PEEK seals

[51Hog]

How much of a gap between the manifold and the nipple can a PEEK seal span. I would imagine that the less gap between the manifold and the nipple, the easier it will be to seal around the manifold, and that the manifold would be better supported. My nipples are 3 3/8" apart and my manifold is 3 1/16" The manifold actually sealed to the nipples and ran for several thousand miles.
The nipples were loose and leaking. They ran for the same distance just sealed from the outside with Ultra grey Sillycone (I just dropped some of the dry silicone into some fresh gasoline 36 hours ago. It appears that the gasoline has NOT had an effect on the old heated silicone!). Pressure test finally failed so I replaced the nipples. I think I need to start looking for a manifold.
Dale

[PanPal]

With the heads loose, you should have a little play to close up the 3-3/8"gap. All mine are O-ring, but the manifold should be snugged up with the heads loose. Do you think the manifold you have has been modified?

[FlatHeadSix]

Dale,

I dumped a box of plumber manifolds out on the bench tonight and measued them. They all appear to be OEM, all have the same casting number: 428-401. Six of them measured between 3.255 and 3.261, one of the chrome odd balls came in at 3.192

Based on that I'd say that stock manifolds are all right at 3 1/4". Panpal is correct about loosening all the cylinder base bolts when installing a manifold, wiggle the cylinders into the best alignment and fit and you should be OK with your stock manifold.

VT, the O-ring manifold on the lower left has the part number you were looking for cast right into it, but it is aluminum, did they also cast those in iron?

mike

[51Hog]

PanPal, You mentioned loose heads.
Is there that much slop in the head bolts and fire ring to be able to move the heads that far?
The Jugs are loose and pulled together as far as they will go.
If the heads will move closer together, I will go ahead and buy gaskets and do it. I do not remember if I tried to move the heads together on assembly or not. I would imagine that I did.
Thanks for the effort of measuring the manifolds Mike.
I just received an original off of eBay. It has a poor polish job on it and some of that Evil Chrome. It measures 3.25 inches long.
Will the PEEK seals span 1/8" each?

[FlatHeadSix]

Dale

I just noticed that Panpal was talking about loosening the heads, I think you will get better results, and find more play, when loosening the cylinder base bolts and moving the entire cylinder rather than messing with the heads. Anyone else got an opinion on this?

mike

[51Hog]

I did not measure the movement, but with the bare eye, Maybe the bases moved 1/32" maybe 3/64" from forced apart to pulled together with a tourniquet rope around the bases.

[FlatHeadSix]

You're probably right Dale, you have to remember that I'm mostly a flathead guy so most of my manifold alignment and adjustment experience is limited to whatever play I can find in the cylinder bases.

mike

[Cotten]

Please remember that 61" Pans (and all Knucks) had a narrower manifold than 74's.

The reason PEEK works at all is its remarkable tensile strength. Bridging the gaps has confounded lesser materials such as nylon, teflon, etc.

1/8" on each side should pose no problem. But like any assembly, it should be tested upon installation, re-torqued after a few heat cycles, and checked with regular maintenance.

...Cotten
PS:
I do not advocate loosening cylinders or heads after they have seen service, as the gaskets are compromised.
They should be shoved together square when assembled in the first place.

Often worn or distorted manifold spigots must be lathe-turned true and round again before fitting with ferrules.
Beware that evil chrome makes that extremely difficult.

[51Hog]

Thanks Cotten.
Just installed the manifold. Went in with no problem. 5/64 space on each side of the manifold.
Pressure tested and no leaks---That is----in the intake system.
I did find part of my rough running problem tho.
The Porcelain on the rear plug is not sealed well where it enters the nut.
There is a major leak. Crazy because I would expect to see dark exhaust around the porcelain. It is clean.