Topic: 68 big block rear intake vacuum fitting

[WT8095]

I'm looking for the correct combination of intake manifold vacuum fittings for the following application:

S code 390GT
San Jose plant
2/7/1968 build date
C6 transmission
Air cleaner vacuum motor
No brake booster
No A/C
No tilt column
No speed control

Starting from scratch - original engine is long gone. I have a donor 1968 S code engine, tag date Dec 1967. The donor car was manual transmission and had power brakes, so I'm thinking the vacuum fittings will be somewhat different, and the printed documents I have access to are unclear for my combination.

Photos:
1) My donor engine. Note the fitting threaded into the manifold has one spare outlet that's capped (cap is torn). Amended: the piece of rubber on the top port may in fact be a piece of hose, not a torn cap. The other piece of the fitting has a female compression thread for the brake booster and one spare outlet that is capped.
2) From the WCCC website. The fitting in the manifold is the same general design as my donor fitting, but does not have the spare outlet. The second piece has the female compression threads for the booster, plus two additional outlets. One of those is used for the trans vacuum line and the other is capped.

Question 1: which manifold fitting would be correct for my application: with spare outlet or without? Or is there another option?
Question 2: which second fitting would be correct? Both photos show fittings for use with compression fittings, which my car did not have. This opening would have to be plugged. Or was a straight hose barb (like a 373724) used, threaded directly into the manifold fitting?
Question 3: where is the air cleaner vacuum motor connected?

Any "field observations" or photographs would be greatly appreciated.

[krelboyne]

Your top picture shows a hard line going to the brake booster. I have seen the brass fitting with nipple for the PCV transfer tube with a hex plug in it, if without disc brakes or other vacuum needs. May have been a non-Mustang application though.
Wouldn't the side vacuum valve in the intake need ported vacuum? (same as distributor advance). Instead of constant vacuum, as found from intake manifold?

[Bob Gaines]

I'm looking for the correct combination of intake manifold vacuum fittings for the following application:

S code 390GT
San Jose plant
2/7/1968 build date
C6 transmission
Air cleaner vacuum motor
No brake booster
No A/C
No tilt column
No speed control

Starting from scratch - original engine is long gone. I have a donor 1968 S code engine, tag date Dec 1967. The donor car was manual transmission and had power brakes, so I'm thinking the vacuum fittings will be somewhat different, and the printed documents I have access to are unclear for my combination.

Photos:
1) My donor engine. Note the fitting threaded into the manifold has one spare outlet that's capped (cap is torn). The other piece of the fitting has a female compression thread for the brake booster and one spare outlet that is capped.
2) From the WCCC website. The fitting in the manifold is the same general design as my donor fitting, but does not have the spare outlet. The second piece has the female compression threads for the booster, plus two additional outlets. One of those is used for the trans vacuum line and the other is capped.

Question 1: which manifold fitting would be correct for my application: with spare outlet or without? Or is there another option?
Question 2: which second fitting would be correct? Both photos show fittings for use with compression fittings, which my car did not have. This opening would have to be plugged. Or was a straight hose barb (like a 373724) used, threaded directly into the manifold fitting?
Question 3: where is the air cleaner vacuum motor connected?

Any "field observations" or photographs would be greatly appreciated.

Ether picture will work . Hex head plug added to plug booster vacuum. Difference would be the pcv tube, short hose/clamps and intake fitting would be painted with the engine . The brass fitting added for vacuum options and brake booster was added after painting and remained unpainted brass. The brass fitting was supposed to only have enough nipples for options but with that said I have lost count of how many times I have seen more nipples then needed on untouched brass blocks used but with rubber caps installed. The C6 modulator valve gets it's vacuum from one of the nipples on the unpainted brass block. I don't think the air cleaner used this block as a source for it's vacuum because it was constant.

[WT8095]

Your top picture shows a hard line going to the brake booster. I have seen the brass fitting with nipple for the PCV transfer tube with a hex plug in it, if without disc brakes or other vacuum needs. May have been a non-Mustang application though.
Wouldn't the side vacuum valve in the intake need ported vacuum? (same as distributor advance). Instead of constant vacuum, as found from intake manifold?

Interesting that you've seen the side port plugged. It's the easiest route for me, given the pieces I already have. I'd like to get it correct the way Ford installed it of course. Your observation helps. Do you recall which fitting you've seen plugged, the small one in my first photo or the larger block shown in the second photo?

The vac motor goes to intake vacuum as shown in the attached illustration from the Ford emissions manual for 1968. The service manual has a more complete explanation but I don't have a copy here at work     I just need to confirm where it connects to the manifold. I have a suspicion that it may go to the fitting that's screwed into the manifold. I described it as having a capped port on top, but that may not be a damaged cap - I think it may be a chunk of hose.

[Bob Gaines]

Interesting that you've seen the side port plugged. It's the easiest route for me, given the pieces I already have. I'd like to get it correct the way Ford installed it of course. Your observation helps. Do you recall which fitting you've seen plugged, the small one in my first photo or the larger block shown in the second photo?

You must have missed in my post where I discussed that which block is used is not a absolute. The manual indicates the block with only the specific number vacuum nipples needed was to be used. The real world is different . In fact it appears that many different ones were used and the un needed vacuum ports simply capped off with a rubber cap.

[WT8095]

You must have missed in my post where I discussed that which block is used is not a absolute. The manual indicates the block with only the specific number vacuum nipples needed was to be used. The real world is different . In fact it appears that many different ones were used and the un needed vacuum ports simply capped off with a rubber cap.

Hi Bob, I did see your post. I get that it was not an absolute, so I'd like to know what kind(s) are usually seen in this circumstance. I've got a grand total of one engine that I've seen in person, my donor engine, and I did not see it in the vehicle. You've seen many more of these in person than I have, so I'm relying on observations from you and others. Have you seen the first kind used with a plug, as Steve reported? Or do you usually see the larger block kind (again with a plug for no booster)? Or is there another kind(s) that was used that didn't have the tapped hole for the booster connection? Even if there's no exact "correct" fitting for this application, I'd like to avoid using one that would never have been used at the factory.

Thanks for the paint info. I was going to ask if the second part of the fitting was painted, but you answered before I asked     I take it that means the second fitting was added at the vehicle assembly plant, not at the engine plant?

[J_Speegle]

Question 3: where is the air cleaner vacuum motor connected?

Ford diagrams located in the library show the vacuum motor being connected with the vacuum port located on the front of the engine in front of the carb. Generic drawing shows the vacuum motor being on the snorkel for some reason - likely just to save time rather than redrawing

Uses a blue striped hose

[68 S Code]

+1 to was said above by JS

[WT8095]

Ford diagrams located in the library show the vacuum motor being connected with the vacuum port located on the front of the engine in front of the carb. Generic drawing shows the vacuum motor being on the snorkel for some reason - likely just to save time rather than redrawing

Uses a blue striped hose

Yep, I see that, I'm guessing you're looking at the illustration I've included below (1968 emissions manual)? It also shows the thermactor diverter valve (I forgot to ask about that) being connected to the rear intake fitting with a black stripe hose.

So that's what the documentation shows - do your observations (you too 68 S code) match what's in the drawings? Any photos, anyone? Sorry for being a pest about it. The documentation is a bit sketchy on these details, and right now I'm mainly trying to establish whether the fittings I have were plausibly used for my application, or if I have to add different ones to my "wanted" list.

[J_Speegle]

So that's what the documentation shows - do your observations (you too 68 S code) match what's in the drawings?

They match where the drawings show they hooked up to

In general the diagram matches what was done on 390's in 67 and 69

Any photos, anyone? Sorry for being a pest about it. ...........

What fitting are you using/have at the front of the intake?

Have looked through my picture collection a number of times as I viewed this thread unfortunately I have no clear usable pictures (or ones with the air cleaner off) - most restored, played with or not visible.

I would guess that CJ's are similar in design and have seen the large port used by the PB hard line plugged on many applications with no PB.

Have only owned one of these cars (68 390) and it didn't come or leave with an engine
 

[WT8095]

They match where the drawings show they hooked up to

In general the diagram matches what was done on 390's in 67 and 69

What fitting are you using/have at the front of the intake?

Have looked through my picture collection a number of times as I viewed this thread unfortunately I have no clear usable pictures (or ones with the air cleaner off) - most restored, played with or not visible.

I would guess that CJ's are similar in design and have seen the large port used by the PB hard line plugged on many applications with no PB.

Have only owned one of these cars (68 390) and it didn't come or leave with an engine

Thanks Jeff, that's good feedback. Your observation of plugs corroborate's Scott's observations. The front fitting from my '68 donor engine is shown below. I have a '67 S code engine that has the same front fitting. The back fittings on the '67 are the same design as the '68, but neither of the two pieces has the extra port that the '68 pieces have. I'll refrain from posting photos of that in a '68 discussion (unless requested) to prevent causing confusion down the road 

Does the early consensus seem to be: for the rear, I can use both of my existing pieces, with the thermactor line going to the one screwed into the manifold, and the trans line going to the second piece? The booster port on the second piece would be plugged. Front would have the air cleaner motor line. Sound right?

[J_Speegle]

Does the early consensus seem to be: for the rear, I can use both of my existing pieces, with the thermactor line going to the one screwed into the manifold, and the trans line going to the second piece? The booster port on the second piece would be plugged. Front would have the air cleaner motor line. Sound right?

Think that makes sense and will work. You can use the two ports on the front fitting for the air cleaner vacuum door and for the distributor as shown in the diagram

[WT8095]

Think that makes sense and will work. You can use the two ports on the front fitting for the air cleaner vacuum door and for the distributor as shown in the diagram

Makes sense. In my limited experience I haven't seen any other styles for the front. Thanks for the input everyone! Of course, if someone runs across photos in the future, please add them.

[68 S Code]

I printed out the diagram even though I know i have the big vacuum, electrical, emissions book down in the library. I will have to go out in the garage but the good news is the air cleaner is already off since the RE-re-built carb was just installed this weekend. The first rebuild lasted a total of 3 miles (Ok four years and only 3 miles) before the accelerator pump was leaking like a sieve.

[TLea]

which block is used is not a absolute. The manual indicates the block with only the specific number vacuum nipples needed was to be used. The real world is different . In fact it appears that many different ones were used and the un needed vacuum ports simply capped off with a rubber cap.

+1  I have seen hundreds of these and the only absolute is there are always enough ports. Regarding the rear fittings, I think the second picture with the nipple coming out of the top of the larger rear fitting is a later detail, like around intro of CJ engine 4/68 ish. The rear small block can be 1-3 nipples and I've seen as many as 2 capped. I agree with others motor goes to front steel fitting