New Motor High idle

[F-BIRD'88]

The mix screws are only out 1/4 turn because these are not 2x4 tunnel ram carbs. The idle circuits are set up for single 4 bbl use. Now you got 2 carbs , double the fuel flow at idle in the idle circuit.

[PRH]

If there is no restriction to those huge discharge ports, then I think there is a bunch of unregulated idle mix being fed into the motor, which is why the primary screws have to be set at no more than 1/4 turn.

That secondary idle circuit needs to be analyzed before going any further imo(especially after seeing this posted below)

Everything is custom on them, including aftermarket base plates

[RD_Racing]

Post the carb model number etc.
What is "custom" about them?
What got changed?

Everything is custom on them, including aftermarket base plates, modified to accept 4 jets (even though it only has one metering block).. They are 600's but suppose to flow 660.. I purchased them from a guy that is friends with the owner of Quickfuel and branched off on his own and sells modified custom Quickfuel carbs. I know a few people that have the exact same carbs on their tunnel rams and they all claim they run better than anything else they have used.. Mine do too except it just doesn't seem right below 1400rpm.. But then again, as mentioned above I have tried other carbs and the results are the exact same so I moved on from the carbs being the culprit.

[RD_Racing]

Here is a video of it ideling at about 1450.. Hope the link works

https://www.youtube.com/watch?v=BjEpIZZ ... e=youtu.be

[F-BIRD'88]

Try the extra spark timing.. Give it all the idle timing it wants 60 deg what ever.. Just to see Better?
Now reverse the diz pick up polarity.
Timing has changed? Or same?
Is the engine GROUNDED to the car body?
Run a ground wire from valve cover bolt to firewall.
Would not be the first time....
What is the pri and sec throttle T slot exposure on both carbs? Too far open? Too far closed?

Possible metering block fuel circuit blockage..
Wrong gaskets... Junk in metering block...

Got any 2 eddy carbs to try on it?
They do not even need to match...just try em..

Better...?

[PRH]

you should see if the boosters are dribbling before going much farther.

[RD_Racing]

you should see if the boosters are dribbling before going much farther.

I will check that too.. Thanks

[F-BIRD'88]

Tachometer set wrong.. Cylinder # choice set on 6 cyl instead of 8 cyl. Reading higher rpm.

[RD_Racing]

Try the extra spark timing.. Give it all the idle timing it wants 60 deg what ever.. Just to see Better?
Now reverse the diz pick up polarity.
Timing has changed? Or same?
Is the engine GROUNDED to the car body?
Run a ground wire from valve cover bolt to firewall.
Would not be the first time....
What is the pri and sec throttle T slot exposure on both carbs? Too far open? Too far closed?

Possible metering block fuel circuit blockage..
Wrong gaskets... Junk in metering block...

Got any 2 eddy carbs to try on it?
They do not even need to match...just try em..

Better...?

I will add more timing and see how it responds.. I already did check the polarity on the dizzy earlier this spring, that was one of my first thoughts. Engine is grounded with a strap to the frame and im running a motor plate in the front.. T-slots are not more than square.

Here is another video of a sbc 421 with the exact same carbs and idles perfect at 1000rpm and has great throttle reponse.. Mine has great throttle reponse too.

https://www.youtube.com/watch?v=GKQVGGJ ... e=youtu.be

[F-BIRD'88]

While it is idleing. Put a finger over each of the 2 carb air cleaner stud holes.... Vacuum?

[F-BIRD'88]

What is that vacuum line on the plenum?
PCV? Or ?
What else is connected to the carbs or plenum.
Be sure there is no vacuum leaks at the 2 air cleaner stud
Holes... Even if there is a stud in the hole.
Take the stud out...
Check for leak. With a finger...
Check tach rpm with external mechanics tach
Hand held Digital lazer mechanics tool are cool.
Will read any white paint stripe off the spining balancer.

[F-BIRD'88]

I "second" the call on the secondary side idle circuits..
Wrong throttle base (lack of ifle fuel transfer track or blocked (wrong gasket, build error)...
On a 2 corner idle carb. There is 2 channels in the throttle base that bring fuel from primary idle screw to secondary idle.. This combines with the fixed sec idle fuel oriffice in the sec metering plate. Idle fuel discharges from all 4 idle circuits of each carb at idle..
No telling how it has been "customized".

[RD_Racing]

What is that vacuum line on the plenum?
PCV? Or ?
What else is connected to the carbs or plenum.
Be sure there is no vacuum leaks at the 2 air cleaner stud
Holes... Even if there is a stud in the hole.
Take the stud out...
Check for leak. With a finger...
Check tach rpm with external mechanics tach
Hand held Digital lazer mechanics tool are cool.
Will read any white paint stripe off the spining balancer.

I just had it running again and checked a few things..
The air cleaner stud holes are blind holes so they cant such vacuum
Zero on the balancer was done with an indicator on the piston so I know its right
Vacuum at 1400rpm is at 8hg (I said 9hg earlier but I was wrong)
I used carb cleaner again and found no vacuum leaks
The only vacuum port is on the intake and it goes to the trans so I pulled that off and plugged it and it had no effect. However the idle speed increased before I could plug it..

I don't think its related to the carbs, like I said earlier I had 2 totally different carbs on there before and had the exact same results..

I had the idle set a 1400rpm and did a burnout and after I left off the gas it stalled.. If I had a looser convertor and left it at 1400rpm it would probably be perfect..

[RD_Racing]

What is that vacuum line on the plenum?
PCV? Or ?
What else is connected to the carbs or plenum.
Be sure there is no vacuum leaks at the 2 air cleaner stud
Holes... Even if there is a stud in the hole.
Take the stud out...
Check for leak. With a finger...
Check tach rpm with external mechanics tach
Hand held Digital lazer mechanics tool are cool.
Will read any white paint stripe off the spining balancer.

I just had it running again and checked a few things..
The air cleaner stud holes are blind holes so they cant such vacuum
Zero on the balancer was done with an indicator on the piston so I know its right
Vacuum at 1400rpm is at 8hg (I said 9hg earlier but I was wrong)
I used carb cleaner again and found no vacuum leaks
The only vacuum port is on the intake and it goes to the trans so I pulled that off and plugged it and it had no effect. However the idle speed increased before I could plug it..
I pulled every plug and they look the same and actually don't look to bad now
I increased the timing to 42, which smoothed out the idle a little but still wont idle well below 1200

I don't think its related to the carbs, like I said earlier I had 2 totally different carbs on there before and had the exact same results..

I had the idle set a 1400rpm and did a burnout and after I left off the gas it stalled.. If I had a looser convertor and left it at 1400rpm it would probably be perfect..

[RD_Racing]

What is that vacuum line on the plenum?
PCV? Or ?
What else is connected to the carbs or plenum.
Be sure there is no vacuum leaks at the 2 air cleaner stud
Holes... Even if there is a stud in the hole.
Take the stud out...
Check for leak. With a finger...
Check tach rpm with external mechanics tach
Hand held Digital lazer mechanics tool are cool.
Will read any white paint stripe off the spining balancer.

I just had it running again and checked a few things..
The air cleaner stud holes are blind holes so they cant such vacuum
Zero on the balancer was done with an indicator on the piston so I know its right
Vacuum at 1400rpm is at 8hg (I said 9hg earlier but I was wrong)
I used carb cleaner again and found no vacuum leaks
The only vacuum port is on the intake and it goes to the trans so I pulled that off and plugged it and it had no effect. However the idle speed increased before I could plug it..
I pulled every plug and they look the same and actually don't look to bad now (a little gray ish)
I increased the timing to 42, which smoothed out the idle a little but still wont idle well below 1200

I don't think its related to the carbs, like I said earlier I had 2 totally different carbs on there before and had the exact same results.. The other carbs I had on here ran perfect on my previous motor too..

I had the idle set a 1400rpm and did a burnout and after I left off the gas it stalled.. If I had a looser convertor and left it at 1400rpm it would probably be perfect..