"Can't have both with a VP-7 cam and SU's"
Frank is spot on with this...true, true....
and this is, in fact, quite normal. Cam grinds are all a matter of "compromise"
in terms of the low rpm/high rpm cylinder filling (efficiency) profile.
The vacuum produced at idle is pretty low
relative to the stock cam or more mild grinds. And there is quite a bit of
contamination of the incoming fuel charge
by left over exhaust gases from the last
combustion "event" due to relatively poor
low-rpm scavenging of the "hairier" grinds.
You can ammeliorate this trait (a bit) of hairier grinds by tuning to a higher
idle speed....1000rpm or so. Or, you can convert
to a "fixed choke" Weber, which unlike the "variable choke" SU, has a
separate, tuneable idle circuit and is thus
more user friendly to some extent in this
respect. That's about it.
You'll also find that
idle rpm will more markedly decrease with the VP-7 as you "load" the alternator
with headlights, etc. Here again,
a case of relatively poor vacuum at low rpm.
and yet another reason to tune to a higher idle speed with hairier grinds.
Cap'n Bob
Basic Frog
Cap'n. Bob '60 :{)
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