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post #61 of 141 (permalink) Old Sep 22nd, 16, 11:56 AM Thread Starter
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Re: Stumble on secondaries

So I know this is an old thread but finally after oil pressure issues and life issues I was able to get back on this.

Timing:
Base timing (no vac) is set at 12-14 degrees
All in timing (no vac) of 34-36 degrees at 3000 RPM
Vac advance of 8 degrees (Do I need more???) https://static.summitracing.com/glob...1_frm29643.pdf

Carb:
I went back to stock metering rods (still larger secondary jets)
I put in the pink step up spring

Car drives good primary performance is pretty good still a small stumble with the secondaries (not sure if I should do another spring or try rods). Also getting a little bit of backfire occasionally when going into the secondaries (not sure if it's the accelerator pump shot or the jets). I'm also getting a little bit of diesling when I shut the car off sometimes (I'm guessing idle mixture) When I first took the car out it wasn't warm and when I let off the clutch to accelerate the car sputtered died and possibly had a small backfire through the carb (not sure but there was a pop somewhere) I'm not sure if that's idle mixture or if it wasn't warm or something else only did it 1 time.

Thoughts?

1955 Ford Thunderbird
1969 Triumph TR6
1972 Chevelle - 396, 4 Speed
1992 Acura Integra
2002 Yamaha R1
2004 Dodge Ram 1500
2012 Dodge Durango Citadel

Last edited by Tegguy; Sep 22nd, 16 at 12:49 PM.
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post #62 of 141 (permalink) Old Oct 22nd, 16, 5:56 PM Thread Starter
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Re: Stumble on secondaries

So I've unfortunately given up on this. It seems like everything I do something else goes bad and doesn't fix problem #1. I've decided to take it to the only shop in the area that will work with Edelbrock carbs. I just have to wait for them to have room to get me in.

1955 Ford Thunderbird
1969 Triumph TR6
1972 Chevelle - 396, 4 Speed
1992 Acura Integra
2002 Yamaha R1
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post #63 of 141 (permalink) Old Oct 23rd, 16, 8:43 AM
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Re: Stumble on secondaries

This very thing happened to me just recently when I got my car back from the shop that pulled the engine to clean up the engine and restore the whole bay. After the engine was reinstalled - the same stumble and backfire occurred when stepping on it. The shop looked into the secondaries and that was not the problem. Evidently, the previous owner had the tank out and when it was reinstalled, he put a new rubber fuel line in from the tank that was too long. The fuel line was collapsing when the fuel pump called for more fuel. Trimmed the line back and all is well.

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post #64 of 141 (permalink) Old Oct 23rd, 16, 9:06 AM Thread Starter
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Re: Stumble on secondaries

Quote:
Originally Posted by George Halpin View Post
This very thing happened to me just recently when I got my car back from the shop that pulled the engine to clean up the engine and restore the whole bay. After the engine was reinstalled - the same stumble and backfire occurred when stepping on it. The shop looked into the secondaries and that was not the problem. Evidently, the previous owner had the tank out and when it was reinstalled, he put a new rubber fuel line in from the tank that was too long. The fuel line was collapsing when the fuel pump called for more fuel. Trimmed the line back and all is well.
thanks for the thought its confusing cause if i get in the throttle a little then back off then go full throttle it'll go like crazy no stumble. I suppose it could be a fuel line issue.

1955 Ford Thunderbird
1969 Triumph TR6
1972 Chevelle - 396, 4 Speed
1992 Acura Integra
2002 Yamaha R1
2004 Dodge Ram 1500
2012 Dodge Durango Citadel
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post #65 of 141 (permalink) Old Oct 24th, 16, 11:27 PM
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Re: Stumble on secondaries

Hi Dustin,

Sorry, I haven't been keeping up on this since my last post. So, pleas excuse if some of this has been covered.

If you have an adjustable fuel pressure regulator, set it to 5.5 PSI. Pull the carb top and verify float height and float drop. While the top is off, ensure not trash in the bowls. Pay attention to the secondary jets, since that's where the problem occurs. Check fuel lines as mentioned. Put a new fuel filter on it and ensure a tank of fresh fuel especially if you haven't driven it much.

Plugs, cap, rotor and wires are healthy (i.e. relatively new)? 12V wires to coil are clean and tight? No vac leaks in the carb gasket, intake gaskets or any hoses?

Yes, I suggest giving it a more base timing. Is it 12, or is it 14. If 12, give 14. if 14, give it 2 more and back off the mechanical by 2.

Do all carb tuning FULLY warmed up. This doesn't mean a jaunt around the block, drive it until up to engine temp.

Tuning an Eddy is a process of making step changes in the order the manual describes, one step at a time and looking for small changes. Most tuning will be with rods and jet combination. Eddy's book has a "power" direction and a "cruise" direction in about 4% increments on a graph. Make your changes according to the rod and jet combinations on the "power" axis on the graph. Play with rods/jets before you play with step up springs or the accelerator pump. Ease into the throttle rather than stomp on it. If you don't notice an improvement, keep going in the same direction. If you think it got getter, go one more step and see if it gets worse; if it does then back up. If you go four or five steps on the power axis, go back to the "power" baseline and change the "cruise" setting and then repeat with the next of combinations of the power setting. Generally, popping out the carb indicates lean and out the tail pipes means rich but it can get confusing.

The step up springs are calibrated out of the box for a vacuum setting. Thus, you can run a vac gauge into the car's cabin and know when you are getting into the power portion of the rod. Although you are worried about the secondary opening, the air door on the carb and engine demand should mostly take care of that for itself. Really, what you can tune for is the transition from the power step on the primary jets to the secondaries. I'll say again, spend most of your time looking for slight variations in drivability as you gradually get on and off the accelerator pedal.

Once you get the slight changes dialed in, then you can start to stomp on it and get into squirters and pump shots; or step up springs.

Zeke

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64 Chevelle
90 Corvette ZR1
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post #66 of 141 (permalink) Old Oct 25th, 16, 6:46 AM Thread Starter
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Re: Stumble on secondaries

Quote:
Originally Posted by zeke67 View Post
Hi Dustin,

Sorry, I haven't been keeping up on this since my last post. So, pleas excuse if some of this has been covered.

If you have an adjustable fuel pressure regulator, set it to 5.5 PSI. Pull the carb top and verify float height and float drop. While the top is off, ensure not trash in the bowls. Pay attention to the secondary jets, since that's where the problem occurs. Check fuel lines as mentioned. Put a new fuel filter on it and ensure a tank of fresh fuel especially if you haven't driven it much.
Last time I had the top of the carb off I took the time to clean everything out. I do not have an adjustable FPR. Tank has fresh fuel in it. I can try a new filter. What would I look for in the fuel lines?

Quote:
Plugs, cap, rotor and wires are healthy (i.e. relatively new)? 12V wires to coil are clean and tight? No vac leaks in the carb gasket, intake gaskets or any hoses?
Everything is new I put new plugs in it last time I pulled the motor. 12V wires are making a good connection. I can't hear any leaks but i haven't sprayed starting fluid or anything to check but there is no noise like a leak.

Quote:
Yes, I suggest giving it a more base timing. Is it 12, or is it 14. If 12, give 14. if 14, give it 2 more and back off the mechanical by 2.
I'll be honest I don't know if it's 12 or 14 it's hard to get a good angle on the timing plate but I believe it's closer to 12.

Quote:
Do all carb tuning FULLY warmed up. This doesn't mean a jaunt around the block, drive it until up to engine temp.
Last time I did this (before the previous post) I let the car idle until it reached about 185.

Quote:
Tuning an Eddy is a process of making step changes in the order the manual describes, one step at a time and looking for small changes. Most tuning will be with rods and jet combination. Eddy's book has a "power" direction and a "cruise" direction in about 4% increments on a graph. Make your changes according to the rod and jet combinations on the "power" axis on the graph. Play with rods/jets before you play with step up springs or the accelerator pump. Ease into the throttle rather than stomp on it. If you don't notice an improvement, keep going in the same direction. If you think it got getter, go one more step and see if it gets worse; if it does then back up. If you go four or five steps on the power axis, go back to the "power" baseline and change the "cruise" setting and then repeat with the next of combinations of the power setting. Generally, popping out the carb indicates lean and out the tail pipes means rich but it can get confusing.

Quote:
The step up springs are calibrated out of the box for a vacuum setting. Thus, you can run a vac gauge into the car's cabin and know when you are getting into the power portion of the rod. Although you are worried about the secondary opening, the air door on the carb and engine demand should mostly take care of that for itself. Really, what you can tune for is the transition from the power step on the primary jets to the secondaries. I'll say again, spend most of your time looking for slight variations in drivability as you gradually get on and off the accelerator pedal.
I measured the vacuum at idle and went to a step up spring 1/2 the vac value. I'll swap them back to the original springs and start from scratch and see if I can figure something out if I can find time.

Quote:
Once you get the slight changes dialed in, then you can start to stomp on it and get into squirters and pump shots; or step up springs.
Thanks for taking the time to respond I'm just getting frustrated with the whole thing between the oil pickup issue that made me pull the engine twice and this issue.

1955 Ford Thunderbird
1969 Triumph TR6
1972 Chevelle - 396, 4 Speed
1992 Acura Integra
2002 Yamaha R1
2004 Dodge Ram 1500
2012 Dodge Durango Citadel

Last edited by Tegguy; Oct 25th, 16 at 4:16 PM.
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post #67 of 141 (permalink) Old Oct 25th, 16, 2:59 PM
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Re: Stumble on secondaries

Quote:
Originally Posted by Tegguy View Post
Last time I had the top of the carb off I took the time to clean everything out. I do not have an adjustable FPR. Tank has fresh fuel in it. I can try a new filter. What would I look for in the fuel lines?


...I'm just getting frustrated with the whole thing between the oil pickup issue that made me pull the engine twice and this issue.

A few more questions... when was the last time you "cleaned" out the carb?

Do you run any fuel stabilizer? I have been hearing the newer fuels break-down much quicker, and perhaps the insides are getting gummed up with deposits? with the other issues, sounds the the carb may sit for extended periods with old fuel...

Once you go RAT, you never go back...
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post #68 of 141 (permalink) Old Oct 25th, 16, 4:15 PM Thread Starter
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Re: Stumble on secondaries

Quote:
Originally Posted by 1966_L78 View Post
A few more questions... when was the last time you "cleaned" out the carb?

Do you run any fuel stabilizer? I have been hearing the newer fuels break-down much quicker, and perhaps the insides are getting gummed up with deposits? with the other issues, sounds the the carb may sit for extended periods with old fuel...
What do you mean by "Cleaned" out the carb. When I cleaned everything I got all the deposits and gunk out of the fuel bowl (I think that's what it's called) underneath the top plates where the jets are. I have not used any stabilizer at this point.

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1972 Chevelle - 396, 4 Speed
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post #69 of 141 (permalink) Old Oct 25th, 16, 11:56 PM
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Re: Stumble on secondaries

Hi Dustin, sorry it took all day to get back to you.

Yes, let's go back to the out of the box step up springs. Your logic on vac settings isn't wrong, it's just that we don't want to mask the jet/rod settings. Eddy likes the springs to be for drivability after we have the basic tune.

If you have a 185 t-stat, then you are fine. If it's a hotter thermostat, let it warm up. Drive it around a bit before tuning. Since we are dealing with secondaries, we need to assume that most of the time that that matters, the engine is going to be as warm as you are going to get it.

Pull the carb top again, and set float height and float drop. Look for any trash (little bits of stuff) or gumminess and residue (as mentioned) while you are in there. If you have rubber fuel lines, look for little black specs -- bits of rubber from when the hoses were cut. Eddy won't honor a warranty return if it has hose bits in it. That tells something about how sensitive this is. Look IN the secondary jets for this stuff with a strong flash light.

Timing, please err on the side of too high for initial advance until we get to the point where it's hard to start. (I have 18 in my SBC with Eddy carb, heads, intake and cam.) Go for 14 and back off your total. Do this: Set your step up springs back to the out of the box setting. Warm it up and drive it around a bit to be sure it's warm. Gently ease into the secondaries. Do this constantly until you can time and again feel the stumble in the same way every time. Then, go an bump up the timing. Drive it the same way you did before, feeling if it's acting the same way or a little better. Anticipate a small change. If you have it, give the timing 2 more degrees. If you don't, let's leave it at 14 and start playing with rods and jets.

As far as vac leaks, let's assume you have everything sealed up since there is nothing obvious. That said, I think a vac leak, if you had one, would not be audible for the type of problem you are having. That would be enough of a leak that it wouldn't idle well.

Zeke

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post #70 of 141 (permalink) Old Oct 26th, 16, 2:41 AM
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Re: Stumble on secondaries

Quote:
Originally Posted by Tegguy View Post
What do you mean by "Cleaned" out the carb. When I cleaned everything I got all the deposits and gunk out of the fuel bowl (I think that's what it's called) underneath the top plates where the jets are. I have not used any stabilizer at this point.
If you were getting deposits and gunk in the fuel bowl, then its probably safe to assume there is gunk elsewhere too... Smaller passages, needle & seat, accel pump, etc should all be cleaned out...

May or may not be contributing to your current problems, but it may be worth cleaning it out thoroughly when/if you decide to bring it back to a "stock" baseline (as has been suggested)...

I also am wondering how much of the stumble may be due to the "economy" carb (the 1406 is calibrated "lean" IIRC) on a larger engine... Are there other things that aren't easily changed due to the economy aspect?

Once you go RAT, you never go back...
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post #71 of 141 (permalink) Old Oct 27th, 16, 7:59 PM Thread Starter
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Quote:
Originally Posted by zeke67 View Post
Hi Dustin, sorry it took all day to get back to you.

Yes, let's go back to the out of the box step up springs. Your logic on vac settings isn't wrong, it's just that we don't want to mask the jet/rod settings. Eddy likes the springs to be for drivability after we have the basic tune.

If you have a 185 t-stat, then you are fine. If it's a hotter thermostat, let it warm up. Drive it around a bit before tuning. Since we are dealing with secondaries, we need to assume that most of the time that that matters, the engine is going to be as warm as you are going to get it.

Pull the carb top again, and set float height and float drop. Look for any trash (little bits of stuff) or gumminess and residue (as mentioned) while you are in there. If you have rubber fuel lines, look for little black specs -- bits of rubber from when the hoses were cut. Eddy won't honor a warranty return if it has hose bits in it. That tells something about how sensitive this is. Look IN the secondary jets for this stuff with a strong flash light.

Timing, please err on the side of too high for initial advance until we get to the point where it's hard to start. (I have 18 in my SBC with Eddy carb, heads, intake and cam.) Go for 14 and back off your total. Do this: Set your step up springs back to the out of the box setting. Warm it up and drive it around a bit to be sure it's warm. Gently ease into the secondaries. Do this constantly until you can time and again feel the stumble in the same way every time. Then, go an bump up the timing. Drive it the same way you did before, feeling if it's acting the same way or a little better. Anticipate a small change. If you have it, give the timing 2 more degrees. If you don't, let's leave it at 14 and start playing with rods and jets.

As far as vac leaks, let's assume you have everything sealed up since there is nothing obvious. That said, I think a vac leak, if you had one, would not be audible for the type of problem you are having. That would be enough of a leak that it wouldn't idle well.
Thanks I'll try this when I get a chance but it might be a little while life is hectic right now.
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post #72 of 141 (permalink) Old Nov 5th, 16, 11:35 AM Thread Starter
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Re: Stumble on secondaries

Quote:
Originally Posted by zeke67 View Post
Hi Dustin,

Yes, I suggest giving it a more base timing. Is it 12, or is it 14. If 12, give 14. if 14, give it 2 more and back off the mechanical by 2.
Couple quick questions:
1) How do you back the mechanical advance off or do you mean vacuum advance?
2) What total timing should I start to get concerned about being too much? I am currently running 93 octane.

1955 Ford Thunderbird
1969 Triumph TR6
1972 Chevelle - 396, 4 Speed
1992 Acura Integra
2002 Yamaha R1
2004 Dodge Ram 1500
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post #73 of 141 (permalink) Old Nov 8th, 16, 7:41 PM Thread Starter
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Re: Stumble on secondaries

Anyone? I'm hoping to maybe play with this over the weekend.

1955 Ford Thunderbird
1969 Triumph TR6
1972 Chevelle - 396, 4 Speed
1992 Acura Integra
2002 Yamaha R1
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post #74 of 141 (permalink) Old Nov 16th, 16, 6:55 PM
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Re: Stumble on secondaries

Hi Dustin,

1.) I meant back of the mechanical, that way you don't have to worry about your total timing going up by 2.
2.) 36, maybe 38 at 3600 RPM.

For where you are in the tuning process: Since your distributor has 22 degrees of mechanical advance, I suggest checking it with a dial back light at 3500 RPM and look for 36 degrees. (36-22=14 degrees of initial). If not, set it there. If you do, bump it to 38.

I re-read the post and if I'm following you correctly, you haven't driven the car much in 6-7 years but the carb looks clean. It might be worth a rebuild anyway. A plugged air bleed or emulsion hole might look okay but still be plugged.

Zeke

67 Chevelle
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90 Corvette ZR1
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post #75 of 141 (permalink) Old Nov 16th, 16, 7:52 PM Thread Starter
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Re: Stumble on secondaries

Quote:
Originally Posted by zeke67 View Post
Hi Dustin,

1.) I meant back of the mechanical, that way you don't have to worry about your total timing going up by 2.
2.) 36, maybe 38 at 3600 RPM.

For where you are in the tuning process: Since your distributor has 22 degrees of mechanical advance, I suggest checking it with a dial back light at 3500 RPM and look for 36 degrees. (36-22=14 degrees of initial). If not, set it there. If you do, bump it to 38.

I re-read the post and if I'm following you correctly, you haven't driven the car much in 6-7 years but the carb looks clean. It might be worth a rebuild anyway. A plugged air bleed or emulsion hole might look okay but still be plugged.
1) I'm confused can you possibly help me out. I thought the only way to back off mechanical advance would be to change the weight and spring but that would change the all in RPM. I'm currently all in at 3000 RPM's with my current setup and that's 34-36 degrees (I'd have to double check). Is there another way to change the mechanical advance (without impacting the base timing)?

2) I'll look at double checking it's at 36 and if it is I'll try 38.

That is correct the car has sat a lot while a lot of other things were put together. I can try to rebuild this but I have never even attempted to rebuild a carb.

1955 Ford Thunderbird
1969 Triumph TR6
1972 Chevelle - 396, 4 Speed
1992 Acura Integra
2002 Yamaha R1
2004 Dodge Ram 1500
2012 Dodge Durango Citadel
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