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Re-jetting a Carter YF?

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Oregoon
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Re-jetting a Carter YF?

Post #1 by Oregoon » Sun Mar 30, 2014 11:54 pm

Hey there,

Shortly before my the 240 in my '66 F100 started telling me some bad knock-knock jokes, I took it by a friend's place and he hooked it up to his exhaust gas analyzer. Those are the kind of friends we all need!

Anyway, it's jetted way too lean, which I suspected anyway, given my plugs ashy white coloring.

I'm going to be putting another I-6 in my truck (naturally!) and it'll be either a 240 or a 300. Regardless of which, I need to re-jet my carb. The Portland Swap Meet is next weekend, so hopefully, I'll find a good engine sooner rather than later.

How hard is this? Can anyone walk me through it? I'm not entirely carb-illiterate, and understand enough to know each carb has it's foilbles... Also, where can a guy find Carter YF jets?

Thanks in advance!

1986F150six
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Re: Re-jetting a Carter YF?

Post #2 by 1986F150six » Mon Mar 31, 2014 9:29 am

Is it possible that your truck has a vacuum leak causing the lean condition?

Oregoon
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Re: Re-jetting a Carter YF?

Post #3 by Oregoon » Mon Mar 31, 2014 11:24 am

Nope, we hit it with the infrared too. I'd already gone after it with starter fluid and hadn't found anything and a proper check confirmed what I already knew. I just had my manifolds surfaced, used new gaskets, and everything is ship-shape in that department.

Timing is 6 BTDC, too.

My buddy owned a shop for years and recently retired to work out of his home-shop. All he does is mechanical work on customs and restos, and he specializes in carbs. He must have a thousand or more in his basement, all catalogued and ordered. He says he's seen this before with off-the-shelf Carters, since they can be used on so many applications. I am tempted to pull my carb and see how it does on another friend's Chevy 194--that's how lean it's running.

Anyway, all that aside, how hard are they to re-jet? Obviously, I could ask my buddy for some help but he's nowhere near my place, his time is money (like everyone else), and my budget is tied up in finding an engine. Also, I simply want to do it myself. He's both busy and trying to be retired and doesn't need me hassling him.

So, do I pull the top of the carb off and put a new main jet in, or is there more to it?

motzingg
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Re: Re-jetting a Carter YF?

Post #4 by motzingg » Mon Mar 31, 2014 3:05 pm

yep, its pretty simple. they are basic little carbs.

navigate to the link if the image doesn't display correctly:
http://oldcarmanualproject.com/manuals/ ... 19_jpg.jpg


i'm pretty sure its just a 'low speed jet' and a 'metering rod jet' but the 'metering rod' is also a tuning component, you might have a mis-matched metering rod (us motorcycle guys call them a 'needle') and jet.

here is the metering rod assembly.

If you buy a rebuild kit, they usually have that pic i attached printed out for you on a big sheet of paper, still might want to take photos of the stages of carb disassembly while you are doing it, however. Here is a picture i took from when i did mine.

Image

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THE FRENCHTOWN FLYER
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Re: Re-jetting a Carter YF?

Post #5 by THE FRENCHTOWN FLYER » Mon Mar 31, 2014 6:19 pm

Before changing jets I would try the metering rod adjustment. It has always fixed any YF mixture issues I've seen. The screw in the background raises and lowers the tapered rod in the jet. Raising it will fatten up the part throttle mixture without fattening up the WOT mixture, which I suspect is not too lean anyway. Plug readings at WOT mnust be taken after running the engine at WOT and not letting it come back down to idle while running or the WOT reading will be affected.

Modern plugs will tolerate a leaner mixture and may look white, even though the mixture is correct. This is especially noticeable on fuel injected engines.

My buddy John would always send his driver (aka his wife) down the track with a ratchet plug wrench and a spare plug. She would kill the engine at WOT, coast to a stop, change the plug in question, and bring the unsullied plug back to the pits for inspection. He was an absolute wizard at tuning Weber IR systems.
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

Oregoon
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Re: Re-jetting a Carter YF?

Post #6 by Oregoon » Mon Mar 31, 2014 6:27 pm

That definitely seems the easiest place to start.

I presume we're talking about the black Phillips screw in the picture?

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THE FRENCHTOWN FLYER
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Re: Re-jetting a Carter YF?

Post #7 by THE FRENCHTOWN FLYER » Mon Mar 31, 2014 9:12 pm

yup
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

Oregoon
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Re: Re-jetting a Carter YF?

Post #8 by Oregoon » Tue Apr 01, 2014 7:32 pm

Thanks for the heads up! I'll check it out tomorrow.

motzingg
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Re: Re-jetting a Carter YF?

Post #9 by motzingg » Mon Apr 07, 2014 12:44 pm

oh duh, totally forgot that was an adjustment point

Oregoon
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Re: Re-jetting a Carter YF?

Post #10 by Oregoon » Mon Jun 02, 2014 1:17 pm

BUMP.

So, got a new engine in there--a '71 240--and am back to dealing with my tuning issues. Despite all manner of fiddling with the metering-rod, my engine remains very lean. And, despite new intake/exhaust gaskets, a proper torquing, and a stock air-cleaner, the carb makes a whooshing noise you can literally hear a block away. It sounds like natural gas-plant. Something in there--throttle plate, air-horn, etc--is banged-up or has a sharp-edge and whistles to beat heck.

My motor came with another Carter YF, which needs rebuilt. For giggles, I put it on there and fired it up. No idle to speak of, but it didn't make a peep compared to the reman I've been working with.

Going to rebuild the old one and see how my truck likes it.

Still wondering if anyone knows the correct jet-size for a YF on a 240 cid. I'm about 200' above seal level, if that matters.

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