Carb Issues - PLEASE HELP

[RustyPile]

There's a good chance that particular carburetor IS the one he has.. "Mechanical secondaries, no choke or fast idle.. He did state that much.. Someone probably told him to get a Quick Fuel 650 CFM.. You and I know better, but him not knowing much about carburetors, he may have googled and came up with the same thing you did... Well, I guess we'll all know if/when he comes back with those pictures....

 

[1987_chevy_]

87chevy, we need to know exactly what carburetor you have, can you provide that information??.. The one in the link is TOTALLY not for the street. It has no provisions for a choke, no power valve - a plug instead, jetted way to big, and finally, it has mechanical secondaries.. It's a race carburetor and when installed on a stock or near stock low rpm engine, it will exhibit every problem you're experiencing..

A choke greatly aids cold engine run. It's a method to enrichen (less air, more fuel) the fuel/air while the engine warms up. A power valve aids fuel metering under part throttle conditions and helps the engine handle varying load conditions. Vacuum operated secondaries allows the engine to "choose" the rate at which the secondaries open.. All these qualities are necessary for the operation of a street engine, but none of which are desirable in a full race engine..

If your camshaft is one of moderate to extreme duration, due to diminished manifold vacuum, you'll experience some drivability issues that you'll have to learn to live with.. The greater the engine displacement, the more tolerant the engine is of "long" duration cams.. Put a cam in a 265 - 283 cid old Chevy that gives it a lumpy rumble.. Take that same cam and put it in a 383 - 400 cid engine and it will be almost silky smooth..... This explains why you can put a wild ass cam in a big block built for the street, and it's just a big ol' ***** cat....

87Chevy, I sincerely hope this helps you..

I brought the truck back to the guys that tuned it, turns out the distributor moved and it's fixed now and runs so much better, it has a little bit of hesitation because it needs a bigger accelerator pump which I'll get in the spring

 

[1987_chevy_]

There's a good chance that particular carburetor IS the one he has.. "Mechanical secondaries, no choke or fast idle.. He did state that much.. Someone probably told him to get a Quick Fuel 650 CFM.. You and I know better, but him not knowing much about carburetors, he may have googled and came up with the same thing you did... Well, I guess we'll all know if/when he comes back with those pictures....

What pictures do you need?

 

[RustyPile]

What pictures do you need?

Pictures of the carburetor.. We'd like to know which 650 CFM carburetor you have. There are a few and some are not suitable for street engines.. For one thing, a mild street engine shouldn't need a large accelerator pump.. There are several things not related to carburetor settings that can cause hesitation..

 

[1987_chevy_]

Pictures of the carburetor.. We'd like to know which 650 CFM carburetor you have. There are a few and some are not suitable for street engines.. For one thing, a mild street engine shouldn't need a large accelerator pump.. There are several things not related to carburetor settings that can cause hesitation..

It is a quickfuel 650 cfm hotrod series carb

 

[RustyPile]

It is a quickfuel 650 cfm hotrod series carb

Not my first choice for a mild street engine.. Over engineered is the way I'd describe it.. It can be made to work on the street, but not a carburetor for the faint of heart.. By design, it's very adjustable, too adjustable for most applications. Air bleeds and other items are screw ins.. Dual metering blocks with idle mixture screw in both. One has to have a LOT of carb tuning experience to get it going.. Every time the weather changes, the carb "setup" has to be tinkered with..

Get ready for some hair pulling learning experiences.. When you get this one figured out, you'll be ready to run with the big dogs....

BTW.. I'm curious --- how did you come to choose this carburetor??

 

[1987_chevy_]

Not my first choice for a mild street engine.. Over engineered is the way I'd describe it.. It can be made to work on the street, but not a carburetor for the faint of heart.. By design, it's very adjustable, too adjustable for most applications. Air bleeds and other items are screw ins.. Dual metering blocks with idle mixture screw in both. One has to have a LOT of carb tuning experience to get it going.. Every time the weather changes, the carb "setup" has to be tinkered with..

Get ready for some hair pulling learning experiences.. When you get this one figured out, you'll be ready to run with the big dogs....

BTW.. I'm curious --- how did you come to choose this carburetor??

A neighbor of mine is

Not my first choice for a mild street engine.. Over engineered is the way I'd describe it.. It can be made to work on the street, but not a carburetor for the faint of heart.. By design, it's very adjustable, too adjustable for most applications. Air bleeds and other items are screw ins.. Dual metering blocks with idle mixture screw in both. One has to have a LOT of carb tuning experience to get it going.. Every time the weather changes, the carb "setup" has to be tinkered with..

Get ready for some hair pulling learning experiences.. When you get this one figured out, you'll be ready to run with the big dogs....

BTW.. I'm curious --- how did you come to choose this carburetor??

a neighbor of mine runs the exact same carb on his car. He loves it so much and his car runs beautifully. So I decided to try it out! I've had it professionally dyno tuned so it runs decent as of right now! It needs a bigger accelerator pump, but it'll get that in the spring.

 

[gpmorgan]

The pumps on it are probably the 30cc pumps which should be plenty for a sbc.

 

[74 Shortbed]

Don't need bigger pump capacity, just increase squirter size a bit and maybe adjust pump shot duration. Also, "dyno tune" and "street tune" are two completely different worlds..