I've read that the #5 heads are considered best overall SBO heads, but wouldn't #6 or #7 be better because of their larger valves (same 64cc chambers)? Do they all flow the same? I'm still very new to the world of Oldsmobile.

- GoldOlds

 

5 or 5a heads from the late 60's early 70's are the best according the Dick Miller.

6 heads are good too, but are rare, they were used in Canadain cars.

The flow between 5, 6 and 7 are close. If there is no little "a" like 5a and 7a, this means they have the hardened valve seats so they can run unleaded gas.

You can also use Big Block heads on the Olds Small block. But opening up the cc cambers too much, will cause a loss in compression, thus a loss in power.

The trick is, take a set of BBO heads, have them milled to .010, and you have flow of BBO heads with a SBO combusion chamber

 

So a stranight #7 head (not 7a) will run todays fuels just fine? I was told I would have to get the heads rebuilt to run unleaded, guess my info was wrong.

 

A 7 head will run today's fuel fine, but it will cause problems in the future.

Go to your local auto parts store and buy a bottle of lead. About 3 or 4 bucks a bottle, but you gotta run it iat every fill up

 

Can that be done? I thought all Olds motors had "non-adjustable valvetrains," meaning that if you mill a set of heads, you have to shorten the pushrods to keep everything working properly... or something like that.


- GoldOlds

 

There are Olds heads that are non adjustable, but I'm pretty sure they were pre 1968. '68 and up, are different

 

By "different" do you mean "adjustable?" That probably sounds like a stupid question, but I want to make sure I don't misinterpret what you're saying. Thanks!

- GoldOlds

 

Yes, but maybe somebody else can confirm this before you buy

 

In the Performance section of this web site, there was an article (Valvetrain Geometry) about using shims to adjust the height of the rockers if you milled the heads or went with longer rods. So it can be done.

 

The heads on the olds motors have non-adjustable rocker arms. You could shim under the rocker hold down stems if needed. However, the thickness of shim added would be less than the amount of material that was removed from the head. I'm not sure what that ratio would be.