got a chance a picking up some #6 heads.......are they better than #8's?
I havent heard much about them. Ive been told that #5 and #7 are best.
Whats the deal with #6's??

 

5-6-7 are all good SBO heads. Similar size chambers (all smaller than the chambers on #8s). #6 heads were used on all 1970 SBOs, including the W-31 when fitted with larger valves. Don't know who's telling you not to use #6s, but they're wrong.

 

I'd use the #6 heads over the #8 ANY DAY (64cc vs. 79cc). From what I've heard, the #6 heads are rare. Valve sizes are 1.995/1.624 unless they're from a W31, in which case the intakes are an even 2.000 - I think. Unless the owner is asking a ridiculous price or if they're cracked/damaged, jump on 'em! They'd do your late 70s 350 (assuming your #8 heads are on their original motor) a world of good.

- GoldOlds

 

Correct

I'm afraid you've heard wrong. #6 heads were used on EVERY 350 Olds built during the 1970 model year. Production figures were probably in the half million cars range that year, with likely over half of those carrying 350s.

Also not correct. First, 1.995" rounds off to 2.0". The numbers you quoted (1.995/1.624) ARE the W-31 valves. Lesser 350s got 1.880/1.567 valves.

That is correct.

 

I'm gonna go for the #6's!
Thanks guys!

 

Perhaps a silly question, but couldn't you just shave a set of 8's?

C.J.

 

Yes, until you run into the problem of the non-adjustable valvetrain.

 

Thanks, Joe - guess I got a few facts mixed up (maybe it's the #6 W31 heads that I was told were rare?). Anyway, the newfound info brings about another question; what's the difference between #5 and non-W31 #6 heads, aside from the years they were produced?

- GoldOlds

 

I thought I read that 6 was only on Canadain cars, thus making them rare

 

If you are referring to another (unnamed) thread, BWAHAHAA! If not, then I'm not laughing.

Either way, thanks.

C.J.

 

#6 heads used valve rotators, #5 did not. As a result, the spring pockets in the #6 heads are deeper, requiring a shim if you don't use the rotators or enabling you to run a taller spring with thicker wire (ie, stiffer) without running into coil bind. And just for completeness, the #7 heads used rotators on the exhaust valves only, so they have a deep/shallow combination of spring pockets. Note that 68 Ram Rod 350 motors and 69 W-31s also used #5 heads with the bigger valves.

I'm afraid you read wrong. Every single 1970 350 Olds came with #6 heads. The desirability (as opposed to rarity) may be the deep spring pockets as noted above, which allow stiffer springs to be run if you dump the rotators.