I have a carbed 350 with a stock rochester carb. The car is a 5 speed. I want to know what you guys recommend for a carb that will be faster is it vacuum or mechinal?

 

It's not so much a question of better so much as it is whats better for you and your application.

For manual trannied applications I always recommend manual secondries.

 

can you help me understand why mechinal is better than vacuum.

 

Shifts in a manual trannied car produce much more abrupt changes in vacuum than with an auto tranny. VS carbs often have problems keeping up, and bog during shifts.

 

so what is involved putting in a mechianl one. do some hoses not get connceted or what. im a beginner so sorry for my inexperience.

 

Mechanical or vacuum is built into the carb itself. Any vacuum lines attached to the carb that go somewhere else will be attached to either carb.

"Mechanical" and "double-pumper" are two names for the same type of carb. Holley and Demon are the only "true" mechanical designs out there. Edelbrock, Carter, and q-jets have mechanically-operated secondary throttle blades, but also have an air valve system that regulates actual air flow through the secondaries based on engine demand. Holley and Demon are the only ones who make a "true" vacuum secondary system as well, but that's another topic since you need to understand mechanical double pumpers for your application.

The main issue you will encounter putting a double pumper on your engine is actually mounting the carb to the intake manifold. Unless you have an aftermarket intake that has a dual-pattern mount on it, the square-bore mechanical will not bolt to the spread-bore stock intake manifold. You'll either need to use an adapter, or put on an aftermarket manifold.

Unless your car is Canadian, your stock Rochester should be computer controlled (if it's still the factory system). If that's the case, you will also need to change the distributor to a vacuum/mechanical design in order for the engine to work with the aftermarket carb. And, that would be an exception to the first paragraph, because the vacuum distributor will have a vacuum line going to the carb that the CC distributor will not.

Now, going back to your original question: Which carb to put on that will be faster? The answer very well may be, "The one you have on now." Don't underestimate that ol' q-jet, they aren't that bad of carb if you do things they like. Making it work is probably the most cost-effective performance improvement. HEI improvements (coil, module) also help power above 4500 RPMs.

 

thanx for the info five7kid. The carb i have on there is a cc rochester but it has been rebuilt about 2 or 3 times and i think its just getting old. it still perfoms good but i think a brand new carb will let me get a little better accelteration. also there is the stock manifold on there to. can you tell me if this would be a good carb as a replacement? http://www.jegs.com/cgi-bin/ncommerc...br=76&lastcat=

what do you think of that as a replacement?
thanx for the help

 

It will bolt onto the manifold, but:

1) Your stock q-jet will flow more.

2) I've never heard anyone that was happy with one of those things.

I thought my q-jet was holding the '57 back last summer, got a Holley. Guess what - same times, a little slower perhaps, drives "different" but not necessarily "better".

I've come to the conclusion that my ignition is the problem, not the carb (old points-type distributor with electronic conversion - long story), but the old principle of ignition causing 90% of carb problem appears to hold once again.

You're probably being held back more by your ignition than by your carb. For about $130, you can get an Accel HEI coil and CC module - a lot less than $350 for a carb and $150+ for distributor.

 

like i said before i know the carb is worn pretty bad. so what parts should be rebulit on the carb? yea i was looking into something like msd is that the same as hei coil?

 

Actually, that's the first time you've said it's worn - how do you know that?

MSD is more than just a coil, and you still need a coil. It would help, but would be overkill for most street cars. The coil & module would probably do fine.

Simple timing advancing and q-jet tuning will do wonders to an old "worn out" carb. Not saying your's isn't worn, just don't want you to set yourself up for disappointment - or, "fix" the problem by replacing something that has to be changed in order to use something you didn't really need to start with.

 

I say ditch the Q jet and get a regular 650 double pumper. Get a decent aftermarket manifold too while you're at it

Definatly forget the 6210 Holley you put the link up too..those things are aren't Holleys best idea ever.

 

Im pretty sure its worm cause it has been rebuilt not completey like a whole tear down. but i think the floats and jets have been replaced a couple of times. that is why i think it is worn and sometimes it just doesn't wanna pull past like 4-4500k. I have been thinking about just getting new manifold and carb. How hard is it to put on those yourself? or should i just bring it somewhere to get it done?