Put these Solex Carbs on and had some stumbling on the blast off. Took one off and bingo works like a champ. Never messed with progressive linkage but I under stand the concept. Any thoughts?
I’d think with that intake you’d want to run off both at the same time. I’ve no experience with more than a single carburetor, but seems you’d have to over fuel a few cylinders to give proper mixture to the others.
With progressive set up - Secondary carb is a dumper, on progressive it will open at usually 50 - 60 % of wide open throttle, (you choose how much) usually built differently from primary carb. Needs to be completely sealed when not in use. With that manifold I would run both on fixed linkage, - 2 x identical carbs and balanced. Smaller jets or whatever is required. If it runs beautifully on one carb, right through to full revs, - consider changing to single carb manifold ?
Yes she runs great on two carbs after the stumbling. So this is why I am thinking Progressive linkage would help with the take off. Stock valves to much fuel at take off.
A rich bog (stumble) at take-off (especially with A/T, but also with S/T) often is related to setting the idle too rich. https://www.thecarburetorshop.com/Troubleshooting.htm#Bog Try readjusting the idle mixture control screws leaner, with a corresponding increase in throttle opening, to maintain the idle RPM. Jon
Not necessarily true. Many dual quad setups out there with 2 identical carbs, progressive linkage, secondary carb is fully functional and the engine idles on both carbs.
Can you take a picture that shows the carbs and linkage, and not the rest of the car and background? I can't see any detail in the photo you posted.
yes, I should have said “usually”. I am a one finger typer so try to word my posts carefully and keep them short and to the point. I don’t think your idea of dual quads on his little 4 cylinder is really practical …….
Thanks for the picture, it helps a lot! Add a rod here, so that the end on the rear carb can slide in the fitting, until it hits the stop. You'll have to adjust the travel so they both open all the way at the same time. One end of the linkage is mounted further from the throttle shaft, so the travel of the rod, is longer than the travel of the slide fitting. Hard to explain, but that's how progressive linkage works.
Well, the number of barrels or the size of the carbs is beside the point. Progressive throttle linkage does not require secondary carbs without idle circuits. That is all.
I guess much depends on how you use the engine. If this is a trailered race car, then progressive might be acceptable. If you plan to cruise, drive in parades, just have fun with the car; I would HIGHLY suggest tuning out the bog and run solid linkage, with both carbs running all of the time. Running progressive linkage will result in overfueling to the cylinders directly under the primary carb, and underfueling to the cylinders under the secondary carb. EDIT: The above sentence is referring to inline engines, as the OP has an inline engine. It should not be taken as a comment about V-engines. How much overfueling/underfueling is acceptable? Your call, not mine. But show me a factory dual carb installation on ANY inline engine (other than the horrible 2x2 on 1941 Buicks) with progressive linkage. Check out the non-H.A.M.B.-friendly English, German, Italian, and Japanese sports cars. And if you cannot tune out the bog, check the second line in my signature block. Jon.
Years ago when I first put the blower motor in my old truck, I had progressive linkage on it. A fellow who knows a lot told me the same thing, that the rear cylinders would get lots of fuel, and the front ones would starve. Well...I drove that thing like that for 20k miles, and the plugs always looked the same front and back. Then I put the same setup in my 55 and drove it another 80k miles, and still the plugs always looked the same, and the engine generally worked fine. I'm just curious whether the same thing would apply to an unblown inline engine? I guess there's one way to find out... But I certainly agree that he needs to get the carbs working right, if they can be made to work right (ie they're not too big for the engine). Many of those foreign sporty cars have variable venturi carbs, so they can't bog unless they run out of damper oil, or something.
Jim - I think the key your success was the blower. I would be interested in results on an unblown inline engine, but it will not be MY engine I probably should have also referenced the 3x1 in the '53-4 Corvettes in my example. Jon
I've had dual carb intake (Offy dual quad) on a SBC for a number of years, with progressive linkage, with zero problems from unequal distribution of fuel. Spark plugs have even coloring, and the engine idles and drives smooth. As originally setup by Dickster it had Rochester 2G carbs on it; I drove it like that for a number of years and really enjoyed it. It ran far better than the single 2GC it originally came with. I fairly recently changed those carbs out for a pair of Carter WCFB's, and I retained the progressive linkage; it idles on both carbs. It performs even better with the WCFB's than it did with the 2G's, smoother more consistent idle, smooth engagement of the secondary carbs, the engine seems to just love it. The drivability is excellent. The only issue I've had is not being able to get it to idle down as low as I'd like, I'm completely off the idle stop screw on both carbs and it still idles around 800 - 900 rpm IIRC. I did notice the transfer slots on both carbs were more exposed than I thought they should be (both carbs were rebuilt before I bought them). I've procrastinated trying to address that as it really runs so damn good as it is other than the idle speed; but I don't think that is an indicator of unequal fuel distribution.
Also, I know this thread is about an inline engine, but wasn't the Chevy dual quad intake setup with progressive linkage? Idle'd on both carbs, right?
I thought so, too. The funny thing is the guy who told me it wouldn't work, said it was because it had a blower on it. I don't know. I guess we'll see what happens with this A.
When I tried progressive linkage on my 2x4 TR , I saw significantly darker plugs under the active carb . the engine was not nearly as responsive either . switching to 1:1 linkage did not affect fuel economy either .
I don't believe the short runner , small plenum 2x4 manifolds suffer from mixture problems nearly as much as long runner , large- er plenum manifolds do . Yes ,IIRC ,The factory dual quad manifolds all ran progressive & idled on both carbs . I don't remember a lot about wcfb's , but can you adjust the secondary flaps to be closed more ? I have close to the same situation , primary's bare!y open , 8-900 rpm idle ,secondaries closed to where they won't stick . I even had to put 2° back in the distributor to reduce initial timing .
It looks to me like.......(here-we-go!) with the dual carbs you would NEED to run a straight linkage. Each carb serves primarily 2 cylinders each. IF progressive....the rearward carb can NOT give the front cylinder what it needs! As far as a bog when you "mat" the accelerator...... .Welp, it IS your car and you know it will BOG from...too-much-too-fast. 'Walk-into' the accelerator....g-r-a-d-u-a-l-l-y so it don't bog...........or gear it so low you can't bog it down! More initial timing is also your friend when tuning the bog outta the carbs 6sally6
A lot of rodders are concerned about one carb being closer to the ports than the other carb resulting in problems with rich or lean mixtures in some cylinders. However, if you look at a stock 6 cylinder or straight 8 with a single carb the distance to the ports from the carb vary significantly and yet they still run very well with no significant mixture variance. Therefore I say if the OP tries progressive linkage on his setup it will probably work out ok.
some would debate that the secondary carb must be completely sealed to avoid vacuum leaks closer to the cylinders that the secondary carb sits over, therefore creating a leaner mix to those cylinders. So - Why don’t the tri-carb setups run the front carb or rear carb as the primary ?
It's probably a good idea to equalize things as much as possible. But they don't need to be totally equal, to work.
This would only be a problem with carburetors with no idle circuit. If the carburetor has an idle circuit the air flow through the carburetor will pull fuel through the idle circuit and would not result in a leaner mixture. The only difference would be from non-atomized fuel droplets that fall out of the air flow and into the cylinders closest to the carburetor, but that would be the case regardless of whether the secondary carb was "completely sealed" or not.
Each carb serves all cylinders with all open plenum manifolds , Isolated runner ( no plenum manifolds ) " can" be one barrel per cylinder dependent on the manifold configuration , however , generally IR manifold runners are use with fuel injection.
IR manifolds for use with carbs often have a "balance tube", which lets one carb feed both sides during low load situations. Try the progressive linkage, and see what happens. Maybe it'll fix it, maybe not. Keep an eye on the plugs.
Well, that means it wasn't me who told you that Aftermarket blowers are not in my field of expertise, and I don't offer advice on them. Have a lot of experience with factory blown 1957 Fords, late 1950's and early 1960's Studebakers, and early 1960's Corvairs; even a wee bit with 1930's Auburns, Cords, Duesenbergs and Grahams, but no aftermarket. Always interested to read about them, but that is where it stops, for me. Jon.
Well my question has really turned into quite a conversation. But I am not going to be running two 4 or a blower, although I have seen one with a super charger on a banger. My Bog issue is on the back burner. I have to fix the Valdez Leak coming out the rear main before I get the carb issue addressed. Will report back as soon as the gusher is fixed. And thanks to all for your input.
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