Carburetor and Fuel System
Title: Leaky
intake
Post by fourthgear on Oct 16, 2006, 12:51pm
panacea
You need to see what condition the threads in the head are in and if you just need to replace the threaded nipples. If threads are bad or damaged you will need to send them to some one(Headhog ) to either repair the threads or have o-ring type inserts welded in( I had the o-ring inserts welded in, not by headhog, but locally )I also had set screws in mine to lock the nipple in( the holes were welded over ), it should be a type of rivet if it still was a plumbers type.There are real good thread loc type sealers out there that will seal the treaded part if in reasonable condition.
Post by panacea on Oct 17, 2006, 1:52am
I don't think the threads are still in there, these are steel inserts with "O" ring style manifold(S&S). The rivet has been replaced with a set screw thru the side into the insert. I don't think they would come out without destroying them or I would re-install them with a better sealer. I'll try the RTV, if that doesn't work I'll try putting a vacumn on the plug hole and let it suck in some green locktite around the insert, I sound desperate don't I? Mike
Post by fourthgear on Oct 17, 2006, 12:52pm
panacea
Yep, you sound desperate. I think you will find that when the motor heats up and cools a couple of times , you leak(s) will come back . The only way to do it and not worry about it is to repair it properly and yes that means pulling the heads and take them to some one to repair. Repairing the threads in the head ( if you want to keep them OEM) or have the welded in o-ring set up. The problem with trying to seal with a sealer is the insert is steel and of course the head is aluminum and they expand and contract differently. The welded in o-ring adapter is aluminum and mine worked out real good , just make sure they pressure test the welds after words. Now finding some one to do the repair that has experience to do it is the problem. HeadHog( is in Ohio ) will do either one and do it right . I had a place here in Florida , D&C Head repair in Orange Park and after showing them how to pressure test the manifold and heads , they did a fine job . He had done dozens of this type of job and used a flow bench to test them and believed that was a good test . Well they tested mine and then I tested mine and I took them back and showed them what was the standard for testing for leaks, since they leaked all over the place and that took care of it and now have a updated testing proceedure and I would recomend them because they did do a stand up job.
Post by 57pan on Oct 17, 2006, 5:27pm
panacea,
Your signature says you're in the mpls area - I assume that means Minneapolis, as in it's-almost-winter-and-you-can't-ride-anyway. Now's the time to take it apart and do it right so it's ready for spring.
I made the mistake last year of not rebuilding my hubs over the winter even though I knew that it was one of the unfinished items on my list. Shortly into the riding season I detected some noises in the front end and ended up with my bike up on the lift during the best riding weather of the season.
(BTW - I highly recommend the work that Star Hub Pros does converting the hubs to tapered roller bearings.)
Post by panacea on Oct 22, 2006, 2:29pm
fourthgear/57, Thanks for the insight, I was able to remove the threaded inserts and found the threads on the front head completely gone.The rear looks fine although it was also leaking.I'm going to send the front into Headhog for thread repair. My search for new o-ring nipples found part # 401-637 in the JP cattalog, in the description they come with a seal that goes bettween the nipple and the head( there is a groove along the mateing surface on my old ones, but there was no seal used, other than a thread sealer). I also noticed the nipple was not bottomed out tightly in the threaded hole before the set screw was installed, which i'm sure is how they set up the manifold spacing. Are there shims that can be used for installing the nipple tightly while still holding the manifold spacing correctly? Thanks for the help guys..Mike
Post by Richard Maundrell on Oct 22, 2006, 6:38pm
Panacea:
Getting the nipples to seal on early Pans is not easy. Cotten will tell you that it is one of the most difficult, if not the most difficult, of all jobs on early panheads - period.
Looking at the design of the nipple, it is difficult to understand how the Motor Co. could have expected it to do anything but leak. The threads on the nipple are not deep, they are not tapered and, to make matters worse, a hole is drilled through the nipple to make way for the rivet. Rivets have their uses, but an application where preventing an air leak is critical is not one of them. If there is a pipe-fitter or plumber on the list, perhaps he could comment on the chances that a joint of this kind can be made to hold air at 15 psi and continue to do so after several heat/cool cycles.
If you have the threads in the head restored, you will still need good sealer. Chemistry has made great advances since the plumber's manifold Pans were made, but finding the right sealer for this job remains a problem. Cotten recommends Fluid Weld, but, whatever you use, it will have to be able to withstand high temp, vibration and exposure to gasoline.
One more thing, as if the situation were not bad enough already, some of the replacement nipples on the market are improperly made. If you are having Head Hog restore your threads, let him source the nipples.
Good luck!
Post by panacea on Oct 22, 2006, 9:02pm
Richard,Thanks for the reply, I can use all the Insight into fixing this leak I can get! Don from Headhog suggested Yammabond on the threads which is what i've used in the past assembling engine cases. I seems to remain somwhat pliable which I would think effective in an expanding/contracting joint. I'm not familliar with Threadlock but if Cotten uses it then I'll check it out if I can find it. I'm still wondering how to set the intake spacing between the two nipples, If I fully seat them into the head the gap where the o-ring sits becomes way big. maybe spacer shims are available for between the nipple and the head. I thought ignorance was supposed to be bliss! Mike
Post by Richard Maundrell on Oct 23, 2006, 4:22am
Panacea:
Have you considered converting back to the plumber's manifold with a pair of Cotten's Peek seals? This arrangement will solve your spacing problem, provide a very good manifold/nipple seal that (unlike O-rings) will not deteriorate in service, and it will restore the original appearance of your heads.
But you would still have to solve the problem of sealing the nipple to head joint. I've tried loctite thread-locker, Fluid Weld and HPF Hylomar in this application without success. I've heard that Yamabond is great for sealing cases, but is it gasoline resistant? I'd be interested in hearing what others on the list recommend for this application. It has been suggested to me that, when you really need threads to seal, you can't improve on a small amount of JB Weld, but please tell me there is a better answer!
regards,
Richard
Post by Cotten on Oct 23, 2006, 2:13pm
Seal-Lock's "Fluid-Weld" isn't the 100% perfect thread sealer either, although it is perfect for the rivet. (But ~$15 for a 2oz. bottle just to do two rivets is beyond the scope of most do-it-yourselfers.)
It is just the best sealer I have found so far.
Sealing the threads is actually secondary, but prudent. All of this would be easier if the gas wasn't so digestive. Test any prospective sealer in crappy gas before committing to assembly!
I have sealed pinholes by drawing an isocyanate urethane inward with a vacuum aspirator: a band-aid on a band-aid.
The primary seal is the shouldered face of the nipple upon the counterbore in the head. Two wide flats rarely seal well against each other. (Knucks did better with a thin lip on the head.)
When these surfaces are marred or out of square, a thin, compliant sealing washer can work. I cut them successfully from PEEK.
When the threads are gone, I suggest re-threading for an oversized nipple.
Replacing a nipple successfully is a long, tedious, and often frustrating operation.
(Attempting it in the chassis is begging for punishment!)
....Cotten
Post by Mbskeam on Oct 24, 2006, 12:35am
The primary seal is the shouldered face of the nipple upon the counterbore in the head. Two wide flats rarely seal well against each other. (Knucks did better with a thin lip on the head.)
When these surfaces are marred or out of square, a thin, compliant sealing washer can work. I cut them successfully from PEEK.
oooooh I see now.......ya learn somting new every day....thanks....
thats what you guys where talking about on the FHP site
I bet that if it cost only 15.00$ to stop a vac. leak, most would be happy at this price.....knee replacements ain't cheap ya know....LOL
mbskeam
Post by panacea on Oct 24, 2006, 3:57am
Cotten, Where could I find an oversize nipple? (no fat chic jokes). Mike
Post by Cotten on Oct 24, 2006, 1:28pm
Mike!
Anyone with a lathe should be able to cut a nipple to your exact spec. But before you shop for a nipple, you must first determine how you will re-thread the head.
I have succeeded in hand-chasing lightly damaged threads to .010" oversize, and cutting a nipple to fit it. The tool is a short section of the old nipple raked to a cutting edge, and silver-soldered to a handle.
A gentleman in Wisconsin has a rare and expensive tap to take it to a full oversize, and also makes appropriate nipples. But I do not believe he monitors this forum, and hesitate to flood him with requests until I get permission.
I hope that Don at Headhog has also focused on this problem. If he can attract a market, I'm certain he can fixture up for welding and re-cutting threads back to original specs. (Someday that will be sought after to repair many of the welded-on o-ring nipples.)
....Cotten
Post by panacea on Feb 10, 2007, 1:18am
Yes, Don has the cutter to recut intake threads, after welding over the old ones. His home page has a picture of a head being re-cut. Mike
