Heat cycling EMs - different question

QSHIPQ at aol.com QSHIPQ at aol.com
Fri Oct 26 16:33:33 EDT 2001

Ken, the simple answer is YES.

Heat cycling happens pretty quickly on turbo cars, a couple weeks in the car 
should be  more than enough.  That Dialynx manifold is a brick house, and I 
doubt, if it's properly heat cycled, then shaved, that you will have any 
problems with it.  I know for a fact the one Bob Dupree has exibited no 
cracks whatsoever, and has been ABT tweeked for most of it's 200k+ miles.  It 
was warped badly, but not cracked, and it yanked a couple of exhaust studs 
out with extreme prejudice.  The perfect candidate for a turbo car is a high 
mileage uncracked manifold, Dialynx, 1pc or 2pc (last preferred).  Get the 
manifold ground flat, install with the superceded (late style) studs, washers 
and nuts.  Done.

WRT heat cycling.  I don't use any "aftermarket" available cycling for either 
manifolds or brake rotors.  Nothing beats 'as installed' , or in the case of 
the manifold, as stressed in heat cycling.  A new manifold cryro or heat 
cycled isn't really heat cycled IMO, because it wasn't stressed/cycled as 
installed.  It also costs 100USD or more to heat cycle a manifold up to 
1300degrees and back again (my wife never cooks at that temp anymore 
either;).  You also won't have as many heat cycles for that money as you 
would in a single week of driving the car everyday.

Ceramic coatings?  Don't hurt, don't help IME/O.  The turbo on the I5 is so 
close to the head, your heat losses (specifically heat gains = velocity) 
aren't high enough to get any noticeable gains in performance.  Given the 
severity of the EM runners in terms of abuse, a couple mils of coating will 
wear quickly, even the CC boys admit this.  So CC the outside?  Ok, but I'd 
worry alot about heat soaking during shutdown.  I look to the porsche turbo 
cars for more on CC.  They can put it anywhere they want.  The only place you 
find it in their turbo cars is on the exhaust runners of the head.  The 
hardest place to put it, and the most expensive.  All else is as casted.  
Should tell you something.

Lots of folks on these lists have had great success milling the EM's and 
putting them back on the car.  1pc, 2pc or dialynx.  Add 035145880 if you 
want to get extra support of it once installed.  Get the upgraded studs, 
washers and nuts.  Lots of cars that have had this done, routinely replace 
motor mounts without EM cracking problems.


Scott Justusson

Ken writes:
My question is:  Is having the EM mounted on a chipped turbo for a while, 
enough of a heat cycling to do whatever treatment to the metal that "can" be 
done to it?  Or, would some specific schedule of treatment provide further 
"benefits" (warpage to a final shape)?  IOW, if there more that can or should 
be done to heat cycle it besides just install it, drive it, warp it, and 
machine it?For those with knowledge or opinions about thermal treatments of 
metal, does heat cycling offer any benefits that cryogenic treatment would 
not?  For example, for the ultimate in stress-relieved/consistent metal, 
would some sort of active heat treatment beyond installation in a car have 
any benefit, if I were to do the cryogenic thing anyways?  If so, what would 
that treatment be?My fear for any homebrew, kitchen oven, methods of heat 
treatment, would be that I would adversely affect the hardness of the metal 
and make it too brittle or too soft.  Perhaps this is more a function of the 
speed at which the temperature changes, as well as the maximum temps 
achieved.  I know if you quench metal it makes it harder, or softer?Thanks,Ken

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