Spark plug read, IFR/IAB and primary jet

[PRNDL]

Yeah man, the carb settings have me confused. This is why: The engine is happy. Runs great. Strong and pulls hard. No symptoms. Other than a stinky idle, which I thought was normal due to a lumpy cam.

My only issue is at full temp and only at WOT, I get some blue smoke out the tail pipes. This caused me to check my plugs and saw how black they were.

Settings:
My confusion is that I have my primary transition set perfect and all 4 corner idle mixture screws are at exactly 1 turn. Anything less, and I mean anything, causes vacuum and rpm to drop and the engine becomes unhappy. And I get a stumble. The mixture screws are nice and responsive and closing even 1 will cause the engine to stall.
I thought that if the IFR’s were too big, an indicator would be that the mixture screws would operate at very low settings. Like 1/4 turn to 1/2 turn from seated. And if the IFR’s were too small, the mixture screws would respond at over 1-3/4 turns to 1.5 turns from seated. I seem to have set this thing the leanest I can. Car runs great. If it were not for the smoke and plugs, I never would have thought to post this post.

After stumbling on all this I noticed my new break in oil was black and a quart down. I worried this was a bad rebuild or something.

I read a few post online that AED carbs run real fat, but I figured that was how they were initially set.

[Tuner]

Yeah man, the carb settings have me confused. This is why: The engine is happy. Runs great. Strong and pulls hard. No symptoms. Other than a stinky idle, which I thought was normal due to a lumpy cam.

My only issue is at full temp and only at WOT, I get some blue smoke out the tail pipes. This caused me to check my plugs and saw how black they were.

Settings:
My confusion is that I have my primary transition set perfect and all 4 corner idle mixture screws are at exactly 1 turn. Anything less, and I mean anything, causes vacuum and rpm to drop and the engine becomes unhappy. And I get a stumble. The mixture screws are nice and responsive and closing even 1 will cause the engine to stall.
I thought that if the IFR’s were too big, an indicator would be that the mixture screws would operate at very low settings. Like 1/4 turn to 1/2 turn from seated. And if the IFR’s were too small, the mixture screws would respond at over 1-3/4 turns to 1.5 turns from seated. I seem to have set this thing the leanest I can. Car runs great. If it were not for the smoke and plugs, I never would have thought to post this post.

After stumbling on all this I noticed my new break in oil was black and a quart down. I worried this was a bad rebuild or something.

I read a few post online that AED carbs run real fat, but I figured that was how they were initially set.

How many miles on your break in oil? Gas dilutes oil and turns it black.

A leaking fuel pump could be dumping gas into the crankcase, however the #75 MJ you mentioned could easily be 5 sizes larger than your engine needs. The gasoline is apparently getting into the oil from somewhere and when the oil is diluted it will pass rings and valve guides more readily than fresh oil, so that, and the carb jetted so rich, is a recipe for exhaust smoke.

[PRNDL]

I figured that black oil was from deluged oil, but based on my minimal experience, I figured it would smell like fuel and maybe the oil level would increase due to the fuel in the oil. The oil was a quart low and did not smell like gas.
Unless the diluted oil was so thin that is was easy for it to get past the rings.

I’m running an electric pump with regulator.

What’s interesting is my first set of plugs, the ones before this set I have in the photos, were far worse. This AED carb had 77 jets in the primary. The carb card indicated they should have been 75. AED sent me some 75’s to make it right plus some 73’s just in case. This set in the photos were run on 75 primary jets.

I did not think about the smoke being a rich mixture. It did smell rich but looked blue. I assumed it was oil.

The smoke is only at WOT when hot. With it without the PCV hooked up.

[ClassAct]

I figured that black oil was from deluged oil, but based on my minimal experience, I figured it would smell like fuel and maybe the oil level would increase due to the fuel in the oil. The oil was a quart low and did not smell like gas.
Unless the diluted oil was so thin that is was easy for it to get past the rings.

I’m running an electric pump with regulator.

What’s interesting is my first set of plugs, the ones before this set I have in the photos, were far worse. This AED carb had 77 jets in the primary. The carb card indicated they should have been 75. AED sent me some 75’s to make it right plus some 73’s just in case. This set in the photos were run on 75 primary jets.

I did not think about the smoke being a rich mixture. It did smell rich but looked blue. I assumed it was oil.

The smoke is only at WOT when hot. With it without the PCV hooked up.

That’s a bigger main jet than I use on 750’s but without knowing the rest of the tuneup I can’t say if they need to be that big or not. I doubt it but you never know.

[MELWAY]

An .036” IDle jets is enough for a 1050 dominator

As other experienced guys on here have said
Get it down to .028”-.030”. And then tune with
Air bleed
This will make a huge difference

[Tuner]

Something a lot of people seem to forget, or don't know because they are so young all they have experienced as a daily driver is a production car with EFI, is a properly tuned carb for a street driven car will be too lean to run well on a cold start, will not idle at all, and will have "drivability" hesitation problems until it runs at least several minutes.

I am amazed how it can be so many young 20-something kids who work for repair shops cannot start a car with a carburetor because they don't understand how to use the throttle for accelerator pump enrichment on a cold start and they seem baffled and annoyed because they have to do two things at once, turn the key and move the accelerator pedal.

[PRNDL]

I’m in Florida. No choke on this 750. Starts fine and I feather the throttle until the idle holds and temps come up. All evaluating and tuning done at full temp after a good drive.

[Tuner]

After an overnight soak at 60 deg. a carb engine should be stubborn for at least a few minutes .... unless it is too rich. Yours starts fine because it is calibrated so rich it is essentially on the choke all the time.

[HQM383]

Yeah man, the carb settings have me confused. This is why: The engine is happy. Runs great. Strong and pulls hard. No symptoms. Other than a stinky idle, which I thought was normal due to a lumpy cam.

My only issue is at full temp and only at WOT, I get some blue smoke out the tail pipes. This caused me to check my plugs and saw how black they were.

Settings:
My confusion is that I have my primary transition set perfect and all 4 corner idle mixture screws are at exactly 1 turn. Anything less, and I mean anything, causes vacuum and rpm to drop and the engine becomes unhappy. And I get a stumble. The mixture screws are nice and responsive and closing even 1 will cause the engine to stall.
I thought that if the IFR’s were too big, an indicator would be that the mixture screws would operate at very low settings. Like 1/4 turn to 1/2 turn from seated. And if the IFR’s were too small, the mixture screws would respond at over 1-3/4 turns to 1.5 turns from seated. I seem to have set this thing the leanest I can. Car runs great. If it were not for the smoke and plugs, I never would have thought to post this post.

After stumbling on all this I noticed my new break in oil was black and a quart down. I worried this was a bad rebuild or something.

I read a few post online that AED carbs run real fat, but I figured that was how they were initially set.

Each engine wants its amount of air/fuel to idle clean when at running temp. This is regulated through the needle and seat of the idle mix screw as you know. The amount of fuel available in the idle channel with a .035” or .030” IFR may only require a small change in the clearance of needle to seat of the idle mix screws to regulate the air/fuel the engine wants to idle. It’s when the throttle is opened and fuel starts through the t-slot the difference in IFR is truly known.

With oil consumption the other guys may be spot on that there may be a leak on the bottom side of the intake gasket and/or a pcv operating fully open when it shouldn’t. This will be best diagnosed with a systematic approach that removes any over fueling from the equation that will isolate better observed symptoms of oil consumption. Installing the .033” IFR and .082” iab and observe the effects will improve some conditions and may highlight others that may be there. More informed decisions can be made.

[rgalajda]

" I have a set of .033 IFR and 73 jets on my bench in the garage. I even have a set of .082 IAB’s. "

It is obvious that the carb is too rich. Install the .033 IFR and the 73 jets. Leave the IAB at .075 for now.

Deal with the oil issue after you get the carb close.

IFR up high or down low does not matter at this point.

Report back as to how your engines idle quality is.

Merry Christmas

[PRNDL]

Merry Christmas

Will do

[rebelrouser]

Something a lot of people seem to forget, or don't know because they are so young all they have experienced as a daily driver is a production car with EFI, is a properly tuned carb for a street driven car will be too lean to run well on a cold start, will not idle at all, and will have "drivability" hesitation problems until it runs at least several minutes.

I am amazed how it can be so many young 20-something kids who work for repair shops cannot start a car with a carburetor because they don't understand how to use the throttle for accelerator pump enrichment on a cold start and they seem baffled and annoyed because they have to do two things at once, turn the key and move the accelerator pedal.

I taught automotive for 26 years and I fully support your statement about young people raised on EFI vehicles. They seemed baffled that when explaining clear flood mode by stepping throttle to the floor that was something also done on a flooded engine with a carb. The other thing is spark knock, none of the younger generation have ever heard spark knock from an engine lugging up a hill for example. I always described it as a noise like jingling change in your pocket.

[PRNDL]

Just an update incase this helps anyone in the future. Went from .035 IFR to .032 and it did the trick. Also, went with a PCV valve that had a smaller orifice on the bottom and all the smoking has stopped.

Thanks everyone.

[BobbyB]

Just an update incase this helps anyone in the future. Went from .035 IFR to .032 and it did the trick. Also, went with a PCV valve that had a smaller orifice on the bottom and all the smoking has stopped.

Thanks everyone.

Good deal! Do you have the part number of the PCV valve that worked for you?

[PRNDL]

It says 2072 on the side.

It’s the one on the left. Simply a smaller hole.

image.jpg