Carb findings

Coadster32

Veteran Member
Lifetime Gold Member
Oct 2, 2013
2,375
Milford,CT
For quite some time I noticed the high idle cam was intermittently working on my Eddy 1406. It was more annoying than anything, and not really a big deal, just pedal the throttle until it gets warmed up. I took the carb off to clean it for the winter, and realized that the high idle cam itself was sloppy on the shaft it was on, and sometimes not actually centered on the screw, and slipping off. I made a washer about .040 thick, and inserted it to take up the slop. During the course of time, the screw end got rounded over a bit. Got that squared away, and filed the steps a bit sharper on the cam as well.
The spacer/washer is made out of white delrin, simply because that what I had laying around. If anyone else does this, just make certain not to make it woo wide, and bind up the secondary blade lockout. Hope this maybe helps someone else out as well.

20230120_140205_resized.jpg

20230120_140212_resized.jpg



Below is the underside of my carb as it sits on the idle speed screw. You can see the "transfer slot" is exposed at idle. I know that it shouldn't be that way. As expected, the idle air/fuel adjustment screws seem to not make any change. If I lower the idle speed, it stalls forcing me to keep it there. I'm thinking that I should chose a metering rod that is smaller in diameter for the jet that it sits into. This should flow more gas at idle, then maybe I can turn the idle speed screw in enough to get it off of the transfer slot. Is my thinking right on this? The choke seems to be set correctly, as I have had no issues with it's function. The cam has a bit of a thump to it...vacuum is a bouncy 14 at idle, then vacuum goes solid to 20 at about 2000rpm.

20230120_140234_resized.jpg
 

biker

Veteran Member
Dec 7, 2014
5,561
Canada
Good catch on the choke cam. That does look like too much transfer slot at idle.

So. Closing the idle speed screw down will cause engine vacuum signal to pull harder on the idle circuit. That is where your issue might be. The idle circuit isn't calibrated well enough to support the engine at idle speed. Make sure nothing is plugged in your idle circuit, set the idle speed screw to make your transfer slots "square" and set the screws to factory recommendation for the carb.

If it still won't idle, try to figure out if it is needing air or fuel. Some idle circuits are really sensitive and going even a quarter of a turn can be too much one way or the other.

Do you have a PCV hooked up? You can tune the idle somewhat by making sure the PCV isn't sucking too much through the valve. Too much vac pulled through PCV system is vac that is not pulling on your idle circuit.

Vacuum advance hooked up? Is it on full manifold vac or ported vac source? Any idea what your inital timing is at idle?

I only ask those questions because there is lots of interplay between idle speed screw/mixture screws/pcv/vac advance and initial timing when you have an engine with a decent performance cam. It's like the old song about the knee bone being connected to the shin bone.... all those factors conspire to make a decent or crappy idle.
 

Coadster32

Veteran Member
Lifetime Gold Member
Oct 2, 2013
2,375
Milford,CT
Great video, and thank you for it. I watched a couple from him, but obviously missed that one. A lot of what he said as problems, I'm experiencing for certain. One that stands out is the idle dropping a few hundred RPM when putting the car into gear. Could need more timing. Below are things that I have checked/done/confirmed. One thing to add is that the car was running pretty decent before I sealed the air cleaner to the opening on the cowl hood. (I did this when I redid the heads two years ago). The cowl hood has no trap door to open or close. I posted questions on if that would create issues with the carb, but really just trial and error. https://nastyz28.com/threads/cowl-induction-air-flow.332997/ (Biker is in this thread)

After being involved and following this thread https://nastyz28.com/threads/pcv-question.335329/ , I ended up putting a breather in the driver's side valve cover, and a FV178 PCV valve in the passenger's side valve cover. I have an air/oil separator in-line going back to the carb to keep things clean. The line has no vacuum leaks in it, and the valve pulls open pretty easily, I'd say below 5". This could be the wrong valve for my setup, but has been in the car for quite some time. (Biker is in this thread also...and have read the CVV bible as well) https://nastyz28.com/threads/pcv-vacuum.332627/

Vac advance is hooked into manifold vacuum, (enter lengthy threads here as well). I tested it today, and it starts advancing at 7" and goes all in at 15". My idle falls below the 15deg to pull in the vac advance all the way...but it's close. Perhaps an adjustable can is warranted?

Initial timing is set at 12deg. Mech advance does another 24deg, curve starts about 1200rpm, and all in around 2500rpm. I believe vac advance adds another 12+deg.

No leaks in the brake booster line, vac advance line, or pcv line. There's no tranny shift vac line, as it's a manual valve body TH400. Sprayed carb cleaner around carb base and intake manifold while running, and idle stayed the same.

Camshaft is Comp Cam Xtreme Energy 236/242 hydraulic roller., Harland Sharp 1.5 roller rockers.

MSD distributor 8361, MSD Blaster coil 8202, MSD 6AL box, and MSD 8.5mm super conductor wires. Cleaned and tested spark plug leads to inner distributor cap, and Ohms readings are good to factory specs of 40-50 ohms per foot. New rotor and spark plugs are on the way.

While the plugs are out, I may recheck/adjust valve lash settings on the rocker arms/hydraulic lifters. Two years ago I set them to 5/8 turn past lash. They are poly-locks, so they shouldn't have moved.
 
Last edited:

FS87LT

Veteran Member
Apr 3, 2010
147
DFW, TX
I was wondering about the cam in the motor, which you supplied the information on. THAT might be the issue. You have to open the primaries too far in order for the engine to have enough air to idle on, due to the cam duration specs. The carb is designed more for a stock cam's air requirements. So you open the throttle farther at idle, which exposes more transfer slot, as a result.

The fix? Drill a small hole in each of the primary throttle plates. To admit more air at base idle, so the throttle plates can close more and be in the "design location" at hot base idle. Without those little holes, you can have issues getting the engine to idle decently at all.

I read about this in an old book on Holley carburetors, back in the later 1970s. The HPBooks book on Holley carburetors, which came out in about 1978 or so. It mentions the size of the holes, too. There might be a YouTube video on that, too?

Isn't the 1406 a 600cfm carb, or thereabouts? Perhaps a 750cfm carb might work better with that cam? Bigger primaries, mainly, to allow more idle air into the engine.

But do investigate the tutorials on drilling the holes in the primary throttle plates to possibly fix your problem.

Just some thoughts,
FS87LT
 

biker

Veteran Member
Dec 7, 2014
5,561
Canada
Great video, and thank you for it. I watched a couple from him, but obviously missed that one. A lot of what he said as problems, I'm experiencing for certain. One that stands out is the idle dropping a few hundred RPM when putting the car into gear. Could need more timing. Below are things that I have checked/done/confirmed. One thing to add is that the car was running pretty decent before I sealed the air cleaner to the opening on the cowl hood. (I did this when I redid the heads two years ago). The cowl hood has no trap door to open or close. I posted questions on if that would create issues with the carb, but really just trial and error. https://nastyz28.com/threads/cowl-induction-air-flow.332997/ (Biker is in this thread)

After being involved and following this thread https://nastyz28.com/threads/pcv-question.335329/ , I ended up putting a breather in the driver's side valve cover, and a FV178 PCV valve in the passenger's side valve cover. I have an air/oil separator in-line going back to the carb to keep things clean. The line has no vacuum leaks in it, and the valve pulls open pretty easily, I'd say below 5". This could be the wrong valve for my setup, but has been in the car for quite some time. (Biker is in this thread also...and have read the CVV bible as well) https://nastyz28.com/threads/pcv-vacuum.332627/

Vac advance is hooked into manifold vacuum, (enter lengthy threads here as well). I tested it today, and it starts advancing at 7" and goes all in at 15". My idle falls below the 15deg to pull in the vac advance all the way...but it's close. Perhaps an adjustable can is warranted?

Initial timing is set at 12deg. Mech advance does another 24deg, curve starts about 1200rpm, and all in around 2500rpm. I believe vac advance adds another 12+deg.

No leaks in the brake booster line, vac advance line, or pcv line. There's no tranny shift vac line, as it's a manual valve body TH400. Sprayed carb cleaner around carb base and intake manifold while running, and idle stayed the same.

Camshaft is Comp Cam Xtreme Energy 236/242 hydraulic roller., Harland Sharp 1.5 roller rockers.

MSD distributor 8361, MSD Blaster coil 8202, MSD 6AL box, and MSD 8.5mm super conductor wires. Cleaned and tested spark plug leads to inner distributor cap, and Ohms readings are good to factory specs of 40-50 ohms per foot. New rotor and spark plugs are on the way.

While the plugs are out, I may recheck/adjust valve lash settings on the rocker arms/hydraulic lifters. Two years ago I set them to 5/8 turn past lash. They are poly-locks, so they shouldn't have moved.
Thanks man, sorry for going through the whole gamut all over again, I knew u had an issue before, just couldn't remember everything that was addressed.
The one thing that jumps out is vac advance. Get a can that will fully deploy under your idle vac reading. And limit it to 10*. As it is, 12+ is a bit much, but the bigger issue is that the additional timing added by the can is probably fluctuating because it cant fully deploy at idle.
 

Coadster32

Veteran Member
Lifetime Gold Member
Oct 2, 2013
2,375
Milford,CT
After going through some of my older posts, it's funny/sad how my brain absorbs it in from the way more experienced on this board, learn what it needs, gets the job done, and if it all goes well for a while....gets partially purged from my memory. I really appreciate you posting initially, (and certainly back up again), and going back through the basics. I was heading in the direction of a new vac can a couple of years ago, and just didn't do it for whatever reason. I do see the gage fluctuate a bit at idle, so I think it's in order. Seems as though it would have been a lot easier to do when I had it off the car a while back, as it looks as though the factory can is riveted in place.

I also watched a few other videos on drilling a small hole in the throttle plates. It seems as though almost everyone of them have a cam that reeks a bit of havoc at idle as well, and has the same transfer slot issue. Interesting to say the least, as the theory seems to line up. If I can't get it right with the timing, I'm not too afraid of trying that on this carb. It is a bit on the smaller side for the motor anyhow. Some say to have the throttle plates cover up the transfer slot all the way, and some say leave a square of it exposed as Biker suggested. I'll keep digging on this I suppose. Being off-season, I have some time on my side to get it sorted out. Open to any suggestions.
 

biker

Veteran Member
Dec 7, 2014
5,561
Canada
Yep, you are on the right track. The timing and vac advance/idle mix stuff is all a real individual thing for each engine combo. It's worth trying the vac can before drilling holes, your cam isnt crazy, and you do have a decent vacuum reading.
The goal is to provide the idle circuit with as much vacuum signal as possible so that it is working hard and has lots of adjustability. Then have the transfer slots timed to make a smooth transition.
With mine, I found using the right pcv made sure that it wasnt just a giant vac leak at idle, robbing signal from the idle circuit.

Crankcase does not need a ton of (pcv) airflow at idle to be effective.
 

Coadster32

Veteran Member
Lifetime Gold Member
Oct 2, 2013
2,375
Milford,CT
If my pcv pulls in a lot with my vacuum numbers, is there a way to get a stiffer pcv, so it doesn't pull in so much at idle? Not a whole lot of charts out there to look at in this regard. Not really willing to spring for the $100+ adjustable one that I see either.

I spoke with MSD yesterday about an adjustable can, as I didn't know if the aftermarket ones will fit. I confirmed that the stock vac can I have does 10' advance at 15inches. He said that I should hook it up to ported vacuum anyway. (I expected him and Edlebrock to say this, as it's emissions, blah-blah). I did see an "Uncle Tony Garage" video where he takes his car for a ride, and shows how the vac-advance works both ported and manifold. He's all about the ported. The above video also says to try ported as well. Everything else leads me to manifold, as I currently have now. I thought that if I go back to ported, when the throttle blades start opening, then vac can should pull in as off idle, my cam pulls about 20inches. I would lose my fluctuating vac-advance at idle, but not certain if it is needed anyway. Getting more confused again as research goes on.
 

biker

Veteran Member
Dec 7, 2014
5,561
Canada
If my pcv pulls in a lot with my vacuum numbers, is there a way to get a stiffer pcv, so it doesn't pull in so much at idle? Not a whole lot of charts out there to look at in this regard. Not really willing to spring for the $100+ adjustable one that I see either.

I spoke with MSD yesterday about an adjustable can, as I didn't know if the aftermarket ones will fit. I confirmed that the stock vac can I have does 10' advance at 15inches. He said that I should hook it up to ported vacuum anyway. (I expected him and Edlebrock to say this, as it's emissions, blah-blah). I did see an "Uncle Tony Garage" video where he takes his car for a ride, and shows how the vac-advance works both ported and manifold. He's all about the ported. The above video also says to try ported as well. Everything else leads me to manifold, as I currently have now. I thought that if I go back to ported, when the throttle blades start opening, then vac can should pull in as off idle, my cam pulls about 20inches. I would lose my fluctuating vac-advance at idle, but not certain if it is needed anyway. Getting more confused again as research goes on.
I went thru the same vac advance issue. When I couldn't get rid of a stumble, I switched to ported, and my stumble was gone. At 16 degrees initial timing, I had plenty of timing for a good idle and it made idle speed adjustments easier and more stable. You have 18 initial which is plenty,

However, i still feel like that is a band-aid to cover up the fine-detail timing/pcv/carb issues that I had.

I did bite the bullet and go to the Wagner adjustable pcv, as my pcv was pretty much wide open at idle.

I went back to full manifold vac, a bit less initial, more mechanical timing and the stumble is gone. With less vacuum going through the pcv at idle, I have stronger vac signal and more stable idle.

Last issue I have is my idle mix screws are less than a 1/2 turn out, which tells me I need to lean the idle mix circuit.

G72Zed sent me some IFR and IAB options, but my car is in storage for now, so will wait til spring.

So, all this to say, try ported vac source and see what happens!
 




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