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Discussion Starter #1
hey guys i got a 600cfm holly carb on my 351w in my 73 mach.

it seems as if i tune the thing it will run good. but a few months down the road or so, it will start acting up. such as hestitation and fuel economy goes down. but if i tune it again, the hestiation stops and fuel economy goes back up.

is this normal to always need to f#%! around with the carb every couple months?

i did hear a while back in this room, that holly carbs do have to be played with often and like edelbrocks or so you can set it ad then forget it.

this normal for a holly carb?

i set the carb 3 months ago. then i got awesome fuel economy and power with no hestitaton. then the last 2 weeks i found hestiation if you acceleration anyting more than just 1/3 throttle off take off. this morning i push it in like 1/2 way and it hestitated.


then i came home and set it. i pushed in the throttle only 1/3 of the way, NO HESTITION, and the tires spun. it performed nicely.

do i have a mechanical problem? i mean this carb is only 15 months old. i hope this is a normal problem with holly's.

<font size=-1>[ This Message was edited by: XolieX on 4/25/02 12:59am ]</font>
 

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Can you explain more about what you do when you "tune the carb"?

I know that years ago, I could fill up with gas at one particular station/brand and the engine would swing 100-250rpm at idle, but but fill up at any other station/brand, it would idle smoothly and never touch the carb. The car waas a 70 Mach I with 351C-4v, mild cam and 780 holley with v/scondaires.
 

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I've seen some Holleys take a tune set and hold it for two years. Others, you have to mess with 'em every month or so. I re-set the float levels about every two or three months on my 600. Just a part of the fun of owning one, I suppose. I don't have any hard proof on this, but it seems the more you full throttle them, the more often you have to re-tune.
 

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Welcome to the wonderful world of Holley. You have to remember that these things are sensitive to so many things, mostly weather related. It is getting warmer out there, dryer / moister air and barometric pressure fluctuates (excuse me!).
You look at most racers at the tracks. They are constantly checking atmospheric pressures, dew points, elevations, etc and making the carb adjustments to compensate.
As for a set and forget carb, yes the Edelbrock / Carter carbs are more user friendly (I don't believe I said that!) and are more of a out of the box and go fuel system.
Fred
 

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I have two Holleys the 750 I bought new and have run it for years.The only problem I have ever had is the float sticking about a month after I bought it.I talked to the speed shop where I bought it and he said to run an inline fuel filter.I doubted this was the problem as I never had any problem with the ford carb,but I put one on anyway.That was the end of my problems.A few years later I put it on my mustang and the problem reapeared until I put an inline filter on it too.I now run a 650 dp on the stang and both carbs work excellent.I never have to mess around with the carbs to keep them running properly as I've heard a lot of people say.
 

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Discussion Starter #6
so this kind of normal to have to play with it kind of often?

i like the q-jet looks like and i was talking to a friend and said that the holley 4175 has the same effect of a q-jet.

anybody got experience or knowledge about one?
 
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