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Which carb, 600 Holley vac sec or 750 Edelbrock? (Read 1721 times)
imacarfan2
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Which carb, 600 Holley vac sec or 750 Edelbrock?
12/05/10 at 22:55:26
 
I'm helping a friend swap a 360 into his Spirit and wanted thoughts on which carb to go with. This is going to be a mild buildup as he doesn't want anything crazy. This is about as mild as you can get. It's a low compression 360 with a Performer cam (the old-style, smaller cam, not the Performer RPM), Performer intake, free-flows out to 2 1/4" duals, 998 with stock converter and a 3.15 twin grip rear axle. He's going to be using it mostly for just driving around, but his wife is dying to take it to the track for some racing. I have two carbs to choose from and don't know which to go with. I have a 600 Holley vacuum secondary or an Edelbrock 750. Which do you think might work better in this application? I know I could try them both to see what works better (and we might just do that), but thought I'd see what the masses said first.
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Re: Which carb, 600 Holley vac sec or 750 Edelbroc
Reply #1 - 12/06/10 at 20:01:00
 
Tough question. A 360 with mild moifications would need about 650 CFM, so one is just s bit too small and the other a bit too big. I am partial to Edelbrock. But having said that, if the choice were mine, I'd rather run the 600 wide open than the 780. Since you are using this as a driver, the 600 would service the engine better than the 780 which might have a tendency to load the plugs up at lower RPMs.
 
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Re: Which carb, 600 Holley vac sec or 750 Edelbroc
Reply #2 - 12/06/10 at 22:33:34
 
Ed,
  The cfm rating is just a rating for how much air the carb will flow at a specific pressure drop, and even then the manufacturers aren't that accurate. The amount of fuel going into the engine is a function of how the carb is set up (jetting, etc.) a 1050 can be made to run lean and a 500 can be made to run rich both on the same engine. Also keep in mind the carb will only flow as much as the throttle plate opening allows. Any carb should flow the about the same amount of air at the same idle speed on the same engine. However,in theory, the smaller carb should be more responsive at partial throttle openings.
 
Dave Z
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Re: Which carb, 600 Holley vac sec or 750 Edelbroc
Reply #3 - 01/07/11 at 05:16:13
 
I'd go with the 600 for that application.  It will be a snappy little carb for ya...
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Re: Which carb, 600 Holley vac sec or 750 Edelbroc
Reply #4 - 01/07/11 at 18:19:59
 
I'd say go with the 750 Edelbrock.  Just from my limited experience I'd say the 600 is too small and would choke it off.  The 360 I've been running in the Ambo the last few years has a .480 lift cam, free flows, and a good 2 1/2" exhaust.  Started out with a 780 Holley vacuum secondary - it ran fantastic even with the stock manifold and Moroso spacer.   Shocked   That carb developed problems so I stuck a 650 Holley DP on it - performance was down some and mileage sucked.  I then stuck a Performer manifold and 650 Edelbrock on it (running now).  Performance is OK but you can tell this thing wants more carb - if I had a 750 Edelbrock I'd like to swap that on there and see how it runs.   Wink   As it is I'd love to get that 780 Holley fixed someday but as I learned before running Holleys on the street can be problematical unless you are familiar with them - after my problems I almost wanted to carry a spare one in the trunk to keep from getting stranded.   Cheesy   The 750 Edelbrock might not be a racer's dream but they are pretty much fool-proof on the street and the 600 seems a little small - maybe on a 304 with a mild engine.   Smiley   (my 2 cents)
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imacarfan2
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Re: Which carb, 600 Holley vac sec or 750 Edelbroc
Reply #5 - 01/07/11 at 19:27:37
 
I'll probably end up going with the 750 Edelbrock, but I might try both just to see what happens. The car will be running 25" tall tires and 2.87 gears, so the snappy-ness of the 600 might be needed. We'll see...
 
I actually ran the 600 Holley on my old 304 with a Performer intake and Crane 260 cam. It worked pretty well. I had a 650DP on for a short while, too. It seemed to like it, until the carb developed a problem and was replaced with the 600. Therefore, I never got to fully test the 650DP on the 304 like I wanted to.
 
Now that I think about it, the 304 saw quite a few carbs in the time I ran it. It had a 500 Carter, a 600 vac sec Holley, a 650DP Holley for about an hour (if that), and a 750 vac sec Holley. Yikes! Shocked
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