383 build. Any recommedations?

Yes, belt drives are spendy. Unnecessarily spendy for a 6500 RPM motor.

You can really take your pick between the two, the differences will be slight at this level.  

I like them because gear drives have a longer life than a chain set-up. I havent come across a chain I could reuse yet. We all have our reasons  

Belts are not the end all for timing solution. They may be fine for a race application where components are changed after a few runs, but on a street car they will require changing more often than a chain setup.
 The raised maintenance cost is not worth it compared to a gear set up. Ever wonder why the belt drive manufacturers do not list the life span of the belt? Can you guess will happen to an engine when the belt breaks? Bent valves, busted pistons, and possibly a bent rod since the SBC is an interference engine. When a modern engine is designed to run a belt timing set up, they normally make the engines non-interference. This means that the valves will not contact the piston if the timing gos to CaCa due to a broken belt. Also, most OEM's are getting away from belts and going back to chain drives.

The good thing about chains is that they will stretch, and you may skip a tooth, but nothing bad happens. Belts do not stretch they pop. Not much of a cushion for a street car.


ok, I'm off my soap box...

Jake  

Im anxious to get this motor together. It'll be a month or to but I like the strategy. Lowering my cr, going with gears, roller cam, and deciding to install a windage tray and a scraper to my oil pan. All small cost effective parts. Only a minor set back but I believe it will be worth it in the end.  

Engine building is not to be rushed so good for you. Once you have the parts list you want to use remember to stick with it and not get carried away thinking bigger is better. I've seen alot of good combos trashed because people change to a bigger cam,bigger port volume heads,etc.  

go with an internal ballanced crank the give of a less violent frequancy and tend to last a little longer and i would trust it to rev higher as well
i have a 85 shortbox chev that i did a 383 in and it runs low 13 with no traction and pegs off rev limiter at 8000 no prob . its a 010 block with ported 882 heads....my first port job half ass to the extreme but this thing suprises me every day lol and i have an edelbock performer 600 series carb and everythig is about the same as far as oil pump intake forged pistons ....but mine are flat tops with a 2 cc valve relife and i run 10.5 to 1 compression and it runs fine on regular lol  

i second gettn my first hobby car was a 76 monte with a solid 375-400hp 355.now my buddy had a 72 caprice with a 402bbc and him and somebody who knew what they were doing did a cam and manifold swap and it ran like a raped ape.so naturally now i want a bigger cam.so being 18 yrs old i go find the k-kit from comp for the biggest small block hyd flat tappet they made,not knowing one thing about the rest of the motor.needless to say i didnt want to run so i buy a stall converter and 750 carb,and maybe drove the car 5 miles and i wouldnt idle had massive oil leaks so i  parted every peice i could over to my chevelle,radiator,stall,all accessories,carb,and sold it for 700 lol i guess thats how you learn  

kovari,
you might want to go with a 750 carb. With 383 running 8000 rpm at 85% vol. eff. you are recommended to use 750 cfm. Stock 350's had about 80% ve so with your ported heads, headers, aftermarket intake and slightly higher cr you get put at ab out 85%. I only plan on 6700 at the most. So having a lower max rpm lowers my cfm necessity to about 670. With a external balance crank i am still rated for 500hp. If i use a higher quality harmonic balancer/damper i think it'll be fine. It is still a good suggestion though.  

Jonathan,

That formula isn't all that relevant to an engine running at 8000 RPM anymore. With improved booster design carburetors are running in extremely low vacuum environments. That old formula also does not account for turbulence and displacement by fuel in the airstream. These factors make that old formula give very low ratings for CFM ratings in high performance applications. In fact, Pro Systems Carburetion recommends using a carb CFM size of around 20% larger than that formula suggests.

Also, it should be realized that with any high performance engine that less restriction is more power as long as fuel atomization and induction wave tuning don't suffer. That means that you should use as large a carb as you can get away with even if the formula says to use less.

Even then we are dealing with mass-flow ratings rather than more directly applicable cross-sectional areas or venturi diameters, but we can make some good approximations with flow ratings as long as you keep in mind the test pressures.  

Everyone has different recommendations. The formula is just an easy way to get a quick figure not knowing alot about a motor. Still a 750cfm would be more suitable than a 600. the combo he is running is being restricted by a performer carb. And if you go by the extra 20% you are talking about his combo will need a 900 cfm carb. That in my opinion is a little overboard. I know a lot off people do it. Just not me.  

What happens when the carb is too big and has to be jetted down several sizes?  

Is the 20% jump in carb size for all carbs or just the carbs from the company you mentioned?  

Carb "size" or carb mass-flow in cubic feet per minute of air, as you're referring to, is independent of the fuel "size" or available fuel flow to the engine.

If a engine has a carburetor with too large a venturi or a poor booster design then actually the fuel side usually has to be richened to compensate. Poor signal to the booster causes the engine to require more fuel be thrown at it to run properly, not the other way around.

That particular company (Pro Systems) recommends when using the age-old CFM equation to use a value approximately 22.5% larger - that is for any high performance engine I suppose but it is still just a formula. I'm sure for a real max-effort build they would recommend empirically determining the proper carb size.  

So he still needs a bigger carb. Like i recommended. Like you said a carb is decided by the final tally of the motor. But the cfm formula is still a great way to get the basic cfm you want for your motor. Also 22.5% is figured on some high dollar motors. im sure the percentage drops with the quality of the motor. I also depends on  how your carb is built, like you were saying. Giving scientific explanations only confuses most people. U think to much. Alot of us are backyard mechanics who just want a specific hp range under 500hp. If we wanted a 1500 hp alcohal motor. We might use some of those scientific facts.  

That is still not highly scientific, that is simply what Pro Systems says to use. Although I do highly respect their opinon and agree with it to an extent.

You are correct though for this situation you may not be a carb that large, but if it is truly running around 8000 RPM then you need a fairly large carb!