[Formulas]

The thing about 3/8 pressed in studs is when you stray away from original rocker lock nuts, they keep the rocking stress off of the thin sections of the stud

[4zpeed]

Just do your homework that's all I'm saying, there's a certain amount of money it's going to take to put the heads you have in service, that's if you decide on the 068 or upgrade. If you can find a set of big valve screw in stud heads available that already meets some of the criteria, weigh your options. Think about any future upgrade as well.


Frank

[i82much]

do they make anything that would allow you to use a conventional drill press to tap the holes?

[Dragncar]

Originally Posted by i82much

do they make anything that would allow you to use a conventional drill press to tap the holes?

Bridgeport !

[b-man]

Originally Posted by i82much

do they make anything that would allow you to use a conventional drill press to tap the holes?

Yes, a Tapmatic.

https://www.travers.com/product/tapm...ead-85-001-144

However for $915 you’re better off doing it by hand or paying a machine shop.

You’d better have a drill press that’s in good shape with the table perpendicular to the drill.

[i82much]

Originally Posted by b-man

Yes, a Tapmatic.

https://www.travers.com/product/tapm...ead-85-001-144

However for $915 you’re better off doing it by hand or paying a machine shop.

You’d better have a drill press that’s in good shape with the table perpendicular to the drill.

That's cool ... but yeah ... not worth it for the average guy.

[b-man]

It all boils down to you’re best off staying with a factory performance cam and stock 1.5:1 rockers if you’re not going to pony up for the valvetrain upgrades required to run higher spring pressures or higher ratio rockers.

Trying to make the factory designed non-adjustable valvetrain into one that’s adjustable can’t be done correctly unless you get rid of the factory bottleneck studs whether they’re press-in or screw-in style. As already pointed out above the stud loses support at the bottleneck when you move away from the stock non-adjustable rocker nuts.

Will the bottleneck studs break if you run an aftermarket cam with higher lift and non-stock adjustable nuts or polylock nuts? Maybe or maybe not, gamble if you like.

On an extremely limited budget?

Then stick with either a factory cam or something close that doesn’t require an adjustable valvetrain.

Even with the 068 cam the press-in studs can back out, especially so if the heads have been through a shake-and-bake modern machine shop cleaning process which can tend to loosen up the factory press fit on the studs. The dealers did stock slightly oversized replacement press-in rocker studs so it wasn’t all that uncommon to find some of the studs backing out when these cars were new.

You always hear about valvetrain failures of one kind or another from people who put a big cam in their engine but didn’t address the other things required when you do that.

[67Lemons]

Well folks as always I appreciate the information (education) & with most things there is unfortunately no free lunch. My original intent with this engine since it is completely original & untouched was to just throw a four barrel & cam in it since the rest of this car is modeled after a day two type of build, guess I’ll stick with that plan at this point. If I ever decide to go further I’ll deal with the heads & rods later down the line. I’m sure the 068 will be enough fun at this point, if the direction of this build changes at some point later I’ll deal with it then.

[b-man]

NOS 068 cam overkill.

1964 9770716 421 HO heads, same exact ones were shared with the GTO 389 that year.

ARP studs, these early style 389/421 heads didn’t have factory pushrod guide plates (pushrods were guided by machined slots in the head itself) so they need the rocker stud bosses milled down by about .250” to accept the ARP hex bottom studs. The machine shop installed 7/16-14 Heli-Coils to accept conventional BBC-style studs.

ISKY retainers and some NOS H-O racing VS-11 springs. Crower Enduro 1.5:1 stainless steel roller rockers. Manton 5/16” pushrods with a wall thickness of .118", made from chrome moly tubing with a hard melonite finish.

I very well could have used any aftermarket cam with up to around .500” lift with ease but the theme of this build was to closely duplicate the performance of a stock 370 HP 1964 421 HO. The closest cam grind I could find that had specs nearly identical to the 9770543 421 HO cam was the NOS GM 9779068 I found.

[4zpeed]

Not something you'd wanna do with you're average small valve head that's for damn sure...


Frank

[4zpeed]

Originally Posted by 67Lemons

I’m sure the 068 will be enough fun at this point, if the direction of this build changes at some point later I’ll deal with it then.

Just realize as been mentioned, you're dealing with 55 year old stuff and even using the 068 it's safer to upgrade those heads. In my humble opinion the answer to your initial question of 'next step up' would be big valve heads, but at the very least screw in studs would let you sleep better and I'll leave it at that, best of luck with your build.


Frank

[b-man]

Originally Posted by 4zpeed

Not something you'd wanna do with you're average small valve head that's for damn sure...


Frank

It was kind of my last hurrah for Pontiac engine builds. A nice cruiser engine I could stuff into my 1964 Le Mans convertible and drive off into the sunset of my life, retirement.

I probably spent $1500 just doing the heads. Bigger valves really don’t fit because they’re so close together, we ended up cutting down the heads of some Chevy valves that were the correct length if I recall correctly. My friend Mick who so graciously handled this build for me laid back the closed chambers on the spark plug side and even offered to port the heads but I prefered leaving the ports as-cast.

So I pretty much spared no expense on what was essentially the restoration of one of the best Pontiac street engines ever produced.

I think the early Tri-Power performance engines embody the essence of what most people thought when they first saw a fast Pontiac.

[Formulas]

Youin's need to think outside the box, This bolts down on flat / perpendicular to studs guide plate useing the bolt hole for the guide plate...
Its a aircraft structural controlled tooling drill bar 5/8 od drill bushing with 1/2 id.. no bridgeports no trees in the forest..

something like this can be easily fabbed up from from stock for the average guy from steel bar stock drill bushing not mandatory

[67Lemons]

Originally Posted by Formulas

Youin's need to think outside the box, This bolts down on flat / perpendicular to studs guide plate useing the bolt hole for the guide plate...
Its a aircraft structural controlled tooling drill bar 5/8 od drill bushing with 1/2 id.. no bridgeports no trees in the forest..

something like this can be easily fabbed up from from stock for the average guy from steel bar stock drill bushing not mandatory

That’s brilliant but don’t you need to machine the stud bosses to make room for the screw in studs?

[b-man]

Originally Posted by 67Lemons

That’s brilliant but don’t you need to machine the stud bosses to make room for the screw in studs?

Only on the early style 1966 and down heads and some low-performance 1967, transition year.

No machining down the stud bosses is necessary on the 1967 and later heads that came from the factory with guide plates and press-in studs, they’re ready for stud pulling and tapping as they sit.

[dataway]

I've got one of these I use in the shop. Not sure if a cylinder head would fit in it. A little finicky but workable.

https://www.grizzly.com/products/gri...-machine/g8748

[67Lemons]

As I mentioned above. There are a pair of #62 heads available locally but they have 72cc chambers which would probably be too much compression for the street with my stock pistons in the ‘68 short block?

My current 15’s are supposed to be 75-78cc’s from the factory, will the 72cc heads raise compression too high for pump gas with the stock original pistons in my 1968 400?

[PAUL K]

62 heads are usually 75 CC from the factory and come in around 76-78 CC after a rebuild.

[67Lemons]

The CL add states they are from a 1969 428 & Ron’s Pontiac page lists them at 72cc so I was concerned
Ron’s:
1969 428 370 hp 2.11 / 1.77 72 cc Screw

CL add
https://nh.craigslist.org/pts/d/cont...704145179.html

[b-man]

All the 1967 - 1970 400 and 428 big-valve high compression heads are listed as having 72cc chamber cylinder heads but very few actually are.

The later years had the larger chambers, and the ones used in automatic transmission applications were the ones that almost always received those heads.

1969 #62 were usually 76 to maybe 78 and the 1970 #13 were anywhere between 77 and 81. Both of these heads were used on the 400 GP automatic transmission applications among others.

I’ve seen the #62 heads on 400 Firebird stick shift cars as I had one myself (standard 330 hp) and on a 1969 T/A automatic. My 4-speed 400 had factory A/C so I’m guessing that’s why the 62 heads were used.

Probably the only true 72cc d-port heads (670, 16, 31, 48) were used on Ram Air, HO and non-air conditioned stick shift cars, but again you still have to cc the heads to be sure.

There were very few engines that came anywhere close to the factory rated 10.75 or 10.5:1 compression, most were around 9.6 to maybe 10:1. The 1969 and 1970 Ram Air III stick shift engines with the #48 and #12 heads were the only engines other than round-port RAIV engines that actually came close at around 10.5:1.