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How To: make Teflon intake gaskets

July 18, 2010


This week I was working on the 1916 Excelsior motor.  The old copper gaskets that seal the intake manifold to the cylinder heads were worn and battered.  The intake manifold vacuum leaks will make a motor run lean, and give poor idling as the motor struggles with the air/fuel mix.


On the top of this photo are the old copper gaskets, complete with yellow Teflon tape that was used to pack around the intake collets.  Below are some new white gaskets.



The first step was to spend $23 for a 1.5” by one foot bar of PTFE Teflon from McMaster Carr.  Part number 8803K18.  This material is great for many reasons:  it withstand the temperatures, resists fuel, is easy to work with, and is soft enough to work as a gasket.

This material is the easiest thing to cut that I have ever machined.  I bored that 1.25” hole in two passes with a 3/4” end mill in a boring tool holder.  A quick pass or two for the OD dimension, then part them off to length.  In five minutes of work, I had about a dozen parts ready to use.  PTFE does require a bit of deburring, but it is very simple to do.



The intake manifold mounts directly to the Schebler carb.  To mount the intake onto the motor, a nut screws onto the cylinder head.  The nut has an internal taper which compresses a split collet.  The collet face pushes against the Teflon washer, crushing it against the cylinder head.  The gasket keeps the vacuum sealed at the head joint.  The fact that the collet closes down diametrically against the manifold keeps the vacuum from escaping.

IMG_4276 IMG_4281


On the left, the nut has been removed to show the split collet.  The taper on the collet is squeezed by a taper in the nut, tightening it evenly onto the intake manifold, while the nut threads pull everything toward the head.



Almost ready for a ride.  Don’t worry about that pushrod on the right, I’ll get to that later when I put the intake valve and rocker back into place.  🙂


Now it is time to work on the next thing.  When prepping two bikes to run across the USA, there’s always a next thing…

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