i want to build a 850 holley.i have been looking for one for a while now and dont want to spend 300-500 on a used one.my question is has anyone used the cheep bodys and base plates that are for sale for around $60.00 each?i have a 750 doublepumper now.i am thinking about useing the metering blocks and bowls from my 750 and putting them on the new stuff.can i do this?or are they different?i would like to use proform stuff but money is tight and i dont see it getting any better.
I think that will work just fine. Pay attention to the idle circuit, but that should be within the adjustment range of your existing metering block combination. Of course, main jets will likely change, not necessarily up, and power valve, too. I have played mix n match a couple of times with good results. The parts in question are pretty standard. I haven't used the aftermarket parts, but know a few that have. I'm not aware of any raging anger.
Actually, the throttle plate for the 850 dosn't have idle circuit channels and you need a metering block that has idle circuit adjuster screws like the primary in your 750. All the 850's i have seen have 4 corner idle circuits (even the vac secondary). The 750 (most, not all) have the idle ciruit adjuster screws in the primary metering block, the secondary has none, the idle circuit drops thru the throttle body and is delivered to the venturii below the throttle blades, there is a channel in the throttle plate that feeds the secondaries from the primaries. You would need to have two primary metering blocks, both need to be from at least a 750 cfm carb, ones from say a 650 will have the idles restrictors on the small side. As usual, it is expensive to buy brand new pieces as i haven't seen the larger ones on ebay at a good price. Probably better to buy a good used one and rebuild it yourself. I just read your comment about the idle circuit, and you do care because it is always active and does things in a different way than what simple increasing the jet size can do. It will just make your life miserable without the idle circuit.
Opel, There is nothing wrong, in my opinion, with a lot of the budget mainbodies and base plates out there. The biggest problem for me with them is I always hand built/modified holleys and with these low cost parts being made it has taken a fair amount of work away from me!!! Anyhow, they all can have problems, not every part is checked 100% for flaws...most are m*** produced and that is where a problem can come in. Holleys are the same way, I have ordered metering blocks dorectly from holley and had them show up without threads in them for mixture srews, main bodies without tapped holes for bowl srews etc. IT HAPPENS. Nothing is perfect. I say go for it, you may have a little here or there that you will have to fix, but then again it might go together and be fine. You do want to be concered with the idle circuit, if you engine is loading up when it idles, even for a few seconds, it will effect the engines performance. The idle circuits are very important do not over look them. The four corner idle that was already mentioned is by far the best way to go to help keep that engine crisp while idling and also with throttle responce. Even guys with trans brakes that are always at wot when racing, benefit from having a good idle circuit. You do not have to build it with the four corner idle, but if you want the best tunable setup with the bigger carb I would. If the aftermarket base has the idle fuel channel in it from primary side to the seconday side then you would be ok, but if not your idle circuit will be a *****. There are differences in the 750-850 metering blocks...not that you have to worry about the differences unless you need a maximum amount of fuel flow. The main metering wells/circuit and power valve circuits are different. I've done a lot of swapping/mix-n-matching, and you more than likely will not have to worry about using your blocks with the 850 main body and base plate. I guess my suggestion would be go ahead with what you can afford, and find a used primary metering block from another 750 or bigger carb and use it as your secondary one. Good luck. By the way, why are you not concerened with the idle circuit? What is the carb being built for engine/purpose? Just curious.
Go to a swap meet and pay $100 or less for a rebuildable one, that's what i do, i've never owned a car that wasnt holley'd or stromberged even the non runners
i have never really rebuilt a holley before just changed jets,p.v.and excelerator pumps.the carb on my car now is i think a 750,but for some reason i keep thinking 700 or 730?anyways i want to have the main body without the choke and stuff.yes i could have it milled off but for $60 new why?the carb is going on my opel.it is race only.right now it idles at about 850-1000 rpms.im not sure but i thought that at that high of idle the idle circuit is basically byp***ed.the car has a transbreak and i leave the line at 4700-5300 rpm.i have been having to jet it up to 87 front and 92 in back.sometimes more or less depending on weather.it does have front p.v. and i think its a 2.5.if i remember right the va*** is about 6-8 lbs.the motor isnt a slouch.11-1 big solid cam torker intake and side exhaust{if thats what you want to call it}i just think i need to step up carb but im not really sure about mixing parts,and dont have the money to buy stuff and figure out that they dont go together.maybe someone has a carb they want to get ridd of for a decent price?
If youve done that, then you pretty much have rebuilt one, they are pretty simple, Just DONT get non holley rebuild kits, parts dont fit right in those
I have used the proform main bodies on both 750 dp's and vac sec's with mixed results. The first one I did was on a 750 dp on a 67 Chevelle I work on for a guy with a 461 BB with a mild roller cam and ported oval port heads. It makes 540 horse on the dyno. It worked out real good. These bodies make a 750 about 830. The one I put on a vac. sec. leaked and didn't work so good. I put one on another 750 dp on my Dad's 62 Vette with a 427 and lost e.t. and went back to the regular 750 main body. I think if I did it again I would by the main body from Holley. It is a little more expensive but I think it would be better quality. You will have to do some jetting changes but that's about it. Good luck
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