Dear Listers:
In the first place, mating surfaces should be
*clean*. This doesn't mean just wiping them down with
a rag, but getting them really clean. If an engine is
apart (or a cylinder head is off), give it a good
solvent wash, folowed by good old soap and water (Wisk
is a marvelous grease-cutter!). Rinse with clean
water, borrow your wife's hair dryer and dry it
thoroughly. Use a small wire brush on gasket surfaces
(check your local welding supply shop - they usually
stock toothbrush-sized stainless steel brushes for
about a buck apiece) then apply your favorite sealer.
After many years of working on various and sundry
racing cars and cursing at gaskets in general (and
British gaskets in particular), I've developed the
following guidelines. They work for me, but no
guarantees, OK?
Sump gaskets, timing chests, valve covers, etc.:
Blue RTV Silicone
Head gaskets: Nothing at all. (Just make damn
sure the head is flat and properly
torqued down.)
Gearboxes: Hylomar (and sometimes a thin paper
gasket) or Loctite gasket-maker.
Exhaust Manifolds: Orange RTV (Hi-Temp)
Fasteners: Loctite of the appropriate grade, and
safety wire where needed.
A few tips on using the various RTV and Anerobic
materials:
1. RTV: Starting with a clean surface, lay an
even, uninterupted bead (about 1/4" wide)
all the way around the edge of the
removeable part. Let stand until it forms
a fairly firm skin, then gently put into
position and start the attaching fasteners
just enough to bring the mating faces into
contact. Leave for about twenty minutes
(times depend on temperature), then torque
normally.
2. Anerobics: Threads should be clean and
free of dirt, oil, and old locking
compound.
It doesn't hurt to chse the threads in the
holes with a tap and yes, Whitworth and DIN
taps are readily available. Squirt a little
LocQuik Primer into the threaded hole, and
apply the Loctite to the threads (just a
drop!!!). Run in and torque to correct
setting.
You'll notice that I keep harping on proper
torque;
more damage is done by not using a torque wrench than
you can imagine (try a rod-bolt failure at max RPM)!
Also, and most especially with sheet-metal parts like
valve covers and side plates, if you torque down too
hard, then you distort the sheet metal, and build a
nice leak.
The last Pro car I worked on (a Trans-Am Camaro,
13.5:1 compression, 590BHP) stayed dry all the time.
I'd also recommend that anyone who does their own
maintenace/race-prep obtain a copy of Carroll Smith's
"Prepare to Win"...it's worth its weight in gold!
Hope all of this helps.
Sincerely,
Bill Hoskins
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