Desmogging help
Laughing Gas
Joined: Aug 2011
Posts: 1,116
Likes: 0
And what about the guys who can't run smog? I have an 85 engine..not sure if it ever was computer controlled or not cuz when I for it..it was the stock EVERYTHING..and it had the egr tube. Would this be considered "pre smog"? Cuz now..I'm running the offy intake..4bbl carb and so on..and there's no way to rub smog. All I can do is tune my carb or dizzy
Tuned
Joined: Jun 2003
Posts: 307
Likes: 1
From: South Florida
And what about the guys who can't run smog? I have an 85 engine..not sure if it ever was computer controlled or not cuz when I for it..it was the stock EVERYTHING..and it had the egr tube. Would this be considered "pre smog"? Cuz now..I'm running the offy intake..4bbl carb and so on..and there's no way to rub smog. All I can do is tune my carb or dizzy
70 and before were pretty well smog free except for the pcv system, but that is a good thing anyway, lots better than the draft tube setup.
You can virtually eliminate everything, if done correctly, with the proper timing and a/f ratios. None computer controlled carbs can be modded to give the proper delivery, though difficult when modifying air bleeds, rod tapers etc.
A gazillion engines ran well before any smog was added.
If you are running an hei powered ignition, that's about as good as it gets, full advance of 35° max in at around 2500rpm and no more than 50° with vacuum advance.
With your 4bbl, you can pretty well set any a/f throughout the range and that is the last step in engine setup. Ideally set up with an a/f meter, but, plug reading works, even with e10 gas.
Make sure you have the best cooling system possible, it accounts for more engines failures than anything, by a long shot.
It is against Federal law to modify any oem emissions equipment period. You don't have to hide from a federal cop, the states take care of regulation, some exempt older vehicles, some don't care at all, some are tough. Your choice.
Laughing Gas
Joined: Aug 2011
Posts: 1,116
Likes: 0
I'm running duraspark and plan on running 10 btdc on my dizzy..hopefully I can learn how to time it. As said before..ill listen to how it responds and reacts..and if it does ping..ill retard it a lil a go from there. My issue is..is that many engines..including the 300 were build before smog..then in the 70s smog was added. Besides the computers..I'm not sure what else changed on the engines? You figure that if you replace the computer stuff and carb with non smog..then the engine would be fine..just like a 300 in the 60s
Fleet Mechanic
Joined: Jul 2011
Posts: 1,916
Likes: 4
It's not the idle mix thats the problem its the running mix. This is controled by several things on a Carter. The main ones are the main jets, metering rods and the air bleeds.
Have you ever checked to see what your running mixture ratio is going down the Highway? You do this by running an o2 senser in the exhaust and recording the voltage output at different speeds and loads.
In my testing, a YFA is too lean no matter what you do to it and I didnt test just one, I tested several YFAs from different years. I put the largest jets made, no go. Then I started making my own jets with larger holes and support to center the metering rod, it was a no go, close but still to lean.
I am glad your engine runs perfect. There are always exceptions to every rule. Maybe you have a YFA that is a model I did not test.
I am not here to start trouble. I have just spent hundreds of hours and a lot of money trying to figure this out. I have also done the same testing on Toyoto truck 22r engines with emissions removed. I ran into identical problems.
I readily admit you can pull the emissions equipment and it will run pretty good but you risk excessive combustion temps (read this as short valve life, cylinder scoring, head gasket leaks and more)
I am just trying to let folks know what I found in my testing.
By the way an engine can be pinging and have excessive combustion temps and not be heard in the cab and the temp gauge will show the engine has normal coolant temperature.
Just my two cents.
Have you ever checked to see what your running mixture ratio is going down the Highway? You do this by running an o2 senser in the exhaust and recording the voltage output at different speeds and loads.
In my testing, a YFA is too lean no matter what you do to it and I didnt test just one, I tested several YFAs from different years. I put the largest jets made, no go. Then I started making my own jets with larger holes and support to center the metering rod, it was a no go, close but still to lean.
I am glad your engine runs perfect. There are always exceptions to every rule. Maybe you have a YFA that is a model I did not test.
I am not here to start trouble. I have just spent hundreds of hours and a lot of money trying to figure this out. I have also done the same testing on Toyoto truck 22r engines with emissions removed. I ran into identical problems.
I readily admit you can pull the emissions equipment and it will run pretty good but you risk excessive combustion temps (read this as short valve life, cylinder scoring, head gasket leaks and more)
I am just trying to let folks know what I found in my testing.
By the way an engine can be pinging and have excessive combustion temps and not be heard in the cab and the temp gauge will show the engine has normal coolant temperature.
Just my two cents.
What kind of lean condition are we talking about here? Is it 15:1 or greater? It can't be incredibly bad or we'd notice a rather profound lack of power (I'd think). From what I'm hearing, it's bad enough that after an extended period of time (not as an immediate effect) it can cause damage, but not in the relatively recent time period. Are we talking years?
I haven't had an oxygen sensor hooked to my truck to record the A/F ratio, as I've always set my fuel mixtures at idle with a vacuum gauge and it runs just fine from what I can tell. Plenty of power, pretty decent gas mileage, with no audible pinging.
The excessive combustion temperatures makes me wonder as well... If the combustion temperatures are high enough to cause burnt up valves, why wouldn't it register on a mechanical temperature gauge as the motor running too hot? If it's pinging, but it's not audible, how can it be assumed that it poses a risk of causing a cracked piston? How do you know if it's pinging when it isn't audible? And more so, how many miles did it take for the burned valves to become apparent?
Interested in hearing more about your findings.
Laughing Gas
Joined: Aug 2011
Posts: 1,116
Likes: 0
I don't think anybody was trying to start trouble. There are a lot of variances that can be messed with. A lot of us swapped intakes and carbs along with doing a dizzy recurve. No problems. You're messing with a stock yfa..that's different. Although..I wonderingif you mess with your timing if it'll ping and get hot?
Senior User
Joined: Oct 2005
Posts: 146
Likes: 2
From: Wichita Falls TX
A Carter YFA cannot be jetted to compensate for a removed EGR.
YFA air bleeds are enormous.
You can take the jets completely out. and the mixture will still be too lean and eventually damage the engine.Been their, done it, it don't work.
If you use a Carter, the YF is the only option that will work.
Not all carbs will work. Sounds good in theory but it don't work on the street.
DSII does not have the right curve for non-EGR, although it can be modified.It will work stock but it will ping at partial throttle with a load in high gear.
YFA air bleeds are enormous.
You can take the jets completely out. and the mixture will still be too lean and eventually damage the engine.Been their, done it, it don't work.
If you use a Carter, the YF is the only option that will work.
Not all carbs will work. Sounds good in theory but it don't work on the street.
DSII does not have the right curve for non-EGR, although it can be modified.It will work stock but it will ping at partial throttle with a load in high gear.
The EGR on my 76 Maverick with 250 quit working, and yes, I had part throttle ping. However I took the top off, and screwed the needle up 1 turn and it went away. So yes, you can adjust the mixture for no egr on a YFA.
Fleet Mechanic
Joined: Jul 2011
Posts: 1,916
Likes: 4
Tell us more.
Senior User
Joined: Oct 2005
Posts: 146
Likes: 2
From: Wichita Falls TX
The metering rod. I turned the adjusting screw one turn counterclockwise to raise it up. You will have to experiment with yours. Might need more or less. But my part throttle pinging went away. Even in the summer with the AC going.
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