Chevy Nova Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter #1
Hey guys as some of you know I just picked up my 1971 nova, I have a question about it. It has a 4 speed muncie with 396 full roller motor and apparently 3.73 gears 12 bolt rear end. When I drive down the country roads at 80kmh the car revs at 5000rpm?? Is that normal? Thanks in advance for the help!
 

Attachments

·
Registered
Joined
·
9,982 Posts
Are you sure you are in 4th gear?
If you work backwards:
80 km/hr equals 50 mph, or one mile every 1.2 minutes. A 26" tire turns about 800 revs/mile. 800 revs in 1.2 minutes is 667 rpm. Multiply by the rear gear ratio will give the driveshaft rpm - 2486 rpm - round off to 2500 rpm
Divide the engine rpm by the driveshaft rpm 5000/2500 = 2
Somewhere there is a 2:1 reduction in your gearbox.
Muncie ratios:
M20 Wide-Ratio 1963-’65
First Gear 2.56:1
Second Gear 1.91:1
Third Gear 1.48:1
Fourth Gear 1:01
Reverse Gear 3.16:1

The only thing close is second gear, which occupies the same bottom of the H as 4th.

Is your tach set up for an 8-cylinder? A 4 cylinder setting will double the displayed rpm.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #5
I never thought about the tach setup I just installed it, didn't know there was a 4cyl and 8 cyl setup. I'll take a look at it today, but it sounds like its definitely revving higher then 2500rpm if the revs drop in half for 8 cyl. Thanks guys, I'll get back to you as soon as I check it out.

Are you sure you are in 4th gear?
If you work backwards:
80 km/hr equals 50 mph, or one mile every 1.2 minutes. A 26" tire turns about 800 revs/mile. 800 revs in 1.2 minutes is 667 rpm. Multiply by the rear gear ratio will give the driveshaft rpm - 2486 rpm - round off to 2500 rpm
Divide the engine rpm by the driveshaft rpm 5000/2500 = 2
Somewhere there is a 2:1 reduction in your gearbox.
Muncie ratios:
M20 Wide-Ratio 1963-’65
First Gear 2.56:1
Second Gear 1.91:1
Third Gear 1.48:1
Fourth Gear 1:01
Reverse Gear 3.16:1

The only thing close is second gear, which occupies the same bottom of the H as 4th.

Is your tach set up for an 8-cylinder? A 4 cylinder setting will double the displayed rpm.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #6
Thanks Mike! I changed the tach to 8 cyl and now its revving at 2600rpm and for some reason stopped sounding like its revving too high. Must of been a mental mind thing.
 

·
Registered
Joined
·
9,982 Posts
Thanks Mike! I changed the tach to 8 cyl and now its revving at 2600rpm and for some reason stopped sounding like its revving too high. Must of been a mental mind thing.
Amazing how your mind will trick you. Good to see you have it going.
 
1 - 7 of 7 Posts
Top