New Carter YFA

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Apr 12, 2013 | 09:06 AM

zer0vector

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New Carter YFA

I hate to start another one of those threads (and I've read just about every one of them), but I need some help walking through this carb install and tuning.

I've put a non-feedback reman Carter YFA on my '85 F150 I6. I have also switched over the ignition system.

After installing the carb he fired right up but there are some tuning issues I need help on. I have a vacuum gauge and a timing light.

1. Using the vacuum gauge, I can only get a decent reading with the distributor very advanced (according to the timing marks, they way off the gauge, maybe >20). The marks could have shifted, so that's not terribly worrying.

2. Using the vacuum gauge, I can only get a decent reading with the mixture screw backed way out, maybe 3 1/2 turns. (so that means super-rich, right?) This seems far considering what I've read.

I can get about 18.5" max on the gauge by the way.

So where do I start? I know there could be about a hundred things wrong, but I've tried to eliminate vacuum leaks (all the feedback sensor stuff is disconnected) and all the unused vacuum ports are plugged.

Apr 12, 2013 | 10:54 AM

1986F150six

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From: Sheffield, AL

Do you have the vacuum line to the distributor cannister disconnected and plugged while reading the vacuum gauge?

Was the carburetor rebuilt?

Apr 12, 2013 | 11:12 AM

zer0vector

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Yes, the only vacuum items hooked up are the brake booster, the PCV valve and the gauge. All other ports are plugged.

The carb was a rebuilt YFA from Rock Auto listed for a 79-80 F150 with the 300. I figured that would get me away from the feedback but still setup to run with the EGR that's there.

Also, I should throw in that I'm at 2000 feet, as I've read that might effect vacuum readings.

Apr 12, 2013 | 11:29 AM

Harte3

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From: Spokane, WA

I'm in the 2000-2500 elevation range and draw 18.5 vacuum on a 600 rpm idle with a modified engine so 18.5 might be about right. When I go to areas 1000 feet or less it gains about 1 hg.

Apr 12, 2013 | 11:31 AM

zer0vector

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Yeah, from what I'm reading it's about an inch per 1000 ft, so maybe my readings weren't so bad after all.

I just took him for a spin and I got what I think is pinging under acceleration (like a rattling noise) So that means I should retard the timing, correct?

Apr 20, 2013 | 10:23 PM

6fifty_f1fifty

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Joined: Apr 2009

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From: San Diego

Retarding it a little may help, I am trying to figure the same problem with mine. Kind of a pain in the butt when you don't have a garage or driveway though...

Apr 21, 2013 | 06:48 PM

6978sghfbjklgdfsjhkl

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a little input.

You've said you've change the ignition, does that mean you have changed the original distributor?. Do you still have the EGR hooked up?. It seems to be common practice to "re-curve" you distributor once having modified the original factory emissions settings. If you choose to run a higher octance fuel this may help.