Why more power in 70 350?

Hello,

The June 1994 issue of Collectible Automobile has a feature article about 68 to 72 GS and GSX's. The article states that 68 and 69 350 motors had 280 horse power and 375 ft. lbs of torque. However, the 1970 350's had 315 bhp and 410 ft. pounds of torque (even more than the olds Rallye 350). The article states that the displacement and the compression ratio did not change in 1970. So, why did the 1970 350 have more power than the 68 and 69 350's?

Thanks,

Mike

 

I thought the compression DID change. That's why everyone wants the 70 model:grin:

1970 350 compression ratio was 9.0 to 1. Does anyone know the ratios of the 69? 1971 WAS 8.5 TO 1.

 

I believe the GS 350 (315HP variety) had 10.25 to 1. The 70 2bl version I own, for example, had 9.0 to 1.

I understand the heads vary slightly between years as well.

my .02

 

I think that it's in the cam, or the fact that 1970 had one year only rocker arms, possibly a real 1.6 ratio.

The 4 bbl 68 and 69 engines were 10.25:1 as was 1970. They were oil-through-the head and had specific rockers.

 

compression

the volume in the heads of a 70 is slightly lower than that of newer years (71-71) thus giving it higher compression.

too bad i only have the 2bbl one though.... that will change in time though..

Nate

 

"70 350

The 1970 hi compression engine had a different timing curve for the distributor (weights and springs) and the carb had different jets,springs,hangers, rods, etc. The compression ratio (10.25 - 1) was the same, the rocker arms 1.6 -1 were the same, the heads were the same volume. Probably more importantly is that the ratings were tweaked across the board in 1970. What a great year for muscle cars.

 

Its the pistons too:laugh:

Rob

 

For your reading enjoyment -

Thread #1

Thread #2

 

Any thoughts about carb jetting and rods just a thought also. I have really never heard any discussion on the 70 Carb for the 315hp 350.

 

few things here

there are the specs of the jetting here of a 70 carb.

http://www.v8buick.com/showthread.php?s=&threadid=13513

its a current thread i was looking for some info on. I'm not sure how it compares to the 71-72 years

 

Re: "70 350

That's pretty cool that the carb was different.
Maybe If I ever go back to a Q Jet I'll look for a 1970 carb!

As far as the rockers, I have heard some opinions that the 68 and 69 rockers are actually 1.55 and 71 and up stamped steel rockers are 1.50, leaving the 1970 as the only true 1.60 ratio. Could be a fairy tale, however.