1981 straight six manual 4x4 project

[Ford F834]

Thanks guys for the great information that keeps pouring in. I am starting to get a little bit better picture of this whole process now.

On the carb, I looked at that baseplate number, but I could not find it on the charts that David sent me for YF identification:





I don't know if I stated this explicitly anywhere, but on my truck the EGR system has been removed and the catalytic converters deleted.

I have heard about slipping harmonic balancer problems with the IDI, but I wasn't aware that the 300 balances did it. I guess it's worth checking. What is the best way to do this? I've found time via a screw driver in the spark plug hole method on the 240 with a broken distributor shear pin but that does not seem super accurate for checking the balancer notch.

Also, my balancer had two notches in it... any idea what the other one is used for?

[PetesPonies]

The key on the crank snout will be at 12:00 when the engine's #1 cylinder is at TDC. But there are two times in the cycle that this happens. You need to find the correct one. I always use a small piece if toilet paper or light paper towel. I remove the plug and push the paper into the hole slightly. Crank the engine around by hand, the paper will shoot out on the compression stroke. Then move the engine slightly to align your timing marks at TDC or zero. When you have that done, remove the balancer bolt and see if the key is straight up and down. If it is not, your balancer has shifted or you are using the wrong timing marks.

[Gary Lewis]

I use a method similar to Pete's.  Once the paper has blown out, assuming you aren't going super fast when cranking, I then stick a straw or something soft in.  Crank the engine further, slowly, and find the spot that has the most of the straw out.  That will be TDC or close.

But, the best way is with a piston stop.  It is an adjustable bolt with a rounded head that screws into the spark plug hole.  With trial and error you adjust it so that the piston stops close to TDC.  Let's say 10 degrees, although how much doesn't really matter.  You then turn the engine back the other way and gently come up against the stop again.  Exactly 1/2 of that is true TDC.  You can mark the balancer with a sharpie and if the mid-point is under the TDC mark the balancer hasn't slipped.  You don't have to be super accurate as if it slips it usually slips a lot.

[85lebaront2]

Great pictures! On the vacuum ports, the one on the side the number is on was probably for the EGR system, it was used to operate a vacuum amplifier as it probably goes into the venturii for a very low vacuum signal, the one on the throttle body should be for the distributor vacuum. Carburetor is probably from the mid 70s (sort of looks like the one my 1977 F150 300 had on it). 7388S is a Carter ID number, now if someone has a good carburetor PN listing for the YFs maybe you can pin it down.

[Gary Lewis]

How’s this: http://www.carburetion.com/CarbNumber.asp?Number=7388S

[85lebaront2]

Gee, talk about luck, he actually has the correct application carburetor for his truck.

[Ford F834]

Thanks Gary! That's great! And it is luck that it's the right one for the application. Mine does not have the bowl vent, shown in the picture, but otherwise seems accurate. This will help make sure I get the right rebuild/seal kit 🙂

[85lebaront2]

Don't go by the picture, it is a later model than 1981, probably a non-feedback 1985 or 1986.

[Gary Lewis]

Jonathan - It was the right carb for the application.  But with the EGR blocked it isn't.

Bill - What typically needs to be done to dial an EGR carb in when the EGR has been deleted?

[85lebaront2]

If everything else is still the original, specifically timing, you would need to lean the main jet slightly. That being said, first I would look at the plugs and second if it needs "tweaking" there should be a small aluminum plug, like a miniature freeze plug in the top of the carb where the air filter sits (BTW, that air filter is cute, but even for a one barrel is too small), under that plug is a hole down to the small Philips head screw on the metering rod hanger, clockwise is richer, counterclockwise is leaner.

Since the YF metering rod is similar to the older carburetors it has both a vacuum and mechanical control. At cruise the mechanical linkage limits the down travel so the mixture is partially dependent of throttle opening.

[Gary Lewis]

Bill - That's exactly the kind of info I was looking for.  

Instead of you writing a "book", how 'bout writing a page on tuning YF's?  I can put it on the website on the current YFA page, but put the existing info on rebuilding in one tab and your "tuning" writeup in another tab.

[85lebaront2]

Ok, but I will let you set up the tabs, maybe for all the carburetors? I can even speak VV if needed.

[Ford F834]

Awesome info., thank you Bill! That air cleaner was an emergency solution from when my '68 broke down on the side of the road and I bought that junkyard carb to get it home. It is indeed horrible and causes a noticeable loss of power. I now have one of the large flat style straight six air cleaners on it that David sent me.

[Gary Lewis]

You just send me documents, in pdf or Word, and I’ll set up the tabs and do all the website work. Thanks!

[85lebaront2]

Looks good! Glad I could help you with it.

[Ford F834]

This morning I filled up the truck and got my first unloaded mpg calculation. Unloaded, yes, but the day that I drove it to work it decided to snow. So about 75% was through slush and powder, about 50% in 4wd with the hubs locked in. Speed was about 62 below snow line, then decreasing to 25 in places. I measured 153.0 miles with the gps and 10.17 gallons of fuel calculating out to 15.04mpg. Not bad.

I will say that with the hubs locked in for snow the front end was getting noisy around 45mph. It works fine for now and for what I need it for but will need attention at some point.

I am driving the truck to work tonight, and will pick up my Diesel engine block from the machinist in the morning. We will see what the next run will return for mileage... being higher speed but no snow.

[Gary Lewis]

That's good MPG for those conditions.  And I suspect it'll be more like 17 when you get a good reading w/o the adverse conditions.

As for the front end, check out the u-joints - both in the drive shaft as well as the axle shafts.  The axle shaft ones are a bear to change, but can cause noise.  Try leaving it in 2Hi and locking in one hub to check for noise.  Then swap to the other hub to see if anything changes.  Or, go to 4Hi and leave the hubs unlocked.

[Ford F834]

Thanks Gary. The front driveshaft u-joints are new, and the slip yoke is solid so it has to be the axle shafts 😔. With the hubs locked in I hear it in both 2Hi and 4Hi. It needs upper ball joints also. I was not able to get them to move in my driveway, but the guys at the tire shop pried with a long bar against the concrete floor and showed me the play... barely any on the passenger side but noticeable on the driver side. I just can't do a full rebuild on it at this point. Yeah it has some wear but it's still useable  

I am still having some carb issues. It starved out once on the snow day going downhill at 73 mph. (Fastest I have ever pushed it since I've owned it... and no that wasn't in the snow!). It did it again on my way to work tonight after a coffee stop just as I got it going in 4th gear. I guess I will do the solvent dunk + carb kit and hope that takes care of it.

With my current timing and tune up the truck feels the best on the highway running 62-64mph. My tach is reading right about 2,000 + change which is reasonably accurate. Pulling the mountain grades I hold 52-55 mph in 4th just letting it do its thing without flooring it. The grades include some pretty long stretches at 6%. Pretty tame straight six stuff, I know, but a bench mark for later reference as I work at tuning it up. I hear no pinging or knocking, fuel is 87 octane regular. Verde valley is ~3,200' climbing to just over 7,000' near my job. Perhaps I can squeeze just a bit more out of it 😉

[1986F150Six]

That sounds good, Jonathan, except for the fuel starvation issue. The Frenchtown Flyer has in previous threads, indicated that with the aerodynamics of this body, the fuel consumption significantly increases after 62 mph. I get my best mileage @ ~60 mph. My son's truck gets its best @ ~65 mph.

[Gary Lewis]

Yes, the aerodynamics are worse than a proverbial barn door as these trucks have recesses, like headlights, that capture the air.  That's why Ford flushed them in '87.  

Could your fuel problem be icing?  Do you have heat plumbed to the air cleaner?

As for timing and tune, have you ever had pinging?  If not, you probably don't have enough advance dialed in.  I think we've talked about that before, but best MPG is going to be just short of pinging.  And that occurs at part-throttle, which means you need to adjust the vacuum advance.