Question for Air Cooled Engine Builders About Case Machining

hulbyw Insano Dub Head

819 posts · joined Sep 2009 · 21 Mar 2018, 7:25 pm

#1039783

I will start off by saying I have only assembled an aircooled motor twice. I have had a new case bored for 90.5 barrels. The barrel moves slightly sideways when I did a test fit tonight, that is the fit of the barrel in the case is a little bit sloppy. The machinist did have a barrel when he did the work. This doesn't seem correct to me. Not sure how everything is going to line up and stay tight (e.g.the heads) when the barrels can move around a bit. Is this standard practice nowadays or should I be taking it back to the machinist.
Cheers

curvedscreen Learner Dubber

11 posts · joined Jan 2014 · 25 Mar 2018, 2:59 pm

#1039816

Hello I hope that this is some help I checked a barrel and case and there is .015 clearance cheers John L.

bevoracing Officially Full-On Dubber

327 posts · joined Jan 2009 · 26 Mar 2018, 3:07 pm

#1039831

Gene Berg says it all here :-
http://www.geneberg.com/cat.php?cPath=2990
He says a stock case has .015 - .020" of clearance to allow for cylinder growth. He says to maintain original clearance.
That .020" (0.5mm) would feel quite loose when it's cold. The cylinder and the case expand at different rates & times. That's why the sealing surfaces must be in good condition and sealed correctly (I use Permatex No3) or they leak. That area is notorious for leaking, along with all the other areas on a VW engine. 😉
Good luck
Tony

Country Buggy King & Link Pin Overhauls, Type 1 & 2 King Pins, General Machining.
http://forums.aussieveedubbers.com/viewtopic.php?tid=74138
My car is KO813

hulbyw Insano Dub Head

819 posts · joined Sep 2009 · 27 Mar 2018, 9:35 pm

#1039844

Thanks John and Tony. Sounds like the machining on my case is ok
Cheers.......................Wayne