Dave_B Posted February 23, 2020 Share Posted February 23, 2020 My 41 Special model 47 came to me with a single carburetor and a cracked exhaust manifold. I looked into just replacing the exhaust manifold but on closer inspection the valve body below the carb was cracked too so I decided to replace the whole mess with a dual carb set-up. I bought the parts out of the Bugle and got a reasonable deal. I used the carb that came with my car (Carter 663S) and found another one on eBay. Shot of the engine with the original set-up. Side-bar: notice red engine paint on fuel lines. Dual carb manifold in place Ran out of file space, more to come. Dave 2 Link to comment Share on other sites More sharing options...
Dave_B Posted February 23, 2020 Author Share Posted February 23, 2020 I decided to mount the rear carb on the same spacer as the front carb. I removed the long studs and swapped them out for ones I pulled from the old manifold. Here you can see the carburetors in place. 1 Link to comment Share on other sites More sharing options...
Dave_B Posted February 23, 2020 Author Share Posted February 23, 2020 (edited) Here is a shot of the throttle linkage. I used original linkage parts that came with dual manifolds. I opted to have a direct link to rear carb. I made the rear link from the linkage that came from my original set-up. In the bottom picture you can the linkage winding around the exhaust manifold. Edited February 23, 2020 by Dave_B Clarity (see edit history) 1 Link to comment Share on other sites More sharing options...
Dave_B Posted February 23, 2020 Author Share Posted February 23, 2020 I'm having fun with the technology. Can't seem to get the files in the right order. Oh well I'll just make multiple entries. I got the plumbing done, below that is the trial fitting of the air filter. Bottom pic shows the extension piece between the rear carburetor and air filter. 2 Link to comment Share on other sites More sharing options...
Dave_B Posted February 23, 2020 Author Share Posted February 23, 2020 (edited) I drove the car to the muffler shop with open exhaust. It was loud. I didn't get pulled over for excessive noise. Ha! They fitted the Y pipe and connected it to existing exhaust pipe. The muffler shop also made the extension piece for the air filter. All painted and looking good. Went for a test drive and she runs really well. Nice bottom end torque for backing up hill slowly to get out of my driveway and on the interstate there is plenty of power. Next, I'll be checking the gas mileage. Dave Edited February 23, 2020 by Dave_B correcting typos (see edit history) 4 Link to comment Share on other sites More sharing options...
valk Posted February 23, 2020 Share Posted February 23, 2020 Nice work. Looks like you made a sleeve for the rear carb so the air cleaner would sit right? What do you intend to do with the rear carb choke and heat tube? Peter Link to comment Share on other sites More sharing options...
valk Posted February 23, 2020 Share Posted February 23, 2020 Shoot Dave. I just realized who you were - we met at the Rockville show a while back. Hope you're doing great and look forward to seeing you at the local shows. Link to comment Share on other sites More sharing options...
Morgan Wright Posted February 23, 2020 Share Posted February 23, 2020 That's awesome. I thought I was the only one who got rid of excess copper tubing by making a big circle with it. (I have actually made pigtails like the moonshiners do). Link to comment Share on other sites More sharing options...
Dave_B Posted February 24, 2020 Author Share Posted February 24, 2020 22 hours ago, valk said: Nice work. Looks like you made a sleeve for the rear carb so the air cleaner would sit right? What do you intend to do with the rear carb choke and heat tube? Peter Thanks Peter. Thanks Morgan. Yes, I added the the sleeve to the air filter to make up the difference for the missing "damper valve assembly." I saw your problems with the choke interference with air filter body and I don't trust my metal shaping skills, this was easier. You blazed the trail for me. As for the choke, I have been running it without a choke on the rear carb and it starts right up. The car had a hand choke when I got it, so for now, I put the hand choke on the rear carb and use as needed which, so far, has been never. Go figure. One thing that's bugging me though is the chevy orange valve cover. Gotta paint that thing! Ha! 1 Link to comment Share on other sites More sharing options...
valk Posted February 24, 2020 Share Posted February 24, 2020 My car stumbles a bit on take off when cold but runs great once fully warmed up. I attributed this to the chokes being out of sync but there is no good solution since there isn't a choke tube "port" on the rear exhaust manifold as there is on the front. I have rigged the rear heat tube to just rest against the manifold but since the front is a "ram-air" set-up, ie., exhaust gas goes through the tube to heat the choke vs. just conductive heat thru the steel tube, it doesn't work as well as the front choke. I suppose a "Y" fitting could be fashioned for the single port, but the heat tube lengths would be very different and thus the chokes would still not be the same. Maybe bagging the rear choke altogether - like the original set-up - would work best. Not a big deal so it's down on the priority list...and, err, I agree painting the valve cover would do wonders for your engine bay since everything else looks good. Let us know if you perceive any difference with 2 carbs. Peter Link to comment Share on other sites More sharing options...
Dave_B Posted February 24, 2020 Author Share Posted February 24, 2020 Peter, Basically, I bagged the automatic rear choke. I have the manual choke, just in case. Hey, it left the factory with only one choke on the front and so far that works just fine. Dave Link to comment Share on other sites More sharing options...
Matt Harwood Posted February 24, 2020 Share Posted February 24, 2020 Looks great! I have two functioning chokes on my car and when it's very cold (like below 45 degrees) it becomes VERY hard to start because it seems to be flooding. I believe I will also disable the rear choke and see what happens. I am now of the opinion that two carburetors don't each need a choke on an engine designed to be started and operated on one and may, in fact, lead to the very problem I'm having where it's getting too much gas. It started and ran on one choke when it was new, the dual carb cars only had one carb with a functioning choke, I realized there's no need for twice as much choke with two carburetors operating in sync. Nice work! Link to comment Share on other sites More sharing options...
pont35cpe Posted February 24, 2020 Share Posted February 24, 2020 Most multiple carb set-ups I recall only one carb had a functioning choke. The original Buick rear carb did not have an accelerator pump, running two front carbs you`ve got double the squirt from before, which might be causing a rich mixture. Just guessing.. Link to comment Share on other sites More sharing options...
Dave_B Posted February 25, 2020 Author Share Posted February 25, 2020 Thanks Matt and pont35cpe, your comments increase my comfort that I'm on the right track with the chokes. So far it's working, don't fight it. Dave Link to comment Share on other sites More sharing options...
Bloo Posted February 25, 2020 Share Posted February 25, 2020 One choke and one accelerator pump would be for progressive linkage. I can't imagine how that could ever work well with the carbs tied together by a solid linkage. For one thing, the accelerator pump exists because gas is heavier than air, and takes longer to accelerate than air. On tip in, the squirt of the accelerator pump covers the time that it takes to get fuel moving through the regular fuel circuits. Without it, you would just get a big ball of unmixed air, and probably a backfire. With only one choke, and the carbs tied together, one carb would just let pure air in when the car should be on choke. That can't be good. Also the throttle would be open while cranking on an autostart Buick. There is no reason for the single choke to even work, let alone work right, because the other carb has the manifold open to the atmosphere. There are 3 states of the choke(s) to pay attention to. 1) Closed cold (this is the thermostat coil setting). On most carbs this is almost closed or maybe just barely closed at room temperature. If you do need less for starting with 2 carbs (I doubt it), then set less. 2) What happens immediately after startup. This will often be called "choke pull off" in the setup tables for carburetors. If the engine is too rich after it starts on choke, then you need more pulloff, in other words a wider opening of the choke when the pulloff pulls. It is probably a vacuum piston on these carbs. 3) Choke unloader. This pops the choke partly open at full throttle, and you might never clear a flooded engine without it. Car wont un-flood? Set this more aggressive (more open). If the carbs are tied together, the choke settings should match on both carbs. Fast idle will need to be set less with 2 carbs to achieve the same fast idle speed. Slow idle screws and idle mixture screws also will need to be set less. It may not even want to idle as slow before, due to the extra air leakage of a second carb. 2 Link to comment Share on other sites More sharing options...
Dave_B Posted February 25, 2020 Author Share Posted February 25, 2020 Bloo, I hear what you're saying and it makes sense but so far my experience has been that it starts right up with only the front carb choked. The front carburetor is the same one that was I was running solo and it never used to start so well. It wasn't hard starting but you had to crank it for a few seconds. Now it's just, boom, started. Like I said, go figure? I will admit that now it will start right up but cough once and then all is good. This morning when is was about 45* I started it with the rear carb half choked and it started right up with no cough. Friday morning it will be in the low 20s and I'll try it then and see what happens. As to the fast idle: the two are tied together so when the front carb is on the fast idle cam it pulls open the rear throttle an equal amount, so they are in sinc. Best, Dave 1 Link to comment Share on other sites More sharing options...
Daves1940Buick56S Posted February 25, 2020 Share Posted February 25, 2020 Way to go Dave! Can't wait to see it! Cheers, Dave Link to comment Share on other sites More sharing options...
Dave_B Posted February 26, 2020 Author Share Posted February 26, 2020 Dave. Thanks we should get together Dave Link to comment Share on other sites More sharing options...
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