Carburetor and Fuel System
Title:
Linkert M74-B warped manifold flange
My M74B linkert (on my 30+ years in the family 64FL Police Special) is warped. I've always heard that the brass manifold flange was sensitive to overtightening and heat, etc., but it's never happened before.
Now, after having it running beautiful over a 10 to 16 month period, it's run awful for about a year. Earliest checks I did showed nothing, until a friend woke me up to check the flange for warping.
So my question is what can I do? I've heard brass is soft so it could be nearly straightend by using a press, etc. and then run the flange over sandpaper to flatten it the rest of the way. I've also heard that a good machine shop could machine it flat.
What do you guys recommend?
Many thanks,
Kevin
KC, MO
Post by Cotten on Nov 1, 2003, 12:41am
Kevin!
One of the major reasons that the manifold flange distorts (other than someone falling down on it, or kicking the aircleaner with their knee) is because of the cushy thick gaskets. Stacking them makes it more likely to pull even farther from flat.
The original had asbesto-upon-metal stacked on each side of a hard phenolic spacer. These were much less compressible, and kept BOTH the manifold and carb flanges flatter.
Dressing to flat is easiest on a large stationary disc sander, but the swirl routine on a sheet of emery upon a flat glass sheet works fine with a little patience, and a squirt of WD-40. Be sure to do the manifold as well!
Of course, there can be other vacuum leaks than just at the carb/manifold seam. Take a big cork and punch a hole in it so you can pressure test with soapsuds like http://virtualindian.org/11techleaktest.html
Squirting combustibles around the manifold is barnyard and misses small leaks, and can even be dangerous. But bubbles tell you exactly where and how much of a leak you might have.
...Good luck,
....Cotten
Post by kevsett on Nov 5, 2003, 9:48pm
Cotten,
Very useful information. I truly appreciate it. Could you offer one more piece of advice?
What torque rating would you tighten the 4 carb/manifold flange bolts to when it's time to bolt on the carb?
Many thanks,
Kevin ???
Post by Cotten on Nov 6, 2003, 2:58am
Kevin!
You will find most SAE and other specs to quote anywhere from 18 to 22+ ft/lbs for a 5/16" fastener, but this is way more than appropriate for a brass flange.
Your own hand will be more judicious, if you apply pressure slowly, and feel for the point where it snuggs up to firm,... and re-torque as necessary.
