<VV> Questions, Questions, Questions

Craig Nicol nicolcs at aol.com
Thu Dec 6 16:04:56 EST 2007

Bob Asked: 
What do you think are the implications of the fact that the latest API 
designated oil rated SM has no upper limits on the amout of phosphorous
(ZDDP to 
you) it can contain? That means the SM oils can have plenty of Phos if the 
rules are followed. Of course this SM oil must not have a GF-4 rating (which
evidenced by a Starburst on the front of the container). And furthermore, It

must not have any other Sx ratings along with the SM. If there are further
ratings, the the max PHos will be that of the Sx rating.


Craig Replies:

It sounds to me like the makers are planning lo and hi versions of their
oils – perhaps in response to the market’s demand for higher ZDDP oils.
Perhaps they will label them for older vehicles or somesuch.  I am expecting
some kind of product or solution to solve or salve our needs. 

Bob Asked:

The EM carburetors have a fuel inlet hole to the bowl of 0.058 in. The LM 
carbs's inlet hole is 0.084 in. But both major vendors are offering inlet 
seats with larger inlet holes (and these are for all years of carbs). What
do you 
think might be the mixture implications of using inlet seats with larger 
than stock inlet holes? And how might a newbie compensate for this if it 
requires any adjustments?

Craig Replies:

IMHO, the only combination that *might* be an issue would be a high fuel
consumption 164 with the small inlet. The small inlet *could* cause a drop
in fuel level if the incoming fuel doesn’t keep up with outflow at the jet.
I find this scenario even a little hard to believe since the area of these
needle valve holes is so much larger than the jet size. (Though, granted the
FP pressure is 1/3 than the pressure across a jet at WOT.)  When I read the
Communiqué article, I viewed it with great skepticism but was willing to
listen to a new concept but I really don’t believe it.  I think it’s just as
likely that the design change was to permit faster “dry bowl” refill or
commonality with other Rochester carburetors on higher displacement engines
of some other demon.

Craig Nicol


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