guy's any more info you need for a diagnosis.

 

[TURNA]

factory gauges are famous for being wrong

Especialy in G-body's with there crappy connectors

 

[n33no]

Just smack your dash. It should read fine after that. :lol:

 

[TURNA]

Just smack your dash. It should read fine after that. :lol:

it would be funny ...but it is true!!!!! :lol:

 

[mr evil]

Yep, my tach's ****ed too. I haven't bothered trying to fix it yet, I just hooked up another I had laying around.
It's likely the problem for sure.

 

[86Cutlass383SR]

Since you didn't specify your rear tire size except it was a 14, I tried to calculate it as close as I could.

Assuming a 205/70/14 (25.50" diameter) tire with the 1.00-1 ratio of the TH350 and a 2.14 rear gear your rpm at 65 would be about 1834 rpm.