More 2pc manifolds

Fri Oct 26 15:33:45 EDT 2001

Interesting, I haven't, but YMMV.  The last 85 N/A car I had in my shop, 120k 
on the original and trashed hydr motor (er 3pcs came out) mount, had a total 
of 4 studs holding it in place.  Manifold is clean and uncracked.  Warped 
beyond belief, but not cracked.  

I certainly can *think* of how N/A cars can crack manifolds, but again look 
at that as a heat issue, NOT a motor mount issue.  

For more on heat expansion, Tom C is on track IMO.  Try looking up EM Design 
in Corky Bell's book (pages 126-127), it almost points the finger at audi 
designs (long manifolds), and using large flat washers (all audi manifolds 
superceded to this attachment design)..  He speaks specifically about making 
bolt holes larger as the distance from the center of the manifold increases.  
Further, he sports:  "... on long engines, like the six-cylinder inline (<or 
I5?>), the designer should consider using two manifolds, with 
interconnections from a tubular flex joint."  - Corky Bell.  Enter audi 2pc 

Heat cracking of manifolds in turbo applications is nothing new.  Blaming 
heat cracking on bad motor mounts is oversimplifying a well documented 
physical property of cast iron turbo manifolds vs heat.

Scott J

>Just my .02 cents.  I've seen NA cars with cracked 

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