the carb om my 80 is pretty much screwed, so i looked at reboilding it versus replacing it an decided to just replace, but don't really nkow what to get as for size goes, the carb on it now is an older 4150 Holley 650
what i'm wanting to know is can i go with a 750 or do i need to stay with a 650


thanks
Brad

 

Depends on if the engine is closer to stock, or radical build. If it's closer to stock you're wasting gas and money on anything larger than a 650 with vacuum secondaries. If it's well built high HP a 750 would be ideal.

 

Need a lot more info but the short version is if you do not have custom heads a 750 is to large. A 650 is large for a stock SBC I would go with 625 edelbrock unless you know what you are doing then get a Holley 650.

 

i don't have many specs on the engine other than it has semi-domed pistons, a 292 roller cam, roller lifters and late model center bolt heads (if that means anything) but i am clueless as to compression, hp or torque specs. don't even know how much it's been bored
been trying to track down the engine builder but as usual no luck on that

sorry i couldn't give any more but i hope this helps

 

Well I usually have a get this or don't do that when someone asks about carbs. I am a little on the fence, only because of the roller cam. Stock heads are gonna dictate this I guess, 650 vac secondary. 4150 is a mec. secondary if memory serves. I would rebuild the one you have. Why not? Cheapest option. It ran good before with that carb? Is your car a stick? Sticks can get away with a mechanical secondary carb easier than autos.

I don't know your skill level but Proform and Holley both have come out with a progressive secondary linkage. I plan on using one myself if I hit a snag with my new Proform.

 

the car is auto (TH350)
was not running with this carb on it, had to put another one on it just to get it to run.
why not rebuild it. well i don't know how old it is, (going by the numbers on it it's pretty old). don't know what's been done to it in the past. plus the cheapest rebuild kit i found so far is $95 bucks then i'd have to pay somebody to do the work.
weighing all of that up i figured it would be cheaper and easier just to replace it and have one i know about

BTW the #s are 80783-1 then under that is stamped 0759

 

As long as the shaft isn't worn out, age won't matter. 95 bucks is outrageous for a gasket kit. Call your local parts store and ask for a Holley Trick kit. It would have every gasket you need, the only thing is it only one accelerator pump.

If a new carb is what your hell bent on, then a 670 Holley street avenger is right up your alley.

 

appreciate the info
may try to rebuild if i can find a cheaper kit

 

You might also consider one of the Summit brand carbs. I've got a couple friends who bought them and are very happy so far. They pretty reasonably priced and perform well.
You've got "center bolt heads" so I'd assume they are Vortecs, and will flow pretty good. Any domed piston will have a little higher compression in a 350 than the stock flat tops, so that might also help.
The Summit carbs don't come in a 650, but they have a 600 and a 750. I'd go with the 600. It's only $235 on sale now:
Summit Racing SUM-M08600VS - Summit Racing Street & Strip® Carburetors - Overview - SummitRacing.com

The Holley is this one if you have a sq. bore intake. It's $359:
Holley 0-80783C - Holley Model 4150 Carburetors - Overview - SummitRacing.com

 

I can't make the jump to Vortecs like Vall did. It is very reasonable that someone did that. But anything from 86 or so on will have center bolts, Vortec or not. Can you post a pic of your intake? I would be able to see a Vortec at a glimpse. I'm currently working a deal for a set to put on my truck.