Hey all, I'm new to this and think I may have bitten off more than I can chew. I'm trying to resurrect a 1985 E-350 Quadravan conversion that had been sitting for a few years. It's a stock 460, but with 4 wheel drive added to drivetrain (205 xfer, dana 60 front w/leaf springs, body/suspension lift, and 35"tires).

Initially I was getting horrible mixtures. Replaced the filthy carb with a new Holley 770cfm 4150. New plugs, wires, distributor cap and rotor and it idles fine. A little tuning and it runs OK on the street, but the secondaries won't open. I can still get up to about 55mph, but that's where the power runs out.

What I've noticed: Gaskets are all fine, air moves through the right hole when I move the secondary piston up and down. I've tried every weight spring with no difference. I even ran it without a spring thinking it would have to move then, but it didn't. Manifold vacuum is 22 at idle and steady. It drops steadily as throtle is opened and will ultimately hit zero usually around 40-50 mph.

I've disconnected most vacuum lines to trouble shoot and performance has not changed. Still intact are timing advance, PCV, brake booster, and AT case. EGR valve works and is closed without vacuum. Additional, possibly unrelated, problem: The distributor is frozen in place, turned slightly left.

 

Did you try to move the secondaries by hand? I've had a problem where they were frozen shut and could not be opened with hand, let alone a tiny vacuum actuator. I had to disassemble them, clean up everything and it's working great now.

Hope this helps.
Lou

 

Yes, the secondaries move freely with the engine off. I might try rigging them to open manually. Also, I've been poking around this site and will be checking my fuel line pressure as well.

My newest theory, the vacuum is falling too quickly to open the secondaries when the throtle is opened. Could it be that this carburetor is too big for my engine?

 

The carb is not too big. It sounds like is is defective. The diaphram has a leak or it's vacuum source it plugged. If it's new I would take it back and exchange it for another new one.

 

If the distributor is frozen in place what about the timing?

 

First off why a 770 CFM 4150? The 4150 is designed more for racing, it has metering plates rather than jets, IMO way more than any stock 460 can use. I run a 4160 600 CFM and it works just great and gives me 10-13 MPG on an 86 F250 4x4. Anyway to your problem, you will need to buy a set of secondary springs and Holley says step one spring lighter until secondaries open. if you get a bog you are too light. Are you sure the secondaries aren't opening? Holley again says you shouldn't feel them kick in. Feeling them is the big misunderstanding many have about secondaries opening. Holley says what you are feeling is a lag of too much gas and the engine tring to burn it. All this info is provided with their carbs, at least it was in mine.

 

i don't think there is too much gas. It is a loss of vacuum which creates the bog. gas is not injected into the engine . It has to be drawn in. The pump shot is used to cover this up. F eel free to dispute this boys

 

The accelerator pump only covers for the primaries. When the secondaries open suppose to be unough air flow because of higher revs to pull fuel. I recommend you pull the secondary vacuum assembly and push the rod in to the unit. Put your finger over the bleed hole and rod should stay in. If it doesn't dyaphram is bad. then start the engine with the vacuum of and rev the engine, you should have vacuum at the hole. If not it's plugged somewhere and you need to find out if wrong gasket is causing the problem, seen it before.
Bear

 

Oh yeah, I forgot about the check ball between the top and bottom halves of the vacuum unit. Seen it froze in place before. I always leave it out anyway, as that lets the secondaries open easier. That's an old racers trick. BTW the 4150 style was the first 4 barrel that Holley produced back in the 50's. The 4160 was cheaper as didn't have the second metering block, otherwise they are the same.

Bear

 

I made a cheap mod to get this beast home. Its two hours on the freeway and I really needed the power of the secondary. So I safety wired the secondary linkage, effectively attaching it to the primary so they both open in tandem. Worked. Have to be careful adding gas or you'll flood it, but screems up the on ramps and had no trouble holding speed.

I know the secondaries were not opening before because I saw them (it's a van and I rode with the internal engine cowling off). Bear, I'm going to take the seecondary vacuum thing off tonight and test it like you said, thanks. It doesn;t have a check ball that I can see, instead it has a brass insert. Not sure what that's about.

There might be a vacuum leak in the brake booster. My front resivoiur was empty before I left. Don't know how long thats been going on. At least it will keep me busy blleeding lines and all.

About the timing, I looked for the marks, but with the distributor frozen in place I left this alone. Where might I find them? They were not obvious from below. From the top there's too much stuff in the way. There might be something on top of the fly wheel, but as I said, I gave up looking.

P.S. About 10 MPG as rigged. Woohoo!

 

If it is a 4150 the linkage has to be hitting something, as there are no vacuum secondaries

 

The 4150's can have the vacuum secondaries, the original 4150, List# 1850 were all vacuum and flowed 600cfm(I have one still). The brass insert is to meter the vacuum to the dyaphram, leave it alone.

Bear

 

Many 4150's have vacuum secondaries. By his post I'm guessing this is the carb we're ralking about.

Holley Truck Avenger 770 CFM Carburetor Part #: 0-90770


http://www.holley.com/HiOctn/ProdLin...C/0-90770.html

 

does it have a cat low vac high rrs clogged cat ??????????????

 

No, no cat. The manifold vacuum is strong. I had a friend make a block I could bolt on where the vacuum secondary actuators usullly goes. Then hooked up a vacuum guage so I could measure the vacuum signal there. Best I could get was 1". I'm thinking there must be a clog or restriction in there; or maybe there's a check valve not working. Either way, its internal and not something I can fix, so its going back.
I've rebuilt the old carburetor, so if that works, it will confirm the bad part. Thanks all.