Edel Carb issues

[Dutch Rutter]

With all the carb threads going on I figured I'd throw mine in the ring. Admittedly, I don't know **** about carburetor technicalities. It really all started here
https://www.gmsquarebody.com/threads/need-some-advice-for-shop-bs.27620/page-3#post-528907

After getting the truck back "full adjusted" from the shop I started noticing two issues.

1. When choking the carb in the morning, give it two slow pumps of the throttle and it will fire right up and idle around 1500 rpm (good and like it is supposed to) however, when i apply the brake and put the trans into gear it will drop to my normal hot operating temp and almost die out, almost as if the choke kicks off when going into gear.

2. When putting the truck into park and giving the throttle a blip the RPM will hang at 1500 for a few seconds then will drop to around 1000 for several seconds before finally coming back down to normal idle RPM.

I've checked the linkage, springs and pedal and that all checks out fine and doesn't have any effect on the condition.

I've been exchanging email with Summit tech support because if its a problem with the carb itself I need that ball rolling before its too late to return/exchange. First they had me check vacuum as well as RPMs at idle both in gear and neutral. results listed here.

vac. at idle in park: 13-16
vac. at idle in gear: 6-15

RPM at idle in park: 600-700
RPM at idle in gear: 500-600

No vacuum leaks that I was able to find, will be buying more carb cleaner tonight.
They came back with this

"When time permits, pull the spark plugs to see if any have any traces of oil on the threads. (threads only) Also, see if there is any trace of oil around any of the intake bolts. There is not only too much of a drop in vacuum going into gear, but the variance is too high. Readings don't appear to be steady."

And so far that is where its at. Is there something else that I am missing or overlooking? Could a mis-adjusted carb cause this vacuum readings? I don't have any oil on my intake bolts, and I'm pretty confident I wont on the plugs however, I will be checking tonight.

Really loosing my hair with this thing and thinking Its time to dump the edelbrock and either go with a holley, quick fuel or trash it all and go with an EFI setup.

BTW carb is a new edelbrock 1405 with the electric choke kit added, ontop of a 1" 4 hole spacer that goes to a edelbrock 7101 RPM performer intake manifold. All the seals and gaskets were new and great shape. I'll be using the carb cleaner tonight and checking for any possible leaks in the intake gasket and base gaskets.


edit: should have added this but everywhere else other then those two problems the carb seems and feels to be running and operating great.

 

[QBuff02]

Where are you checking for your vacuum reading at? A swing from 6-15 in gear indicates some potential serious problems. They're probably wanting you to check oil on the spark plug threads to determine if it's got a leaky/blown head gasket, bad valve guides or seals. Which vacuum readings like that could be an indication of. Timing and carb adjustments can affect readings, but generally by only a few inches of vacuum either way. What kind of emissions is still on the truck? How does it shift? I've seen a bad vacuum modulator cause some quirky vacuum readings before. and I've seen emissions play havoc on things as well. I've never truly been a big fan of Edelbrock carbs, but I know lots of people that love them. So Let's try and figure out some basics and see if we can't get in a direction!

 

[Dutch Rutter]

Where are you checking for your vacuum reading at? A swing from 6-15 in gear indicates some potential serious problems. They're probably wanting you to check oil on the spark plug threads to determine if it's got a leaky/blown head gasket, bad valve guides or seals. Which vacuum readings like that could be an indication of. Timing and carb adjustments can affect readings, but generally by only a few inches of vacuum either way. What kind of emissions is still on the truck? How does it shift? I've seen a bad vacuum modulator cause some quirky vacuum readings before. and I've seen emissions play havoc on things as well. I've never truly been a big fan of Edelbrock carbs, but I know lots of people that love them. So Let's try and figure out some basics and see if we can't get in a direction!

That was taken from the driver's side manifold vacuum port on the front of the carb. No emissions left except for the usual PCV which was hooked up at time of reading. Shifting is perfectly timed and normal feeling for the overhauled 700r4. The vacuum advanced on the dizzy works like it is supposed to. My initial is 14 with a max of around 40 something at 3000 RPM then comes back down. The engine itself it very new (around 1500 miles) full rebuild so I would be VERY upset to find something seriously wrong with it but it is possible. I have even replaced some vacuum lines, not all which have been on there before I bought it. The vacuum module for the transmission is also newer.

When I was checking for vacuum leaks I did not have any cleaner but I did physically block the ports on the front of the carb and did not hear any difference in idle. I could try blocking them and then see what the vacuum gauge says if that would help any? I do also plan on checking the rear carb port (used for power brakes) and the plugged port on the manifold behind the carb for leaks tonight with the carb cleaner.

Driving manors seem dialed in quite well. No backfiring, not bogging, no loss of power. It pulls hard and strong. Fires up well and stays running, no stalling or dying issues.

I greatly appreciate the help, and with all this nonsense I'm not necessarily an Edebrock fan but its what I've had in the past and figured stick another one on. If this carb needs returned I have no idea what I would go with instead. But I'm open to anything. Would probably still not know how to go about fine tuning a holley or QF but I'm all for learning.

 

[QBuff02]

Ahhhh… When checking vacuum I always pull from the big port on the base of carb or "T" into the line for pcv or the one (usually the same port but I think Edelbrock's have two) going to the brake booster. That might be a source of some of your fluctuations.. Try tying direct into the big one on the carb and see if that makes a difference in your readings.

 

[Dutch Rutter]

Ahhhh… When checking vacuum I always pull from the big port on the base of carb or "T" into the line for pcv or the one (usually the same port but I think Edelbrock's have two) going to the brake booster. That might be a source of some of your fluctuations.. Try tying direct into the big one on the carb and see if that makes a difference in your readings.

Ahha! I'll do that tonight after work and see whats what. Good thing I knowledgeable carb people here. I'm pretty carb-illiterate.

 

[Dutch Rutter]

Ahhhh… When checking vacuum I always pull from the big port on the base of carb or "T" into the line for pcv or the one (usually the same port but I think Edelbrock's have two) going to the brake booster. That might be a source of some of your fluctuations.. Try tying direct into the big one on the carb and see if that makes a difference in your readings.

Ok, this looks a bit better.
idle in neutral: 15 on the gauge at 600 rpm
idle in gear: 11 on the gauge at 500 rpm

these were using the large PCV port on the front center of the carb. No bouncing like before. good constant readings.

I also went through and hosed things down with the carb cleaner while idling bit by bit.. and did not get any kind of change so I'm thinking I am safe form vac leaks, as well as intake leaks, and base gasket leaks. For ***** and giggles I pulled a plug, didn't see any oil on anything and the plug while new seemed fine.

I'll be sending my new findings to the Summit person as well.

 

[MisterB]

With all the carb threads going on I figured I'd throw mine in the ring. Admittedly, I don't know **** about carburetor technicalities. It really all started here
https://www.gmsquarebody.com/threads/need-some-advice-for-shop-bs.27620/page-3#post-528907

After getting the truck back "full adjusted" from the shop I started noticing two issues.

1. When choking the carb in the morning, give it two slow pumps of the throttle and it will fire right up and idle around 1500 rpm (good and like it is supposed to) however, when i apply the brake and put the trans into gear it will drop to my normal hot operating temp and almost die out, almost as if the choke kicks off when going into gear.

2. When putting the truck into park and giving the throttle a blip the RPM will hang at 1500 for a few seconds then will drop to around 1000 for several seconds before finally coming back down to normal idle RPM.

I've checked the linkage, springs and pedal and that all checks out fine and doesn't have any effect on the condition.

I've been exchanging email with Summit tech support because if its a problem with the carb itself I need that ball rolling before its too late to return/exchange. First they had me check vacuum as well as RPMs at idle both in gear and neutral. results listed here.

vac. at idle in park: 13-16
vac. at idle in gear: 6-15

RPM at idle in park: 600-700
RPM at idle in gear: 500-600

No vacuum leaks that I was able to find, will be buying more carb cleaner tonight.
They came back with this

"When time permits, pull the spark plugs to see if any have any traces of oil on the threads. (threads only) Also, see if there is any trace of oil around any of the intake bolts. There is not only too much of a drop in vacuum going into gear, but the variance is too high. Readings don't appear to be steady."

And so far that is where its at. Is there something else that I am missing or overlooking? Could a mis-adjusted carb cause this vacuum readings? I don't have any oil on my intake bolts, and I'm pretty confident I wont on the plugs however, I will be checking tonight.

Really loosing my hair with this thing and thinking Its time to dump the edelbrock and either go with a holley, quick fuel or trash it all and go with an EFI setup.

BTW carb is a new edelbrock 1405 with the electric choke kit added, ontop of a 1" 4 hole spacer that goes to a edelbrock 7101 RPM performer intake manifold. All the seals and gaskets were new and great shape. I'll be using the carb cleaner tonight and checking for any possible leaks in the intake gasket and base gaskets.


edit: should have added this but everywhere else other then those two problems the carb seems and feels to be running and operating great.

Why aren't you doing step 2 before you put the truck in gear to pull away after idling? In other words, pump once or twice, crank, engine starts, idle should raise up to your cold high idle. Once engine is warm, blip throttle to take idle back down and THEN put it in gear.

Sent from my SM-N975U1 using Tapatalk

 

[80BrownK10]

Why aren't you doing step 2 before you put the truck in gear to pull away after idling? In other words, pump once or twice, crank, engine starts, idle should raise up to your cold high idle. Once engine is warm, blip throttle to take idle back down and THEN put it in gear.

Sent from my SM-N975U1 using Tapatalk

Sounds like he wants to drive away before the engine is warm enough to let the choke come off fully?

 

[Dutch Rutter]

Shouldn't you be able to drive the truck (easily of course) while the choke is engaged and engine not fully warm, but warm enough that it doesent stall and oil is moving around?

Then once your at operating temp kick the choke off.

If I we're to let it sit until it hit operating temp it'll be sitting there running at 1500rpm in my driveway for a good 5-8 minutes.

All of my carbs in the past were able to be driven with the choke on. I may be wrong here.

 

[80BrownK10]

Shouldn't you be able to drive the truck (easily of course) while the choke is engaged and engine not fully warm, but warm enough that it doesent stall and oil is moving around?

Then once your at operating temp kick the choke off.

If I we're to let it sit until it hit operating temp it'll be sitting there running at 1500rpm in my driveway for a good 5-8 minutes.

All of my carbs in the past were able to be driven with the choke on. I may be wrong here.

Yes, but why. ***** expensive, I let mine warm up before I go anywhere. This is not some modern efi sensored up motor. I just make sure I start it early enough to warm it up before I go anywhere.

 

[MisterB]

Shouldn't you be able to drive the truck (easily of course) while the choke is engaged and engine not fully warm, but warm enough that it doesent stall and oil is moving around?

Then once your at operating temp kick the choke off.

If I we're to let it sit until it hit operating temp it'll be sitting there running at 1500rpm in my driveway for a good 5-8 minutes.

All of my carbs in the past were able to be driven with the choke on. I may be wrong here.

You're trying to drive a vintage truck, like it's a modern truck. Go out and start it and let it warm up for a good 4 or 5 minutes while you get stuff together or dink around in the garage. Then blip the gas to bring the idle down and then put it in gear and report back to us.

Sent from my SM-T720 using Tapatalk

 

[75gmck25]

I also expect a choke to work well enough to drive away after about 30-60 seconds of warmup, but I know I can't do it with my current Quadrajet.

The choke pull-off works differently on my Quad, so if I pump it about twice and don't touch the the throttle, the pull-off will only move it off-choke a fraction and it will run well on high idle after it starts. However, if I then try to drive off, the linkage allows the choke to open further and it runs really rough until it warms up. I have the choke set a couple of increments rich and it still has this problem.

What type of intake and heads are you using? My choke/warm-up time really increased when I switched to aluminum heads, and I already had an aluminum Edelbrock performer intake. My exhaust crossover heat valve does not work (broken spring), so I don't get extra heat through the manifold during warmup. I plan to buy a new exhaust heat valve, and also hook the thermostatic air cleaner intake back up so I get warm air at startup. Not sure it will work any better, but it seems worth trying.

Bruce

 

[80BrownK10]

I also expect a choke to work well enough to drive away after about 30-60 seconds of warmup, but I know I can't do it with my current Quadrajet.

The choke pull-off works differently on my Quad, so if I pump it about twice and don't touch the the throttle, the pull-off will only move it off-choke a fraction and it will run well on high idle after it starts. However, if I then try to drive off, the linkage allows the choke to open further and it runs really rough until it warms up. I have the choke set a couple of increments rich and it still has this problem.

What type of intake and heads are you using? My choke/warm-up time really increased when I switched to aluminum heads, and I already had an aluminum Edelbrock performer intake. My exhaust crossover heat valve does not work (broken spring), so I don't get extra heat through the manifold during warmup. I plan to buy a new exhaust heat valve, and also hook the thermostatic air cleaner intake back up so I get warm air at startup. Not sure it will work any better, but it seems worth trying.

Bruce

My q jet functions similar to your except without the rough high idle when the choke opens back up fully. I have an edelbrock intake and an edelbrock chrome aftermarket air cleaner. No factor heat hose from exhaust manifold or air cleaner in mine.

 

[Dutch Rutter]

I also expect a choke to work well enough to drive away after about 30-60 seconds of warmup, but I know I can't do it with my current Quadrajet.

The choke pull-off works differently on my Quad, so if I pump it about twice and don't touch the the throttle, the pull-off will only move it off-choke a fraction and it will run well on high idle after it starts. However, if I then try to drive off, the linkage allows the choke to open further and it runs really rough until it warms up. I have the choke set a couple of increments rich and it still has this problem.

What type of intake and heads are you using? My choke/warm-up time really increased when I switched to aluminum heads, and I already had an aluminum Edelbrock performer intake. My exhaust crossover heat valve does not work (broken spring), so I don't get extra heat through the manifold during warmup. I plan to buy a new exhaust heat valve, and also hook the thermostatic air cleaner intake back up so I get warm air at startup. Not sure it will work any better, but it seems worth trying.

Bruce

I have a set of aluminum heads without the exhaust cross over. Not having this will make it take a bit longer to warm up. Having that working will help the vehicle warm faster at least to my knowledge.

 

[Dutch Rutter]

@QBuff02 After finding my more normal vacuum readings I'm thinking that my carb is out of adjustment and the shop I took it to just reset the carb to out of box adjustments and did not in fact dial it in.

At least I am hoping those are closer to acceptable levels.