Got all the carbs back together and now when I start the car it idles up to 2000rpm and I can see fuel pushing out over the butterflys on the centre carb even at idle. This must be something to do with the needle and seat letting too much fuel in?
Make sure your lines and tank are spotless. No crud at all. Keep your fuel pressure down to about 4 pounds. Give it another try.
Hudson48, What Shemp has shared is certainly something to check and correct if necessary. If you are still having troubles with the seats seating you might try checking the wire hanger that is used to hang the needle from the float arm. My kits came with two of these hangers each. One had a squared bend in the center section area and the other a rounded type bend. On my carbs the square bent one would hang open at times and the change to the rounded ones cured my problems. It was a clearance thing. If your kit came with two hangers you might want to just look to see what shape the hanger is that you didn't use. Good luck.
2000 rpms is not from fuel spilling over alone. Yes that's a problem but its getting plenty of air too. The two could be related or separate issues. You'll need to know the fuel pressure before doing anything else. You're chasing your tail
Yes, it is needed on a tri power set up with 2G carbs. They don't like anymore the 4lbs MAX. A stock sbc mechanical pump puts out 5.5 -7 lbs if my memory is right.
I have read this myself as far as needing a regulator. I am not disagreeing (actually have a low psi regulator setup for mine), but did all the factory tri-power setups have a fuel pressure regulator? If not, how did they run correctly without one? Thanks
I am running a new mechanical fuel pump on my 1959 348 Chevy without any issues. I can't tell you for certain about the new cars back in the day having PSI Regulators but I haven't came across any, but then my knowledge is somewhat limited too.
Not since the 50,s has anyone made a steel needle type fuel inlet for carbs.... Why did they stop making them? Well, back then they had no way to filter the fuel and set the fuel pressure. At best your engine had an old sediment bowl with a screen, and the pressure was whatever the fuel pump put out. Flooding was common due to trash getting under the steel needle and pressure surges made things worse. The rubber tip on the needle (first Buna N and later Viton) let small pieces of trash embed in the tip and still let it seal. Well all was well and good until the gov. mandates for ethanol to be added to fuel. Now viton will no longer remain stable under some of these additives in most states. Alcohol additives tend to swell most natural and synthetic rubber compounds. If the tip swells up it will stick in the seat and shut off the fuel to the carb. Today we have clean and filtered gas and ways to regulate pressure so a steel needle works fine.The teflon sealing washers allow you to space the fitting for proper float contact. Bottom line..... You may be fine without a regulator, or maybe not. $30 from Holley and no more guessing.
Not since the 50,s has anyone made a steel needle type fuel inlet for carbs.... Why did they stop making them? Well, back then they had no way to filter the fuel and set the fuel pressure. At best your engine had an old sediment bowl with a screen, and the pressure was whatever the fuel pump put out. Flooding was common due to trash getting under the steel needle and pressure surges made things worse. The rubber tip on the needle (first Buna N and later Viton) let small pieces of trash embed in the tip and still let it seal. Well all was well and good until the gov. mandates for ethanol to be added to fuel. Now viton will no longer remain stable under some of these additives in most states. Alcohol additives tend to swell most natural and synthetic rubber compounds. If the tip swells up it will stick in the seat and shut off the fuel to the carb. Today we have clean and filtered gas and ways to regulate pressure so a steel needle works fine.The teflon sealing washers allow you to space the fitting for proper float contact.[/I][/COLOR] Bottom line..... You may be fine without a regulator, or maybe not. $30 from Holley and no more guessing. [/QUOTE] Italicized dark red is really hard to read fixed that for you
If the carb were the only issue and has that much too much fuel, the engine simply would not start. Sounds to me like a massive vacuum leak. Where? Hard to say, just need to find it. When diagnosing a major (or even minor) issue with a tripower, the first step is to isolate the center carb (unless you are running solid linkage). To isolate the center carb, remove the front and rear carbs, and fabricate block-off plates to install instead of the front and rear carbs. Now you can concentrate on making the center carb function correctly. Once the center carb is working correctly, introduce one or the other of the end carbs to the system. If the end carb has no issues, idle on the center carb should NOT change. And as far as the steel/viton needle controvery, we CAN supply (at much higher cost) steel needles for many applications; HOWEVER WE DO NOT RECOMMEND THEIR USE! Guess what ethanol does to steel? http://www.thecarburetorshop.com/Steel_needles.jpg Take a good look at the needle on the right! That brown stuff is not molasses! Jon.
Don't overlook a hung up float. With it running, give the top of the fuel bowl a hard rap with the plastic handle of a screw driver or hammer handle. If this is it, it should fix it on the spot. Bob
I don't understand all this talk about needing a regulator for a rochester carb and a stock mechanical fuel pump...they all came from the factory without one...who decided we now have to have one? Of course they all came from the factory with sintered bronze internal fuel filters...I wonder if these filters acted like a regulator?
Too many readers and not enough tuners. They read about 97s needing regulators for electrical fuel pumps and assume it applies to Rochester's. I'm running 2 97s on my stude motor with the stock mechanical fuel pump and no regulator. I've never had a problem with Rochester's on a stock fuel pump. It's the same as all flatheads overheat. Often repeated with no actual experience. I am currently doing what Carb King said it runs off the center carb but the ends are blocked off until I get the rest of the bugs worked out. Eventually I'll pull the plates but for right now it's only a 2 bbl. Oh yeah no regulator. It's a brand new engine and I don't want to risk washing out the rings until it's broken in. I rebuilt the carbs so who knows. The only flooding carbs that I have ever had were due to dirt in the needle and seat.
Larry, There is a local guy who put a remanned fuel pump on his 235 and it was overiding the float. He took it back and the next one did the same thing, we finally put a regulater in line. Some stock replacement parts these days are just not stock replacement parts.
Borrow or purchase a fuel pressure gauge, and temporarily install between the fuel line and the carburetor. This way you know EXACTLY the pressure. And I agree with the Beaner; many offshore replacement parts are at best suspect. Jon.
Using this thread of mine to open new discussion.I have the 3X2 setup with Rochestor 2G's.I have played around with minor settings on the idle mixture screws and get it to idle OK but when out on a run it will suddenly falter and on some occasions die completely. I think it has to do with the front carb and maybe to a lesser extent the rear carb.I have set the linkage arm between the front and rear carb to make sure they are pushed fully closed.When the car is running(with the front and rear air filters off) if I close my hand over the rear carb I think there is a slight pull on my palm but the front carb the pull on the palm is more obvious and two things happen.1.Fuel is pumped into the carb and then the car dies if I hold my hand over it long enough. I know there should not be any vacuum leak but is this a vacuum leak when the you can feel this pull on the palm.If so then the butterflys may not be fully closing but the bases are brand new with specially machined butterflys and no idle circuits.
G'day, We are running a tri-power on a 327 in Dad's 63 Nova. We bought after market baseplates with the proper shafts for correct outboard carb operation. The car ran like crap. We are running an electric pump with a regulator with the pressure less than 4 pounds. Finally gave up and took it to "the engine builder." He took the carbs apart and found the expensive baseplates were machined wrong and were not allowing fuel to flow. The outboard were nothing but giant vacuum leaks when opened. After a little machining and rebuilding the carbs, the car goes like stink. If you have after market base plates you may wish to check them. ms
One thing to also consider is that all 3 carbs are not adjusted the same. End carbs should be adjusted so that the throttle blades are just off full closed. Next the end carbs are set leaner than the center one on air fuel as they don't really do much at idle or part throttle. The best way to adjust is to fully close the end carbs and adjust the center one. Then start to adjust each end carb. Good luck
Just like Tommy said, I had to tear apart my center carb and take the blow gun and blow out the needle and seat area. I couldn't see any dirt or anything and it looked fine but after I blew it out it ran flawlessly.
You are chasing your tail with this thing. Listen to Jon and block off the end carbs first. Get the thing to run good with the center and then dial in the other two. IMHO, if you have air flowing thru the end carbs at idle with a progressive set up it ain't gonna run right! And as for not needing a regulator......I had a sbc with a 3x2 progressive and a new airtex pump that, when checked, was delivering 6.5 lbs of pressure. Regulator fixed that, end of my problem. Lots to check here. It is a process of elimination. Good luck. Let us know what you finally find.
A few things that haven't been mentioned yet, and i'm just throwing my thoughts into the ring for examination: 1) We should determine where (as in what vehicle) the carb originally came from. a) Either the carb was not re-assembled correctly and/or the float settings are not correct; We should verify this against what the manual for this particular carb application says. I.e., 64 olds cutlass, 78 monza etc. b) Are you using a choke, and if so, is it setup correctly? c) i am surprised that my 2G calls for 7.5 to 9 (?!?) lbs of pressure according to gm documents. But we should still check and verify fuel pressure. NOTE: i am not saying any of the above is correct; These are my views and how i would approach the problem. Feel free to criticize, critique, or augment.......
P.S. It's Rochester, not Rochestor. Rochester is/was the city where the fuel division of general motors was based.
Check the accelerator pump plungers, they make two different diameters. Had a similar situation last year.
The base plates did sit in the box for awhile and I was going to clean the machined surfaces in the throats of the base plates with some light emery paper but just forgot before I put them back on the car.However the "suck" on the front carb is very strong and may signify something else. The manufacturer has a good reputation. Another thing is that on his recommendation i am using 58 jets in the middle carb and 56 in the others.I took out 52's.This was all based on engine specs supplied.
Just for funs and giggles, remove your secondary linkage and run the engine. Sometimes overzealous adjusting that looks correct is indeed NOT. If idle smooths and vaccum pull is gone in front carb readjust your linkage. And on the subject of "stock" mechanical fuel pumps, the originals in the 50's and 60's put out between 3.5-5.5 PSI and new and rebuilds no put out as much as 7.5 PSI, thus the need for a regulator. And a regulator is not worth a shit if you don't have a good fuel pressure gauge to monitor it. Your issues have nothing to do with jetting.
Thanks Dickster27.I disconnected the linkage between the front and rear carbs and much better running.The front linkage to the butterflys has a little play in it even when disconnected and just the slightest touch will open it a fraction and start sending fuel in and then it stays in that slightly open position(won't return unless done manually) and creates the vacuum and some fuel flow into the front carb. I haven't got a pressure regulator/gauge on yet and that will be a bit of a nightmare to fit if I need it.
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