I'm planning to go dual quad on my 350 4 speed (mild roller cam, street driver, progressive linkage) Tired of waiting out the backorder for a low rise complete kit, I bought a used C-26 low rise intake and have a new 500 cfm #1403 electric choke for the rear. I was going to order #1404 manual choke for the front carb but rethinking that... Would I be better to go with a #1903 500 cfm and use it on the rear and move the 1403 to the front (w/removed choke)? The 1903 lists dual carb and improved idle circuit and smother transition. or just stick with the plan of another #1403? Also what is a good baseline jet and rod set up for both carbs as a starting point?
I'd stick with plan A, that way you'll have the same style of carb front and rear, instead of an AVS and a standard AFB style. Jetting is pretty rich out of the box, 2 of the 1486 tuning kits should should get you where you want to be. It just takes time and patience to tune. JMO
Don't you need smaller carbs for a 350 engine? I like the looks of 2x4s, but 1,000 cfm seems like it would create issues on a mild street driven engine. I plan to run a 2x4 set-up on a 500 Cadillac, and I'm going to have 900 (or less) cfm. I'm going to modify it and just use the throttle bodies to control air flow while actually using hidden injectors to control fuel. Can't really talk about it here, but before you buy your carbs I would make sure they will work the way you want. I read some info on 3x2 set ups and they talked about issues caused by people using the same carb for the secondary carbs as they used for the primary. Might want to install an O2 sensor and some type of guage so you can monitor fuel/air ratio while getting the carbs set up.
The Edelbrock carb design will only use as much cfm as the engine demands, it's hard to over carb with it.
Toss two 500s with non-progressive linkage on it and see what happens, I bet you like it more that the progressive. -Abone.
I ran two 650s on a C-26 on a mild 350 with a 700R4 auto trans. The C-26 is good for mild mannered street driving. I did experience a slight bog with the carbs initially, I had to richen it up with metering rods and jets. I initially ran a progressive linkage, however, this made the front cylinders run a little lean, so its best to run the linkage setup non-progressive. I would also run a fuel pressure regulator set to 6 psi. I think you can run a GM HEI distributor, but it will be crowded. I ran a GM points style distributor that was converted to HEI, a PerTronix electrical ignition would work in a points style distributor too. Mine always ran good and got surprisingly good gas mileage on the highway.
I run two 500s on my roadster with chokes removed . engine is a 327 with a 30 30 mechanical cam . Starts fine with a single pump of the accelerator , idles very well and pulls strong to 6500.
I’ve used progressive linkage 5 years on an Edelbrock manifold and wouldn’t have it any other way. Chevrolet did them that way from 1956 to 1961 on small blocks and 62-65 on 409’s. It it was good enough for thousands of them it’s ok with me..
I run two 600 cfm Carters on a 355 with an Offy low profile 2x4 with the chokes wired open, one to one straight linkage and have absolutely no issues. I have 4 cars with 2x4 setups and all have no chokes and straight linkage.
Thanks Guys, sounds like another AFB instead of mis-matching with an AVS is the way to go. I've heard pros and cons to both linkages, I have an early factory progressive so may try that first with a little richen set up. Thanks for the tips!
The thing that I was thinking about is "velocity" thru the venturis when at WOT. An engine can only draw in a certain amount of air no matter how large the intake tract is. If someone has a larger than necessary intake, the volocity will be less. When you move all the way back up the intake tract to the venturis, velocity is needed to pull the fuel along. If you flow the same amount of air thru a larger opening, the velocity will be less. In the many varied installations that are done, an engine may function acceptably in many applications. The question is whether its functioning as well as it can function. Might want to read the article attached below for a better explanation. https://www.motortrend.com/how-to/what-size-carb-for-my-engine/
The argument of progressive/solid linkage is similar to the "my dog is bigger than your dog" argument (see last paragraph). Either can be made to function. Personally, I prefer solid linkage, and, with the exception of factory "numbers matching", will set up street dual quads only with solid linkage. If the customer wants progressive, he can do his own. On a trailered race car, either will work equally well. My testing has found better throttle response, and better fuel economy on street driven vehicles with solid linkage. Progressive linkage is a function of the requirement of various racing sanctioning bodies in the 1950's and 1960's that, in many classes, allowed internal engine modifications, but stock carburetors must be used. Since the internal mods could increase both volumetric efficiency and maximum RPM, correct sized street carburetors could be too small for maximum performance, and the car manufacturers put oversize carbs on the engines, but with progressive linkage. Had a friend that grew up in the city where I lived and then moved to the west coast, and raced in the NASCAR West series. Raced a 312 Ford with dual quads (progressive linkage). His team found the car to be faster by switching to solid linkage, and limiting the opening of the secondaries on both carburetors. Won the championship in, I believe, 1957, so knew what he was doing. My current personal dual quad is two 625 CFM genuine Carter AFB's (modified) on a Ford 390, with solid linkage. Runs like a scalded dog. And I no longer have a dog, so my dog is not bigger than your dog! Jon
Years ago I ran two Edelbrock 500 cfm on a SBC 355 cid. 510 lift cam and a old low rise offy intake. After a little tuning , worked great. What ever you decide on carbs, match them and tune, that is key!
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