I am in the middle of converting my 70 vista to a 4 speed (m20). The diff has 3.08:1 gears and the rear tires are 275 60 15s. The motor was completely rebuilt by the previous owner and has very little miles on it since. It has new pistons though I'm not sure what compression ratio they are but using a bore scope I can see that they have a shallow dish, the heads are #6 with a fresh valvejob and hardened seats. I have a new edlebrock 650 carburetor and a performer rpm manifold as well. What I am trying to figure out is what would be a nice cam with a little lump to it but retain the ability to use the a/c. Another concern is finding a clutch that won't be to hard to push but perform ok. I also have flowmaster mufflers and headers. I know you guys build some wild motors but in this case I want to pick the right cam/lifters /springs and clutch. Any help is appreciated...

 

I understand not being able to get too lumpy a cam but remember I want to use the a/c so I wouldn't want it too big anyway, I just don't want a boring smooth idle.

 

i ran that 260 cam and it ran great and sounded good too. it really liked the 3.42 gears i tired 3.73's with no major improvement. its a great cam

 

I'd be checking the back ot the crankshaft for the pilot bushing hole - without it you're restricted to automatic.
I believe the M-20 is a close ratio [2.20 1st gear] and won't be too good coming out of the gates - you'll like the wide ratio more. [2.54 1st]
3:08's are pretty good on the highway, but very light on acceleration.

 

The m20 has the better 1st gear but I still don't think I'll be smoking very many people off the line, but it's mainly going to be a cruiser anyway. I got an adapter pilot bushing from the parts place and will be enlarging the hole in the back of the crank rather than cut the input shaft.

 

Am I able to run the stock rockers and springs with it?

 

if you are talking about the cam yes it took stock rods and springs

 

From what I've heard on here, those 'adapters' might last 1000 miles, or not!
here's a link -
https://classicoldsmobile.com/forums...g-install.html

 

X2, and thanks.

If you're going to stay with the 3.08 then your choices are limited. To keep some low end I'd probably do a single pattern Erson Hi Flow AH, 220/220 on a 110, lift is .504 on both. Stock rockers will work. Run it about 4 degrees advanced and you shoud be fine, if you have 9.0:1 or better. It will be heard as well.

 

Another clutch choice would be South Bend Clutch. Brian or Peter can help you, whether a stock replacement or a racing clutch. 800-988-4345

 

That sounds like a large cam, will it still build vacuum and be ok with a/c? This motor has stock rebuilt heads with no modfications as far as porting or aftermarket valves or springs. What rocker, vale spring, and pushrod set up is required for it?

 

With the 4 speed you can always just raise your idle but if you're really worried about vacuum we can go a little more conservative with a 214/220 @.050. You can use the stock valvetrain with springs in the range of 100# on the seat and 275# or so open.
If you go much smaller you may not hear it as much as you want.