rebuilt the carb as I had a flooding issue (fixed) but prior to the rebuild, the secondaries didn't work. New diaphram installed (made sure no leaks) but still they don't work. Unless this is an easy fix of something Im missing, can I convert to mechanical secondaries as opposed to vaccum?

thanks

Bill

 

Are you just checking by revving the engine while watching the secondary linkage? There has to be a load on the engine for the secondaries to open.

 

yes...thats what Im doing - just reving it up.... if thats the case (needs load) then I'll go drive it and see whats hap'n when I get home

thanks!!

Bill

 

Yep, it must be under a load. They open by the vacuum signal being drawn thru the front barrels.

 

i had the same problem, and went to a lighter spring under the diaphram on the vacuum secondarys this will cure your problem it did for me 85 f250 4x4 351

 

I just returned from a 2200 mile trip to and around Colorado. I'm still kicking myself for not having the carb rebuilt before we left, but part way down I began to have serious doubts that my 4180 secondaries were working properly. With the last rebuild I had the quick change spring adaptor installed, changed to a lighter spring and had had it working good, but it didn't seem right now At a campground in NW Kansas I ran into a great Canadian guy who was working the wheat harvest with a custom harvestor crew. He started talking to me about how nice it was to see an old truck actually working and when I shared my concern about the carb he showed me a little trick.

I swung into an implement dealership (hardware store would've done too) and got a short #6 machine screw, a couple washers, a nut and a lockwasher. As he'd instructed, I put the washered screw into the slot on the driver side of the secondary carb linkage, slid on the washer, lock and nut and adjusted it so the primary linkage rod that runs in the slot would contact the washers at ~1/2 throttle to start with. After a couple of adjustments I got it so the secondaries started opening about where I wanted them. They didn't open all the way mechanically but I felt it was better than nothing. If the secondaries were working with vacuum this made it a sure thing and the vacuum would do the rest. Did the rest of the trip running what I now call the "Trevor Modification".

It may not be totally "kosher", but it works.

Roger

Clyde S Dale, my chestnut brown & tan 5th wheel workhorse is a
1984 F250HD XLT RCLB 4X2 8600 GVW
460 C6 3.55's
67,500 original miles (and counting)

 

Yeah, that's the cheater screw mod. Really not the best thing to do, if you stomp on it the secondaries pop open uncontrolled and the mixture goes way lean.

 

Any non-factory modification has risks, but for working instead of "show boating" it worked just fine. Not too often do I "romp on it" when pulling a fifth wheel

 

As long as you ease into the secondaries slowly, it will work, but without the accelerator pump in the rear, if you open it too fast, it will lean out and bog severely causing a backfire and blown power valve.

 

and I can tell ya about blown power valves...finally had the chance to rebuild my 4180 2 weeks ago. Power valve rotated on its shaft! needless to say I found my flooding problem. I followed the above advice and I "think" the secondaries are working - sounds like it (I think) will have to get out on the road proper to try it

Bill