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A lot of the above...
Sometimes a slow timing curve will make a car seem doggy until it gets going. Other times distributor issues, such as stuck weights, condensation/moisture under the cap, module issues, etc. can be masked as carb issues. Any time there is a stumble when you mash the gas, a lot of people first point at the carb, whether it be a lean issue, trash in the bowls, etc., but it can be other things as well. There's nothing necessarily wrong with a dual carb setup. As some of these guys attest, they can be easy to use and will perform well. Another HUGE variable that has a bearing on this is how radical the engine is. If it's a 425hp engine with a mild cam and a dual plane intake, then it's going to be easier to mess with than a 600hp with a large overlap camshaft and a single plane intake. |
Flygirl ... yes to both on the ignition . Before you ever touch a carb , make sure the ignition is dead on ... plugs right heat range , plugs correctly torqued , wires in good condition , gap correct , initial at least 18 degrees ( I run 22 degrees , but the ERA is very light , Galaxie not so lite ) , correct max advance ( 35 to 39 degrees on most FE`s , but varies from engine to engine .... read your plugs ) , and the curve is correct for that engine . Then , and only then ,. start on the carb (s) . There are a few people left who still know how to set up curves on FE distributors ... and I can tell you from my experience , it can make a major difference .... or just use an MSD , Duraspark etc that is set up correctly . If you go that route , there is a lot of knowledge on this site about who , what and where people are who can work on those distributors or give you guidance .
Bob |
Thank you!
Regarding the plugs in the proper heat range, that primarily has an effect on fouling (too cold) or preignition (too hot)...right? The only thing I know to look for on the plugs themselves is for is a nice light to medium brownish color (not black and sooty), and no evidence of physical damage. And driving the car, no preignition (difficult to hear on these cars, they're so loud) or signs of loading up during lower speed operation. Is there a better, more scientific way to narrow down the heat range? What would I see, if anything, on the plugs if max advance or the timing curve is improperly set? Would there be physical damage that was apparent...? Or is it more of a color shift? I still can't quite understand the relationship between the heat range of the plugs and ignition timing. Or are they not closely related? |
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First of all, I will say that if timing is way off, you can damage the engine and you will probably start to see flecks of aluminum (from the piston) on the spark plug itself. Other than that, there is a "band" that you will be able to see on the ground strap of the plug. The strap has a 90° bend on it. If the timing is pretty spot on, you will see a "band" right in the apex of that bend. Different amounts of timing will move that band back and forth on the strap. Too much timing will push it towards the threads, not enough will push it towards the tip of the electrode. This all has to do with heat transfer. So by reading a plug, you can tell if an engine is running rich, lean, if it has a blow-by issue, and you can also tell how close you are on ignition timing. I forgot to add.... You can see where you are on the heat range by looking at the last few threads of the plug. You want a couple of threads on the plug to show signs of heat. |
spark plug reading
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2 x 4
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I think someone put that Cobra engine in backwards.
Ha ha. Thanks for the link to the spark plug reading site. Excellent!! |
Flygirl ... good link that Dwight gave you , but be advised that it applies only if you do WOT runs and then shut off clean . However , it gives you enough that you can get in the ballpark and is a great primer on plug reading in general .
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Yes but, generally speaking, all the same things apply. Toasty tan is the optimum color, very slight soot on the base ring, and the annealing midway on the ground strap. I bought Don Gould's tuning guide here and it really helped me learn a lot about how all this works. Spark plugs are a periscope into an engine and if you learn this stuff and the basics of how a carb works, you can really get your engine purring. |
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Ok,it's not in a Cobra,and it's not an FE
But,I used the dual Holley 715's from Carls Ford Parts and an original open plenum Ford casting on my Boss 429. Works great,no real tuning issues.Minor jet changes and different power valves was all I really did to them. You can't beat the wow factor. However,If you were racing your Cobra the side hung floats in the fuel bowls would likely cause issues in the corners. |
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