Bullnose Enthusiasts Forum

New/Repro YF carburetor for the 300 six

Classic

List

Threaded

128 messages Options

12345 ... 7

Ford F834

Re: New/Repro YF carburetor for the 300 six

Administrator

Gary, that is one of the problems I am hoping will go away with this new carb. It was infrequent, so time will tell if this eliminates it. The old carb also suffered from nose dive idle when I pushed in the clutch and rolled to a traffic stop (had to set racing idle to prevent stall). This seems to be gone, fingers crossed. Also, about 70% of the time it would diesel/run backwards when shut off. This also seems to be fixed.

SHORT BED 4-DOOR DIESEL: 1986 F350 4x4 under construction-- 7.3 IDIT ZF5+GVOD

STRAIGHT SIX 4X4: 1981 F150 2wd to 4x4-- 300 I6 close ratio diesel T19, hydroboost brakes, Saginaw steering

BIG F: 1995 F-Superduty under construction— converting to 6.9L IDI diesel ZF5+DNE2

Gary Lewis

Re: New/Repro YF carburetor for the 300 six

Administrator

If it fixes all that it'll be a miracle. Especially for the price!

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

1986F150Six

Re: New/Repro YF carburetor for the 300 six

Administrator

That is very promising news, Jonathan!

Ford F834

Re: New/Repro YF carburetor for the 300 six

Administrator

Thank you David! And thank you for spotting it on eBay and sending me the link 🙂. Once again your tireless search talent has greatly helped me

Ford F834

Re: New/Repro YF carburetor for the 300 six

Administrator

Folks... I have discovered a problem....

As you may recall I thought my timing was set over-advanced. It was. A lot. I moved it back to about 14* and went for a ride. It ran like absolute crap 💩. It behaved like I had the choke on. I got home and pulled the vacuum hose and found that I have absolutely NO Venturi vacuum out of the single vacuum port provided on this carburetor. I do not know if this is a defect, or perhaps a packing oil issue?

I may investigate more later, but for now the solution is to run the distributor off of full manifold vacuum. I think I would get smoother idle with Venturi vacuum, but manifold vacuum is working. It is running better than it was with crazy advanced static timing.

Gary Lewis

Re: New/Repro YF carburetor for the 300 six

Administrator

If I remember correctly, some of the YF/YFA's had a strange ported vacuum that only reached ~10" of vacuum at cruise. Might that be what you have?

Gary, AKA "Gary fellow": Profile

Ford F834

Re: New/Repro YF carburetor for the 300 six

Administrator

Hmmm... I guess I should track down my vacuum gauge. Even when I rev it up to say 2,500 rpm I can’t feel anything at all with the hose on the tip of my finger though. Also, there is no change in how it runs with the port unplugged (simulating a leak). I didn’t think to blow through from the distributor end of the hose to see if it is blocked. I should check a few more things tomorrow.

ArdWrknTrk

Re: New/Repro YF carburetor for the 300 six

Administrator

There should be less and less vacuum as you open the throttle.
Ported vacuum should start as soon as you crack the throttle plates into the transfer ports (hence "ported")

I'm hoping this is easily resolved, Jonathan!

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

1986F150Six

Re: New/Repro YF carburetor for the 300 six

Administrator

In reply to this post by Gary Lewis

Gary Lewis wrote

If I remember correctly, some of the YF/YFA's had a strange ported vacuum that only reached ~10" of vacuum at cruise. Might that be what you have?

Gary, we saw this on the Carter YF on my truck. It had about 5" Hg @ idle and never exceeded 11".

Gary Lewis

Re: New/Repro YF carburetor for the 300 six

Administrator

Yes! That's where it was.

Jonathan - I'd be tempted to put a bit of compressed air on that port and see if it is just clogged. It is really just an opening into the low pressure area, so it wouldn't take much grease to clog it.

Gary, AKA "Gary fellow": Profile

1986F150Six

Re: New/Repro YF carburetor for the 300 six

Administrator

Gary Lewis wrote

Jonathan - I'd be tempted to put a bit of compressed air on that port and see if it is just clogged. It is really just an opening into the low pressure area, so it wouldn't take much grease to clog it.

Or, take the vacuum hose currently connected to manifold vacuum, which should have ~21" @ idle, and connect the "distributor end" of the hose to the carburetor vacuum [Venturi] port. Perhaps the greater vacuum will suck out the obstruction?

Gary Lewis

Re: New/Repro YF carburetor for the 300 six

Administrator

Certainly can't hurt anything. And, it might fix it.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: New/Repro YF carburetor for the 300 six

Administrator

Maybe squirt some carb cleaner through all the passages like suggested?

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Rembrant

Re: New/Repro YF carburetor for the 300 six

In reply to this post by Ford F834

Question for you guys: What is the barb at the top of the carb for?

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

ArdWrknTrk

Re: New/Repro YF carburetor for the 300 six

Administrator

I always thought that was the bowl vent, but I may be mistaken..

Could be ported

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: New/Repro YF carburetor for the 300 six

Administrator

In reply to this post by Rembrant

At that angle I think it is filtered air for the heated choke system.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: New/Repro YF carburetor for the 300 six

Administrator

The choke seems way off on the other side???

Unless you mean filtered air inlet for the choke stove?

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: New/Repro YF carburetor for the 300 six

Administrator

Yes, filtered air that goes down to the manifold and back to the choke.

Gary, AKA "Gary fellow": Profile

Ford F834

Re: New/Repro YF carburetor for the 300 six

Administrator

In reply to this post by Rembrant

Cory, I believe that barb may have something to do with Evap emissions recovery or the air cleaner warm intake/emissions valves? The heat riser is on the other side of the carb and connects to the choke housing with a flare nut.

Update for today: I could not blow or suck air through the vacuum hose when connected to the carb. I had sprayed the ports with carb cleaner before installing it, but I tried again (copious amounts) and no change. I tried backing out the brass barb a little in case it was bottomed out in a 90* port and blocking the passage, but that didn’t help either. I tried putting suction on it with a mightyvac, and with direct manifold vacuum but again there was no change. The port is completely plugged.

The next step, I suppose, would be to remove the bottom plate of the carburetor and investigate what can be seen. Either that or try to force compressed air through the port. I did not have a fitting to try this.... but the bottom line is the truck is running very well on manifold vacuum, and I’m not going to mess with success as they say. Sorry for those who may want closure to this issue, but with the truck in daily use I’m not inclined to tear apart the new carburetor. I need the truck running and I can’t afford any more time since it is working on manifold vacuum.

I drove the truck to Kingman today, mix of freeway and city driving, and it is performing about as well as I have ever had it. I would still like to replace the pickup in the recurved distributor and go back to running that instead of the stock one, but as it is right now I cannot complain. It’s running really well and I’m still impressed given the price point.

Ford F834

Re: New/Repro YF carburetor for the 300 six

Administrator

In reply to this post by Gary Lewis

Gary Lewis wrote

Yes, filtered air that goes down to the manifold and back to the choke.

Okay, this is making sense... although I believe it is usually missing parts on the engines I’ve seen. I’m vaguely remembering a thin tube with an orange silicone hose on the manifold set from the 4x4 donor.

12345 ... 7