[Joe-Touring]

I currently running a 0.040 over 326 while my 400 is being built. I brought it out of winter hibernation a couple days ago and now have a pinhole in a head freeze plug. Of course it’s in the rear next to the firewall. So I need to pull the heads.

It has 1967 #143 heads on it currently. I believe they are around 72-75cc. I also have a set of 1967 #061 heads that have are pretty much ready to run. I cc’d em at ~75ccs. An interesting thing about these heads is that the 061s replaced the 143s mid year on big car 400s.

I know that the later open chamber heads flow much better than the closed chamber heads. The 143s will have 1.96/1.66 valves. The 061s have 2.11/1.77 valves.

My question: Will the better flowing heads overcome the valve shrouding issues on a small bore 326? Or do I run the worse flowing small valve heads?

[Joe-Touring]

A few extra details:
I have a set of Milodon SS valves for closed chamber heads
I have an MLS 0.036 head gasket set for a 326
I am planning on running a Melling SPC-4 cam
Compression ratio will be ~8.7:1

[b-man]

The only possible issue I see is the valve to bore interference with the 2.11 intake valves.

Be sure to check for that at full valve lift before sealing the deal, otherwise why not run the 061s? If they’re fresh then do it.

Be advised that the rockers and pushrods from the 143 heads aren’t compatible with the 061 heads.

[Joe-Touring]

Originally Posted by b-man

The only possible issue I see is the valve to bore interference with the 2.11 intake valves.

Be sure to check for that at full valve lift before sealing the deal, otherwise why not run the 061s? If they’re fresh then do it.

Be advised that the rockers and pushrods from the 143 heads aren’t compatible with the 061 heads.

How much clearance is recommended? Ah yes, forgot about the valvetrain differences. Luckily I have a set of rockers and pushrods ready to go.

[Joe-Touring]

To provide some illumination, I grabbed a head and gasket to see how well they would get along. Im no expert, but this seems bad:

[25stevem]

Even if the 061 heads would have worked for your bore size I would not run them!
That extremely open chamber shape was only used for that half year time span because it was so prone to ping and then the engineers dropped it like a hot potato!

It did however burn cleaner then the 68 and up D port chambers.

As you can also see the 061 chambers are a bit shallower then the 670 heads and the 72 cc 68 and up D port heads so your would also be limited to less valve lift with the valve notch placement in your 326 pistons and also due to the fact that your bores themselves have no chamfers.

I also see that the deck surface finish on your 061 heads is extremely course which is not good.
I would be concerned with normal expansion and contraction with heat up and cool down cutting up a gaskets fire ring pretty fast.

[b-man]

Replace the core plugs in your 143 heads and bolt them back on.

Slide your new cam and lifters in the along with a new timing chain set and drive it until the 400 is ready.

At least you’ll have fresh head gaskets and a cam and timing set that’s not worn out along with your coolant staying where it belongs. You’ll notice an improvement from upgrading the cam and replacing the old worn cam and timing set, win win.

Just make it an easy fix and move on to building your new 400.

[242177P]

Originally Posted by Joe-Touring

... pinhole in a head freeze plug. Of course it’s in the rear next to the firewall. So I need to pull the heads.

Leave the old freeze plug in place, and just slap an expansion plug inside of it. Yeah, it's shallow, but a short term fix really is ideal. The 326 is already on borrowed time, JB Weld and duct tape are your friend. At least until the 400 is ready.

[tom s]

3.718 bore is awful small to try to use any large valve heads.We had issue with a 4.030 bore.Dave chose a 2.05 intake and a 1.66 for our build.Tom

[Jay S]

For tight spots and temporary fix’s, a tighten able 1 1/4” to 1 3/8” expansion plug might be helpful. Get a couple, if one leaks the others aren’t far behind.

https://www.tractorsupply.com/tsc/pr...iABEgL8NPD_BwE

[77 TRASHCAN]

I've used those rubber plugs. My experience is to only use as temporary fix. If you do, check them to make sure that nut stays tight. The rubber will shrink through heat cycles.
I had to use 2 of these on a 5.9 Cummins, in a bus. The turbo and exhaust manifold would of had to come off to install the stock steel plug...no time for that. Thankfully that bus is gone from the fleet!!!

The rubber plug would be good enough, until the 400 is up and running!!!

[77 TRASHCAN]

The head gasket in post 5 doesn't look like it is made for that head, as others have eluded to.
I'm wondering about its design. The sealing ring that seals the head to the block has all that extra material inside of it. Not sure I've seen that on any head gasket. That extra material inside the sealing ring serves no purpose. Even if it was captured between the block and head, with the CORRECT head, it serves no purpose.

There appears to be a smaller sealing ring inside the main sealing ring. Not sure on all this.
A head gasket has to seal the head and block. This one obviously does not....

I see it is a multi layer head gasket, which is supposed to be some of the newest technology.

[gtospieg]

Not trying to hijack this thread... but can '68 17's or '69 47's be used on a 326? I know they have the smaller valves but curious if there are any reasons not to use them on a 326.

[b-man]

Originally Posted by gtospieg

Not trying to hijack this thread... but can '68 17's or '69 47's be used on a 326? I know they have the smaller valves but curious if there are any reasons not to use them on a 326.

Probably a couple of the better options right there.

The 72cc 10.5:1 1969 #46 400 - 428 heads are a nice option, they’re right about 9:1 on a 350 and should be close to 8.5:1 on a 326, 1.96/1.66 valves and press-in studs.

[25stevem]

The only thing to be concerned with if you put 68 and up heads on a 326 are these.

1) don’t run more then .420” lift to be on the safe side of PVC.

2) also in this same vein do not mill the heads anything more but for clean up purposes.

3) you need to use the 68 and up push rods.