IIRC fmc400 used the stock cable on an Edlebrock and has some nice pics posted of the bracket and installation.

 

It depends on the orientation of the carburetor on the manifold. On the Holley 390, I was able to use the stock cable. Just needed to fab up a new mount that I made out of $8 of plate steel I got from Home Depot.

Hope your install goes well for you. Take pictures! Looking forward to hearing about the Truck Avenger. Is that the 470?

 

Well I went and looked at at FMC400's 'creampuff' F-100 and his edelbrock throttle linkage is on the opposite side from mine. Mine is going to be on the radiator side of the carb. I did a quick mock up and it looks real iffy. I think rather than stretching the stock linkage tight (and at an angle) to make it work I think I'd rather order a lokar and have the slack in it to do it right. But I think I COULD make the stock work, it would just look half-arsed.

I think I'm going to go the way you did Abandoned and use a piece of plate steel and bend it upward ninety degrees. The thing about this clifford manifold is that it has two bosses next to the plenum on the engine side but they aren't drilled or tapped. Just two wads of extra aluminum sticking off the manifold right there. I noticed on the offy they ARE drilled and tapped for bolting the stock log manifold heat riser to but since the clifford isn't designed to mate to the stock log exhaust why those bosses ARE there but yet NOT tapped I have no idea. But anyway, I think I'll use those to mount a bracket to.

I know you guys are going to laugh at me and say I'm overcarbed and I'll have no low-end LOL. But it's a 670CFM truck avenger. I'm hoping that with the vacuum secondaries and the annular boosters holley uses in the primaries on this carb I will still have enough vacuum signal to get great low speed fuel mixture out of this carb but still have the benefit of a less restricted flow when I wrap the engine up. That's the theory anyway. I'll keep you guys posted about how this setup ends up working.

 

Hopefully it won't be too big. That's pretty big for the 300.
They say the best way to tell if it's overcarbed is that if the secondaries never open, it's just too big.

Another mathematical formula to use for size is:

(Engine CI * Max RPM * Volumetric Efficiency) / 3456

Volumetric Efficiency is basically how well your engine uses what it has. Theoretically, most engines are around 80 - 85%. Mild building about 90%. Performance work: 95%. Race track applications: 100%

That being said, you'll probably be around 90% with a higher flowing intake and exhaust, so:

(300 * 4500 * .9) / 3456 = 351

That basically states that's what your engine can use at it's best. Even at 100% VE, you'd have to rev your engine to 7800 RPMs to be able to put that 670 to use.

Juuuuust something to think about.

 

The book that really changed my thinking about carb sizing was 'how to build horsepower vol. 2: carburetors and intake manifolds' by David Vizard. It's a great read and I highly recommend it. The book was about porting and modifying carbs and manifolds and one point he especially drilled home well was that it's not ever a problem to have too much carburetor CFM. A carb problem that is labelled too much carb is a problem of low booster signal resulting in poor fuel atomization. Booster signal basically being the vacuum created by the bernoulli effect as the air is drawn through a venturi and that signal then acting on the main jet and air corrector jet to draw in fuel\air emulsion.

With a given amount of air entering an engine through the carb be it a small amount at low speed or a massive amount at screaming RPM, the booster signal is dependant not only on the amount of air, and not only on the venturi diameter, but also on the design of the boosters in the venturis.

As an example from the book: a mid size V-8 cruising down the road is drawing about 75 CFM of air. When tested on the author's flowbench at 75 CFM a stock Holley straight leg booster produced a signal of 4.5 inches of water, a Holley annular discharge booster produced a signal of 7.8 inches of water, and a Carb Shop's Super Booster produced a signal of 8.8 inches of water. It's the higher booster signal that I am hoping will compensate for the bigger venturi carb on my 'little' 300.

As another side note Holley gives their CFM rating based on 1.5 inches of mercury pressure drop across the carb. Meaning 1.5 inches of mercury suction to draw that much air through the carb, any carb can flow more than it's rating, it will just need greater than 1.5 inches mercury suction to do it. That's why small carbs steal high RPM power, because if the engine has to fight against say 4 inches of mercury of restriction in the carb to get all the CFM it needs, it's a greater pumping loss.

There is a mathematical formula for determining what a carb with flow at different pressure drops: (original CFM rating) / (square root of( original pressure drop/new pressure drop))

So the 670 CFM truck avenger at say 1 inch of mercury will flow: (670)/(square root of(1.5/1)) = 546 CFM

and at .5 inches of mercury: (670)/(square root of(1.5/.5)) = 386 CFM

Pretty close to the 351 CFM that you calculated for me at 90% VE. So now I have to determine whether this carb will still provide a good vacuum signal and therefore a good atomized mixture at the only .5 inch of mercury drop it's going to being seeing. My GUESS is that the better vacuum signal of the annular boosters will compensate most of the way, probably not all the way unless the carburetor was modified, which I may attempt down the road, or I may not, not sure. But only road tests and tuning will tell for sure whether this theory holds any water (or mercury )

Whew!! Boy er muh fingurs tie urd

 

I forgot to say that the annular boosters are only on the 670 and 770 CFM truck avenger. Not on the 470 or 390 CFM. That's basically why I chose the 670. If they were available on the 470, I would have probably gotten that one instead.

 

Hey 91Bronc, that's actually really interesting information. In that case, that would be really cool if you could get that 670 tuned nicely and sounds like the annular boosters should help some.
Are you interested in gas mileage with this setup? Just curious if you think the 670 will be able to be gentle on gas when you want it to be.

Again, thanks for the great tech writeup!

 

Good mileage would be nice, of course, but I don't have an honest clue about how the size of this carb or its booster design will affect it. Up until now all the carburetor experience I have has just been: 'put in an auto parts store rebuild kit, bolt it back on, twist the idle screws until it idles right, drive'. I've read theory and things but have not done any real world major adjusting. This will be my first and I'm excited and ready to learn, but I have no experience to guess what mileage will be. On the plus side, this is just going to be a backup truck plus maybe a daily driver while I'm doing any bronco projects, but that's it. So mileage isn't really crucial.

Time will tell, amigo. Time will tell