To be fair John, I may have misquoted him.  He certainly said i may have to mess with the secondary springs to control timing of secondary opening, but he may have only been referring to it in relation to the weight of the car, cam peak rpm range, etc.  I may have misheard him relating it back to manifold vacuum.

Thanks!

Ron Grove

Wauconda, IL

I question the Jegs tech guy's knowledge of carburetor operation.  He said secondary springs may have to be juggled due to the lower vacuum because of the cam.  The secondary operation is not based on manifold vacuum, but venturi vacuum.  The secondaries open when venturi vacuum in the primaries indicate the need for more throttle opening.  Just my 2 cants.

John - "The Hoosier Hurricane"

My carb of choice for the Y-block is the Autolite 4100 spread-bore built by Pony Carbs. They will set it up for your driving conditions. It has worked flawlessly on my 57 Custom 300 for many years. Check out their website.

Called Jegs tech again.  This guy recommended the 465 as being more than adequate, even with my cam.  Indicated that Id have to play with secondary springs due to lower vac, but it should work fine with some tuning.  I think thats the one Ill order and see how it goes.

I do want to say THANKS to everyone who chimed in.  I honestly cant tell you how much I appreciate your thoughts and input; thanks again!!!!!

Ron Grove

Wauconda, IL

Ron, I have a RV cam, it's around 210>215 @ 50, it's a lower end cam, ideal for cruising but loses some on the top end. 75 on the interstate isn't a struggle but on a trip up to northern Minn. to a show I was in the 18 mpg range so I'm happy with it. Gary

       

Gary, 55 Vicky, St. Germain, Wisconsin

 

i know you cant buy them new but the autolite 4100 remains my favourite.

It is in the last issue of Y-Block Magazine.

If I remember right, it came in 3rd, after a modified Holley 600 and a Speed Demon 650.


Lawrenceville, GA

Charlie, was the dyno test you refer to something here or elsewhere? Any idea where I could find it; I tried a forum search and didn't find it...

Thanks!

Ron Grove

Wauconda, IL

Well, like I said, you can get opinions and advice all day. You just gotta try it.

The 465 did very well on the carb dyno test and a Street Avenger was not tested. So, the 465 is a safe bet.


Lawrenceville, GA

Dang it, Charlie!  I was settled on the 465 until you threw your vote again to the 570!  I still might try the 465 next because it will flow 18% more than the 390, and will bolt in place easily (single fuel feed, no relocation of coil, oil bath fits, etc)  Still not 100% decided though...

Gary, you say you have a mild cam.  Do you happen to know the specs?  Everyone (articles, etc) refer to "mild" cams, but i dont have a point of reference as to what specs are mild vs. aggressive? 

Thanks to all for the input and patience.  In case you havent figured it out yet, I tend to overanalyze things....

Im trying to get this decided in the next fvew days so I can send the demon back to Jegs before we go on vacation to AZ for 2 weeks, so hopefully I can come home to my shiny new carb!

Ron Grove

Wauconda, IL