my 2 barrel carb have just had it, ive rebuilt it, had a carb guy rebuild it just done. i have a edelbrock intake i bought off ebay and i got a 750cfm edelbrock carb ive had for awhile... what im asking is that carb too much for a stock 302?
the car will run with a 750. the motor will never come close to using all 750 cfm. the edelbrock uses a vacuum plate for the secondaries. that plate will never open all the way but that will make it so the car will run ok with the 750. a 600 cfm will give you a much better throttle response
I learned the hard way, about carbs... I have a fairly stock 302 and 600cfm is right on the edge of being to big... One of the best running 302's I've ever owned is in my old mustang, I put a 500cfm 2bl Holley on it (because I couldn't afford a new intake) and that thing screams... It still runs great 7 years later...
There are numerous cfm calculators on the web. http://www.csgnetwork.com/cfmcalc.html For a 302 engine, 450-500cfm is about right.
First off.. there is far too much misinformation being spread here and you may want to step back to study a bit more before tearing your stuff apart and end up having to tune carb/s anyways(possibly both). Course.. if you like to just bolt it on and call it "close enough"?.. you may get lucky.. and Bryant gives good advice since it's fairly easy to swap around more accessible parts like these if either combo goes downhill too much. And as Bryant also mentioned above.. the Edddy's are pretty decent at speed sensing(better than a vac sec Holley in that respect unless you start fiddling with secondary diaphram spring tensions) and will only supply you with the amount of air that the engine can use under load. No more.. and no less. Which is why you can easily run an 800 Quadrajet on a small motor. Depending on your motors spec's.. you'll just need to recalibrate the larger carbs fuel curve to help compensate for the fact that you'll be living mainly off the primaries air/fual curve rather than really using much.. if any.. of the secondaries.. again, depending on your little motors modifications/rpm range. The bigger thing to keep in mind here is that the calibration of those Edelbrock carbs changes based on the intended application. In other words.. they have economy/street versions of the 750(and the 600 as well) which have electric chokes and can be used on small blocks AND big blocks. And manually choked performance versions with fatter calibrations to suit larger cams on small OR large motors(based on part number differences). Given that the throttle bores don't change between any of those same size variations.. it's all in the calibration from the factory with additional tuning required if you really want to have things close to perfect for your particular combo(cam, gearing and vehicle weight makes a difference too). Of course it's nice to start out with the properly sized carb for the application and it's easier/cheaper in the long run rather than having to nearly completely retune it to go on a different unspec'd application.. but it can.. and certainly has been done. A couple more quick observations here. Well.. quick for me anyways. A Holley 500 2bbl has the same throttle bore sizes as a 750 4bbl but larger than a 600 4bbl(not sure about the venturi size.. but it's fairly large too) and that carb has been successfully used by many on everything from 4 cylinders to larger "restricted motors". The Holley 600's have 1.563 throttle bores.. and 650's through 800's have the same 1.687 bores. It isn't until you get to the 850 that the bores increase in size to 1.75. Obviously venturi sizes(not to mention the booster designs on some models) need to change in relationship to the bore/cfm rating and can be far more important than the bore size alone as a measure of metering efficiency. The Eddy 600 has 1-7/16 primary bores with 1-11/16 secondaries whereas the 750 has a squarebore setup of 1-11/16 all the way around. Now.. obviously a 750 Holley mechanical would be tougher to tune for a small motor like yours.. with the need for adjustable secondary linkage(and/or properly calibrated right foot) as compared to a vac secondary version of the same Holley 750 carb which can more easily be tailored to work on smaller motors(if you know carbs). I know this because I've done it several times through the years.. and many others have too. May not be the perfect part to start with.. but sometimes we just use what we have and make it work. In fact.. on a well prepared motor(small or large) running higher compression and smaller cam(more vacuum).. I actually prefer a larger primary bore due to the fact that it can make for a larger feeling motor during part throttle cruising/initial acceleration blasts. Which is of course why most people see such large part throttle "seat of the pants" improvements when moving from Quadrajets to Holleys even when the cfm rating stays identical. More appropriate to consider.. is the actual venturi size/booster relationship of the carb you're intending to use for an application. That's what really matters since it changes signal sensitivity from the engine at tip in/smaller throttle angles/abrupt opening. BUT.. even that can be tuned closer to what the application needs(if you're REALLY CARB SAVVY).. with emulsion orifice changes/air bleed tuning. This is where Edelbrocks have an advantage over a Holley in that they are designed as smooth bore carbs and have improved metering/emulsion characteristics(in relation to the size of the bore itself). In other words.. there is more tuning flexibility/forgiveness to their design than there would be when running a Holley with too large a bore/venturi. To do the same on a Holley setup.. you'd need downleg or annular discharge boosters to improve booster signal enough to get away with it. Big cams on the street also love the annular boosters on very large carbs too. I see 1,000 cfm carbs on heavily modified small blocks all the time. Also keep in mind that a smaller cam combined with a dual plane manifold is MUCH more forgiving to running too large a carb than a large cam/single plane would be. And using ANY sized carb with vacuum secondaries improves that flexibility even more. So.. after all that hubbub.. I'd still lean towards the carb swap myself.. mainly only because you already have the parts, the throttle bore/venturi sizes are more appropriate for each motor, and the calibrations are likely/possibly closer to what each motor will like with less tuning required to dial them in. BUT.. depending on what model the 750 is.. it's still entirely possible that you may still need to tune it for the larger 351 anyways. Especially if it's a performance version being placed on a stock motor.. or vice versa. Size is only one aspect of the equation.. and fine tuning is key to maximizing its potential. Sorry it got so long.. I started with intentions of only pointing out a few key points.. and it snowballed as I kept leaving/coming back to this reply through the day. Oh well.. at least it's a "one and done" type deal now. LOL
my dad bought a stage 3 summit racing carb and intake kit the carb is 750 cfm but its going on a stock rebuilt motor i dont think that would be good
IIRC.. the "stage 3 kit" just uses an airgap style intake, right? If that's the case.. with the right shorter duration/high lift cam.. you'd be surprised as how little off idle power will be lost. Carb's are just metering devices with more than enough available adjustment to make them cross over some pretty unorthadox lines. The power band would also carry a bit longer before nosing over a cliff.. despite the shorter cam too. Compared to the stock stuff.. it sure wouldn't ruin the motor.. that's for sure.
