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Old 08-30-2003, 08:45 AM
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Dual quad manifold

I have a 1940 Chevy coupe with a 350/350 turbo in it and I would like to put on a dual quad tunnel ram on it. I would like to run just one carb. I have heard that the engine will not run right with just one carb. Has anyone experimentied with this and have any opinions. If you have to run 2 carbs to make it run correctly, what size carbs are the best and what jetting to make it. I would like this to end up being a nice cruiser. I plan on running a GM/3863151 cam. It has 447 lift with 320 duration and 114 degree centerline. The engine is a 30 350 with flat top pistons. I'll also be running 410 gears in the rear.
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Totter

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Old 08-30-2003, 09:15 AM
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What are you thinkin?

Dual quad as in a two carb intake and then only run one carb? Is that what you are talking about doing? That really does not make sense. The intake is designed for two and has indivudal runners that are fed from both carbs. The question is can your engine support two carbs. You say nothing about the engine. If it is stock, it is a magor mistake to go to two. You will just flood everything and it will not run very well. If you go to two carb, keep them small and streetable. Perhaps you could explain what you are wanting to do a little better. I see a big screw up coming. I have never heard of running only one carb on a two carb manifoild. What do you do with the other carb opening?
Please let us know what you do and how it works out.
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Old 08-31-2003, 09:58 AM
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Explanation

I guess I screwd up when I said dual quad. It is a tunnel ram but the top plenum is only for one carb. I've seen them on cars at shows and some at swap meets. From what I have heard it is hard to get the engine to run right because of the runners in the tunnel ram. That is why I asked the question about anyone experimenting with it. The engine is a 30 over 350 with flat top pistons. I plan on running the GM3833151 cam which has a lift of 447 and duration of 320. They used the cam in the 65-67 Corvette.
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Totter
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Old 08-31-2003, 11:19 AM
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Your combination will run, but it will not be optimal for the mild engine you are building. The "151" cam is the tried and true 327-350 horse cam and will have a power range from around 2200-5500 RPM, while a tunnel ram is going to be good from 4000-7500 RPM. You will want your runners long and skinny to help increase low speed power. The advantage of a tunnel ram is that normally, with two carburetors, there is a venturi sitting directly above each individual intake runner with a large plenum between them and as the engine reaches high rpm's, all the cylinders see is a world of properly atomized fuel and air.
When you eliminate the dual four barrel set up, you create mixture distribution problems. and fuel "drop out" as the mixture velocity slows down in the large plenum. Keep your carb on the smaller side to begin with and you will just have to play with your combination to make it run adequately.
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Old 08-31-2003, 01:11 PM
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Carb sizing

Hi Nairb:
Thanks for responding. If I was to go to a dual quad set up. What size carbs would you suggest and what jetting should I start with. I haven't bought the tunnel ram setup yet and I'd like to know what to shop for.

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Totter
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Old 08-31-2003, 05:32 PM
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I would recommend either the Edelbrock afb type, dual quad carbs, which are approximately 500 CFM each or the small Holley 465 CFM carbs that are made specifically for street driven, tunnel ram equipped small block engines.
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Old 08-31-2003, 08:05 PM
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I would recommend a 4160 390 cfm with vacuum secondaries for the street, the 4150 450 cfm has only one delivery nozzle and mechanical secondaries.
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