Carb issue?

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Christopher Vastine said:
I have drained and flipped the carb over and adjusted to a square on the idle transfer slot. With the idle screw that way i cannot add enough timing to get it to idle, but will try again tomorrow
Click to expand...
You need a lil more than square or you will have a tip-in sag or hesitation, as the carb transitions from idle, to low-speed pulling; or even just from neutral to in gear.

When you set the transfer slots like this, and you must, then it will be rich. That is why you bring in the bypass air, to lean it out,back to normal. Then you set the idlespeed with timing; whatever it takes, or doesn't,lol. That will get youa baseline. If your engine is sluggish with the lack of timing ,you have two choices, well ok three choices;
1) fix the IABs so you can run less bypass, so you can run more timing, or
2) get a higher stall TC, or
3) more TM (TorqueMultiplication), aka gears.
BTW,
2500 is not likely gonna be enough stall at 6000 ft
The 3.73s might work

BTW,
With the numbers provided, your Scr maths to 12.2. That sounds pretty good. But remember that your Dcr starts from when the intake actually closes, so at 81* that comes to 8.4Dcr@6000ft. With alloy heads that is a good number. But the cranking cylinder pressure is only predicted to be 142psi, so you know, that cam is killing your idle-pressure. But I'm sure you built it like that for a reason.
However, at 6000 ft, the EFFECTIVE compression ratio at idle will be extremely low, and you may have to settle on a slightly higher than usual idlespeed..
 
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AJ/FormS said:
You need a lil more than square or you will have a tip-in sag or hesitation, as the carb transitions from idle, to low-speed pulling; or even just from neutral to in gear.
Click to expand...

So after adjusting the transfer slot to the square and trying to adjust timing to get up to idle i counted the number of half turns i made on the idle speed screw to get it to idle. Then tried adjusting timing more and backing off the idle screw to get it back to starting postion, but cant. I am about a turn past the top of the transfer slot.
 
didn’t mean it to be smart, just trying to reiterate.
 
Christopher Vastine said:
I will get you a better number but think i went all thw way to 26 degrees.
Click to expand...
Whoa!,
If in fact, the entire length of the transfer slot is exposed under the throttles, at 26* advance, then I have three questions;
1) Are you sure your balancer is indexed correctly to TDC, and
2) are you sure the cam is degree'd correctly?
3) lol, are you sure your timing light is working correctly?
I am assuming you know what the transfer slots look like.
Cuz if this is all correct, then your engine is asking for a heckuvalot of air. And IMO you might need a hi-altitude calibrated carb to start with.
 
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AJ/FormS said:
Whoa!,
If in fact, the entire length of the transfer slot is exposed under the throttles, at 26* advance, then I have three questions;
1) Are you sure your balancer is indexed correctly to TDC, and
2) are you sure the cam is degree'd correctly?
3) lol, are you sure your timing light is working correctly?
I am assuming you know what the transfer slots look like.
Cuz if this is all correct, then your engine is asking for a heckuvalot of air.
Click to expand...

- Yes balancer is indexed correctly
- Cam was installed per manufacturer specs
- I have two timing lights so i can double check
- yes i know what the transfer slot is and have adjusted many edelbrocks.

I will run back through the process tomorrow double check with both timing lights.
 
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But if you did your due-diligence correctly then I have this idea.
Btw I also have a 4.04bore, zero-deck, alloy headed, torque-monster, but stock stroke,lol.
Ok so what (*1) I did was to Tee into the PCV circuit with a short hose and a capped end. Then I drilled the cap bigger and bigger, closing the throttle as I went and retarding the timing, until I got what I thought was a nice idling,nice driving, no tip-in sag, combo. I got the transfer slots to dial in, and the idle timing to 14*, with the mixture screws in the center of their range. So I drove it like that for a while, to be sure. Then I measured the hole, calculated the area, divided it in half, and drilled each throttle to the closest next smaller size. Badaboom!
(*1)
cam was 292/292/108 advertised in at 11.3Scr, with a 750DP at 930 ft elevation. This is the biggest cam I have tuned, and all were at this same altitude, in my garage,lol. IIRC this was rated 248*@.050
 
AJ/FormS said:
But if you did your due-diligence correctly then I have this idea.
Btw I also have a 4.04bore, zero-deck, alloy headed, torque-monster, but stock stroke,lol.
Ok so what (*1) I did was to Tee into the PCV circuit with a short hose and a capped end. Then I drilled the cap bigger and bigger, closing the throttle as I went and retarding the timing, until I got what I thought was a nice idling,nice driving, no tip-in sag, combo. I got the transfer slots to dial in, and the idle timing to 14*, with the mixture screws in the center of their range. So I drove it like that for a while, to be sure. Then I measured the hole, calculated the area, divided it in half, and drilled each throttle to the closest next smaller size. Badaboom!
(*1)
cam was 292/292/108 advertised in at 11.3Scr, with a 750DP at 930 ft elevation. This is the biggest cam I have tuned, and all were at this same altitude, in my garage,lol. IIRC this was rated 248*@.050
Click to expand...

No MSD ignition just stock setup with everything new and old parts as backup. This is the largest cam i have installed on a mopar. I have a snap on dial back and a cheap timing light. I have done a lot of troubleshooting on it. Was thinking maybe intake was leaking internal , so pulled intake to check everything to include cam lobes following cam break in. Triple checked lifter preload and many other things. Runs great with blue springs under metering rods.

I am at 6900 ft above sea level.
 
AJ/FormS said:
You need a lil more than square or you will have a tip-in sag or hesitation, as the carb transitions from idle, to low-speed pulling; or even just from neutral to in gear.

When you set the transfer slots like this, and you must, then it will be rich. That is why you bring in the bypass air, to lean it out,back to normal. Then you set the idlespeed with timing; whatever it takes, or doesn't,lol. That will get youa baseline. If your engine is sluggish with the lack of timing ,you have two choices, well ok three choices;
1) fix the IABs so you can run less bypass, so you can run more timing, or
2) get a higher stall TC, or
3) more TM (TorqueMultiplication), aka gears.
BTW,
2500 is not likely gonna be enough stall at 6000 ft
The 3.73s might work

BTW,
With the numbers provided, your Scr maths to 12.2. That sounds pretty good. But remember that your Dcr starts from when the intake actually closes, so at 81* that comes to 8.4Dcr@6000ft. With alloy heads that is a good number. But the cranking cylinder pressure is only predicted to be 142psi, so you know, that cam is killing your idle-pressure. But I'm sure you built it like that for a reason.
However, at 6000 ft, the EFFECTIVE compression ratio at idle will be extremely low, and you may have to settle on a slightly higher than usual idlespeed..
Click to expand...

With the numbers provided, your Scr maths to 12.2. That sounds pretty good. But remember that your Dcr starts from when the intake actually closes, so at 81* that comes to 8.4Dcr@6000ft. With alloy heads that is a good number. But the cranking cylinder pressure is only predicted to be 142psi, so you know, that cam is killing your idle-pressure. But I'm sure you built it like that for a reason.

Is there a better grind cam that you would suggest that would work with current setup?
 
6900! holeeeee.

Christopher Vastine said:
Is there a better grind cam that you would suggest that would work with current setup?
Click to expand...

I'd like to but, that is beyond my comfort zone.
What are you trying to achieve.
I can only tell you what the Wallace Calculator predicts.

Here is the Ica (Intake Closing Angle) number for decent pressure
Static compression ratio of 12.2:1.
Ica of 60* @6900ft
Effective stroke is 3.25 inches.
Your dynamic compression ratio is 10.10:1 .
Your dynamic cranking pressure is 182.97 PSI.
V/P (Volume to Pressure Index) is 183

But notice the ridiculously high V/P of 183
This would make a low-rpm tire-shredder, but at only 60* Ica, the top-end power is gonna be severely limited. Awesome tow-truck engine.

Here it is with a more typical Ica of 68*
Ica of 68* @6900
Static compression ratio of 12.2:1.
Effective stroke is 3.04 inches.
Your dynamic compression ratio is 9.51:1 .
Your dynamic cranking pressure is 167.03 PSI.
V/P (Volume to Pressure Index) is 156
Now the pressure is coming up nicely, and the V/P is about what I run which makes an excellent streeter

Here is about the latest Ica I would run in that hi-altitude engine
Static compression ratio of 12.2:1.
Ica of 72* @6900
Effective stroke is 2.92 inches.
Your dynamic compression ratio is 9.18:1 .
Your dynamic cranking pressure is 158.21 PSI.
V/P (Volume to Pressure Index) is 142
this pressure is not bad,and
The V/P is now a typical 360 cube number closer to sealevel, still strong but nothing to brag about.

Here is what your current combo might look like
Static compression ratio of 12.2:1.
Ica of 82* @6900
Effective stroke is 2.61 inches.
Your dynamic compression ratio is 8.31:1 .
Your dynamic cranking pressure is 135.34 PSI.
V/P (Volume to Pressure Index) is 109
Those numbers look like a smog-era 318, at ~800ft

Read about V/P here;
V/P Index Calculation

What it means;
If you want hi-rpm power, go for an Ica of 72*
If you want a Mac-Truck, go for Ica of 60*
If you want a bit of both, go for Ica of 68*

If you want ALL OF IT, switch to a Solid lifter cam of ~72 to maybe 76*, after lashing. This will pick up the bottom end with the shorter ramps.

How to get it;
Aye that's the 64 dollar question.

But hey, you paid a lotta money and spent a lotta time on getting the Eddy cam in there, and I wouldn't be in a hurry to give it the heave-ho. As far as I can tell, it will be a decent driver if you give her what she wants. And once she gets up on the cam it should be a real hard charger.
 
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Christopher Vastine said:
- Yes balancer is indexed correctly
- Cam was installed per manufacturer specs
- I have two timing lights so i can double check
- yes i know what the transfer slot is and have adjusted many edelbrocks.

I will run back through the process tomorrow double check with both timing lights.
Click to expand...


What are the manufacturers specs?
 
Dana said:
Guess I was just typing to see myself type.
Click to expand...

You do not need to drill the butterflies a pcv valve can be used instead.

I would also aim for a min 185 cylinder pressure as that much duration bleeds off a lot of pressure.
 
Why go spend money on a different pcv. There is no crime drilling throttle blades. If you later use the carb on something different, just replace the blades or epoxy them shut.
 
AJ/FormS said:
6900! holeeeee.



I'd like to but, that is beyond my comfort zone.
What are you trying to achieve.
I can only tell you what the Wallace Calculator predicts.

Here is the Ica (Intake Closing Angle) number for decent pressure
Static compression ratio of 12.2:1.
Ica of 60* @6900ft
Effective stroke is 3.25 inches.
Your dynamic compression ratio is 10.10:1 .
Your dynamic cranking pressure is 182.97 PSI.
V/P (Volume to Pressure Index) is 183

But notice the ridiculously high V/P of 183
This would make a low-rpm tire-shredder, but at only 60* Ica, the top-end power is gonna be severely limited. Awesome tow-truck engine.

Here it is with a more typical Ica of 68*
Ica of 68* @6900
Static compression ratio of 12.2:1.
Effective stroke is 3.04 inches.
Your dynamic compression ratio is 9.51:1 .
Your dynamic cranking pressure is 167.03 PSI.
V/P (Volume to Pressure Index) is 156
Now the pressure is coming up nicely, and the V/P is about what I run which makes an excellent streeter

Here is about the latest Ica I would run in that hi-altitude engine
Static compression ratio of 12.2:1.
Ica of 72* @6900
Effective stroke is 2.92 inches.
Your dynamic compression ratio is 9.18:1 .
Your dynamic cranking pressure is 158.21 PSI.
V/P (Volume to Pressure Index) is 142
this pressure is not bad,and
The V/P is now a typical 360 cube number closer to sealevel, still strong but nothing to brag about.

Here is what your current combo might look like
Static compression ratio of 12.2:1.
Ica of 82* @6900
Effective stroke is 2.61 inches.
Your dynamic compression ratio is 8.31:1 .
Your dynamic cranking pressure is 135.34 PSI.
V/P (Volume to Pressure Index) is 109
Those numbers look like a smog-era 318, at ~800ft

Read about V/P here;
V/P Index Calculation

What it means;
If you want hi-rpm power, go for an Ica of 72*
If you want a Mac-Truck, go for Ica of 60*
If you want a bit of both, go for Ica of 68*

If you want ALL OF IT, switch to a Solid lifter cam of ~72 to maybe 76*, after lashing. This will pick up the bottom end with the shorter ramps.

How to get it;
Aye that's the 64 dollar question.

But hey, you paid a lotta money and spent a lotta time on getting the Eddy cam in there, and I wouldn't be in a hurry to give it the heave-ho. As far as I can tell, it will be a decent driver if you give her what she wants. And once she gets up on the cam it should be a real hard charger.
Click to expand...

I reread the posts and your calculations are based on a flat top piston. I only mentioned kieth black pistons, but not which ones(23cc). I read the 12-1 compression ratio again and thought no way could I be that far off. Punching in the numbers on the wallace calculator with the cam i get the below information. Now i may have done something wrong but i think this is more accurate. A 12-1 cr will not run at this altitude on pump gas and i was building a 10-1 cr motor.

Static compression ratio of 10.1 :1.
Effective stroke is 3.60 inches.
Your dynamic compression ratio is 9.19:1 .
Your dynamic cranking pressure is 158.48 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 7.81 :1.
V/P (Volume to Pressure Index) is 176
 
Here’s one lesson I’ve learned in 30 years of dyno testing.......

You know how to tell when the carb you have is a good match for the rest of your combo?

When you can bolt it on, make a few slight adjustments with the turn of a few screws...... and it just works.

If there are no issues with the motor itself....... the right carb “works”...... and the wrong one doesn’t.

I have seen that scenario play out countless times.
 
PRH said:
Here’s one lesson I’ve learned in 30 years of dyno testing.......

You know how to tell when the carb you have is a good match for the rest of your combo?

When you can bolt it on, make a few slight adjustments with the turn of a few screws...... and it just works.

If there are no issues with the motor itself....... the right carb “works”...... and the wrong one doesn’t.

I have seen that scenario play out countless times.
Click to expand...


^^^^^THIS^^^^^^^ If you are going with a carb that isn’t actually set up for your combo you’d better make sure the carb is as tunable as it can be and that the tuner understands (as best as this kind of thing can be understood) what to tune.
 
This isn’t meant as any kind of “dig” at anyone....... more of an observation from being in this business for a long time.

“Most” people aren’t really very good at tuning, or even more so.....modifying..... carbs.
When the carb in question seems to be as mismatched for the engine combo as the OP’s does........ most people are going to be lost in terms of what kinds of mods would be required to actually correct it so it was close to 100% good.
Sometimes this is necessary....... like in NHRA stock and SS, where most cars are required to run the correct oe carb.
And those don’t offer any kind of low speed drivability with the big cams that are used in those classes.
So, the circuits are modified and recalibrated out of necessity.

The people that really understand how the carbs function...... don’t need to go on line and ask how to tune/modify the carb.
They understand how it works, and just dive right in.

So, when you have one that still doesn’t even come close to providing satisfactory drivability after you’ve messed with all the things you currently know how to do....... then it’s very likely some “modifications” are going to be required(not “adjustments”).

As with about 99% of the advice gleaned from the Internet...... there will be several schools of thought on exactly what modifications need to be done.
How does the person who falls into the ranks of people who don’t “know” how to go about it already, determine which advice they should follow?
And, do they really “understand” why they’re doing the suggested mods?

Of course, in the OP’s case....... he doesn’t have a combo where it’s “required” that he use this carb that appears to be a poor match for the application....... and could just install a more appropriate part that didn’t need modifications performed for it to run properly.

Or...... decide that he wants to learn to be someone who in the future doesn’t need to come on line for carb advise.

I don’t see it being feasible to actually “learn” how to modify carbs by perusing forums on line.
Get some carb books, read them until what they’re talking about really clicks....... then, getting on some of the carb forums will help guide the direction you need to go, and the suggested mods will be “understood”.
There’s a lot of trial and error when you’re working through a new combo.
Ultimately....... there is no substitute for getting your hands dirty and seeing if the mods do what you’re hoping for.
 
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