help! jet size for dual quad detup on big block stroker

[3rdelke]

my son and I are building this car, have no clue what we are doing, its a 477 stroker, hyd lifter, roller rocker, cam is .545 lift, .050 dur. using a stock manifold, and two carter afb 750s, the guy building them wants to know how to jet them. bought a jet kit but I need to have some kind of idea how to jet them initially, so the car will atleast run. thanks

 

[747mopar]

Trial and error is the only way! I'm no card genius nor am I a Carter guy but my way of thinking is start with the factory jet sizes and go from there. 750 cfm's is going to need roughly the same amount of fuel regardless of how many carbs you have to keep the ratio right I would think.

 

[lewtot184]

stock iron inline intake?

 

[3rdelke]

yes, stock iron intake

 

[lewtot184]

750's throttle bores won't fit that intake without some work.

 

[khryslerkid]

750's throttle bores won't fit that intake without some work.

The bores on the manifold are 1-7/16, 1-11/16, primary and secondary.The 750 carbs are 1-11/16 primary and secondary. I'm using 600s on my original iron intake that do match up.

 

[lewtot184]

i thought the factory manifolds had 1 7/16" and 1 9/16" bores,....? i know they used pretty small carbs. this set-up in the pic is a nice reliable package.

 

[3rdelke]

not sure I made myself clear. the intake is a stock 413 cast iron, so the carbs wont work?

 

[lewtot184]

not sure I made myself clear. the intake is a stock 413 cast iron, so the carbs wont work?

you need to measure the throttle bore hole sizes in the intake manifold. they need to be 1.68.

 

[khryslerkid]

The primary bores on the stock 2/4bll. manifold measure 1.560. (1 9/16) The secondary bores are 1.680 (1 11/16). The primary bores are too small for a 750 cfm carter which measures 1.680 (1 11/16) primary and secondary.

The 600 cfm carb has a smaller primary of 1.430 (1 7/16) and 1.680 (1 11/16) secondary, that will work but you need 1" spacers under them for linkage clearance.

Hope this helps...

You can have the primary bores opened up, if yours havent already been but the money to do that would be better spent toward a good aluminum one like lewtot has...

 

[3rdelke]

thanks, guys. im still a little confused, I bought the manifold and carbs from the sharpest mopar in our area. cant belive he would miss something like this. the bores in the manifold looked the same to me, with just a casual look. the guy that built the carbs is also pretty sharp. he would surely have seen this or not? hate to pull the carbs as he has the linkage all set up. any more ideas?

 

[miller]

Do both primary and secondary throttle plates on both carbs open fully? Even if you need to separate the linkage to test them. Things could have already been done to the intake, to make it work.

Just look down the bores, and have a peek.

 

[747mopar]

An easy way to tell if they will fit properly is take some paper and lay it against the bottom of the carb and lightly tap around the edges with a small ball peen hammer. The sharp edges of the carberator will cut the paper leaving a perfect pattern to lay on the intake to check for clearance, for the bolt holes place the ball end of the hammer into the holes and tap the hammer with another hammer. This is a technique used for making your own gaskets but should serve the purpose as long as you don't get hammer happy.