dbaldie

I recently purchased a 4-barrel intake manifold and carb from an estate, to put on my sons’ 67 mustang 289 (original 2 barrel) automatic. Rebuilt the carburetor with a “Hygrade” rebuild kit i bought from Honest Performance, having soaked all the parts in carb cleaner overnight, and blew out all the air passages with compressed air. Put it on, and got it running, but have a couple of (minor?) problems I need to iron out.

the carburator's an autolite 4100, model c6pfh. 1.08 primarys, at 468CFM.

1) Although the vacuum secondary butterfly shaft is nice and loose when the engine’s off, when I punched the gas, the secondary’s started to open, and then sticks in the “slightly open position” so the car over-revs… it does this every time, and they WONT return to closed, DON’T seem to open more than just a hair (about .060"). However, like I say, when the car’s NOT running, they’re nice and loose. I DID put the spring in, in the direction shown on the diagram, but I suppose I MAY have switched the two springs (the vac secondary and the accelerator pump). Still, that doesn’t SEEM to be the issue, coz when it’s running, if you manipulate the little lever on the side, it’s REALLY “stiff”

2) The idle mixture screws seem to do little, if anything. I adjusted them to 1-1/2 turns out initially, but turning them in or out does nothing for the idle, unless they’re seated… then the car acts like it’s going to die.

3) the power valve (economizer valve) didn’t come with a “thick washer” that was anything CLOSE to a good fit, so I used a much thinner washer that was in the kit… is this a problem?

So, does anybody have any clues about what these problems might be, and how to correct them? It’d be nice to know without having to go have it rebuilt again! Btw, I also replaced the (leaky) 2 row radiator with a brand new 3 row one, coz I realize this engine may run hotter now…

any help would be GREATLY appreciated... i'm letting my son use one of MY cars while i'm trying to get HIS fixed, and THATS not something i want going on forever!

2+2GT

Make sure the choke lock-out is not interfering, it's supposed to prevent the secondaries from opening when the choke is on. Do the secondaries return freely with the carb on the bench?

dbaldie

yes... i dont see anything though, that would keep them from opening at ANY time, given the proper vacuum. however, as long as there isnt any vacuum, they open and close very freely. it's only under vacuum that they get "sticky".

hotrod351

well if everything is free then id would think of the vacuum being the problem. if its the vacuum that opens them and its not closing all the way then id pull the vacuum line off when they stick to see if they close, if not then some linkage some where is binding. to bad you could find another carb to try to see if it did the same thing.

dbaldie

there is no separate vacuum line on this carburator... it's apparently an internal passage to the vac secodary diaphragm. im thinking of taking off the diaphragm just to see if the gasket is perhaps covering part of the hole. other than that, im stuck~

jay67fast

Try this website---If they can't fix it, no-one can!!!

http://www.network54.com/Forum/88781/

Hope this helps
Jay