Conversion manifold problem

[Pan57Johan]

What is the proper distance between with the "conversion rings" installed on the heads and a o-ring manifold? I need to know how mutch to machine the manifold since its to wide to fit.

Thanks, Johan

[Cotten]

Johan!

The manifold should install between the head's with a minimum of ~.032" on each side. It is intended to "float".

If you are referring to hard plastic rings intended to fill the gaps upon 0-ring manifolds and heads in order to use later shovelhead "band" seals, beware that they are subject to softening and distortion in some modern fuels, risking future disaster.

Beware also that installation of the later bands requires either removing and replacing a head, or stretching the bands past their limit, not to mention your patience.

If you are referring to conversion nipples for 'plumber's to 0-ring' updates, I can only warn you that hundreds if not thousands of heads have been trashed by poor technique installing that "better idea".
If it is too late, please pressure test each nipple separately with low airpressure and soapy water, using a large cork or stopper: http://virtualindian.org/11techleaktest.html

If absolutely no bubbles form, then I suggest using JAMES viton O-rings and stock-design clamps.

Good luck!

....Cotten

[jdpan]

Why doesn't the manifold fit? You shouldn.t have to machine anything unless the conversion was installed incorrectly or you have some kinda funky manifoild. My guess is you tightened the heads without dry fitting the manifold first? I've done that before and ended up destroying a perfectly good SnS manifold before the lightbulb went off..

[indianut]

Cotten, I am just curious. I have never messed with the Plumber to O Ring Nipples, but, even though we how know how to seal the Plumber Fittings properly, what can go wrong with the Conversion Nipples?

[Dave_R]

The only time I see the newer manifolds not fit after a conversion is if the heads were "decked" too much, or as jdpan suggested, not doing a "dry-fit" of putting the manifold in place before you tighten the head bolts.

[Cotten]

Cotten, I am just curious. I have never messed with the Plumber to O Ring Nipples, but, even though we how know how to seal the Plumber Fittings properly, what can go wrong with the Conversion Nipples?

Indianut!

The overwhelming problem with conversion nipples is the destruction caused by amateurs tearing out the original nipples, head's threads and all, which very well have been fine otherwise.

But the time one considers the effort to repair them, most folks realize their effort is best spent to go back to original design.

....Cotten

[Pan57Johan]

One of the heads had broken threads, so a machine shop made oversize nipples witch has been locktighted, they can be what makes the distance between the heads to narrow. And it is a conversion from plumber to o-ring. So you would recomend that I loosen the heads and retork them again before machining the manifold to se if it gets better. Can the head gaskets be reused if the engine has not been started?

Thanks for all good anwers so far!

Johan

[steinauge]

Intake manifold alignment is critical to intake seal and is generally done during assembly. To align the intake manifold after the fact install new head gaskets,hold the intake manifold square against one nipple in the head and observe the gap on the other side between the manifold and nipple, if the gap is straight lightly snug 2 head bolts on each head and recheck,if still straight proceed to torque head bolts,if not rotate the heads until the gap is straight then snug two headbolts and recheck etc. If your intake nipples really are too wide take the manifold back to the machine shop and have them machine the inner shoulder (where the O ring sits) back and then narrow the manifold as required.DO NOT just file the inner lip down until the manifold will go in! HTH

[Cotten]

Johan!

As Steinauge points out, your custom conversion nipple now requires that the manifold be shortened upon a lathe.

OMANICUT.jpg (37.31 KiB) Viewed 1520 times

I suggest that only the side with the oversize nipple be trimmed.

But please do not cut until you are certain that the conversion nipple is sound.
Have you pressuretested it with soapy water?

And beware, Loctites are not particularly resistant against modern fuels.

Good luck!

....Cotten

[Pan57Johan]

I will collect the parts to build a "pressure tester" soon, havent done it yet.

Johan

[Kuda]

I will collect the parts to build a "pressure tester" soon, havent done it yet.

Johan

All you need to test the intake nipple is a good sized rubber stopper (any hardware store), a bit of tubing, and an air pressure regulator. Push the tubing through the stopper, hook it up to the regulator, jam the stopper in as well as you can (a valve spring clamp helps here, or a long zip tie or two), and away you go. I would STRONGLY recommend testing the conversion nipples before you do anything else. I chased a starting problem for years before I finally traced it back to bad conversion nipples. Oh, and they were sealed with what I *think* was JB weld, which did eventually fail enough to be noticable when cold.

-Kuda
'49 panchop (back to plumber's intakes now and well sealed)

[Pan57Johan]

The clamps I used were the ones with two bolts (see pic.), over tightened. The orings looked really bad, I guess I had my starting problem there. Is the other clamps on the picture better? Just missing the rubber stopper to perform leaktest.

Johan

Fam.Juni11 054 - Kopia.JPG (94.1 KiB) Viewed 1375 times

[Cotten]

Johan!

Both designs of clamps over-tighten.
Please find a set with #10 screws instead of 1/4" bolts.

Bubble-testing while installing will let you find the "sweet spot" where it seals best, and will warn you if the clamps are over-tightened.
Then, bend your carb support to mate to the manifold without stress.

#9 rubber stoppers should be available at beer and wine-making shops.
(One fellow used a small rubber ball from a pet shop.)

Part of the extrusion of the O-rings can also be blamed upon swelling from fuels, as well as over-tightening.

Good luck!

....Cotten

[Pan57Johan]

What do you mean by #10 screws? Any pics or number of sutch clamps? Im from Sweden so I have a bit of a language problem.

Thanks

Johan

[1950Panhead]

Johan,

Screw sizes
#2 .087"
#4 .113"
#6 .138"
#8 .163"
#10 .188" (use this size)
#12 .213"
1/4" .250"