Hey all, I'm getting ready to rebuild my father's 1970 olds cutlass convertible (w25 option) can I get some recommendations on pistons and cam?
it's the original motor, and he wants to keep it looking that way if possible, but he would like a bigger cam and maybe some headwork, so stock iron intake, quadrajet, stock exhaust manifolds, stock exhaust, th350 with stock converter and stock rear gears, I'm guessing 2.73. Power brakes. He would also like it to run on 87 octane.
he had the thing rebuilt about 10 years ago and he has put maybe 10k miles on it, it has allot of blow by coming out the breathers, and after a compression test it has 1 cylinder at 50psi and all others 185-195psi. I believe when they rebuilt it they re-used the stock pistons and probly changed the rings. They also put in a (262 cam)not sure on the other specs.
he was always disappointed by the power it had but he did like that it ran on reg 87 gas.
any recommendations on a good cam and pistons?

 

Cutlassefi stroker rotating assy & cam + a bit of gear = FUN.

 

Factory rear for a 1970 Cutlass would be an O-Type, and that rear doesn't have a 2.73 ratio. The standard no-cost gears were 2.56, but optional gears were available. You should probably verify what the rear gears are prior to deciding how to build the engine so that you get the compression and cam that will work well with the gearing.

Using factory high compression (10.25:1) pistons would make running 87 octane more challenging than something in the mid-9 range.

 

It probly is 2.56 then, I know the thing drives well on the freeway and is a dog taking off, no posi traction, 14" wheels, 245-60-14 tires, would it have a spec tag or stamping to ID it?

 

2.78 was an available Type-O ratio. That's what mine had. There is a 2-character stamp on the axle tube that will tell you what is in it, or you could change the fluid and check the numbers on the gears directly (or estimate by jacking up the rear and rotating the driveshaft and counting revs of the tires or visa-versa).

 

Even a 3:08 gear will wake it up a bit but still be able to cruise at 65/70mph no problem. Probably a stock rebuilt with a small RV cam would be the best without opening up a can of worms. Dual exhaust of course. Jmo

 

Would the l2321 or l2320 pistons be too high on compression? I was also considering the pistons cutlassefi offers but that's still around 9.25-9.5.

 

Below is a picture of the code on an O-Type rear with 2.56 gears.

 

I'll look for that tonight when I stop by his house, I'm guessing that's drivers side back side?

 

Passenger side

 

These are the ratios available in 1970.

 

Ive got the R2

 

 

What would you recommend for a cam with those pistons?
70 cutlass convertible
350 4v OEM ram air w25
2.56 gears, th350, stock stall
only real upgrade is the 2.5" exhaust system, but it's still 2" coming out of the manifolds.
I can port the heads of it's worth it.

 

The stock stall is a killer. I have a 9 to 1 350 with slightly better than stock heads, Cutlassefi''s mild 214/214 custom cam, stock stall TH350C, had the stock TH350, same result and 2.78 gears. It also has a RPM intake, headers and dual exhaust. I can barely spin tires off the line but picks up OK at speed. I had a 2004R trans my daughter ran low on fluid with 2300 stall converter. I could lay rubber for a 1/4 block. Needless to say a 2004R is going back in with the slightly better first gear and the same 2300 stall flash converter. It really made a big difference.