Technical > Matt Shaff's Engine Shop

Changing over from injection too carburator

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Roger:
Not knowing the compression of your engine or the specs of the camshaft, I think it’s safe to say that replacing your current alcohol FI with a carburetor & gasoline isn’t much more involved that making the physical switch itself. Get the racing gas recommended by your fuel supplier to work with your current compression ratio and use your current camshaft, or possibly replace it alone with one recommended by a reputable cam company for use with gas. As far a performance difference, consider this: probably the baddest and quickest junior fueler in the world belongs to Frank & Scott Parks. They have run a best (to my knowledge) of a 6.81 ET at Bakersfield a couple of years ago. That’s a 421” alcohol engine running at a weight break of 3.5 pounds/cubic inch or 1475 pounds total weight. Now look at an A/Econ Dragster with a 397 CI gas engine running at a weight break of 3.4 pounds/cubic inch or 1350 pounds total weight. The current record for the class is a 6.60 ET. Both cars have automatic transmissions and both run down the same quarter mile track. The slide rule tells us that the alcohol engine is making about 925 HP and the gas engine is making 930 HP to run at their respective weights. Even though the gas engine is over 20 cubic inches smaller it still makes more HP than the alcohol engine. Hmmmmmmm…

Now while there are bunch of alcoholics on this board there are also a bunch of gas hogs among us too. Gas is more convenient to operate; no need to have someone squirt fuel in it to start it or have a primer system to start, just tickle the accelerator pedal on a gas car to accomplish the same goal. While alcohol runs cooler, it takes time to build the heat in the engine while the gas engine warms up quickly. The down side to gas is the additional cooling system.

But one very critical aspect not addressed so far is the crew help issue, or the lack of in your case and in mine as well. Inexperienced crew members you might get to assist at some races can be dangerous. Last time I took my junior fuel car out I couldn’t find anyone to go with me so I used an inexperienced crew person to squirt some fuel in the injectors. Even though I waved him off from squirting fuel he continued and when the car belched, it lit the fuel coming out of the container on fire and when he realized the squirt bottle was on fire, the threw it out in the middle of the return road at Great Bend. Not cool and not safe. A friend of mine out of Oklahoma had a similar problem with his JF car when he couldn’t find good help and had an inexperienced crew literally douse the entire top of the engine with fuel (he did a poor job of squirting into the stack injectors) and when the engine coughed the entire top of the engine burst into flames right behind the starting line. His car is now for sale because he couldn’t find good reliable help either.

In the end, if it’s race day and you have a car that needs more than one person to successfully operate and you don’t have anyone competent to help you, then all you can do is sit in your shop next to your car on that nice sunny day and wish you had help as opposed to actually getting out to the track and mixing it up with the other racers. Good luck to you, whatever you end up doing.

Oldschool:
I am changing from carb. set up to Enderle injection. I am basically removing the carb. set -up and just installing the Enderle/ tunnel ram set up. I am installing a primer to have that ability to start engine easy.
Selling my cooling system to. I would not worry about your motor,if built well.

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