800 CFM Q JET FOR 496" BBC 1973 CORVETTE WITH A 4 SPEED STICK

[c6silver]

Hi guys, new to the forum. I'm trying to find out if there is an 800 CFM side fuel inlet (Chevy style) divorced choke Q jet out there that can be made to work on a 10.3 compression 496" BBC in a 1973 Corvette 4 speed. The engine will have a Crane blueprint series LS-6 solid lifter cam (240/240 @ .050, 114 LSA) with 1.8 SS roller rockers, a ported aluminum 1969 Corvette Q jet intake, ported/big valve 049 heads and ported/Extrude honed exhaust manifolds flowing into a 2.5" Pypes X pipe exhaust system. The car will have 3.73 to 3.90 gears. If there is no such carb, I have several Buick 800 CFM units that I could use (I don't have the numbers with me right now, but I can get them). I'd RATHER have a side inlet to look stock, but I also need the divorced choke set up. I'd also like to increase airflow to around 900 CFM if possible WITHOUT butchering the carb (no removing the outer booster rings). I'm open to button head screws, throttle shaft milling, and general de-burring of the castings to accomplish the stated goal. This is primarily a street car, so the choke has to work. Thanks for the help !!!

[Ethan1]

Hi guys, new to the forum. I'm trying to find out if there is an 800 CFM side fuel inlet (Chevy style) divorced choke Q jet out there that can be made to work on a 10.3 compression 496" BBC in a 1973 Corvette 4 speed. The engine will have a Crane blueprint series LS-6 solid lifter cam (240/240 @ .050, 114 LSA) with 1.8 SS roller rockers, a ported aluminum 1969 Corvette Q jet intake, ported/big valve 049 heads and ported/Extrude honed exhaust manifolds flowing into a 2.5" Pypes X pipe exhaust system. The car will have 3.73 to 3.90 gears. If there is no such carb, I have several Buick 800 CFM units that I could use (I don't have the numbers with me right now, but I can get them). I'd RATHER have a side inlet to look stock, but I also need the divorced choke set up. I'd also like to increase airflow to around 900 CFM if possible WITHOUT butchering the carb (no removing the outer booster rings). I'm open to button head screws, throttle shaft milling, and general de-burring of the castings to accomplish the stated goal. This is primarily a street car, so the choke has to work. Thanks for the help !!!

 Welcome to CHP!

 You are going to be hard pressed to find one with a divorced choke unfortunately.

[qjetsrule]

According to Cliff, there won't be much performance difference between the 750 or the 800. Remember there are some stock and superstock NHRA Corvettes running 9 second quarter mile times with the 750. Why not try both. Personally I think it is more rad to pop the hood and find the stock carb and intake with divorced choke on a beast machine. Good luck

[Ethan1]

According to Cliff, there won't be much performance difference between the 750 or the 800. Remember there are some stock and superstock NHRA Corvettes running 9 second quarter mile times with the 750. Why not try both. Personally I think it is more rad to pop the hood and find the stock carb and intake with divorced choke on a beast machine. Good luck

 Agreed. The extra 50cfm really isn't worth it. 

[carmantx]

I looked through my notes and didn't see a side inlet 800 cfm divorced choke.

I don't run choke system at all on my street driven cars.  And if the air flow is what is important, why not remove the choke flap?  If you want a choke, though, then disregard.

The 71-74 Buick 455 800 cfm quadrajets are nice units and I have heard they flow about 847cfm without modification.  I build plenty of them for my Buicks and Buick friends.

[Cliff Ruggles]

Correct, there are no larger casting side inlet divorced choke models made.  I've seen a few of the later large cfm side inlet carbs modified for divorced choke set-ups (Marine clones), but have never did this myself.

You would really be surprised at how well a smaller 750cfm casting will power the big 496.  I've street and drag strip tested the smaller carbs on quite a few outings, and they run very close to my much larger 1977 front inlet Pontiac carb.

Removing the outer booster rings really helps them out, as this makes the smaller castings flow around 827cfm, but really that isn't needed for what you are doing.

Another thing that really helps but is somewhat labor intensive is to use a longer arm on the primary shaft to operate the secondaries.  This allows for much greater primary throttle angle for street driving without getting into the secondaries, and helps with big CID and towing applications......Cliff