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Why did the Insulator (gasket) another form as the flange of the throttle valve body?

So the really mentally challenged folks among us would not get in trouble by installing it upside down!

I'll move this to the technical column.

I don't understand the question - do you mean why is the gasket shaped differently than the throttle body flange?

It is clear that the gasket is reversible
The question: the openings of the original gasket do not match with the openings of the throttle flange. Why not?

Gotcha - sorry I can't answer your question though. It does look like it would perform better if the gasket was cut out to match the ports in the throttle body like your picture shows. But, on the other hand, maybe Willys figured out by testing that the engine produced more torque or hp with the port covered. It is clear that since the port is recessed that it is not blocked by the gasket - is this a vacuum port, maybe (I haven't looked at the manual in detail). I'm just picking at atraws here - I'm not a mechanic.

okay I may have missed something but went through the docs and I find the throttle body should be car-1-508s. Also the gasket is car-121-137/wo-116895. I assume he has a different carb than the standard then. I have searched the documents I have and cannot find the numbers given at all.

Are the 38 and 38a1 throttle bodies the same - maybe that's it.

possible but the throttle body looks like the one in the manual.

The holes are that shape to insure reversability and to not weaken the gasket. The larger "U" shaped cuts would have reduced the gasket's two edges to almost nothing. Small diameter holes with larger relief areas is common in fuel metering devices but the gasket has to at least have a hole equal to the diameter of the actual passageway when the passageway connects to an opposite passageway between the two parts. In this case there is no matching passageway in the cylinder head for those two shown in the photo at the top of the page. It can be assumed that the larger bore to accomadate the higher volume flow for the M38A1's F134 required slightly mor vacuum collection space in the area of the gasket and the slot sized used was all that was needed to operate the vacuum circuits in the carb.

The m38A1 (YS950S) carb throttle bore is much larger then the M38 (YS637S) throttle bore and the 637S does not have the same passageways. Therefore no interchange capability.



The carb to manifold gaskets are designed very differently for the two carbs.


This M38 base gasket does not have the hole thru it for the bottom vacuum port you see in it's base.

The throttle body for the YS950S (M38A1 & M170) is 1-897. The throttle body for the YS637S (M38) is 1-508S. Apples and oranges here!

Well there ya go chrisk - if anybody can give you an answer, it will be Wes! Thanks Wes!

"should use a thin gasket 1A-65 above and below the difuser"

I did wonder about that when I mounted the carburetor back when. I guess I should have asked. However, On my carburetor, the mounting studs are lacking a little length for putting a gasket on each side of the difuser. It's been running now for over 5,000 miles.

A lot of folks get by without the thin gaskets but if either side of the diffuser has any metal showing not using the thin gasket will lead to grief down the road.

Wes, thanks for the detailed explanation, it is now quite clear.

Also Matt thanks for thinking.

Best regards from the Netherlands, Chris