Carb for 86 305

[Jims86]

No lift and standard tires on a short bed. Originally came with 700r but it now has a th350. She runs well and has plenty of power but I need better fuel economy. I have an economical car but only drive it when I have to. I love my truck and besides my car is a pos that is just basic transportation. I plan on calling Chris at SMI and see what he recommends as far as tuning. I was hoping to get 15 mpg but honestly I would be happy with 12.5.

She idles at 400 rpms in gear and has no stumble. Feels like fuel injection but I'm thinking it is running rich. It smells rich at idle even when fully warmed up. Once I get my bike back on the road I'll try to tune the Quadrajet.

Crack the idle open to 550 in drive...400 is too low, and it is probably loading up. see how it will run after you do that, and possibly run the idle screws in 1/8 to 1/4 turn.....may clean it up.
Anyone else chime in, but IIRC there is an air bleed on the q jet also....Let me check my old books.
no OD may be the shortfall...any idea what gears you have?


Here is a good one for anyone interested.
http://www.classictrucks.com/tech/0910clt_carburetor_tuning_basics/photo_01.html

 

[hinkv10]

I just hooked up the sunpro tach and I had set the idle by sound. I love the way she rumbles at idle and is a beast. I sit in a parking lot at idle and people look. I just found the codes on the rear axle, looks like it has 3.08 gears, non locking.

I will continue to experiment with this but time is very limited right now. Thanks for the link, I will finish reading it when I have more time.

 

[Jims86]

I just hooked up the sunpro tach and I had set the idle by sound. I love the way she rumbles at idle and is a beast. I sit in a parking lot at idle and people look. I just found the codes on the rear axle, looks like it has 3.08 gears, non locking.

I will continue to experiment with this but time is very limited right now. Thanks for the link, I will finish reading it when I have more time.

550 is still like an idling locomotive...
turn your speakers up!

http://i144.photobucket.com/albums/...5D-8113-10886A6B5E5D-350-0000007B1A6D046F.mp4

 

[HotRodPC]

I gather you're more concerned about sounding impressive than being efficient. Running the idle low like that to sound like a beast as Jim said, you're causing a loading situation and/or extreme rich condition which leads to plug fouling, carbon build up on you EGR and in the combustion chambers.

 

[hinkv10]

I gather you're more concerned about sounding impressive than being efficient. Running the idle low like that to sound like a beast as Jim said, you're causing a loading situation and/or extreme rich condition which leads to plug fouling, carbon build up on you EGR and in the combustion chambers.

No, I am very concerned with economy. I drive my truck everywhere because I just enjoy driving it but 10.5 mpg is killing me. I just ordered a book on tuning the quadrajet off Amazon so I will read up on what I can do. I'm usually very frugal and drive a small car as my commuter car. I would love to get the most that I can out of the old girl.

I'm handy with a wrench but have limited experience working with carbs. Today I installed a jet kit in my *** bike and it was pretty simple so I'm feeling more confident. I may try to switch out the jets in the Quadrajet because it smells like it is running rich. I can smell it when I pull into my garage and I had never thought that running on too low an idle could cause that. I'll post up another thread and share my results and post questions. Thanks again

 

[hinkv10]

Thanks for posting the video on how the truck sounds at 500 rpms. Remember I'm just going by what the tach says. When I get a chance I'll hook up an engine anylzyer thing I got from Sears years ago. The Sunpro is probably close so I know its ideling too low. I was surprised when it read just over 400 rpms.