The Panhead & Flathead Site

Author: kevsett

I just purchased an unused intake (not NOS) and on the inside bottom of the feed throat passage is an imperfection, kind of like a small chunk hole. Without a visual I'm sure my description makes no sense so I'll try to take a pic or two and post.
There are also casting imperfections all along the inside middle of the intake from where the two piece mold was.
So my question is whether these imperfections are a problem for fuel and air to pass along as they head to the intake valves? I've always thought that an intake should be somewhat smooth but several mechanics here where I work seem to think the need for a smooth, polished intake is of little concern.
All I know is that the just purchased intake interior surfaces appear sloppy and downright porous when compared to the stock intake; which still requires a flat grind on the mounting flange surface if I decide to go back with it.

Post by kevsett on Oct 27, 2005, 2:14pm

Here are some pictures of the "pothole" in the right side of the intake chamber.






Post by caschnd1 on Oct 27, 2005, 2:42pm

That is some pretty sloppy casting work. I've always tried to get my manifold nice and smooth on the inside. You might be able to achieve the same result by filling the imperfections with epoxy. The only thing I'd be concerned about is if the epoxy decides to let go it going right into your motor. May not be worth trying to fix.

-Craig

Post by fourthgear on Oct 27, 2005, 3:08pm

I was told a long time ago that it was best to have them a little rough to create turbulence to atomize the fuel better or something to that effect. although some make them like mirrors, Thats a good pit in there !

Post by Rainjester on Oct 27, 2005, 9:02pm

Nothing a little JB weld won't fix but hey, if it were me and my bike, I'd throw it away and find a better one. A nice replacement doesn't cost that much. That one looks a bit too funky to me.

jester-

Post by Cotten on Oct 28, 2005, 2:52am

Panhead intake velocities are nowhere near the cfm where such a tiny pit would be significant (nor polishing for that matter!)
Indeed, turbulance helps keep the fuel in suspension at low velocities.
It is a very real concern, however, that the porosity may breach to the outside. Please pressuretest, as many leaks can be invisible to the naked eye.
If there is no leak, I wouldn't hesitate to run it at all.
(although those knarfs on the o-ring shoulder aren't desireable!)

...Cotten

Post by kevsett on Oct 28, 2005, 6:31pm

Thanks for the responses. If I decide to use this one rather than the stock manifold I'll pressure test it by itself.

Cotton, can you elaborate on the knarfs?

Post by Cotten on Oct 29, 2005, 2:19am

The last pic shows two blemishes on the top half of the 'spigot'. These are typical of a careless dis-assembly.
If re-assembly proves to be sealed by pressuretesting, don't worry about it.

...Cotten

Post by kevsett on Nov 2, 2005, 4:41pm

Thanks everyone for your comments. The original intake flange and linkert flange are both being flattened (figure 8's on sandpaper taped to glass) when time allows so I'll probably keep using it and will worry about the recently acquired intake later. Oh well, it was cheap!