Hey Just Did Holley,offy,headman Setup Last Night And I Have A Question About Setting The Secondary With The Right Spring.when I Punch The Gas The Truck Kind Of Stumbles For A Second And Then Takes Off.so I Got The Spring Kit And Went With The Next Stiffer Spring [the Brown One] And It Still Stumbles When Punched.so Do I Go To The Next Stiffer One,witch By The Way Is The Stiffest In The Pack(the Black One).or Is Not A Spring But Possibly A Jet.

 

I did the Clifford/Holly390 4bbl/GM HEI mod and coil swap. My van also bogged down. It was a dist. timeing issue. I did a redneck timeing with out a scope, e-z to do in a van. Had the inside motor cover removed, and made adjustments on the backroads as the motor was running. I made half-doz. stops and adjustments and it's real close. I still have some fine tuning to do, but I did nothing to the carb yet. Don't forget the stock carb settings so you can get back to stock if need be.

 

My Holley, Offy, Hedman set-up has pretty much the same problem, although I have no problem driving it it's not perfect yet and have made no adjustments yet, so let us know what you do so I can try it on my truck. I also should check my timing, but if you do something different with good results I would like to know. Thanks!

 

That doesn't sound like a secondary spring problem to me. I am a noob with Holleys, though. I'd change the squirter or the pump cam first. If you are at a steady speed and try to stomp it to get through traffic, but it stumbles then takes off, it sounds like too much gas too fast.

I could be wrong. :P

 

I was having the same problem couple of weeks ago, ended up bumping the timing two degrees, and got rid of it. I would check the timing first, then go to the squirter next. The secondaries should not be affecting you until you are well under load and into the throttle.

 

Had the exact same problem too. The secondaries opened too soon w/ the stock spring. Installed the "quick change" secondary spring kit, and as everyone noted the BROWN one worked best. BLACK is stiffer but a bit too stiff, the secondaries won't ever open fully. Wish there was one more in between the two... but there's not [actually called Holley to double check]. The 390 is set up for the L6 in a car "out of the box", so it does take a tiny tweek in heavier vehicles.

Timing adjustments are in order, but for me it was the addition of a better ignition system that got rid of the bog 100%. It also woke up the throttle response in a big way and netted slightly over 1mpg better mileage.

Be sure to check the clearance for the primary and secondary throttle levers. I had to install spacer plates under the carb for the main linkage to clear [it was hitting the intake at about 3/4 throttle]. The plates then interfered with the little secondary lever on the opposite side. Had to notch out the plates to let it swing down when the secondaries open [pic of the mod in my gallery].

 

So 83VAN, which intake manifold do you have in your van? Offy DP? If so did you have any clearance problems with the dog house next to the carb/intake manifold? My Clifford is really close. Only had it running for two days. So far ok. Did you have to bend/modify any sheet metal on the dog house? I talked to a guy who has a Offy and he said his would not fit in my van.

 

tried timing adjustments,installed an msd 6al and still have brown spring in.do i rejet it?oh by the way does anyone else have a problem seeing the grove on the pully for timing,and what is the factory timing setting for a 76 300ci. if this helps the bog happens when starting and when i punch the gas while crusin.did a nyone here have to put a softer spring in their carb.

 

ok i was looking at all your galleries and saw that the primaries are facing the motor mine is the oppisite could that make a difference

 

My van is an '83 and there are no issues with the doghouse.
Have the Offy DP intake, Holley 390 carb, and stock EFI headers. The intake fits no problem... but when the carb goes on it's tight. Take a peek at my gallery and you can see for yourself. The carb's secondary fuel bowl just kisses the insulation on the side of the under-dash firewall, and there's maybe 4.5" vertical clearance.

Two big problems with a 4bbl in the van are a good air filter setup and the tranny dipstick. The carb is so close to the side firewall no regular air cleaners will fit. I initially used a Mr. Gasket 6" dia chrome air cleaner, fit fine but seemed too restrictive. Now using an Edelbrock "Pro-Flow" air cleaner which is a small triangular job, washable foam filter element w/a wire mesh cover sitting on a nice "velocity stack-ish" base. Tight fit but it works. They're only $20 and you can pick one up at any auto parts store. You can also get an "offset base" air cleaner for regular 12" or 14" filters... but they're not cheap and I'm not sure if they're offset enough to fit. Next on the list is fabbing up an intake box w/ a remote air filter, now it's just sucking hot air from the top of the engine compartment.

The most hair-pulling problem has been with the C6 transmission dipstick. It's bent to come out beside the stock carb, but with the new intake/carb there's plenty of stuff in the way of its former path. Spend way too much time bending mine to have it be just barely accessible over the top of the air cleaner. No one makes a flexible replacement C6 dipstick long enough to be practical for "under hood" access in a van, so you might try one of the stubby versions and just live with removing the doghouse to check your tranny fluid. I can check mine [with difficulty], but to add any fluid I have to use a funnel + 3 feet of plastic hose.

 

If you have an open intake [Offy C or Clifford equivalent] the direction probably wouldn't make much difference beyond making the throttle cable hookup a pain. If you have the Offy DP intake and have the carb reversed [primaries outside, secondaries inside] it certainly would make a difference. The DP intake is designed to have the primaries run through the small volume inside/ top runners, and the secondaries the larger rear/bottom runners. It would still work reversed... you'd just lose much of the benefit of the engineering they put into the DP, and I'm sure it would make the bog problem much worse.

Rear end/ tire combo is also a factor. If you have a taller [lower numerical] final drive ratio then your acceleration isn't going to be as snappy. My van originally had a 3.08 gear w/ 235/75/15 tires and there was still a hint of bog when the secondaries opened. Changed to a 3.50 gear and the bog was [finally] history.

 

Thanks for the info 83VAN. I have the Clifford 390 Holley hei mod set up. The van is running great. I will take a rest from wrenching on it and get the feel of the carb and the way it runs. The air filter was a chalange. I spent two mornings at the bone yard racking my brain on air filters. I had a air box patern all made from cardboard that was going to mount on the driver front side behind the head light. I was going to run 4" duct to the carb and hang a K&N 4" cone filter inside the air box. This was too much stuff over the motor. What I have now is a 5 1/8" id x5" tall "can" with a flat plate welded to the top. A 4"dia exhaust pipe is welded to the side and that is where the K&N filter is connected now. I will make a heat shield and feed the carb with the stock fresh air duct when I get time. I used the stock carb cable and made a bracket. Works great. I got a good feeling about the filter set up that I have. K&N is a good product. And it sounds really cool when it's at full honk. I have a 3 speed manual trans so I don't have the auto trans dip problem, but the motor dip tube rusted and broke. Ford wants 60 buck for that tube. I said that some kind of a mistake, check again. No, it's 60 bucks. I repaired mine with a new brake line and a union for about 8 bucks. I will post more info on my learning from this project. Still newbe on this site. Have not figured it all out yet. Can't even sort the gallery info e-z yet. Can't get to your gallery. Got to go now. Just back from a 100 mile bike ride (1992 ZX7 Ninja)and still a bit rummy. A great spring day ride. Tomorrow will get the 300 KTM dirt bike out. The van is the dirt hauler. Enjoy the week end, I will.

 

Sounds like we have the same idea on the air cleaner setup; my play was [is] to fabricate a made-to-fit air box to mount to the top of the carb then run a piece of flex duct [much like the OEM cleaner] to the stock intake location behind the grill. Air filter would be remote mounted, probably a generic cone style filter... biggest one that will fit the location.