what size carbs??

[Darrell Ratchner]

Jimbo, the 1849 is listed as a 550 CFM Vacuum Secondary Carb. It should not have a metering block, but should have a metering plate inside the float bowl. This should fit on the 2x4 intake. The 550 cfm, in a vacuum secondary should work out good. I have not used them but the venturies are small.
Any other questions specifically? Primary main jet is a 62, Secondary metering plate is a 134-5. I'm at 6000 feet elevation so I always have to lean the carbs. I cannot give you much help there. Good luck Darrell

[chopper]

Rob:

As far as I can tell, yes, the secondaries are opening. The heavier secondary springs seemed to resolve a relatively heavy bog when the throttles were opened rapidly from low power position. How do you recommend reducing the power circuit by 50%? Is this something accomplished by changing the power valve or is some other type of modification required? The present problem is a frequent light "pop" out the sidepipes during moderate deceleration, with an occasional loud one during heavy deceleration. The pipes have been checked for leaks by a respected shop here in town, leading me to think the carbs are still just running too rich. Truth be told, I've never been really happy with these carbs and am wondering if the 0-9776 carbs may be a better way to go. The little Holley formula about carb size tells me I should be running about 850 cfm total anyway, perhaps two 450s would give better results?

Darrell:

I'm running the carbs on a H&M manifold which came on the car. The carbs are presently set up with a sort of "progressive" linkage. The engine idles through both carbs but the forward one opens slightly ahead of the aft due to a slot in the linkage on the aft carb. I have had several opinions expressed as to whether or not the linkage is supposed to operate this way. Some folks have said they think there's a locking piece missing and that both carbs should operate simultaneously. Others have told me that the linkage is supposed to run as a progressive unit. Any opinions?

[Trans-Am Jim]

Darrell:

Thanks much. No more specific questions.
After a springtime worth of tuning, I ended up with 60 main jets and a green spring (I believe that's the intermediate stiffness) in the diaphragm for the secondaries. My next project is to play around with different cams for the accelerator pumps and to fiddle with the shooters themselves. I love fiddlin' with the carbs - sometimes I think I'd be a good candidate for Webers


Chopper:
I have the progressive linkage also. I set it once so that both carbs were opening the same amount simultaneously, and it seemed that part-throttle acceleration was not as smooth. I reset the slider so that the pin is about midway in the slot and it feels better. Another one of those things to fiddle around with until you find a setting to your liking, I guess

Later,

[edwhite7]

If I recall the size of the carbs to use also depends on the type of manifold, single plane or dual. The dual plane will requirer a larger carb due to its design. I used dual 600's with vac secondaries on my dual plane but am happier with dual 450 and mech secondaries on my tunnel wedge which is a single plane. PS the summit cataloge does show the incorrect picture. That is how I got the mech. secondaries on my 450's.

[SCOBRAC]

Mike,

Holley List #0-9776 have no choke or vacuum secondaries.. I have a pair you can try if you want. I love mine. I know pleanty of guys that run 600's and love theirs too.

As for size you are all trying to pee up a rope... While what Rob said is true keep in mind that for homogonization purposes Ford errored on the side of caution while using the larger carbs.. My 450's do not "act" like a single 780. They act like two 450's and when properly tuned are more than enough carburation for up to 500 HP. That isn't to say you might not want to try a pair of 550-600 cmf units.. They would be ok too.. a little fat and more likely to load up in traffic, bog out and generally smell like you were driving a Chevy truck. But they would run fine...

I would not suggest using twin vacuum secondary carbs even when equalized they tend to open at different times.. But that is just my preference. I will tell you that for this area chokes, especially electric chokes are not needed. The 0-9776 is a good trouble free unit. but then so is the 600... You can see mine at my photo page..

Regards,