resend of carb tips

Damon 'Fugly' Kuhn's Carter Setup White Paper

EDELBROCK / CARTER SETUP

Ok - here we go - first some general rules and then some more specific tips. BTW my sense of humor may offend some ...I accept no responsibility for mental anguish....

GENERAL RULES

1) DO NOT TAKE IT OUT OF THE BOX , TEAR IT DOWN AND MAKE IT BETTER!! But you say "I think it needs to be richer , leaner, ETC" -WHY??? ...many, many years of hard work by engineers versed in the product they produce have gone into this design, and chances are they know better than you or your buddy Mr Carb Guru (hereinafter referred to as CG) what works. My racecar is jetted one size bigger all around than the carb came from the factory-not too many engines will have a more radical cam or more messed up signal than this, so don't go putting bigger jets in "JUS BECUZ' "

2) Insure you don't over torque the hold downs- if your gasket is worn out or your intake top looks like the side of a wrecked dump truck -fix it first...

3) If you car /truck /tank /boat etc ran like crap with the old carb and it runs like crap with the new carb....it's probably not the carb.

4) Get the proper carb for your vehicle- undersized carbs, while great for response will be dead at the top end, run richer as a rule (excess velocity causes main circuits to come in wrong) and usually get worse mileage. Oversize carbs (especially vacuum / air secondary type) will have an untunable low end bog, lazy acceleration and nearly impossible idle problems. Somewhere in between is what we are looking for. A simple equation to get you close : ((Max rpm X CID) / 3456 )X V1. V1 is a variable representing the efficiency of your engine . Use .85 for a normal street engine, 1.00 for a fairly stout street engine ( we're talking close to strip car here) 1.2 for a highly modified strip only vehicle. (Yes< I know these are not the same numbers as some books show, but they work for these carbs) BE HONEST (you don't have to tell anybody) -along those lines do not use 7600 for the rpm on your hydraulic cam 8.5:1 street engine.

EXAMPLE: 440, hydraulic street , 5800 max rpm. ((5800 X 440)/3456) X .85 or ((2552000)/ 3456) X .85 or 738 X .85=627 or a 625

440, 620 lift mechanical, 6800 rpm max ((6800X440)/3456) X 1.00 or ((2992000)/3456) X1.00 or 865 X 1.00=865 or 800 (biggest) or 2 X 500

SEE how much difference it makes????

Typically, you can get away with 1 size bigger / smaller eg a 750 will probably be fine on you stock 440 ...but you say " CG said his likes a dominator"....does that mean it truly works in an optimum manner?? If you have a high stall converter, 4 speed , don't care about mileage/ drivability.... by all means put the biggest thing you can find on it....

5) Make sure your timing is set /working properly- not enough initial timing /too slow of a curve will cause bogging, while too much total advance will cause your ride to do the "Herky Jerky "down the freeway and or ping. If you can't get a decent cruise rpm after following the below, try disconnecting and plugging the vac advance on your distributor- if it's better, you probably need to get it recurved.....this is another subject...suffice it to say, most late model stock distributors have too long an advance curve built in and need to be welded up for performance use....

Now on to putting 'er on:

Before you bolt it on- flip it over and make sure the secondaries open all the way when you twist the throttle all the way open. Many times you will find they are only 90-95% open. If you look at the side opposite the throttle linkage, on the secondary shaft, there is a small tang which stops the blades at a specific point. Bend this GENTLY with a set of pliers to allow full opening. It doesn't take much, so don't use your biggest pipe wrench. Now back the idle speed screw (the one on the side of the carb that controls the throttle linkage) all the way out until the blades (primary) don't move any more. Look under the carb now....open the primaries -see the little vertical slots? this is the transition circuit. Screw the speed adjustment back in until it holds the blades at the very bottom edge of these without exposing them-this should be close enough to start the car. On the front now- the two idle mixture screws-screw these all the way in (GENTLY-you can use your fingers) and back out about 2 turns. By the way the drivers side vacuum port is full time and the passenger side is ported-usually the distributor will like ported....Bolt it on the car now....(turn it right side up if you haven't already)

Check for leaks and fire it up. WARM IT UP before you start adjusting things....adjust the idle speed screw to get an idle , steady but not too fast. Now adjust the mixture screws to get the fastest smooth idle -go back and forth until you get the best setting. You should be able to turn the speed setting down a bit as you go. Now turn it off and gently screw the mixture screws in all the way while counting the turns. They should be even and somewhere between 1 1/2 and 2 1/2 turns out. Put them back where they were when you finish checking. If they are less than 1 1/2 turns, you have the wrong springs in the metering rods or it's too rich, or the choke is not wide open-check it first- if it's not fully open when the car is warm, loosen the screws and adjust it for full opening with a very slight positive pressure and retune as before. If they are open more than 2 1/2 turns , you are too lean, or have the wrong springs.

CHECKING THE SPRINGS- This seems to really confuse people, especially those familiar with Holleys. These springs and rods control the power mixture- VERY similar to the Holley power valve. The lighter the spring, the faster , or lower vacuum level they close at . Manifold vacuum controls them-at a high vacuum( idle or cruise) they are held closed by the vacuum. When vacuum drops sufficiently, the spring overpowers it and opens, or raises the rod. The tip of the rod is smaller and therefore richens the mixture. The trick is to have them closed at idle and cruise, and open as soon as the vacuum drops signaling more load. Most performance engines seem to like the orange spring or one close to it. To check it requires a helper. I AM NOT RESPONSIBLE FOR YOU RUNNING OVER YOURSELF-WITH OR WITHOUT HELP!! Here is a way to check it and get close without 246 trips around the block. Unscrew the metering rod covers just enough to turn the covers-turn them to expose about half of the little piston and retighten the screws enough to keep the lids from rattling around.-GENTLY-or you will bend the covers. Start the car -see the little pistons go down? Now have your helper put it in gear (brakes on) - do they stay down? If not, you need lighter springs until they do. To change them, unscrew the plates and remove the pistons and rods-the spring is under the pistons-a magnet or small screwdriver will get them out. Put the next lightest spring in and try again until they stay down. Now comes the fun (dangerous) part-repeat the test only this time have your helper gun the car hard enough to hit the stall speed and let off quickly- make sure your hood doesn't slam you in the head- watch the piston as he lets off- it should jump up and return down...if it doesn't go a little heavier on the spring- if you are out of options, stretch the ones in there just a little bit. Now return to the tuning part above.

Accelerator pump- Usually shipped in the middle hole... usually works just fine right there. If the car goes a little, bogs and goes again, move the rod out one hole and try again...if it bogs and then goes move it in one hole... this is all done after the previous tuning and assumes your timing is correct.

What to do if it's too rich /lean- If drag testing shows it to be good everywhere but at idle, go to one size bigger rod on the big step- The numbers are generally 7147 or something similar. The first 2 numbers are idle and the last two are power step.( 7147 = 71 idle ,47 power) In the case of just needing idle adjustment go to say a 7347 . You can also use these to tune minor all around deficiencies. EG- 7147 start rod- 7355 to go leaner everywhere. You may have noticed you go up to lean, down to richen-this is because the rod is a restriction. While on this note, going up or down 2 numbers on the rods is not the same as 2 numbers on the jets. You must figure cross sectional area to find the percent of change you made. Unscrew the accelerator arm and set aside ( by the way, when you re-assemble the little link should look like an S, not a Z from the front), unhook the choke linkage and remove the metering rods /springs. Take the lid screws out and remove the top. The primary jets are in the floor of the carb below the metering rod holes and the secondaries are on the floor under the slosh plates behind the floats- the slosh plates lift straight out- sometimes they are tight and need to be pulled out with pliers. Go one size up or down all around, and repeat the above tuning. ALSO- the jets are always bigger in the front on these carbs because of the metering rod restriction- NEVER EVER EVER will the backs be bigger. The backs are typically 3-5 numbers smaller -EG 113 pri / 110 sec ....