Some carb adjusting input please
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Postmaster
Joined: Nov 2002
Posts: 3,447
Likes: 1
From: Littleton, CO
Some carb adjusting input please
So I took the 66 donor (with a 79 302) over to get the dreaded emission test as I want to plate it for transporting parts. Well I managed to fail the CO test, telling me it is running rich. Now of course I was not suprised as my track record with the emmision shops is not too keen on anyhting I own older than a 1990. So when i arrived at home, I cannot let things lie so I started backing out the adjusting screws of the little 2-brl carb. Once I got to a point i felt was satisfactory, I screwed teh adjusters back it to see how far out I was. I managed to make it our 5 turns on each side (yes teh air is thin at 5000ft above sea level), but it smelt like it was running richer than before. Now somebody check my stats here, I normally seat the screws and back out 2 1/2 turns. Any further out does lean the mixture - correct??? Of course I know that I can drop down a jet size, but I think I will hold off on that if I fail the test again (it is only $15 with a free re-test). Perhaps a bottle of rubbing alcohol will heat things up enough too???
Laughing Gas
Joined: Mar 2005
Posts: 1,109
Likes: 9
From: Thornton, Colorado
Not to say you shouldn't get your truck running the best it can, but did you know that the laws changed, and if you put Classic plates on a 66 you never have to get an emissions test in Colorado? I was working my butt off until I found that out, and then i went and got plates no questions asked.
Lead Driver
Joined: Aug 2003
Posts: 6,305
Likes: 18
From: Boulder Creek, Ca
On 68 289/302 I usually start at 1 1/2 turns then decrease mixture until slight drop in idle speed then slight increase in mixture; same with the other. After adj. mixture recheck timing. Usually runs around 8 degrees btc, with altitute may vary.
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Postmaster
Joined: Nov 2002
Posts: 3,447
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From: Littleton, CO
Thanks gang. I knew of the Classic plates as I have them on the Cougar, but I am only looking short term on this truck and didn't want to dump the $$$. She is set at 8 degrees, it is usually just right for this altitude as well. I will go back to the drawing board and pull them out 1 1/2 to start with and adjust accordingly...
Senior User
Joined: Aug 2010
Posts: 113
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From: Moreno Valley
Thanks gang. I knew of the Classic plates as I have them on the Cougar, but I am only looking short term on this truck and didn't want to dump the $$$. She is set at 8 degrees, it is usually just right for this altitude as well. I will go back to the drawing board and pull them out 1 1/2 to start with and adjust accordingly...
Adjust each idle screw til you get the highes vacuum reading.
Done
Senior User
Joined: Sep 2010
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From: Atlanta, Georgia
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Senior User
Joined: Aug 2010
Posts: 113
Likes: 0
From: Moreno Valley
Idle 41-16 depends on camshaft and compression
midrange 13.5-14
wide open 13.5-14
never will get it perfect with a carb
but you can buy a AFR gauge and get it closer
best bet is EFI Multi-port
EFI set up properly will turn a 10mpg 390 @60mph into a 17.5-21mpg truck (2wd)
But most shy away from EFI using cost as an Excuse...when really it is lack of knowledge
retrofitting is not that expensive if already rebuidling the engine
midrange 13.5-14
wide open 13.5-14
never will get it perfect with a carb
but you can buy a AFR gauge and get it closer
best bet is EFI Multi-port
EFI set up properly will turn a 10mpg 390 @60mph into a 17.5-21mpg truck (2wd)
But most shy away from EFI using cost as an Excuse...when really it is lack of knowledge
retrofitting is not that expensive if already rebuidling the engine
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Senior User
Joined: Sep 2010
Posts: 193
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From: Atlanta, Georgia
I hear ya. I was just not sure if there were compromises in carbs. I have not messed around with a carb in probably 10 years. I have been playing with EFI. With my Subaru, it is as easy as plugging in the laptop and hitting a couple keys to change idle, timing, etc.
I actually already own a wideband o2 meter. But I didn't know if these liked to idle around 14.7 like modern cars do or if you had to idle them a bit richer due to the carb. Multi-port would be nice, but I am not going to bother till I have a new motor in there.
I actually already own a wideband o2 meter. But I didn't know if these liked to idle around 14.7 like modern cars do or if you had to idle them a bit richer due to the carb. Multi-port would be nice, but I am not going to bother till I have a new motor in there.
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