i want to upgrade my carb from a 600 cfm edelbrock to this 650 dp holley carb it shouldent be to much carb right stock 72 mav 302 with / ported heads , performer 289 intake with 1 inch spacer , long tube headers , powerfire electronic distributor , msd blaster 2 coil , t5 trans with 12 pound aluminium flywheel ( and a few edelbrock stickers ) http://sacramento.craigslist.org/pts/1881687566.html is this carb worth it or should i just wait for something else ?
It's not a bad deal, but looks a little too old to suit me. If it looked new, it'd be a killer deal. I've found that old Holleys can and usually are a pain.
If you are running a stock cam, I don't think you need a double pumper. 600 CFM should be sufficient for your setup if you are a running a stock cam and rear end gears.
yah it is a stock cam and 3.25 rear gears but will get 4.11's and a roller 5.0 with cam when i get the fund's
Yea im with him on this one that older holleys are a pain the one that came with my car i chased the tuneing for a couple months and just got fed up and bought a new edlbrock 600cfm and it works beautifully
The biggest problem with used Holleys is that the guy you are buying it from has probably spent a lot of time "tuning" it and you have no idea what has been changed. With a used Holley (or any other carb) you should start by completely disassembling it and get all the parts needed to get it bak to the original configuration - it can be pricey because it might have different or modified metering blocks, air bleeds and even the body might have been modified. (at that point the carb is most likely junk) Once you get it back to stock configuration you can run it and get some baseline numbers to begin serious tuning.
The problem I've had with old Holleys wasn't from former owner's tuning, but rather from worn throttle shafts and base plates and crud buildup in the metering passages. I now only buy those Holleys that are obviously little used and fairly new. With these the worst problems I've seen were from guys who didn't know how to tune one. Or run fuel filters. The last one I bought (ebay) was a fairly new 570 Street Avenger. The only change I made was to replace the powervalve just as a precaution against the rubber diaphram rupturing. It needed no tuning, other than adjusting the idle screws.
Baddad, Ho;;ey has been incorporating a check valve in the power valve circuit since before the Avenger series carbs. There is little need to worry about blown diaphrams anymore. I am not saying you shouldn't replace it just that as you do, you might want to check to see that the check valve is in place.
the way i'm thinking is if i am buying a carb then why not get a 650 instead of another 600 since i plan to put a roller 5.0 302 and cam in the future what if i get a vacuum secondary carb
In my 35 years of wrenching, I've yet to see a Holley with a blown powervalve. I have seen lots with ruptured diaphrams from sitting on a shelf. That's why I change em.:Handshake
You need to buy Holley manual and read it first. Smaller is almost always better when it comes to carb sizing. . But if you want a 650 look at the 80783 (list number) What makes a carb function is the vacuum created in the throttle bores. This is what pulls the fuel from the bowls. A smaller carb creates a higher vacuum, this makes it easier to pull the fuel and you get a better fuel mix due to it.
i didn't think about that i do have a few videos by bad ass racing engines and one is performance carburetors very good videos http://www.powerbuildingvideos.com/...lts/category_id=2/home_id=2/mode=cat/cat2.htm
I don't need to tell you that I know pretty much crap about all this stuff but . . . in my research the 600 edelbrock has been great out of the box but once you want to tune it seems like you have more options if you have a holley or maybe more people know how to tune holleys around me. The 650 dp might be too much and seems like you can get stumbles with a carb that's too big. bryant gave me some pretty good advice on carbs, he might be another person to ask b4 making a big purchase.
it will drive just fine with a 650. it is biger than needed unless your spinning your motor past 6500 rpm. the throttle responce will be crisper with a 570 or 600 cfm carb.
A 650 DP will work, but a vacuum secondary carb will run rings around it on his motor. All a 650 DP will do is kill his fuel mileage. And the problem with a mech secondary carb is the bigger you go, you'll eventually reach a point where when you nail the pedal from a dead stop, the engine will die, no mattter how you tune the carb. TOO much air combined with not enough vacuum to pull the fuel from the bowls is what'll do it. The only bandaid to help is going bigger on the accellerator pump volume. And with dual accelllerator pumps squirting fuel everytime you move the gas pedal, you're fuel economy goes downhill pronto.
