Widen Intake Manifold

[Ohio HD]

I'm looking for some info from someone who has addressed this before.

This is a Twin Cam motor but Evo is basically the same as far as inlet sealing. The setup has a taller top end than an OEM by a total of 0.070". That equates to about a width increase between the heads of +0.050".

Where the issue comes in is the throttle body is an OEM TBW and uses an integral inlet manifold. I assume this is a problem trying to add material by welding, and also difficult to fixture and create a new extended surface for the seal. He has some problems with inlet seals leaking after a few thousand miles. I assume that the seals harden a little by then. When you mount the TB with the backing plate on the heads, the gap is pretty even to both sides, but larger than it should be.

Anyone ever came cross this and remedied it?

[rigidthumper]

Any chance you could 3D print a high temp plastic ring to aid with seal & stability, like these?

[Coyote]

I just bought a new printer to do high temp materials. Have no idea what temps that part would require though.

[Ohio HD]

That would be a really unique way to add some rigidity to the seal assembly. I should have mentioned, it is OEM style, it's an SE 58mm TB. I looked at the James site, they have two seals listed with a lip, (which I never have seen before) but they're for the standard size intake manifold. I need to poke around and see if there is such a thing for the larger manifold of the 58mm.


https://www.jamesgaskets.com/products/jgi-26995-98-seal-intake-mainfold-rubmetlip

https://www.jamesgaskets.com/products/jgi-26995-97-x-seal-intake-mainfold-rubberlip

[SP33DY]

See page 221 of the S&S 2022 catalog. They have some intake manifolds that are wider than stock. Rather than adding material to the throttle body spigots, it may be easier to fit one of these manifolds. Then you could possibly cut and graft your t.b. to the S&S manifold. Just a thought.

[Ohio HD]

I had mentioned that to him last night that it was a possibility to do that. I think if he needs to add money to the TB, he might replace the SE with an HPI (he has another TB for donor) and then sell the SE. I also told him it may require tuning again. There's probably enough difference in the two TB's that it would need to be tuned. 

This started as a budget cruising build he did some time back. He had some take off 110 heads, bought S&S 4.125" cylinders and dish pistons, he had a used S&S 570. And he had the SE 58mm. 

He has two other bikes so he hasn't really looked hard to solve the intake leak. I think he's tired of it sitting in the garage and not getting ridden. 

Added: I do know that HPI also sells wider manifolds for their TB's.
Added: He also has an S&S 4-5/8 crank, that's why the cylinder height.

[hrdtail78]

I think these are from Jim's.

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[Ohio HD]

I think you hit the nail on the head Jason. I had envisioned a shim and a flat gasket to take up some space. But was sure that the gasket would probably leak. Now an o-ring, that might just do it. Thank you.

Considering his cylinder height difference, of 0.067" and an 0.020" base gasket, he's almost at 0.100" taller, he's at 0.087".

I'll get him to call Jim's about the #721. As I remember the SE TB port is around 1.730" ~ 1.735".

I also think you may have posted about these in the past as I remember seeing that photo.

[SP33DY]

I haven't seen that before. That looks like a great solution!

[hrdtail78]

Another option. 
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[jsachs1]

I think you hit the nail on the head Jason. I had envisioned a shim and a flat gasket to take up some space. But was sure that the gasket would probably leak. Now an o-ring, that might just do it. Thank you.

Considering his cylinder height difference, of 0.067" and an 0.020" base gasket, he's almost at 0.100" taller, he's at 0.087".

I'll get him to call Jim's about the #721. As I remember the SE TB port is around 1.730" ~ 1.735".

I also think you may have posted about these in the past as I remember seeing that photo.

Actually, they were used on some CHOPPER style bikes, when the EPA got involved with the aftermarket. Some manufacturers (S&S), (Jim's), had to make, cylinders taller, so the engines could pass emissions. IIRC, Jim's Machining, was making them, and still may have some. The ones I have are 1.177" diameter inlet X .080" thick, and have an O-ring groove on 1 side.
John
John