1964 Head rebuild

[panhead_kicker]

Hi Folks,
First time I have posted here I believe. I've read alot of the related forum posts and knowledge base. I recently got my pan out of "storage" for last couple of years and decided it was time for some maintenance. After taking care of clutch, brakes, wheels, I started the bike and let it idle for a few minutes. It gave a little puff out the carb and died. I climbed on to kick it again, to find little to no compression. A compression test show no compression in the rear, and a whopping 30 psi in the front. I had never performed a compression test on the bike before. Adding a bit more oil in through the plugs only made a couple psi increase in the front, still zip in the rear cylinder. So, now the heads are off, and they have been dissasembled and beaded. I don't have the knowledge or experience to make some judgements on what all needs attention on these heads. So here is my first of probably many questions: How can I tell if the seats need to be cut or simply ground a bit, and how can I tell when there is not enough seat left to cut or grind on?

[King]

Hi Kicker

Those are incredibly low numbers for a compression test. What did the pistons and cylinder walls look like?

Regarding the heads, the first thing to check is how deep do the valves seat in the valve inserts . Most Panheads have been reground quite a few times and it is not unusual to see the valves “pocketed” to a depth which would preclude regrinding to get a good seat. There are two cures for this; send the heads off to have the valve seats built up and reground, or install oversized valves.

Other things to look for are: cracks from the spark plug hole toward the valve seats, worn exhaust spigots, damage to the head bolt insert threads, damage to the pan cover threads, damage to the intake nipple insert threads, and “decking” problems. Often the head bolt inserts will pull down and cause the deck of the heads to become irregular playing hap with the head gasket sealing

My original heads are facing all of the above but all are curable according to Don Sullivan at Headhog. About 8 years ago the repair options were not so good so I went with STD heads but now I am looking at refurbishing my originals. So keep us informed about what you find out and good luck.

King

[panhead_kicker]

Hey King,
Thanks for the reply. Yeah, I've not had much experience with with this, but I hope to learn enough to know whether or not I NEED to have something done or not. The heads have been cleaned up and examined and appear to be structurally sound, although the deck on the rear head under the exhaust port "looks" lower than the rest of the deck, as the shoulder there seems to drop. That is also the spot where the head gasket seemed to be wet and dark as compared to the rest of the gasket. I think it may have been leaking a bit at that point. I also think when the motor puffed its last gasp, a bit of carbon may have been trapped under the rear intake valve, thus the 0 psi. The carb intake had a splatter of small carbon chunks blown up into it, big as your pinky nail and maybe as thick as a dime. I saw where it dislodged from the underside of the intake valve.

The cylinders are still on the bike, but to my untrained eye, the walls look in pretty good shape, still show a cross hatch , no obvious scrapes , gouges, scratches etc. The cross hatch may be worn a bit at the front and back of each cylinder were the piston probably bears on the walls most. I plan on pulling the cylinders soon to see more.

As far as the seats go, they have been cut one time since '94, that was when I first got the bike. I wonder if I posted a high res picture if anyone could see enough detail to say if they were too deep for another cut or not?

[Cotten]

panhead_kicker!

The depth of the valve seats is measured by the protrusion of the stem above the guide. There is a diagram and spec in the Service Manual.

The maximum protrusion listed is limited by the valve spring pressure. If the springs are shimmed, and the stem "butt-ground' accordingly to restore the rocker geometry, the seats will service at even greater depths.

There comes a point, however, where the top spring collars or rockerarms hit the pancovers!

As King noted oversize valves are quick remedy.
(I have put all four valves in machines at 1/8" OS with great results.)
Beware, however, that rad cams must be checked for overlap interference!

...Cotten

[panhead_kicker]

Thanks Cotten. That was the kick in the seat I needed. (no pun intended). Figure 3B-3 shows 1.545 in. max. dimension. By that measure all 4 of my valves are seated too deeply. 1.560 was my worst. Looks like my seats do need to be attended to. Rats. Big Rats.
About oversized valves... sounds a bit odd. I wasn't made aware of this option. Are the valves actually "undersized" or shorter in stem length? This sounds like it might be a bit easier on a guy's budget, and still get the job done right.

[mbskeam]

the valve head OD is bigger, this lets the valve not go in as deep into the seat pocket, and the new seat will be father out from the old seat surface...

mbskeam

[Cotten]

panhead_kicker!

I don't think you are in dangerous territory at all, but please be aware that the next cut will take them deeper, especially if you replace the guide. (Otherwise, a good hand on a Neway cutter can keep it close to the lowest point without going much farther. )

Oversizes valves (as large as 5/32") were the Factory's idea!
(Some folks cut intakes all the way to Chubble valves, usually at the expense of gas mileage: Performance increase is marginal or negative.)

Imported nitrided 1/8" OS valves are widely available, and good quality. (Nitriding should always be ground from the faces and butts of new valves.)

Please remember that the Service Manual specs were written for the general public; They did not expect service people to shim springs or butt the stems when they could just sell a new valve and eliminate the need to think.

Your motor won't know if you only do the exhausts, which are usually the deepest.

If new seats are your decision, avoid hardened inserts at all cost.

....Cotten

[panhead_kicker]

Ok! Are new valves a must? It seems as though these are simply replaced as a matter of course. I suppose what ever labor cost are involved nowadays to grind valves, quickly makes new valves the affordable path.

Since the terms "nitrided" and imported have come up, I have found, for example, that two types of Manley valves (USA) can be purchased for my needs; "chrome" and "nitrided". Lots of import brands out there, some which are "stainless" too. Can anyone state pros and cons of valves and their finishes?

[Pomike]

I will let an expert fill you in on the different valves. I had Don do my heads. Nice! why don't you yank those cylinders and check the rings, bore etc. That is the cheap and eas y stuff, so don't skip it. Good luck, and let us know what you find.
Mike

[panhead_kicker]

Pomike,
The cylinders are next. I'll probably pull them in the morning. I don't have an inside micrometer to get down in the bore, so I'll have to borrow one, or find a machine shop close to check it for me. Meanwhile I'm still digging around the forum for answers to my valve questions. If anybody's interested, I attached some current head pictures.

head1.JPG

headclean_combust.JPG

[panhead_kicker]

I've only now noticed that my intake valves are larger in diameter than the exhaust, They measure ~1.975 in. dia. Is this what what you guys mean't about using oversized valves? So if I already am running OS intakes, then I suppose new seats are in order. I think I am going to take the advice given on the seats and have them built back up rather than hardened inserts.
The valve guides are marginal at best, I'll have them replaced. All the springs free lengths are about spec, but I can't measure their force. Should I just spring for new springs? The rocker arms look good.

[caschnd1]

Looking at the photo I'd say the exhaust spigots probably need some attention too. They look like they are getting pretty thin. While you are having work done consider having the spigots replaced.

-Craig

[indianut]

You know you can buy valve blanks from Manley and cut them to length and put some keeper grooves in them. Takes about 15 minutes to do a set. I would not TOUCH those seats if they were my heads

[Jack_Hester]

To follow along with what Indianut said, I sent Manley some OEM valves and had them make a couple sets with oversized heads, to my specs. Recut the seats (Neway cutter) first, measured, and ordered. Valves worked perfectly. Cast iron guides are a must, with Manley stainless valves.

I also had Don Sullivan rework a set of '48 heads, a while back. Repoured the seats, repaired/replaced the intake nipples, and replaced the exhaust spigots. You can't tell them from originals.

Jack

[Guest]

you could lap the valves in by hand. get some fine valve lapping compound and a lapping tool (any auto parts store should them) the clymer work shop manual has all the info you'll need.