Tuning help/suggestions

[Rubes]

Thanx Matt, thats
So would the basic procedure be something like;
Idle mixture (primary side only)
Accellerator pump (primary and secondary, since I have mechanical secondaries)
Jets (I have the Holley adjust-a-jet setup on the primary side only)

I know there would be some overlap, so I may need to go back and forth a few times right?

my idlle screws are just barley out (cant remember the exact, but less than 1/2 a turn. the power valve is 6.5 and my idle vacc is ~11. and yet it seems way to rich at idle. I'm thinking of getting the Innovate A/F meter to help with tuning. Since I got many cars, it would be very useful I think.

Kman, dont mean to highjack the thread, can we share??



Rubes

[kman67rsss]

ok thanks matt. just curious, plus i find that knowing a reasoning behind doing something helps me remember for the next time.

Rubes, feel free to step in. I am glad this is benefitting someone other then myself.

[Matt@RFR]

i find that knowing a reasoning behind doing something helps me remember for the next time.

I'm exactly the same way.

Rubes, this is what I do when I get my hands on a new carburetor:

- With carburetors of unkown history, check the throttle shafts for excessive play, check the base plate (and the manifold) for flatness, and check that all the screws are tight.

- Pull the bowls off and do a general visual check, and note power valve ratings and jet sizes. Also make sure that both needle & seats move freely. (Ok, the seats won't move, but you know what I'm saying, damnit!)

- Flip it upside down and set the curb idle screws to where there's .040" of the idle transfer slot showing on the primary side. Adjust the secondary curb idle so the butterflies just start to move, and then back them off to closed, but no further. Note each screws' position. Wire the throttle to WOT and check the accelerator pump linkage-to-accelerateor pump actuator clearence. (That terminology isn't right, sorry). I think it should be around .010", but in reality any clearance is ok, allowing for thermal expansion. Set the idle mixture screws to 1 1/2 turns out from closed.

- Put it back together. Take a permanent pen and write all the numbers you noted on the carburetor somewhere that it will make sense to you later. Also, write down squirter sizes, high speed and idle air bleed sizes.

- Put it on the motor anc start it. Timing will be the first thing you need to verify. After the motor is up to temp, shut it off. Wait 30 minutes and start it again to let everything heat soak. If the motor won't idle on it's own at this point, don't change anything!!! Have someone keep a steady idle going. Set the float levels. Check idle vacuum and compare that to what power valves you have in it. Change as necessary. Mess with the idle mixture screws until it wants to idle. On a good carburetor (read that as a Demon or a professionally prepared Holley), you want to adjust the idle mixture screws 1/8 turn at a time, moving all four equally. You can use the manifold vacuum as a helper when adjusting the idle mixture screws: The best quality idle will have the most vacuum.

- At this point, your goal is to move the curb idle screws the least amount possible. If the thing is nowhere near idling at this point, you need different sized idle air bleeds. You should be able to get a perfect idle without ever touching the curb idle screws, but by balancing idle air bleeds and idle mixture screws. The mixture screws control the amount of fuel going into the airstream, and the idle air bleeds control the amount of air. When everything is just right, you'll still have between .030" - .050" of the idle transfer slot showing (not that you can see it), and the idle mixture screws will be between one to two turns out from closed.

- After all that is when you get to see if you need to mess with squirter sizes and pump cams. That's simple...you mash the throttle and change stuff until it scares you.

OR, you can pay $800-$1,000 for a professional built carburetor that you bolt on and go. I've never seen any pro built carburetor that was more than 4 jet sizes too fat (they never ship them lean), two sizes on the high speed air bleeds, and maybe 1/16" turn on the curb idle.

[Rubes]

Thanx for the time Matt. All makes sense. This was an out of the box Holley.

Rubes

[kman67rsss]

matt, i tried the new power valve, but havent really been able to test it because i gernaded a rear universal and broke the yolk on the rear diff. The cars at the tranny/driveline place as im too busy to fix it. hopefully it will be ready for this weekend or beginning of next week. i will be back in touch though. again i appreciate your time and help.
karl

[Matt@RFR]

Atleast it's making power! lol

[kman67rsss]

a little update. im going to a 50cc accelerator pump. talked to a few racers at the track on wednesday. i was running a 14.2 best at 105. but i had to pump the throttle to keep it going. they said the way it sounded on the track and what i was telling them made them think lack of fuel. picking it up tomorrow. i also ran a few 15.oxx at 104.xx. im leaving the line at an idel then rolling into it. i also rechecked the timing and it was around 42 total. i backed it down to around 32-34 total. seems to start and run a little better now.

[kman67rsss]

ok i installed the 50cc pump, and drove it a little. not too bad. changed the carb cam and it got a little better. installed 74 jets in the primary and it feels a little better yet. gonna play around with the cams some more though.