Power train combo: '66 BB 425hp, M20, 4.11 - what to expect?

[Oliver S.]

I'm interested in a '66 Coupe (BB 425hp, M20, 4.11, no Side Pipes) located in the US. Beside my '65 SB 300hp 3.36 Convertible I haven't driven a C2 - not much around here in Germany and even less BBs (never saw one driving only standing ... 10 years ago). Normal cruising speed would be 70 - 80 mph on our Autobahn. How is it driving such a Coupe with this drive train combo in this speed range?
Actually, I would prefer a 390 hp with < 3.55 Rear End - more low end torque, lower RPM @ cruising. But this '66 is very appealing to me.

Oliver

[Wayne W.]

Re: Power train combo: '66 BB 425hp, M20, 4.11 - what to expect?

Just get a 308 to go in it. A 411 at 80 will be screaming.

[Paul H.]

Re: Power train combo: '66 BB 425hp, M20, 4.11 - what to expect?

A 66 425 horse with 4.11's and a M20 will be quite the stump puller. Not exactly the gears for Autobahn cruising but you will have a hard time wiping the grin off your face when you jump on it at any speed. You can always change out the gears if you get tired of the high revs on the highway.

[Terry D.]

Re: Power train combo: '66 BB 425hp, M20, 4.11 - what to expect?

At 80mph you be taching around 4000rpm, that big block will not be able to pass up a gas station, and if it is stock probably won't last too long

[Steven S.]

Re: Power train combo: '66 BB 425hp, M20, 4.11 - what to expect?

I agree, that would get annoying real quick driving with 4.11's any amount of time at that speed. My BB '66 works very well with 3.36's and I believe if I had access to that Autobahn I'd want 3.08's!

[Duke W.]

Re: Power train combo: '66 BB 425hp, M20, 4.11 - what to expect?

3.08s will make the car sluggish off the line, but if you don't have a lot of hills in your area, no big deal. I have 3.08s/CR T-10 in my '63 340 HP, and it spent the first five years of its life in hilly Seattle. I did a preemptive clutch change at about 50K miles before I headed for the midwest flatland, and that clutch was still okay at 115K when I changed it again.

If you have OE revs per mile tires, 60 MPH is about 2350 revs and 80 is 3100. With a 3.36 revs will be nine percent higher at any speed in top gear.

The standard gear with L-71 in '67 was 3.55 and 3.36 was optional, and, of course, all SHP big blocks had the CR (2.20:1 first gear) Muncie four-speed.

Duke

[Oliver S.]

Re: Power train combo: '66 BB 425hp, M20, 4.11 - what to expect?

Oops, I was wrong. It is a 3.70 Rear End.
I prefer driving on normal country roads. I live near the Swabian Alb and Black Forrest. But from time to time a 60-100 mile trip on our Autobahn takes place. With a coupe I expect longer trips on them.
The 3.36 of my '65 300 hp is very good for my driving habits.
@ Duke, I found your xls sheet for playing around with the ratio. Great help.

Oliver

[Duke W.]

Re: Power train combo: '66 BB 425hp, M20, 4.11 - what to expect?

...glad you found the gear chart useful. It's a quick and convenient way to analyze changes to transmission ratios, axle ratio, and tire revs/mile.

If anyone else is interested:

https://www.forums.ncrs.org/showthread.php?102350-Excel-gear-chart-downloadable

Duke