<VV> Top Cover Gaskets/ Lose Screws

[Joel McGregor]

I feel your pain.  I think you have actually uncovered the problem.  They are all using screws so they can't get them properly tightened to begin with.
I've taken apart plenty of old Corvairs that were loose and plenty that were tight also.
This (loose bolts) reminds me of the Yamaha 490 list.  Most people there think that it's just common knowledge that you have to use Loctite on everything on those bikes.  I've been riding them since the mid 80s and I've never had anything come loose and I don't use Loctite.  I do properly tighten things.  I have pretty extensive experience with motorcycles that use aluminum cases with various steel parts attached to them.  I've never seen that cause things to loosen.  99.9% of the screws I remove from motorcycle aluminum cases are tighter than when they were installed.  I'm assuming that is due to the slight corrosion of the dissimilar metals involved.  Yes, most of them have screws.  Pan head Phillips to be more precise.
There are lots of air cooled motorcycles running around that have iron cylinders and aluminum heads that don't have any issues with head gaskets.  They also don't have any forced cooling or shrouding to even out temps.
Has anyone had any of their bolts come loose that they personally properly tightened?
I have had lots of automatic transmission valve body bolts come loose when I tightened them to spec.  That problem went away when I started using my own specs.
Joel

-----Original Message-----
From: virtualvairs-bounces at corvair.org [mailto:virtualvairs-bounces at corvair.org] On Behalf Of Smitty
Sent: Monday, June 25, 2012 11:43 PM
To: virtualvairs at corvair.org
Subject: <VV> Top Cover Gaskets/ Lose Screws


Smitty Says;  Sent from my 15 year old Dell PC.  Just for the record, the use of screws when talking of bolts offends me.
Every time the subject of the coefficient of expansion difference between the Crankcase baffle and the block and the block cover comes up, I hear about how much slipping and sliding is going on between them.  I say bull feathers.  That plate is not made of glass.  It has ductility.  It may not like it much but it is forced to stretch and shrink with the materials it is sandwiched between.  Like I have said before.  I haven't used gaskets there for better than 20 years.  I mill file both sides of the steel plate to make sure it is perfectly flat and then with the thinnest coat possible I apply RTV to both sides.  Again I say, I have never had a leak there.  But then I properly torque the bolts.  It is all I can do to keep from slipping into sailor profanity when people talk about the gaskets allowing the pan to slip.  Anyone who has worked more than a few engines has run into the ones where the previous assembler liberally glued on the gaskets with Permatex two and you had to all but break the casting to get it loose and then take a chisel to the residue of the gaskets to get the crap off.  Where was the slippage in that.  How many of you are aware that there is a difference between Early and Late baffle pans.  The Lates are considerable thicker.
Why is that?  The general had a surplus of thicker metal?  I think not.  I haven't turned out engines like Claypool or Sedman or Helt, but I have done my share.  I have found enough Early pans with cracks in them to believe that they simply couldn't keep up with the stress of the growing and shrinking aluminum, so they made them thicker to handle the stress.