["Teacher]

I understand that there are codes on cylinder heads that reflect the configuration of valves, combustion chambers, etc. But being new to Pontiac I don't know a 6X from 4x, or anything else.Could somebody list what each of the more common head codes mean? I am looking to build a 400 for a project and need to know what to watch for. Thanks!

["Teacher]

I understand that there are codes on cylinder heads that reflect the configuration of valves, combustion chambers, etc. But being new to Pontiac I don't know a 6X from 4x, or anything else.Could somebody list what each of the more common head codes mean? I am looking to build a 400 for a project and need to know what to watch for. Thanks!

[Mr. P-Body]

wallaceracing.com

There's a comprehensive list of casting numbers and nominal chamber volumes, as well as ID information.

[captain42082]

type of head is usuall cast on the center exhaust port of the head-check the mentioned website in last post for specs

[tremo]

Here's the direct link: Search for Pontiac Cylinder Heads

Very useful info! Since the project LeMans has a 350ci, I would guess you have #47 small valve heads like me:

1969 350 265HP #47 1.91/1.66 8.6c.r.

The High Output (H.O.) large valve heads are more desireable:

1969 350 325HP #48 2.11/1.77 10.5c.r.

Seee-ya,

Jim.

[1gr869]

Teacher Teacher, you must be a "can do kid" (reading the quote at the bottom of your post). My son sings that song all the time!

[Half-Inch Stud]

how about what the PMD fella's thinking (or succession formula was) for generating the 2-digit Head code listing.

["Teacher]

Okay, so far I've found, I think, that both 4X and 6X heads are for newer engines. Is there an advantage with small valve heads, perhaps a smaller CC for more compression? It looks like maybe they could breath life into a low Comp engine, expecially if one opens up the ports, like we're doing.And perhaps shave about .050. At least they owuld be properly date coded. If one were to put these blueprinted/ ported/ polished heads on a 69 400 block, would he have a correct engine? It looked like the chart did include a small valve 400.Would it still be a GTO engine? How about a 400 two barrel Judge? Just a wonderin'

["Teacher]

According to the chart at Wallace,1969 350 V8 #47 heads have 1.96/1.66 valves and an 80 cc chamber. If, according to the same chart, a 70 cc chamber brings 10.5: 1 out a 400, and a 75 cc chamber gets 10: 1 out of a 400, then it stands to reason that an 80 cc chamber will bring about 9.5:1 out a 400, which would be perfect. Is Wallace mistaken on this? We are porting and polishing the heads as we speak, and if this chart is correct that is very exciting, especially when stock-type pistons are in the low compression range. Add a mild "muscle" cam (270 series) with a stock four barrel and RA exhaust manifolds and we might get that original "Judge" sound and performance out of it. Or is this all a pipe dream? Remember, we're on a tight "school" budget.

[Greg Reid]

I'd go for 16, 96 or 48 heads. Not only are they period correct, they'll have the larger valve sizes at 2.11/1.77. Compression will be relatively high though with only 72cc of combustion chamber capacity. There are ways to deal with that though and still keep the correct heads.
If you don't care about the visible castings (I mean after all, it is a clone) a lot of guys are using the 6X and 4X heads that have valve sizes nearly as large at 2.11/1.66 and around 90cc combustion chambers. That puts cr in a more manageable area and runs well on pump gas.

[johnta1]

The 80cc head will give about 9.5 cr with the appropiate deck height and head gasket thickness.

To determine the CR, Go Here.

[Will]

I would suggest.... nope that's not strong enough. I would highly recommend... Hmmm, no still not quite the import I believe this subject merits. Let's try: I think it would be a serious mistake for you to proceed with your "porting and polishing" work without first reading up on the subject as it applies to Pontiac heads specifically. There are a few critical areas in the ports that need work and will produce results. There are other areas in the port that are a waste of time, and there are a couple areas that if not treated properly will make your ports worse than they started out. Contact the owners of this forum and see if they can't send you a copy of Jim Hand's "How to Build Max Performance Pontiac V8s" book. It is an excellent source for the information you need to properly port a set of Pontiac heads. You can also try searching the archives of long-ago posts here in this forum as fairly lengthy discussions of this subject have been held here in the last couple of years.

My apologies if you are already sufficiently armed with information for this task.

Next up, if you find a set of small valve heads with desireable chamber sizes such as your #47 heads, you will be faced with three obstacles in the path to high performance.

First, you will need to drill and tap the end exhaust bolt holes on the exhaust flanges. No small-valve heads that I've seen have these holes drilled from the factory, including the #47s in my garage.

Second, you will need to remove the pressed-in rocker studs and replace them with screw-in studs. Failure to do so will result in a stud pulling out or breaking with any cam that can truly take advantage of your ported heads.

Finally, get the valve seats cut for 2.11"/1.77" valves BEFORE doing the port work. You will not be able to properly shape the ports to the seats without doing this. You can put a layer of duct tape or two over the seats and then be extra careful while porting to avoid nicking the seats.

The small valve heads entail some extra work and thus extra cost to make them work as a high performance head, but given the costs to purchase large valve heads with favorable chamber sizes you might break even. Of course, if you can do any of the abovementioned work yourself then you'll be ahead of the game.

Oh, and here's a picture that shows you where to find the pertinent numbers on a Pontiac head:

Pontiac Head ID