<VV> A couple of 94mm questions

[Bruce Carlton]

 you My race engine uses 94 mm jugs and I have had no problems and I run the engine with a 6800 to 7000 redline. I run track days and I run the engine hard. I have bored the case for the 94 mm jugs such that the head studs have very little metal between the threads and the bored opening. On the good head stud threads I just put the head studs right back in. On a few stud holes where the threads were suspect or bad, I used helicoils. The engine has been apart twice in it's lifetime and therefore retorqued twice. I made a lot of oiling modifications / improvements such that bearing life is excellent.On the first teardown I had progressive rod bearing wear from back to front  though wear was still within assembly specs, evidently from startup wear. That was solved with the installation of an accusump to prelube the engine before startup. The second teardown showed even, but minimum bearing wear. At most .0003 in. on rod bearings. The bearings went right back in. I hope your experience is as good as mine. If you are interested I can tell you all of what I did to the engine.
Bruce Carlton
    On Saturday, February 24, 2018, 4:45:38 PM EST, Larry Forman via VirtualVairs <virtualvairs at corvair.org> wrote:  
 
 I think that removing the upper studs was needed to do the case boring 
and    this case has been modified and I would not want to throw away 
all that work.  I have replaced head studs before, but normally use the 
wonderful TimeSerts.

Thanks for the suggestion.

Larry

On 2/24/2018 12:13 PM, Marc Marcoulides via VirtualVairs wrote:
> on question 3, why not find another case?
>
>
>> Hi All,
>> I purchased a "kit" to make a 94mm big bore engine when I was at the
>> CORSA Portland National Convention.  I think that was about 2005.  The
>> machinist was named John and I think the last name was Warner.  I heard
>> that he did good work.
>>
>> I am now about ready to start assembling that engine for possible use in
>> either the Devin C or a Rampside.  However, I have heard of horror
>> stories about the 94 mm big bore engines and wanted some advice.  I
>> have heard of some of the 94 mm jugs cracking or splitting at the block
>> end where they are pretty thin.  I checked the bore and it appeared
>> well within specs for both taper and runout.
>>
>> I was thinking of taking a junked head and having it bored out so I
>> could do a trial torqued measurement for possible changes in taper and
>> runout before the pistons and crank are installed.
>>
>> My first question:
>> Is that needed or even recommended or worthwhile?
>>
>> My second question:
>> Am I in dangerous territory with the 94mm big bore jugs?  They seem
>> pretty stout and this will be for a normally aspirated engine, so no
>> turbo pressures involved.  The engine is NOT for racing, except perhaps
>> for the Devin C use in AutoX.  Rpms will likely remain south of
>> 6,000.  I am interested in an engine that will have plenty of power for
>> fun but will not require frequent rebuilding.
>>
>> Third question:
>> Since the upper row of head studs have been removed, what should I do
>> about replacing them?  I normally would use TimeSerts, but these studs
>> are getting pretty close to the larger bored diameter.  I am concerned
>> about taking even more material very close to the edge.  Should I
>> simply replace the studs and call it good?
>>
>> Thanks for any suggestions,
>>
>> Larry
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