67 327/300 HP Cylinder Head ID - Question

[Joe L.]

Re: 67 327/300 HP Cylinder Head ID - Question

Here are some pics of the double humps on the front of the cylinder heads. Notice that the face of hump is rough on the DS (non-original, late 1965 head) versus smooth on the PS (original). PS is hard to see because of the AC on the car. Is that what you were asking about earlier John Z?

Kirk------


This is further confirmation that the non-original head was cast and machined at Tonawanda. Tonawanda cast and machined small block heads have the rough cast face on the "double hump". Flint machined heads have the "double hump" face machined.

[Kirk M.]

Re: 67 327/300 HP Cylinder Head ID - Question

Thanks everybody. Another learning experience for me. Now I just need to find a single early 1967 Flint head and things will be good again!

[Joe R.]

Re: 67 327/300 HP Cylinder Head ID - Question

Thanks everybody. Another learning experience for me. Now I just need to find a single early 1967 Flint head and things will be good again!

Hi Kirk:

Keep in mind that it's pretty easy to have a machinist face the double hump on your Tonawanda head, which should be enough to get you full credit in NCRS judging. This is the "practical" thing to do if you can't tolerate getting a deduction in NCRS judging.

Of course, the "impractical" (but perhaps understandable) thing to do is to purchase a used Saginaw/Flint head with an acceptible date, and then have the head rebuilt. This will end up being expensive.

A single, used 462 head will probably cost about $100 (excluding shipping, which is expensive), but that is just the start of the journey. Assuming the head is rebuildable, you will spend a few hundred dollars on just a basic rebuild, and considerably more if your rebuilder talks you into hardened seats, stainless valves, screw-in studs, and modern oil seals. Then, of course, you will probably want to do the other head at the same time, doubling the cost. It's a slippery slope.

If your engine is running well right now, I suggest that you either leave the head as-is or pull it, get the double hump faced, and reinstall it.

As a long term project, you can try to locate a correct, rebuildable head and simply set it aside for the day when your engine needs to be rebuilt.

By the way, you should be aware that the raw 462 casting was machined for two different sets of valve sizes. In 1967, your 300 HP engine used an intake valve of about 1.9" and an exhaust of about 1.5," while the 350 HP version used 2.02" intakes and 1.6" exhausts (not sure I have the exact numbers correct).

So, when you are looking for a suitable replacement head, keep this difference in mind. To detect the difference visually, you probably need to see examples of both versions. In general, the valves and/or valve seats will appear to almost touch when the head is machined for the larger valves, but there will be a visible space between them in a head that has the smaller valves. The small valve versions are more common in the used parts market. I can come up with a photo of a small-valve head if you like.

[Kirk M.]

Re: 67 327/300 HP Cylinder Head ID - Question

Joe,

Thanks for all the good advice.

So, since I belong to this site, which of your choices do you think I chose? Of course, I am replacing the head with a properly dated one. I found one in Michigan at Tracy Performance Parts that was dated C 3 7 (March 3rd, 1967, which will match well with my C 9 7 - March 9th, 1967 head that is currently on the car). They are rebuilding the head for me and yes it did cost a bit but I think it will be worth it. My car buddy (the one who really knows what we are doing) is going to help me replace the head this spring as the weather warms. We were already messing with that head since a rocker arm had come loose and was clicking, so what the heck, why not replace the whole head!

Needless to say, car guy thinks I'm crazy, but I see it as a great learning experience in that I will get to help him replace the head and learn a heck of a lot about my car.

Car was running fine except to loose rocker before this discovery, so I plan on just replacing the driver's side head rather than getting them both done.

I simply asked them to rebuild the head as original. They seem to have significant expertise in this area and guarantee their work. Hopefully, I'm not doing something stupid! OK, I know it's "stupid" to replace a working head, but you know what I mean.

Also recently purchased a properly dated AC compressor for the car too. The one it certainly is old, but isn't dated. It works, but I would like to get a correct dated one in there.

And I thought I was about done with this stuff after this past winter.


Kirk

[Joe R.]

Re: 67 327/300 HP Cylinder Head ID - Question

Hi Kirk:

If you ordered the head rebuilt "as original," you probably avoided all the added-cost slippery slope stuff, such as stainless valves, hardened valve seat inserts, screw-in studs, push rod guide plates, and modern oil seals. Congratulations on your restraint! For normal driving, none of those expensive extras are necessary, but most rebuilders will try to convince you that they are.

Make sure that you plan ahead for the gaskets you use when you replace the head. You will have some decisions to make about practicality versus NCRS correctness regarding both the head gasket and the intake manifold gaskets. Check the archives for discussions on those topics, or email me for more details.