Re: [AMC-List] AMC Spirit questions

[Tom Jennings <tomj@xxxxxxx>]

On Fri, 20 Oct 2006, John Elle wrote:

> SNIP
> and a Jeep Weber conversion, or a 2bbl-4bbl adapter
> and a Holley 390.
> SNIP
> This done on the stock engine can give an inexpensive boost for the buck
> 'specially when done with a cam. I prefer a Carter AVS or AFB my self
> between 350 and 400 cfm

John, all your comments are good. I have a question on yr carb
ideas above.

What Carter AFx carb is 350 - 400 cfm?

There doesn't seem to be many "performance" carbs (I use that
word loosely) in the under-500cfm range. The Holley 390 (but
Holleys seem to need constant fiddling for reliable treet use
(not their intended use)) and the Webers are about it; the BBDs
are fine too except for the limited adjustability.

But the smallest AFB I know of is 500cfm, and the AVS, isn't
that old, unavailable, and 600cfm-ish?

PS: Here's a small chart of rpm vs. engine CFM for 258 ci,
assuming 80% VE (I hope it's better than that!):

RPM	CFM
1000	60
1500	90
2000	119
2500	149      <---
3000	179
3500	209
4000	239
4500	269
5000	299      <---
5500	328
6000	358

The two arrows are of course likely cruise RPM and max RPM
(stock small AMC, 70's). 2500 is perfect for the little YF,
which is sucked dry at speed. Dual YFs would be nice! :-)

A 500cfm carb on this motor would be unhappy unless you're at a
track at WOT most of the time, and even there it's a bit large.
The Holley 390 is at least sized right.

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