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I have this 600 CFM Holley: http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY-0-80457S&N=700+0&autoview=sku

Also here: http://www.holley.com/applications/CarburetorSelector/0-80457S

I've had it for a looonnnng time but it's still brand new in the box. I just found that it's designed to be completely non-adjustable. I'm trying to decide if that's a good thing or a bad thing.

I'm comparing it to this Holley Street Avenger 670 CFM which is adjustable:
http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY-0-80670&N=700+0&autoview=sku

And Here: http://www.holley.com/applications/CarburetorSelector/0-80670

I'm about done putting my new engine together and need a carb for the top.

I'm expecting somewhere around 400HP from my 355 with aluminum heads, performer RPM air gap manifold, and Comp Cams XE274H.

Do I go with what I have or do I go with something that allows more adjustment? I've managed to pickup a lot of knowledge about engines and building, but I'm still trying to figure out the carb stuff. I'd like to get the right carb on top the first time I put it together. Seems easier to sell the one I have while it's still new if it ain't gonna work. :surprised
 

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I would think you might need a little more carb,possibly a 650 cfm,or at least one you could adjust.
 

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Apparantly the only thing that ir non adjustable is the float level and that might be a good thing as long as you maintain less than 6 psi.:laughing:

It allows for changing secondary springs, choke adjust, curb idle adjust, idle mixture adjust, jet replacements. If you really got serious, you could start drilling inside etc.
That's really all you need. Without a dyno, a/r etc, most people could never tune that precicely anyway.

Depending on what rpm range you will normally drive, it is probably just right. A 650cfm may give you a few horses at 6500 rpm, but this should be good if you are not winding it.
 

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FWIW- I love my BG Speed Demon. I'm running a 575 Speed Demon Mech w/ My Brodix Headed-Hyd Roller 327 w/ a 4 speed. I was able to really dial in the idle w/ the "idle-eze." No need to drill holes!!! And able to adjust on all 4 corners. I set the carb up in 30 minutes-and haven't touched it since. I can't tell you how much time I spent on the Holley-and it would STIILL run too rich. You pick the carb w/ from your cam specs. What a novel idea!

I got the carb from the guy on Ebay (sold tons of BG stuff) for just a few more bucks than the Holley. Best investment I've made as far as engine improvements.

Richard
 
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