I’m having a problem and just not sure what to try next.
The car is: 1956 Townsman wagon, 265 V8 Power Pak Powerglide. EVERYTHING is freshly rebuilt last year. Engine, and that would include: new pistons, rings, turn the crank, all new main and rod bearings; lifters, valves & guides & springs, timing gears; oil pump, generator, distributor, carburetor, water pump, fuel pump, exhaust system, battery, trans, brakes, gas tank, tires (bias) - you get the idea - absolutely everything, nothing untouched. Totally, totally stock configuration, as built. NOS stuff or rebuilt originals instead of repops wherever possible. And then set up with original type vacuum gauges and instruments to exact factory specs as best as humanly possible.
And it runs great, just like the summer of 1956. Drove it from Ohio to New York last summer, and now a total of about 1,000 miles on it. It gets about 16 or 17 mpg, uses just a tad of oil, which yes I run with high ZDDP/zink content.
So here’s the problem - going up a hill, or jumping on it for passing gear at 35 or 40, and the secondaries open up - I get a pretty good shot of black smoke. Soot. Not blue, not gray or white - black, like unburned fuel. It is also very sooty when I first start it and the choke is still on. I get a big shot of black for the first few seconds.
Most stuff I did myself, but various things were sent out for better experts to re-do. One such was the carburetor, a Rochester 4-jet 7008737, original to the car. It came back real pretty and I put it on.
Naturally my first thought was the carb was not right. So I finally found and bought a second 1956 Rochester 4-jet, got the right kit and meticulously rebuilt it myself. Put it on a few days ago. And I get the same results! The choke opens fully when warmed up, the floats are set right, the jets are right, the accelerator pump is right.
What’s going on, what do you think to look at next?
I have thought maybe the spark isn’t hot enough. I’m running AC R45 plugs (original equipment), and the coil and points etc are all new and set up as they are supposed to be.
Going down the road all warmed up the problem is not apparent. But when people are following me, I always get comments about “hey, when you push on it you really get some black smoke!” So it’s there. Not sure what to try next. Many thanks for your thoughts…
Possible cause is unburt gas building up in the mufflers and getting blown out. ...or the carbon remains of burnt gas. This was kind of common on these cars with dual exhaust when they were driven in a normal manner for a time and then kicked in the axx. If it were mine I would take it out and floor it up tp 80 MPH a few times a clean it out. Thats what I did years ago and still do with my '57.
Possible cause is unburt gas building up in the mufflers and getting blown out. ...or the carbon remains of burnt gas. This was kind of common on these cars with dual exhaust when they were driven in a normal manner for a time and then kicked in the axx. If it were mine I would take it out and floor it up tp 80 MPH a few times a clean it out. Thats what I did years ago and still do with my '57.
X2.
Also, todays fuel seems to smoke more than gasoline from 1956. The perfectly white tailpipe which was the sign of a well-tuned engine in yesteryear is gone. The "white inside" was lead residue. A normal tailpipe today is black in color, and if driven much around town, sooty black.
If Gene's suggestion about "turn it on, wind it up, blow it out" (oops, wrong older car ) doesn't solve the issue, take a look at the vacuum advance unit on the distributor.
I agree that normally a properly rebuilt Q-Jet works very well. At one time in the 70's I had 3 different vehicles all with Q-Jets.
They ran great but I did find I a few issues I needed to keep an eye on over the years.
1) Mine all had what I think was called a "phenolic" or non-metal float. Over time these floats absorbed gasoline and got heavier. So even though you set the float at the correct dimension the car ran rich because the float was sitting lower in the fuel in the float bowl. Plus the heavier float was not as responsive to changes in fuel depth. It tended to drop quicker and stay lower longer so it did not shut off the needle valve as quickly.
2) This part may not apply to the early carburetors like yours. Mine had tapered metering rods that were pulled down into the primary jets by higher engine vacuum and would lean the mixture slightly at part throttle. Sometimes these would stick in the up position and the car would run richer.
3) There were some issues with fuel leaks at the bottom of the float bowl due to either casting to machining issues (can't remember which). Fuel would drip directly into the manifold.
Just some ideas. Interesting that currently I am dealing with the same "black smoke" issue on a 1957 Olds with tri-power deuces.
Seems to me that it is merely running too rich. Is the air filter open? I would assume it is. Other than that it seems to be running too rich and more so when you get on it.
Thanks, Gents for these replies. It sounds like the classic old "Blow the carbon out" run is in order! I will do that, and enjoy it.
At least I was pretty pleased with myself that my effort at rebuilding the second carb resulted with it running extremely well, I was nervous about that, there's a lot of parts and touchy adjustments in there, for sure. And it came out really well, runs at least as good as the professionally rebuilt unit. But my effort isn't as pretty, since I didn't re-plate the body and the linkages, etc. Unfortunately, the original problem behavior with the black smoke is identical. But at least it shows me that the carb is not the issue.
Rusty, it is a 1956 Rochester "4-Jet," the immediate predecessor to the Quadrajet, a very similar carb really. It does have brass floats, so that's not an issue. And the bottom of the bowls don't leak through, I have nice clean bottoms on all.
I'll be driving the car from Ohio to Peterborough Ontario next month, nearly a 1,000 mile round-trip to the Central Meet, and was hoping to get this resolved.
I also posted this question on the Tri-Five forums, and the Vacuum Advance got mentioned twice there too, Jon. I had not thought about that. I did put a new diaphragm unit on the distributor, and of course cleaned up and reworked the distributor innards. But they can be touchy about having real good vacuum connections from the carb, so I'm going to pull the distributor and re-check all those components.
I pulled the top off the professionally rebuilt carb, and found that the secondaries float is set significantly high, so I'll go through it and put it back on I think, since it is prettier than the second carb, and is actually the original carb to the car. And we'll blow out the carbon, and re-check advance. If it still wants to puff black smoke, we'll blame it on the crappy gas of 2018 versus 1956. Thanks, all.
Both the Carter and Rochester are correct for my 1957 - like your 1956. I would say the Carter gives about 1 MPG better mileage and either makes the engine run OK. Run about 16mpg against the wind and 18 with the wind at around 65 MPH.
Do you have access to non-ethanol fuel? Try a tank. Even my '40 runs with the tailpipe mostly dark black with ethanol added gas. I run a tank of straight unleaded thru it every once in awhile and the black (rich looking) changes to a light tan.
Mike, I haven't been able to get "real gas" anywhere around here for years now. Maybe I'll find some up in Canada next month? Don't know.
Tony, I would agree, there is clearly some partially unburned gas - but only for very brief periods of time under certain conditions. 99% of the time, things are as they should be, see original post.
Gene, that's right, I get right around 15-16 mpg on the road.
Gene - the OP stated new exhaust system, so probably not years ago; probably with current normal driving. I think you are right, and lots of fun to "turn it on, wind it up, blow it out" In a different lifetime (the mid-1960's), when my wife and I would go home for the weekends; ALWAYS had to blow out the carbon even after a week of city driving.
As for real gasoline:
At least here in Missouri, ALL of the marinas have real gasoline. Something about deathanol destroying the fiberglass fuel tanks in the boats. Of course, the marinas will only pump gasoline into a boat. So if you happen to have a boat with a large tank that you store at home................
This term confuses MOST enthusiasts (almost depending on the age of the enthusiast).
Rochester offered the 4G series carburetors (a 4-barrel variant of the 2G series) from 1952 through 1966 on a lot of varying applications.
Rochester offered the 4M series carburetors (a 4-barrel variant of the M series) beginning in 1965 going past 1974 (1974 is our "cut-off" year, do not know or care about carburetor after 1974).
The 4G series (one with automatic choke would be a 4GC) was a "square-bore" design, where the primary throttle bores and the secondary throttle bores were either equal in size, or very close to equal (I think the most different was a 1 9/16 primary with a 1 11/16 secondary.
The 4M series (one with a "divorced" or "remote" automatic choke would be a 4MV) was a "spread-bore" design where there is a large difference (typical 1 3/8 primary, 2 1/4 secondary) between the primary and secondary throttle bores.
ROCHESTER REFERRED TO BOTH AS QUADRAJETS IN FACTORY ROCHESTER LITERATURE!!!!!
So technically, the term can refer to either series; thus stating the series along with the term Q-Jet causes less confusion to a reader.
Thanks for the clarification about the various model designations. My experience is that the 4M series is an excellent carb. With the spread bore design, the vacuum controlled air valve over the secondary's, and the "power piston" controlling the tapered rods they provided a great balance of power and reasonable economy.
I am always disappointed when I talk with someone who replaced their Q-Jet with an Edelbrock or a Holley because that is what their "mechanic" recommended. When I ask a few more questions I typically am told that the carburetor was not working properly and they cannot be fixed.
Yep, I looked at that map when Chipper put it up earlier. I'll call them and make sure they are still selling it first, and it is just about an hour round-trip to go get that. I think I will give it a try.
Sometimes when you call or physically ask, they don't have a clue what you are talking about. Most of the time here in Canada, the specific pump is labelled right near the nozzle.
I still do a test sample into a bottle with some water. You can find the tests for ethanol on youtube. If there is ethanol, the water mixes into a hazy mess with the ethanol and then turns into something resembling dog snot and lots of it...
1938 Canadian Pontiac Business Coupe (aka a 1938 Chevy Coupe with Pontiac shaped front sheet metal - almost all Chevy!) 1975 4-speed L82 Vette
It seems that ethanol has acquired some new words of disrespect. Pretty soon Uncle Ed out there in the Corn Belt will have to start sneaking into town under the cover of darkness. His former friends may be plucking chickens, looking for a rail and boiling some tar,
Just think, it's Saturday afternoon and he has gotten in the wash tub for that weekly bath and all cleaned up with nowhere to go. Usually, he and the missus goes into town early in the afternoon. Not now. He has to wait around until dusk to even start out.
If this sort of thing keeps up it may come to the point he has to wear a disguise. Fake mustache, grow a beard, dye his hair, wear sunglasses, etc. Mercy!
Wont be easy on his missus either. Same thing for her. She may have to fix up to the point of not being recognized also. Stilettos, short skirt, lots of rouge, bright lipstick. Make the ladies of the night jealous and become more protective of their territory. She didn't know something like this was in the deal when she married ol' Ed. No siree.
Maybe we need to choose our words expressing our dislike for ethanol more wisely. I think this latest barrage may come from the younger members of the Club. Even Chipper merely makes a statement that gasoline pepped up by ethanol attract a little water. So what? According to him even so-called pure gasoline has an element added that does the same thing only in lesser amount. I think that's what he said over in another forum. I don't argue with him. He lis a Chemist and knows his fig newtons (stuff.) Does too!
Best,
Charlie
BTW: "But in youth and beauty wisdom is but rare."
BTW2: Uncle Ed. Cheer up. Growing corn is not as bad as growing tobacco. Or hogs.
BTW3: I still maintain that the instant problem stems from too rich a mixture in the carburetor.
I wasn't trying to provide opinion one way or the other towards ethanol but simply provide details on testing for it and describe how nasty the goop looked. I suppose I could have used "egg whites" or "melted beef tallow" but "dog snot" seemed easiest to picture. Here is one test.
Try an ethanol test sometime and see what words come to mind to describe the goop produced. You won't be able to type the fist few words that pop into your head. I was shocked when I saw it. Mind you it is simply a crude go/no go test designed to produce an obviously visible result and may never imitate real world fuel use but the difference between Pure Gas and Ethanol becomes really apparent.
Filling a water bottle with fuel and shaking it in a public location as shown in some videos may not be a recommended safe procedure..
1938 Canadian Pontiac Business Coupe (aka a 1938 Chevy Coupe with Pontiac shaped front sheet metal - almost all Chevy!) 1975 4-speed L82 Vette
Charlie - thanks for "I think this latest barrage may come from the younger members of the Club." Haven't been referred to as "younger" for quite some time. The term "deathanol" has been around a long time (at least 20 years). All one has to do is the chemistry of burning ethanol, and the derivation of the term is very evident (remember that frog in 7th grade biology???). But if the term is offensive to some, I shall try to find a suitable substitute, although deathanol is a much more friendly term than most of which I am aware. And I AM from the corn belt! Interesting to me that most of the farmers will sell corn to make it, but refuse to use it themselves. Intelligent farmers!
I am a retired farmer and have been using it for years in all my newer vehicles, in fact given the choice I won't use anything else. I usually use regular in my old Chevrolets but will use ethanol in all but one and that is because it's fuel tank needs to be cleaned out (it sat in a grove for years).
Haha, Charlie you are too much! I use ethanol because I want to and in some vehicles I consider it a better fuel than regular (straight gas). As far as making me money, it doesn't because I am retired and no longer farm, but I like renewable fuels / wind power etc. I am hoping to see more renewable fuels in the future and stop some of the pollution! BTW I used to raise hogs too! ;-)
) doesn't solve the issue, take a look at the vacuum advance unit on the distributor.
