Re: [Classic Mustang] Holley vs. Edelbrock

I've no experience with Edelbrock carbs so my knowledge is limited but I do have decades of experience with Holleys. On the plus side, you can virtually fine tune it to any engine application. Even if you have a carb which is too big they sell a secondary housing where you can limit the amount of travel for the back butterflies. ($50 ten years ago) Power valves, jets, bowl gaskets, needles and seats, floats, float springs, accelerator pumps, cams, squirters, and bowl screw gaskets are easily obtainable although other parts seem to be more difficult to get than in years past. (I once snapped the link which opens the secondaries on a double pumper) As Dennis said, if you don't have a garage full of analyzers it can take a long time to tune but once you get it where you want it there shouldn't be any need for changes unless you make some kind of modification which would cause it to need retuning. When you find the right combinations of jets, power valves, accelerator pump cams and squirters it can really wake an engine up. On those carbs which have a rear metering block you can find instructions telling you which holes to drill and then replacing the rear block with another front block and a power valve plug you can change over to four corner idle adjustment. They are simple to work on and with an experienced mechanic standing over your shoulder or one of their tech books in hand you can learn the ins and outs in an afternoon.
       On the minus side, they are mass produced from cheap pot metal. I had an old Holley become porous and sweated gas out the idle adjustment screw holes. Eventually the metal became so tired it started pulling threads out of holes and when it reaches that point it's dead and what you're left with is a friendly pile of carburetor parts sitting on your manifold. The biggest mistake most people make is overtightening the float bows screws. This warps the metering blocks and eventually the bodies. I use the two finger method, using either a nut driver or screwdriver depending on which fastener is on the carb. I use only two fingers on the tool to tighten the bowl and once the engine is warm I go back and tighten a little more to see if the idle changes. A loose bowl may not leak gas on the outside but will allow gas or air to leak from one metering block passage to another. The rule of thumb is snug. If you have to tighten it more than that something is wrong. (This method does not apply when attaching base plates to the bodies, bowl screws only) It's been said Barry Grant and Demon carburetors are just Holleys that work right and except for the idle circuit (going on what I've been told) they're identical.
       I bought a reconditioned 650 double pumper two years ago from a guy in town who does nothing but Holleys. I didn't drive the car very much because it was off the road due to other projects. Right now the engine is on the floor and the real test of my tuning skills and it's performance will come once it's back on the road. (don't hold your breath waiting for me) Holley's have been given a bad rap but their only real drawback is the cheap metal they use when making them. 90% of the problems are from improper tuning or overtightening bowl screws which eventually leads to damage you can't see but you know it when you idle or try to cruise at a steady speed. Later carbs have some modifications for emissions and I have no experience with them so I won't comment. I prefer a carb with a metering block in the rear but an old 600, 650 double pumper, or 700 (for big blocks slightly higher) should be enough for any application from a 260 to a 429 Super Cobra Jet with aftermarket go-fast goodies. Proper tuning is the key. P.S. Mike, I'm jealous you have a friend with an exhaust gas analyzer. That's one of the best tools for tuning a carb. Next you'll be telling me you have a friend with a dyno. The "seat of my pants" may have 35 years experience but nothing beats meters on a car on a dyno.


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