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Edelbrock is the Nickelback of Carburetors. They are commercially successful posers. These carburetors are not really great at anything, and are good enough at just enough that they seem to be the go to carb for anyone looking to throw one on and go, with minimal tuning required. For anyone hardcore about performance, the Edelbrock Carbs get passed up in a hurry, which is a potential reason why they are all over FB marketplace. They are affordable, and offer the promise of quickly eliminating carburetor issues with your ride. Then, when its time to get serious about performance, you discover that the Edelbrock is a limiting factor. Many people are happy with the function and capability of these carbs and many people are happy listening to generic tunes on the radio as well.
I would not advocate buying one of these carbs new. They are widely available used, and they can be dirt cheap (if you are willing to do a rebuild). This is where I can get behind these. From $365 new here, to a used one between $75-$100, the value to performance ratio goes way up. The carb I had the pleasure to get my hands on was the ubiquitous 1411 model, and I got it for $Free. I commandeered it as a castoff from my brother’s 350 derby motor project (a hecho en Mexico reman engine pulled from a wrecked 78 k20).
While googling “Edelbrock carb mods” extensively, to try and figure out how to modify this carburetor to work in a demo derby application (off road-ish scenario), I came across the typical laundry list… off road needle and seat, lower fuel pressure, lower floats…aaaaand that’s pretty much it. I must say I’m not a believer in the off road needle and seat; if it helped very much, surely the carb would be used much more extensively off road, and the spring loaded needle and seat would be a common upgrade on other carbs, no? I also have no intention of lowering the fuel pressure. It seems silly to me to need to regulate from a max 7psi manual fuel pump output, down to 3 or whatever they recommend for off-road, and also sounds like a recipe for fuel starvation under heavy load. That leaves me with lower the floats…yeah sure. The only other tidbit I came across from a short Youtube video I can’t even find any longer. Essentially, the guy had blocked off the fuel crossover passage from the fuel bowls to prevent spilling over from one bowl to the other when one left or right side of the truck is higher. While I did not implement this idea, it did give me inspiration for a mod I had not seen done, extending the vents!
The fuel bowls on a carburetor have to be vented to atmosphere to allow the venturi effect to work. If the vents were to be plugged off, when fuel entered the bowl via the needle, it would generate positive pressure, and an equal amount would have to be pushed out of the carb. Similarly, when the float level rose to close the needle/seat, fuel could not be drawn out of the carb without creating a vacuum inside of it. Though I am curious which would would be the first failure point, carb fuel injection (overfueling) or vacuum venturitis (no fuel), I am certain that a carb without vents would not function properly, and will have to leave the answer to speculation.
On the Edelbrock Carbs there are two vents. They are outside the metering rod covers, and are an oblong, hump plate shape. The shape is what makes extending the vents the most difficult. On Rochester 2G carbs I’ve extended the vent on, it was just a single round hole, which was much easier. Now for a couple important considerations to note on this modification. The vent extension needs to be large enough that as fuel is drawn through the carb it does not create a restriction and thus a vacuum in the fuel bowl. Though not a total vacuum as in my plugged off scenario, a restriction would still lower the pressure in the bowl and create a lean condition. Another factor to be aware of is the position of the vent extension in relation to the air filter. You do not want it to be too close to the top of the lid, where air moving across it could create a low pressure area, also producing a lean condition.
Now with that in mind here is how I modded my carb.
- Choke delete – Saved all parts if ever decide to sell this fine polished piece. This also involved threading the choke shaft holes to 1/4″ if I remember right, and plugging with set screws and loctite.
- Rebuild Kit and off road needle and seat. I know I said its hokum, but I suppose it doesn’t hurt.
- Spectre hard fuel line adapter and 3/8 NPT to 5/8-18 inverted flare bushing to allow me to run hard line all the way from the fuel pump.
- Extend fuel vents up 1″. I used aluminum tubing and JB weld to hold them in place. I had to pinch the tubing down to get it to fit into the weird shape, but then I just drilled the pinched part out from underneath once the JB weld had set up.
- 1/2″ Phenolic spacer, though I wasn’t able to utilize this on the carb’s first derby, as I ended up retrofitting it on quadrajet manifold with an adapter kit.
So far the Carb has one successful run on it lasting probably 20 minutes in a stock class. Engine did not die or overheat during the derby, the governor cover popped of the th350 trans and lost enough fluid she wouldn’t move no more. So if you find this project useful, or you have a tip on preventing th350 governor covers from coming off, please leave a comment below and let me know. Thanks Derby Dudes!
derbytime.net 