[gavin]

I need some info from the past. My buddy got his hands on a 1960 389. It still has standard bores . It’s getting bored out 040 and the crank is 010 and may get away with a polish. He wants to use the original heads because he has an early tri power .We have two sets of heads and of these one set has new rockers. Both sets need new guides .As getting a set of screw in studs with oil hole seems impossible ( if anyone has a set set to sell I’m keen) I am hoping some one here has an article on pinning the studs or some first hand advice. The second thing is I believe Steve25 had an article on modifying early heads and chambers but I can’t find it. I would appreciate being pointed in the right direction. Also does anyone have advice on valve springs to suit a Ram air 4 cam with these heads. The stock rods have been fitted with ARP bolts we would prefer new forged rods but shipping from USA to Australia is chaotic at the moment.The available gasoline in Australia will work with high compression if the cam has wide lobe centre and a bit of duration. All information eagerly listened to. Thanks Gavin.

[steve25]

So these are the 306 casting heads?

[tom s]

I would mill the stud boss and use screwin in studs.I would then use 65-66 rockers with the oil hole and forget about oiling thru the studs.Paul Spotts sells the correct rockers.DONT try to use 67 and later rockers.Steve should be able to help with valves.306 heads did not come out until 1961 and were not factory installed until very early 62 on SD engines.Tom

[gavin]

Thanks Tom for your reply. The problem is 1955-1960 rockers are not interchangeable with the 61 to 66 rockers length or geometry wise. You are forced to use the 60 parts hence will need to pin or find the unobtainable holed screw in studs. It’s would be easier to use 61-64 heads but these are a wee bit difficult to find in Brisbane. I can get some low comp 66 326 heads that will work with some chamber work ( now 58 cc need at least 62 cc) but they need the later manifold. I’m hoping some one has some experience with pining and will pass on the knowledge. Maybe someone also knows where find the chamber and port mod thread. Thanks Gavin.

[steve25]

Gavin unfortunately the valve inclination angle in the 326/ 389/421 heads do no lend themselves well to reworking them into a larger size like the one and only closed chamber 14 degree inclination angle head, that being the 670 casting.

If you go with a piston that has valve notches that total 8.5 CCs then you will have about a 9.75 compression with these numbers.

Head CCs 67
Head gasket CCs 9.4
Deck clearance .020”
Ring land volume. 1.5 CCs
Bore 4.100”
And those valve notches of 8.5 CCs., or a combination of valve notch and a small dish in the piston to get this amount of CCs.
At any rate the heads need to CC checked before any determination can be made .
Decking the block to get that right before boring and milling the heads as needed to get them straight can very fast make for a need of removing 4 CCs more from the pistons to stay on that 9.75 compression ball park.

[steve25]

Running the .469” lift with 1.5 rockets of that cam is not recommended with even pinned studs with a stock top diameter.

[tom s]

Gavin,I used 65-66 rockers on a 60 head.We did not have a issue with them?Maybe my builder worked it out with push rod length?Tom

[tom s]

I just confirmed with a friend that did it many years ago.You just cant use 67 and newer.Tom

[Jack Gifford]

The greatest improvement I've made to the early chambers is milling away the side of the "bathtub", as Mickey Thompson used to do to them. Selecting pistons with a D-shaped dish can maintain a decent-sized squish area, while giving around a 9:1 ratio.

[gavin]

Thanks for the info guys I was sure the later 61-66 rockers didn’t work so will try a set.Both my 63 tempest and my 67 bonneville run quite well on the local gas and are over 10 to 1 compression but I do use octane booster in summer. The ram air 4 cam may have too much lift so I will have find something with a low lift and some duration. Maybe the 068 cam would be enough with jacks chamber mods. I have new crower springs I will have to see how the spring height works out. Steve do the general rules of Pontiac head porting work on the early heads not after race stuff but if they go to 215 to 220 on the intake that would be nice.thanks Gavin.

[steve25]

You should be able to run the .470" lift of that Cam once the valve guide tops are cut for positive seals which is something that he will want to do anyway.
Then aftermarket retainers and the right springs will be needed.

[694.1]

Steve & Jack, you guys would likely know...Milling the chamber as Thompson did, will this help a stock engine or is it more of an advantage with a blower, huge cam, fuel injection, or... This mod is intriguing to me. What parameters is it useful in?

[61-63]

gavin if you would want a set of 540306 heads for that engine I have a never ported pair with a set of NOS valves and correct '61/'62 SD valve covers with stacks. Not cheap and would probably cost a fortune to ship down under.

[steve25]

I can only guess that MT did such with his Aluminum heads to lower the compression to a workable level that would allow those 4 motors to live long enough on a given amount of boost, and yet make the combined total power he needed.

Salt flat runs take a lot longer then only running a motor at a high HP level for 12 seconds or less at a drag strip!

[Jack Gifford]

Mickey just thought the bathtub chambers were a bad idea. He opened them up on both blown and N/A Pontiac engines. I've only done this on the Tri-Power 382 in my '59 GMC- I'm very happy with it.
As for port flow of early heads- my 528511 ('58) intake ports flowed 210 cfm @ .550" lift, with just bowl work and a careful valve job and the modified chambers.

[421mike]

John, what's not cheap in dollars and cents. Mike

[61-63]

$3500 + shipping for the heads, valves, and valve covers. That is top dollar I realize but the heads may be NOS? I've had several sets go through my hands over the years and this is the nicest set I've ever seen.