<VV> A couple of 94mm questions

Larry Forman larry at forman.net
Sat Feb 24 14:35:23 EST 2018

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,


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