how do you tune a carb?

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10-20-2009, 11:26 AM
zero_proto

how do you tune a carb?

I have a 63 nova vert i drive around right now. But it is now running like crap, i hardly drive the car around, so i know that attributes to it. But how would i go about tuning it, what would i need, over all to tune the car?
It has a 307, power pak heads, headers, and an isky 164 cam (similar to the fuel injected 327 cam).

Any help would be appreciated.:coffee:
10-20-2009, 11:47 AM
02Sweet

Quote:

Originally Posted by zero_proto

I have a 63 nova vert i drive around right now. But it is now running like crap, i hardly drive the car around, so i know that attributes to it. But how would i go about tuning it, what would i need, over all to tune the car?
It has a 307, power pak heads, headers, and an isky 164 cam (similar to the fuel injected 327 cam).

Any help would be appreciated.:coffee:

http://lmgtfy.com/?q=how+to+tune+a+carb

You need to be a little more descriptive in what you mean by running like crap. Also what carb is on the car now?
Will the car idle?
It also could be timing and not the carb?
10-20-2009, 01:40 PM
zero_proto

Quote:

Originally Posted by 02Sweet

http://lmgtfy.com/?q=how+to+tune+a+carb

You need to be a little more descriptive in what you mean by running like crap. Also what carb is on the car now?
Will the car idle?
It also could be timing and not the carb?

sorry, i am not sure of the carb, but i know the timing is off, i guess an overall tune. I would probably need to get a timing gun, does autozone have rentals on it. The car is running extremely rich, it idles fine after you get the juices rolling, it does have a pretty lumpy cam.

The car is running super rich, and the other gave me a few sputters.
10-20-2009, 01:44 PM
Smittro

Depending on the carb. If it's a quadrajunk, usually I turn the mixture screws in till she starts to stumble back them off till it quits and then back them out 1/2 turn further. Then thumb the throttle quickly and adjust till she snaps when I thumb it open and closed quickly.. Just be carefull not to bottom out the screws tightly, this can ruin the needles and their seats..
10-20-2009, 01:49 PM
zero_proto

when i get home today i will look at the carb to see what kind it is, then i will post up.
10-20-2009, 01:52 PM
Smittro

Also get yourself a timing light and see what she's set @ as far as timing. By power pac do you mean 1.94's or 2.02's? You may have to look up what your cam likes as far as timing is concerned..
10-20-2009, 01:56 PM
Smittro

Oh and a little heads up on old chevy's they will run 180* out. It will run badly but it will run. This has been the cause of many a head scratches for some guys..
10-20-2009, 02:06 PM
bigrondownhiller

Could also need a rebuild. How old is the carb and what kind is it? If you are not sure a pic will let someone identify it.
10-20-2009, 03:40 PM
zero_proto

okay it is a 1405 maual choke edelbrock. It is a weber casting.
I am looking for the casting number on the heads but i can't find them, and so far my searching has not helped.

Underneath the carb is an edelbrock performer rpm intake manifold. i found specs on the cam awhile back but no luck right now, it is a isky 164 grind number i think
10-20-2009, 03:42 PM
zero_proto

i will also be looking at going by kragens and getting a light gun to check out the timing, i wonder if they have an A/F meter also that i could use, hmmmmm
10-20-2009, 07:26 PM
02Sweet

Quote:

Originally Posted by zero_proto

okay it is a 1405 maual choke edelbrock. It is a weber casting.
I am looking for the casting number on the heads but i can't find them, and so far my searching has not helped.

Underneath the carb is an edelbrock performer rpm intake manifold. i found specs on the cam awhile back but no luck right now, it is a isky 164 grind number i think

for the carb here is the link from edelbrock's website
http://www.edelbrock.com/automotive_.../1000/1402.pdf
it shows where the adjustment screws are for you.

Found this for you too. This just states what Smitro said
http://neptune.spacebears.com/cars/stories/carb.html

LOL its even with the same carb as you!
10-21-2009, 12:21 PM
bamaz28

ah a 600 cfm too
10-21-2009, 03:48 PM
zero_proto

this saturday i will tune it and see how it goes. I will post up what happens =).
10-21-2009, 04:04 PM
02Sweet

Quote:

Originally Posted by zero_proto

this saturday i will tune it and see how it goes. I will post up what happens =).

Any luck with the cam card, or specs?
10-21-2009, 04:51 PM
zero_proto

Quote:

Originally Posted by 02Sweet

Any luck with the cam card, or specs?

no luck yet, but i will know by then.
10-22-2009, 11:04 AM
cycowrencher

You will need a timing light to tune that car correctly. You will also want to buy a vacuum gauge. You can buy a cheap dial back at your local parts place. Warm up the engine, drive around the block, or run an errand, just make sure the car is at operating temp. Disconnect and plug the vacuum advance to the distributor.

The only cam grind i can find from Isky is a 264. This is a .450 lift cam and should have 14-17 inches of vacuum in a 9.0:1 350 cid motor. If that is what is in your 307, you may have a hard time getting 12 inches of vac.

Set the initial timing at 12-14* before top dead center. Your idle speed should increase, unless your timing is too far advanced. Then turn down the idle screw until the car idles at 800 rpm. Turn the dial on your timing light to 35* and rev the engine to 3000 rpm, you should be able to see the 0* mark on the crank pulley. Adjust the dial until the 0* mark on the pulley is zeroed to the timing pointer. Read the dial, this is your total advance, this should be between 35-39*. Once this is set up, it is time to move on to setting up the carb.

Baseline the carb by turning in the bleed screws on the front of the carb all the way in until lightly seated. Now back them out 1.5 turns. Connect the vacuum gauge to a port that supplies manifold vacuum ( this will have a high reading at idle and will fall towards 0 when you rev the motor). Start up the car and read the gauge, you should have between 14-21 inches of vacuum at idle depending on your cam. If the car will not stay running, back out each bleed screw 1/2 turn until the car will idle (If you have to back them out more than 3 1/2-4 turns, your metering rods are too small and will need to read up on how to change them, or pay someone to do it for you). Pick one bleed screw and slowly turn it in until the engine starts to stumble. Then back it out until the vacuum reading peaks. Turn the screw out 1/2 additional turn. Repeat this for the other bleed screw. Readjust your idle to 800 rpm and you should be ready to roll. Disconnect your tools and plug the vacuum line back to the distributor.
10-22-2009, 11:15 AM
02Sweet

Quote:

Originally Posted by cycowrencher

You will need a timing light to tune that car correctly. You will also want to buy a vacuum gauge. You can buy a cheap dial back at your local parts place. Warm up the engine, drive around the block, or run an errand, just make sure the car is at operating temp. Disconnect and plug the vacuum advance to the distributor. The only cam grind i can find from Isky is a 264. This is a .450 lift cam and should have 14-17 inches of vacuum in a 9.0:1 350 cid motor.

Set the initial timing at 12-14* before top dead center. Your idle speed should increase, unless your timing is too far advanced. Then turn down the idle screw until the car idles at 800 rpm. Turn the dial on your timing light to 35* and rev the engine to 3000 rpm, you should be able to see the 0* mark on the crank pulley. Adjust the dial until the 0* mark on the pulley is zeroed to the timing pointer. Read the dial, this is your total advance, this should be between 35-39*. Once this is set up, it is time to move on to setting up the carb.

Baseline the carb by turning in the bleed screws on the front of the carb all the way in until lightly seated. Now back them out 1.5 turns. Connect the vacuum gauge to a port that supplies manifold vacuum ( this will have a high reading at idle and will fall towards 0 when you rev the motor). Start up the car and read the gauge, you should have between 14-21 inches of vacuum at idle depending on your cam. If the car will not stay running, back out each bleed screw 1/2 turn until the car will idle (If you have to back them out more than 3 1/2-4 turns, your metering rods are too small and will need to read up on how to change them, or pay someone to do it for you). Pick one bleed screw and slowly turn it in until the engine starts to stumble. Then back it out until the vacuum reading peaks. Turn the screw out 1/2 additional turn. Repeat this for the other bleed screw. Readjust your idle to 800 rpm and you should be ready to roll. Disconnect your tools and plug the vacuum line back to the distributor.

:yourock::yay:
10-22-2009, 11:19 AM
bamaz28

never used timing light
10-22-2009, 11:29 AM
02Sweet

Quote:

Originally Posted by bamaz28

never used timing light

[ame]http://www.youtube.com/watch?v=UYGU7mTwsZc[/ame]
10-22-2009, 11:36 AM
bamaz28

meaning i never use them, not that i dont know how.
10-22-2009, 11:48 AM
02Sweet

Quote:

Originally Posted by bamaz28

meaning i never use them, not that i dont know how.

OH my bad I take it you use the "street tune" method :lol:
10-22-2009, 12:31 PM
bamaz28

Quote:

Originally Posted by 02sweet

oh my bad i take it you use the "street tune" method :lol:

say what you want but we cranked out over 50-75 sbc no problems
10-22-2009, 04:25 PM
zero_proto

Quote:

Originally Posted by cycowrencher

You will need a timing light to tune that car correctly. You will also want to buy a vacuum gauge. You can buy a cheap dial back at your local parts place. Warm up the engine, drive around the block, or run an errand, just make sure the car is at operating temp. Disconnect and plug the vacuum advance to the distributor.

The only cam grind i can find from Isky is a 264. This is a .450 lift cam and should have 14-17 inches of vacuum in a 9.0:1 350 cid motor. If that is what is in your 307, you may have a hard time getting 12 inches of vac.

Set the initial timing at 12-14* before top dead center. Your idle speed should increase, unless your timing is too far advanced. Then turn down the idle screw until the car idles at 800 rpm. Turn the dial on your timing light to 35* and rev the engine to 3000 rpm, you should be able to see the 0* mark on the crank pulley. Adjust the dial until the 0* mark on the pulley is zeroed to the timing pointer. Read the dial, this is your total advance, this should be between 35-39*. Once this is set up, it is time to move on to setting up the carb.

Baseline the carb by turning in the bleed screws on the front of the carb all the way in until lightly seated. Now back them out 1.5 turns. Connect the vacuum gauge to a port that supplies manifold vacuum ( this will have a high reading at idle and will fall towards 0 when you rev the motor). Start up the car and read the gauge, you should have between 14-21 inches of vacuum at idle depending on your cam. If the car will not stay running, back out each bleed screw 1/2 turn until the car will idle (If you have to back them out more than 3 1/2-4 turns, your metering rods are too small and will need to read up on how to change them, or pay someone to do it for you). Pick one bleed screw and slowly turn it in until the engine starts to stumble. Then back it out until the vacuum reading peaks. Turn the screw out 1/2 additional turn. Repeat this for the other bleed screw. Readjust your idle to 800 rpm and you should be ready to roll. Disconnect your tools and plug the vacuum line back to the distributor.

thanks alot, good info. I will see if i find out the cam specs before i do anything
10-22-2009, 05:21 PM
02Sweet

Quote:

Originally Posted by bamaz28

say what you want but we cranked out over 50-75 sbc no problems

Im not putting down that method I have done it a few times to my older trucks, but a timing light has always yielded better results for me
10-23-2009, 07:28 AM
cycowrencher

You really do not need the cam specs to tune the car correctly. However, if the cam is too big for the motor it will run like ass no matter how you tune it. Do what I posted, and if it still runs badly, search for the cam specs to find out if it is too much for the motor. If you drive that car part time, you need those tools anyway,just to keep it running. It sounds like it ran fine before, so it most likely needs a tune up. Plugs, Wires, Cap, Rotor, and points if it still has them. You may just have corroded points causing the whole issue.

I put a Crane 276 with .450 lift in the 305 that used to be in my 81. It was my first cam swap over 12 years ago. The motor had nothing until 3500 rpm and would pull to 7000. I had a 4 speed at the time, so it was not too much of a dog down low. That motor was very short lived because of the cam. It would not idle below 950 rpm and at 950 it was still "lumpy".
10-23-2009, 07:39 AM
zero_proto

Quote:

Originally Posted by cycowrencher

You really do not need the cam specs to tune the car correctly. However, if the cam is too big for the motor it will run like ass no matter how you tune it. Do what I posted, and if it still runs badly, search for the cam specs to find out if it is too much for the motor. If you drive that car part time, you need those tools anyway,just to keep it running. It sounds like it ran fine before, so it most likely needs a tune up. Plugs, Wires, Cap, Rotor, and points if it still has them. You may just have corroded points causing the whole issue.

I put a Crane 276 with .450 lift in the 305 that used to be in my 81. It was my first cam swap over 12 years ago. The motor had nothing until 3500 rpm and would pull to 7000. I had a 4 speed at the time, so it was not too much of a dog down low. That motor was very short lived because of the cam. It would not idle below 950 rpm and at 950 it was still "lumpy".

will do
10-25-2009, 06:22 AM
louisianagulf

First thing you do is crank it cold and run it for about 10 - 15 seconds and shut off. Feel each cylinder tube for heat. Change out the plugs on the cooler or cold ones. Then go from there. You would be suprised how a cylinder or two down can affect the running of an eight cylinder