The Ford Barn

Paul Bennett · 05-21-2018, 06:41 PM

Later Ford flatheads have a threaded connectors/steel line connecting the distributor and 885 Holley carburetor.

For tuneup using vacuum gauge, I need to "T" into this vacuum line between carb and distributor. I've considered sawing the steel pipe midway and using rubber hose to do the "T" and when done, use rubber hose to put things back together. But sawing the line leaves a permanent scar.

Surely there is a better or preferred way. What do you recommend here?

51 MERC-CT · 05-21-2018, 07:20 PM

The Mercury 885 carb vacuum line that is on the back of the carb. does not provide full manifold vacuum, it is a timed spark port to operate the loadomatic distributor.
Suggest you 'T' into the the line that provides vacuum to the wipers.

DD931 · 05-21-2018, 09:37 PM

A agree with 51 Merc. Tie in to the line from the manifold to the wipers. The line from the carb is designed just for the loadamatic distributor.

fordwife · 05-21-2018, 10:01 PM

As I recall, the line from carb. to dist. supplies venturi vacuum which is the opposite of manifold vacuum.

Paul Bennett · 05-22-2018, 06:26 PM

Quote:

Originally Posted by fordwife

As I recall, the line from carb. to dist. supplies venturi vacuum which is the opposite of manifold vacuum.

If one is opposite the other, which do I put the vacuum gauge on?
Bubba just posted an article of rpm vs vac

2000 rpm - 3.7 In
1000 rpm - 1.7 In

40cpe · 05-22-2018, 07:15 PM

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Bubba's information is specific to the advance function of the distributor. You can use his information to check the vacuum signal the carburetor is sending to the distributor if so desired.

Manifold vacuum is used to check the health/tune of an engine. As stated above, the windshield wiper connection can be used for manifold vacuum tests.

Mike51Merc · 05-25-2018, 07:52 AM

The venturi vacuum on the loadamatic system increases with engine rpms (from increased air velocity passing through the venturi).

This is (generally) the opposite of manifold vacuum which decreases with throttle opening.

The diaphragm on the loadamatic distributor functions opposite of most vacuum advances.

Paul Bennett · 05-27-2018, 02:15 PM

I just read a bulletin which advocated the mechanic to cut a spare vacuum tube and insert a "T" for the gauge. I don't have access to a spare vacuum tube and won't cut my existing tube. Guess the only alternative is removing the tube and fashioning a new one. I suppose the fittings are obtainable. I don't imagine the flare (single/double) is critical.

51 MERC-CT · 05-27-2018, 05:02 PM

Could possibly make up a copper or steel line using the components as shown to fit the carb and distributor.

tubman · 05-27-2018, 06:23 PM

Aren't "brake line fittings" (flare fittings) different from compression fittings (used with the sleeve)?

51 MERC-CT · 05-27-2018, 06:36 PM

Quote:

Originally Posted by tubman

Aren't "brake line fittings" (flare fittings) different from compression fittings (used with the sleeve)?

The 'nut' has a 45° chamfer that will compress the ferrule and is the correct straight thread to fit the carb and dist. It is the only component that is used.

tubman · 05-27-2018, 06:58 PM

Might work. I'd still use the proper "Ford Nut" though.

51 MERC-CT · 05-27-2018, 07:25 PM

Quote:

Originally Posted by tubman

Might work. I'd still use the proper "Ford Nut" though.

I used this method years ago when I didn't care to search for a "Ford Nut".
Worked well until carb. and dist. were swapped for better options.

tubman · 05-27-2018, 08:23 PM

I know what you mean; the last time I needed one, I couldn't find one and had to come on here and beg. "JWL" came through for me though.

05-21-2018, 06:41 PM	#1
Paul Bennett Senior Member Join Date: Sep 2016 Posts: 628	Vacuum splice - late flathead - best access point Later Ford flatheads have a threaded connectors/steel line connecting the distributor and 885 Holley carburetor. For tuneup using vacuum gauge, I need to "T" into this vacuum line between carb and distributor. I've considered sawing the steel pipe midway and using rubber hose to do the "T" and when done, use rubber hose to put things back together. But sawing the line leaves a permanent scar. Surely there is a better or preferred way. What do you recommend here?

05-21-2018, 07:20 PM	#2
51 MERC-CT Senior Member Join Date: May 2010 Location: East Hartford, Ct Posts: 5,898	Re: Vacuum splice - late flathead - best access point The Mercury 885 carb vacuum line that is on the back of the carb. does not provide full manifold vacuum, it is a timed spark port to operate the loadomatic distributor. Suggest you 'T' into the the line that provides vacuum to the wipers. __________________ DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES

05-21-2018, 09:37 PM	#3
DD931 Senior Member Join Date: May 2010 Location: PA Poconos Posts: 723	Re: Vacuum splice - late flathead - best access point A agree with 51 Merc. Tie in to the line from the manifold to the wipers. The line from the carb is designed just for the loadamatic distributor.

05-21-2018, 10:01 PM	#4
fordwife Senior Member Join Date: Dec 2015 Posts: 287	Re: Vacuum splice - late flathead - best access point As I recall, the line from carb. to dist. supplies venturi vacuum which is the opposite of manifold vacuum.

05-22-2018, 07:15 PM	#6
40cpe Senior Member Join Date: May 2010 Location: Star, MS Posts: 4,024	Re: Vacuum splice - late flathead - best access point Sponsored Links (Register now to hide all advertisements) Bubba's information is specific to the advance function of the distributor. You can use his information to check the vacuum signal the carburetor is sending to the distributor if so desired. Manifold vacuum is used to check the health/tune of an engine. As stated above, the windshield wiper connection can be used for manifold vacuum tests.

05-25-2018, 07:52 AM	#7
Mike51Merc Senior Member Join Date: May 2010 Location: Northeast Pennsylvania Posts: 1,582	Re: Vacuum splice - late flathead - best access point The venturi vacuum on the loadamatic system increases with engine rpms (from increased air velocity passing through the venturi). This is (generally) the opposite of manifold vacuum which decreases with throttle opening. The diaphragm on the loadamatic distributor functions opposite of most vacuum advances.

05-27-2018, 02:15 PM	#8
Paul Bennett Senior Member Join Date: Sep 2016 Posts: 628	Re: Vacuum splice - late flathead - best access point I just read a bulletin which advocated the mechanic to cut a spare vacuum tube and insert a "T" for the gauge. I don't have access to a spare vacuum tube and won't cut my existing tube. Guess the only alternative is removing the tube and fashioning a new one. I suppose the fittings are obtainable. I don't imagine the flare (single/double) is critical.

05-27-2018, 06:23 PM	#10
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,316	Re: Vacuum splice - late flathead - best access point Aren't "brake line fittings" (flare fittings) different from compression fittings (used with the sleeve)?

05-27-2018, 06:58 PM	#12
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,316	Re: Vacuum splice - late flathead - best access point Might work. I'd still use the proper "Ford Nut" though.

05-27-2018, 08:23 PM	#14
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,316	Re: Vacuum splice - late flathead - best access point I know what you mean; the last time I needed one, I couldn't find one and had to come on here and beg. "JWL" came through for me though.