<VV> Re: valve seat set screw retention/tap sizes

[Bruce Schug]

>> From: "Tom Willcox" <bakwudz@rcn.com>
>> To: <virtualvairs@corvair.org>
>> Date: Mon, 19 Apr 2004 19:32:58 -0400
>> Subject: <VV> valve seat set screw retention/tap sizes
>>
>> I have a question regarding the "cromwell method" of valve seat 
>> retention:
>> according to two different sources, I am supposed to finish drilling 
>> 1/4
>> inch deep with a 9/64 drill, then tap with a 5/32 bottom tap, then 
>> insert
> a
>> 5/32 set screw.  After searching for hours, my question: is there 
>> such a
>> thing as a 5/32 tap OR fastener?  The only things I have found smaller
> than
>> 1/4-20 are 8-32, 10-32, 4-40, etc.  Am I missing something obvious, 
>> or is
>> this information incorrect?  Where can I find this stuff?  This is 
>> driving
>> me nuts!  (short drive, btw)
>>
>> Thanks,
>>
>> Tom Willcox
>

This thread has turned into a somewhat interesting thread on threads 
(?). But, I have to ask, is this a viable way to get reliable valve 
seats in a Corvair? I've heard it mentioned from time-to-time but I 
continue to hear that the best way to solve this problem is to:

1. Heat the whole head to remove stress (I think that's what it does)
2. Remove all the old seats
3. Machine the head for DEEPER seats
4 Heat the head and install the new deep seats with a significant 
interference fit.

I will add that Bob Coffin installed bullit-proof seats in my heads in 
1986 when he was still in Mass. I have never had a problem with them 
through all kinds of driving conditions: rallys, autocrosses, VIR in 
90+ degree heat, economy runs, street driving with the air-conditioning 
on, etc. Why try to invent the wheel, this wheel works fine for me!

Bruce

Bruce W, Schug
CORSA South Carolina
Greenville, SC
bwschug@charter.net

CORSA member since 1981

'67 Monza. "67AC140"