16mpg with 42 DCNF's on an 1835?

[marcd]

Guys,

I am getting ready to take my '69 off the road upon the finish of my To#¤ta; and I am determined to solve this s^%t gas mileage before I switch to EFI. More than a few guys have told me the mileage should be better, in the mid to upper 20's.

Car has great power, and runs well. We built this motor in '08 and finished it the night before leaving for Bug-In, so we broke it in on the way to California.

I work pretty close to home, so this hasn't bothered me too much before. After work and on weekend I drive the girlfriends car; mostly due to a stereo and climate controls.

I just pulled the carbs to get all the numbers.

1835 w/ 110 cam, light port/polish.
1 5/8 merged with QP.
009 (mex) with compufire (new)


42 dcnf jetting:

Air: 180
Emulsion: F25
Main: 140
Starter: 80F7
Idle: 60
Venturi: 32
Aux. Venturi: 3.5

I am trying to borrow a wideband to datalog the A/F, but I am not sure if I can get it in time to help with jetting.

I have looked through some of the DCNF posts, but wasn't able to turn up very much comparative info for jetting size.

Input?

[Diederick/DVK]

i'm no expert but seeing as there are no posts yet i'll break the ice.

i suspect you could go down on the venturi size and idle jet. does your engine not run a little rich? a wideband should be able to show whether your engine is running rich. don't pull the engine out yet though, try to borrow and hook up an LM-1 a take your '69 for a drive.

good luck!

[rick m]

Don Bulitta, who posts on this lounge, runs 42s. He could give you some insights.  I know that when we cruised to Detroit (from Phoenix/5200 miles round trip) we were all averaging over 20mpg.  My 2110 with 48s was getting 24.  I know Don was doing better than I was with his 42s.

Drop Don Bulitta a line. I am sure he would be glad to provide some input.  Cam, compression, timing and many things factor mileage.

Rick M

[Donny B.]

I would think you could use a 135 main and a 55 idle jet.  The emulsion should be correct.  You didn't mention your compression ratio.  If you are running low compression you will need to advance your timing.  I was running 7 to 1 on my 1776 and ran 38 degrees total advance.  On the road I usually got 24 MPG, but have gotten as high as 30MPG.  You also didn't mention valve size, but even so the exhaust is probably too large.  A 1 1/2 would probably be better suited to your combination.

[Brandon Sinclair]

What is your fuel pressue and did you verify it?

Also did you verify the jet sizes-a lot have been reamed larger then what they are marked.

I agree with Don, you exhaust is too large and then your idle and mains are too large. 

Verify your fuel pressure and timing first and that you have no intake or exhaust leaks then hook up your wideband and take some readings at wide open throttle and see where your A/F readings are and make adjustments.