Inliners International Forums General Discussion Hi Performance Duggan head project

Got this really rough Duggan head about 5 years ago. My machining capabilities have came up with time. I am now ready to try and fix her up.
Originally it was a shaft mount rocker system. Someone years ago decided to mill it out and probably install a stud mount system of some sort. It must not have worked, because it is all gone.
The spring pockets had been run with no steel spring seats and the springs cut though into the intake ports. Bet that introduced a bunch of oil into the ports. Someone welded that up too.
The exhaust guides and all valve seats look new.
Intake guides are gone.

This is a canted valve arrangement.
So, I have it mounted on the CNC to get the bolt pattern that someone drilled into it. Need to duplicate it for the piece to be bolted in.
Wish me luck. This will take a while.

The attractive sounds of the 'bolt-up and go' songs are an easy urge to indulge. Hopefully the damage is reversible with skilled machining . . .

Did you pressure check it for porosity? Maybe it was an experimental cut-and-try piece after porosity was discovered.

You should have bought the raw cast 12 Port head I had. It also had the canted valve arrangement. I still have the casting patterns for the 4 bbl intake shown in the background that fits that head also, and an extra intake I wont be using if your interested.

Can one of you guys fill the rest of us in here? What are we looking at?

Its the original style 12 Port Head made by Frank Duggan, hence the Duggan 12 Port Head. Its what the modern 12 Port heads by Sissell and others are based on.

I knew this was a mistake.

Thank you! That explains a LOT!

[quote]I would guess the combustion chamber is a wedge, with the floor of the intake and exhaust seats at different angles (the complement of their stem angles).
Have you measured the stem angles?[quote]

That data is given in Leo's book.

These were the 12 port heads before Sissells and Joe Deppe.
I have another one that is complete. The rockers look to be the same for both valves. Here are some pics. And a chamber pic.

That head with the rocker shaft is not one with a canted valve configuration, your first head is a canted valve style seen by how the spring pockets are offset from each other instead of being inline like the second head. So the second head will make rocker selection much easier to sort out. The very first generation Duggan heads were canted valve, so this dates the heads you have as the second one being a little farther up the evolutionary ladder in terms of development than the first one. Duggan also purposely made the valve spacing unsymmetrical from cylinder to cylinder on the canted valve heads to get the ports straighter, so you may find it annoying to see their isn't even symmetry in the machining process he did.

Scott,
The second set of pictures is a canted valve head. Same head, just in way nicer shape. It uses the same rockers intake and exhaust on the shaft system. The chamber pic shows the angled valve and the rotation in the chamber.
The next generation put the valves all "inline".

The pics in the last head don't show that very well. The first head is clearly canted when shown bare with no shaft on it.

In this pic at the end of head. See how the exh valve is on a angle?

It doesn't really show it that clearly in the pic, to me anyway. But yeah I know the first gen heads were all canted. The patterns I got from Joe will make the first gen canted valve cylinder head just like those you have.

Deppe must not have sold you the newer patterns. The only reason I say this. He also made a head with valves that were straight inline and used roller rockers on studs.
I have seen those in 4 cyl and 6 cyl versions.

I had gotten one style of each 6 cylinder head from him, one canted and one inline configuration. The 4 cylinder head I got was also the inline configuration. Most all of that head patterns and other stuff except for the block patterns and a few misc. items have gone on to new owners now.

Ahah. That makes sense.

I'd like to have had a working 4banger head!! Now I've got a stocker that's been ported, polished, lumped, and big valves, springs, and studs installed. Reckon I'll build it when I get back on my feet and get a couple of other projects out and gone.

Made some progress on the head. The bolt pattern the previous owner did, must have been done with a drill press. None of the holes were alligned and were also varying in spacing. Well now it has a piece of 7075 cut to fit. Next to fix the intake guides before drilling the rocker stud holes.

Tom , I'm enjoying watching this. It certainly points out some of the advantages in working with aluminum and having real tools.

Thanks Beater!
Currently looking for the right material to replace the intake valve guide bosses.
Going to jig the head up and measure locations for the intake guides, then machine them completely out and press in new guide boss material that is to be welded in. Also filling in the intake spring pockets with about .2 of weld.
Then will re jig it up and machine the bosses for new guides and spring pockets.
It is a process.
Here are some interesting pics. It is a cross section of a Duggan shaft mount head. Notice how little support there is for the intake valve. Well the head I am working on has even less. My spring pockets go into the intake runner and the valve guide seal area is gone.

I've heard that welding on cast pieces can be tricky. How will you prevent the pockets from getting brittle/cracking during cool down?

Curious.