what would my gas mileage be with a holley vs a edelbrock 600cfm carb? how much of a performance difference would there be?

what would be better, a edelbrock performer, weiand, or holley intake?

this would all be on the setup below.

 

a holley 750 with vacuum secondaries thats properly tuned with power valves and the correct main jets for highway cruising will give you better fuel economy than a 600 CFM edelbrock, almost always. it really depends on the motor. if both carbs are tuned perfect than technically fuel economy should be identical. things like acceleration enrichment, secondary engagment, and primary air/fuel ratio all play a part in getting you the best fuel economy however, and a vacuum secondary holley is probably the best chance youve got. it should also make your car run better. spend some time on holley's site reading about carbs and how they work.

on the other hand, if you dont mind using a laptop..
holley sells a TBI fuel injection setup for $1399 that bolts onto a manifold just like a carb but can be tuned using a laptop. fuel economy? you bet.

 

I have a holley 670cfm street avenger and a holley street dominator intake...doesnt do to bad on gas and runs really good.

I like them both.

 

Kingtal0n is right. I had an edelbrock 600 cfm 1406 and switched to a holley 750 vac secondary. My car runs way better and gas mileage increased dramatically. Especially on highway. The edelbrock was brand new. I bought the calibration kit that had all the jets, metering rods, and springs. I really know how to tune the edelbrock well. After some people on the board and others claimed power increases with a holley I decided to get one off ebay for cheap so I didn't throw money away on a new one. Well I got it for $72.00 and rebuilt it with a $30.00 kit.

When I got it on the car it felt way stronger. I couldn't believe the power that it had. I wish I had done this long ago. Now for the gas mileage. Since this is on my street strip car I never was concerned about gas mileage but when I decided to drive it over 3 hours to Bowling Green, KY it did just as good as my friends 4th gen lt1. If not better. We had to get gas at the same time and I think my tank is smaller. My converter is a 3000 non-lockup and have 3.73 gears in the car.

 

do you think a holley 600cfm vacume secondary will be better than a edelbrock 1406 for both mileage and power?

 

Yes but depending on application a 750 vaccum secondary carb might be a better way to go. My personal experiance with both 1406 edelcrap and 1460 holley both 600cfm was swapping from a perfectly tunned 1406 edelcrap to an out of the box 1460 holley and gaining 500rpm and way better throttle responce. An edelbrocks secondarys will start to open with a little under 3/4 throtlle killing highway mileage. A holley will not engage the secondaries unless the vacuume drops below a certain point saving highway mileage.

 

I was able to get 20mpg highway miles on my near stock 350, with exhaust and 3:73s.

that was using an Edelbrock carb, but I'm done with Edel carbs, I'm gettin a Holley 650DP, there goes the gas milage

 

i think i'm going to get a holley 600cfm vacume secondary and get an adapter to use it on the spreadbore manifold. is the holley any taller than a q-jet? i think it'l all fit with a 3", 1"drop filter under the stock hood. can i take that insulating suff off the bottom of the hood? its all crapped up and hanging and gets everything all dusty.

 

Yeah take that crap off it wont hurt anything. Supposedly it can cause your paint to fade but I havent and Its been like that for a year. I have a 350 with longtubes also...

 

why a 600? just curious. A 750 is more "adaptable" to different engines, so if you ever swapped out to a different engine, or changed your powerband, the 750 would bolt right up.

just curious, im sure a 600 would work just as good. but im wondering why you dont go with the slightly bigger carb, it shouldnt affect anything in the way of fuel economy or driveability. it inevitably will affect throttle response slightly, being bigger it would take longer for the main metering system to begin pulling fuel... the fix however, is just a bigger pump shot. no big deal. just curious.

 

I would think a 750 on a 283 would be overkill and actually hurt performance

 

I dident read that it was a 283. Why would you build a 283 when 350's are as abundant as oxegen? Oh well then stick with the 600 and jet it lean.

 

a 283 would accept a 750 just fine. "running quality" has alot more to do with engine vacuum and induction port sizes than anything else... the carb just sort of tops it off. I can get good fuel economy with a 750 on a stock 283. now, when the engine gets Racy and vacuum drops off a lot, its alot more important to size the carb up to the application. if hes only spinning to 6K then his engine only needs 500~CFM @ 100% VE. if he ever superchargers it he will need a 750 anyways. if he ever changes it to another engine he will want a 750 anyways. and if his engine ever desires more air for any other reason, he will want a 750 anyways.
Consider roots blowers for a moment. on my 355 @ 6000 RPMS without the blower I only need 616 CFM MAX. but WITH a roots blower I need at LEAST 870 CFM to keep it happy under full boost. The rest of the time? it functions like a 355 without a blower right? So my carb is an 850, thats 250 CFM OVER what my engine actually could use at any other time. Does my fuel economy / driveability / throttle response suffer? Of course it does, but by about 2% in most casses. the rest of the time, its worth the extra 140 horsepower to have an oversized carb.
By the same token, a 750 with vacuum secondaries is only:
283 * 6000 / 3456 = 491 @ 100%VE
259 cfm overkill
and my engine is
355 * 6000 / 3456 = 616 @ 100%VE
234 CFM overkill.

And keep in mind the vacuum secondaries wont even open till the engine needs to overcome the restriction imposed by the primaries, which may probably never become a restriction. this effectivelly cuts the CFM rating of the carb in half, even though the secondaries will still open @ WOT, the engine will only have to worry about the primaries for cruise / part throttle and it shouldnt affect driveability / fuel economy at all. bigger carbs dont mean crappier fuel economy. they just mean more attention to detail, if they arnt the "best size" for the engine.

No, a 750 may not be the best choice for him right now. I have no idea what the engine configuration is. But it can be done, with proper tuning, and it will make sure he doesnt have to buy a new carb when he changes somthing small. carbs are expensive.