I received an 86 d150. It had a burnt valve when I received it. I fixed that and found that the foam floats had begun to deteriorate. I rebuilt the 1945 carb and spent the money on a coating to prevent oxidization. So now my truck is now able to be driven.

I have set the timing to 16 degrees as shop key states with an automatic. It also states that dual pickup distributors were only used on automatics. Alldata doesn't mention anything other than specs. I get some pinging on load and I assume that is why the valve burnt, that and a small pinhole vacuum leak leaning the engine out and creating more heat.

So now I want to do the HEI upgrade to gain advance based on load. The problem I have is the tube that should have ported vacuum does not have ported vacuum it has full manifold vacuum. All of my ports except for one has full manifold vac. The one that does not I have no ideal what it provides as I cannot read it on a gauge.

My question is, the ported vacuum is it metered? Does it increase as the throttle goes down or does the ported go immediately to full manifold vacuum?

I can electronically create ported full vacuum (using a modern vent valve switching ground at the throttle solenoid ground connector on the front that contacts the linkage. It gets me 4 ohms to ground when the throttle is closed) or possibly could I simply buy just the throttle body portion of the carb and gain ported vacuum? Some carbs this is merely a gasket change to obtain this but there is no info on the carb itself and I don't remember. I wish I had found this site first. I have a feeling that the computer may possibly retard timing at shift points.


My new distributor is from an 83 d150 with a standard transmission and 2 barrel carb. The governor plate is a 9r providing total mechanical advance to 18 degrees. Springs are identical in length, coil amount and diameter of wire and coil. The 2 barrel carb must have had the ported spark tube.

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If it was easy, everybody would be doing it.

Any idea if the ported vacuum comes metered or all in once the throttle shaft moves? On a manual I believe they quoted 12 degrees advance. They give more advance due to the transmission load I would assume.

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It almost certain that a 1986 Dodge truck was equipped with some form of Chrysler's lean-burn computer controlled ignition and/or carburetion system. Are you certain the carburetor you have is a 1945 and not a 6145? The 6145 is a computer controlled carburetor that has wires going into the float bowl.
That is correct for lean burn ignition system vehicles only. You base timing will have to be adjusted when you switch to an HEI ignition.
I doubt it. I have seen dual pickup distributors on manual and automatic transmission vehicles. Pinging on load and a burnt valve are classic symptoms of a failed/failing lean burn system.
Wise move.
Carburetors on vehicles equipped with a lean-burn controlled ignition system were built with a non-ported vacuum tube. This is because the computer gauged engine load in reverse from the older distributor. The computer expected to see full manifold vacuum at idle and decreasing vacuum as engine loaded increased. Most people just replace the carburetor with one that is not for a computer controlled application.
It is not possible to just change a gasket or a base portuion of the carb. You should replace the entire carburetor. An ekectronic solution sounds interesting, but has more potential failure points and is more difficult to create and maintain than a carb that is correct for the application.
No 1983 slant six had a factory two barrel carburetor. It certainly could have been swapped on later, but the two barrel option ended by 1981. The two barrel carb (Carter BBD) would have had the correct ported advance tube for distributor vacuum advance. If possible, I would go back and grab the carb, intake, and air cleaner off that truck. The two barrel carb is a nice upgrade.

In the end, you will be better off just getting a new carburetor that is intended for a non-computer controlled application..

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Casually looking for a Clifford hyperpak intake for cheap.

Thanks for the insight. My carb is a 1945. Numbers on the bowl are 4306460, 40160, 1646. The info beyond 1995 and back gets sketchy in those commercial information databases. We call alldata nodata rather frequently.

Thanks for the help. I need to research source years for carbs now.

Are the aircleaner base circles all the same?

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Aircleaner bases are different between single and double barrel carbs. 1980s carbs are really hit or miss with regards to the correct ported vacuum advance nipple. You are better off looking for a late 70s or very early 80s Holley 1945.

HERE is a possibility,

THIS ONE looks really good for the price.

THIS ONE is also a good choice if you are looking for a new Holley 1945.

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Casually looking for a Clifford hyperpak intake for cheap.

The HEI upgrade is a very good one. Disabling the Lean Burn will remove all computer control over spark advance, which will be purely the product of initial (base), mechanical (centrifugal) and vacuum advance. Once you do this, 16° BTDC will be too much initial advance; try about 8° at hot/curb idle with the vacuum advance disconnected.

Your idea to emulate ported vacuum for spark advance sounds similar to the thought I had when I was tinkering with a later ('89) Dodge pickup. The vacuum "seen" by the distributor would not be quite exactly the same as with an actual ported spark, but it would be very similar, certainly similar enough that I doubt there'd be any discernible difference in how the engine would run with that setup vs. actual ported vacuum.

Ported vacuum starts with a small(!) hole or slot located just above where the throttle plate sits in its closed position, so no vacuum with the throttle closed, and (more or less) manifold vacuum with the throttle open. That small hole serves as an orifice to smooth out the vacuum signal to the distributor so the timing isn't jumping all over the place in response to transients. If your present vacuum port (the one that would be a ported vacuum port except it's not) does not already have a small orifice behind it in the carburetor casting, you'll want to put a small restrictor orifice somewhere in the line for that purpose.

As long as you are in the neighbourhood, emulating ported vacuum, see if you can figure out how to send manifold vacuum to the distributor with the throttle closed and the vehicle moving as described here (one way to do this, of course, would be to scare up one of those valves—they aren't parts store items, or wrecking yard items any more, but they do show up from time to time).

The charcoal can is very much worth keeping functional. The Lean Burn computer does not know or talk to anything in that system, but if your system is incomplete or hacked, the know-how to make it work is here (part numbers in it for the canister and purge valve are obsolete; currently-available items are canister and purge valve).

The EGR is probably worth keeping, too. It may or may not have interaction with the Lean Burn computer, depending on your truck's emissions configuration (49-state, California, Canada) and the accuracy of my recollection. Probably not. You will want to upgrade to the transducer-equipped EGR valve which does a much better job of flow metering in accord with engine load so you get more of the potential benefit and less of the potential drawback. This valve also uses separate orifice plates rather than built-in ones, so you can adjust/tune the amount of EGR flow. I have a complete table of EGR valve orifice plates to hole size (from which flow rate can be calculated…and custom plates can be made if you don't happen to have the pre-made one you want).

You can just leave the Lean Burn box sitting there doing nothing and keep using your existing air cleaner. 1bbl and 2bbl air cleaner base necks are not the same—2.125" for 1bbl, 2.625" for 2bbl. The last year for the 2bbl in North America was '83—the '82-'83 Dodge Truck Factory Parts Cattledog lists 1bbl and 2bbl intake manifolds, air cleaners, choke thermotats, choke modulators, carburetors, and throttle/kickdown linkage parts. Things get weird in the '84-'86 cattledog, which lists 1bbl and 2bbl intake manifolds, air cleaners, and throttle linkage parts for the 6-cylinder engine, but does not list any 2bbl carburetors for the 6-cylinder engine. The 2bbl setup was likely still offered on export models, but not in North America after '83. Confirmation comes from RockAuto, which lists a 2bbl carburetor for the 6-cylinder trucks in '83 but not in '84.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I started the conversion when I got off work last night.


Faux vacuum works. I used one of the solenoids on the fender well. I used a 5 pin relay and when the throttle shaft is touching the throttle solenoid tip it switches position as the relay then has ground. With the throttle off the the throttle solenoid the relay reverts to the resting position where I wired the ground. No delay or flutter issues.

The truck is really alive now. Before the only way to pass was to floor it and have the transmission downshift.

I think it may need some more initial timing. I am wondering if 10 degrees will be better as it is a bit rough at idle and heats up pretty quickly.

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Timing via mechanical. It appears like mechanical advance starts coming in at 1200 rpm and ends at 2250. With a total advance of 16 degrees. At 10 base my total timing is 26 which seems pretty low. The factory rec spec is 16 with this distributor.

Vacuum applied to distributor at idle is 20 degrees.

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There should be no vacuum applied to the distributor vacuum advance at idle.

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Casually looking for a Clifford hyperpak intake for cheap.

That's late/slow
That's not enough.
What distributor, exactly, are you using? And where did you find this spec?
Vacuum applied to distributor at idle should be ZERO.
Er...that means you removed it from the job it was doing before, then, right? What was it doing before?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Factory specification base timing for an engine equipped with a lean burn ignition system is 16 degrees. This is no longer valid if you have switched to another ignition system.

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Casually looking for a Clifford hyperpak intake for cheap.

I applied vacuum with a hand held pump. Just to see where the can was set at.

Smog pump activation. Pump no longer exists. I believe but I will have to check and verify it. Egr amplifier is gone and it hooked to both solenoids.

Distributor was from an 83 pickup. The govenor plate is a 9r which I believe locks it out at 18 degrees.

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Spec was the same for an 83 with a vacuum advance in both shopkey and all data. VIN M states 12 degrees not 16 I apologize.

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I would not trust those databases for vehicles this old. Go to the source and get a true factory service manual.

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Casually looking for a Clifford hyperpak intake for cheap.