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Considering a carb upgrade and maybe an intake too

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GranTorinoSport View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GranTorinoSport Quote  Post ReplyReply Direct Link To This Post Topic: Considering a carb upgrade and maybe an intake too
    Posted: 23-February-2015 at 9:42AM
So on my 75 Sport with the 521, I am currently running an edelbrock 600 cfm performer carb and a performer intake. It is a mild build, low CR and 2.75 rear gears. The torque converter is stock rpm's (although a much tougher build).

I think it is not too much of a stretch to say I have way too small of a carb on the engine. It was what I had sitting around at the time, so I took the opportunity, rebuilt it and stuck it on. It doesn't run badly, but I think I am missing out on some potential, and perhaps better driveability over the RPM range.

What got me thinking a bit more was if the intake was anything to be concerned about as well. I wanted a performer for hood clearance, and the fact the car is basically a daily driver with a monstrosity of a motor in it.  I was thinking an Air-Gap intake might be the ticket, seems like they work well at lower RPM's while providing advantage at higher RPM's. I'm a little skeptical that an Air-Gap would actually fit, but worth consideration for sure. (FYI I run a 1/2" spacer for heat and use a stock 460 style air cleaner)

So I think an Edelbrock 750 cfm would be a no-brainer, but perhaps I am good with the intake I have?


Edited by GranTorinoSport - 23-February-2015 at 10:59AM
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Rockatansky View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 23-February-2015 at 3:04PM
the secret to the Airgap is the cut down plenum divider, this allows the whole carb to feed both sides. the trick is in how far to cut it down to retain low end, the simple mod goes way back
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ya gotta watch the test bench settings the various carb manufacturers use for rating their carbs, they're not all the same, in fact they're all different. the Eddy's / Carters seem to cfm less than a Holley, the 750 Eddy will act like a maybe a 625 Holley
 
I know don't buy a Demon but for just for this point, the Demons cfm more than Holleys. a 650 Demon will act like a 800 Holley, possibly the reason so many guys have issues with them. and there is a NEW Demon line out BTW, they look like redesigned Carters with optional thermo mid-bodies... the 'ThermoQuad' is back
 
but anyway I'm not so sure the 750 Eddy is gonna make you squeal, 850 AVS maybe?
 
here's my 750 I just had to have, still NIB so I can't say how it runs & I don't have a 521 either so...
 
 
 
no vac taps but knocking them in isn't a really big deal
 
 
that performer has got to be pluggin the Big Boy's nose! makin me Wheez just thinkin about it
 
CJ heads? look at the ' Blue Thunder 429 4V HP Intake '
 
 
 


Edited by Rockatansky - 23-February-2015 at 3:05PM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote aquartlow Quote  Post ReplyReply Direct Link To This Post Posted: 23-February-2015 at 3:32PM
Totally agree with Rockatansky's reply. That 521 needs some CFM! I run an 870 Avenger(with some tune work done on air bleeds and metering blocks) on my "little" 466 and it made quite a bit of difference coming from a "tuned" 770 Avenger to the 870. Intake choice is another matter, most have/need to compromise due to hood clearance issues(I am in this group). I run a regular Performer with a phenolic 1" 4-hole spacer, but your 521 will like the bigger plenum/runner size of the Performer RPM/RPM Air Gap. I have heard many good things about the Performer RPM manifolds as compared to a Weiand 8012 or 8021 but most comparisons were made with the intakes installed on a "smaller" cubed 460 to 472, not a 521. Good luck. Todd 
 
BTW, Rock, bolt that beautiful new carb to something and hammer down Thumbs Up.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarkGubinski Quote  Post ReplyReply Direct Link To This Post Posted: 24-February-2015 at 1:18AM
I agree the 521 needs more air. How about the Torker II?
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