Which of these two diagrams is correct...the top or bottom one?

The difference is the hoses at the dizzy vacuum can...they cannot both be right.

[NOTE: I deleted the incorrect diagram originally posted...the diagram remaining is the correct configuration]

My '74, L-jet is set up to the top diagram since I have only one port on the throttle body.
I forgot to mention that the port on the dizzy vacuum not in use, I blocked off with a rubber boot. I do not leave it open to atmosphere as noted on the diagram.

I have tried both on a 76 2.0 liter.
For emmisions, when you have the retard hose connected, it pulls that advance back very quick...
That is good for emmisions, but it sucks for shifting...it snaps you out of advance to quickly.

We eded up pulling the retard hose off the distributor
Leave the port on the distributor open so it does not create a vacuum and never allows the advance to come back.
We then left the hose attached to the throttle body, and plugged the end of the hose to eliminate the vacuum leak.

Our 73 1.8 only has one port on the throttle body
72 1.7 has only one port on the throttle body
76 2.0 liter has two ports, but we are configured as above.

We tried it both ways and found that the rapid reduction in advance created a very poor idle condition when warm.

Rich

Mine is the bottom since I have two ports on the TB to the dist.

I have a question:

Since my L-Jet is on a true GC 2.0 motor, I have breathers on each head. What am I suppose to do with those? I currently have a hose connecting them together.

You will blow all your gaskets by doing that.
the vents are to let the head pressure escape.
You are leaving that pressure in the heads, balanced, but its still there.
This pushes to much potential pressure back into the case...a bad thing.

You can add an external vent box (CB performance or Chris Foley)
OR
You can plumb them into the intake like the original design via the aircleaner.


Rich

Rich, that's pretty interesting. I have my decel valve hooked up and so far, no issues with idling or rapid timming pull back. I've been nothing but impressed with L-Jet since the day I slapped it on my 2.0 engine.

I haven't tried to run with that vac line removed. Would I yield better fuel ecomony?

doubt it...I think the fast retard is for fuel economy and emmissions.
It sucks when autoxing...

Rich

If I pull the hose off of one of the heads, the engine dies (Vac leak). Same thing if I removed the oil fill cap. So I'm not sure a breather box would resolve it?

Porting them to the air cleaner would be a vac leak.

There isn't any ports left on the TB or plenum to connect them to.

Hmm.

Anyone know or have a picture of where the head breather hoses go on an L-Jet 1.8????????

My little pea brain wants to know.

Uhh, Excuuuuuze me...

This is a thread about the diagrams I posted....

Hey Jeff,
I added some more info on my reply, #2 thread.

Sorry Jeff, you're right.

My thoughts are that both are correct, even though it looks like you connect the same port on the dist to different ports on the TB depending on if you have single or dual port TB.

So I think it really depends on what TB you have. Single port or dual vac port.

But again, I think both diagrams are correct.

I still think it's odd the head breather lines are not shown.

Hi Jeff I replied right away but forgot to hit the "post" button! The second diagram is the correct one. The larger front pointed toward the side vacuum advance port is connected to the front of the throttle body and the rear smaller one sticking up in the air is connected to the rear port on the throttle body sticking up into the air. After Jan 1 1974 the vacuum advance was discontinued so there was no port at the back top of the throttle body but one remained sticking up on the advance. The assembly line workers just stuck a small piece (about 2.5 inches) of 3.5 line on the port and left it breathing to the wind. There is absolutely NO REASON to plug it as it connects to nothing and does not influence the vacuum system

I think this discussion would benefit from identifying the differences between the throttle body part numbers. The PET calls for these P/N's for the 1.8L engines:

022 133 062 H throttle body <= M EC0 037 551 914-1,8
022 133 062 R throttle body >= M EC0 037 552 914-1,8
022 133 062 L throttle body <= M EC0 037 551 914-1,8 (CAL)
022 133 062 S throttle body >= M EC0 037 552 914-1,8 (CAL)

I have a couple of TB's. The one installed on my '75 1.8L has only one rear-pointing vacuum port (P/N ends with 022 133 067C, IIRC). A hose goes from the rear port to the left side of the dizzy. So pretty much the same as diagram #2 except with a short piece of hose off the right side of the dizzy can "breathing to the wind". (I also have a tee off the TB to dizzy can hose that goes to the EGR valve.) It runs well and passes emissions no problem.

I have another 022 133 067A (that was pulled off a '75 1.8L L-jet) with two vac ports that I'm contemplating trying out to see how things run with the dizzy can retard port connected.

Maybe the p/n's ending in "067" are VW Bus TB's?

i am running the bottom diagram on the motor i just installed. no problems yet. daily driver

My 74 is set up to the bottom diagram.

Thanks everyone, looks like the bottom diagram is correct. I will delete the first one out of this post to avoid any future confusion by anyone who finds this thread. Al, your set-up has no vacuum advance, have you tried hooking it up the other way? You may notice a difference on acceleration.

I'll give it a try and report back. Thanks.

You got me wondering so I went out to check my setup and it is correct to the diagram but as mentioned earlier I do not have port #2 on my thottle body. Are you suggesting I reverse the connection at the vacuum advance housing? Yellow hose to where the pink hose is?

Yes...

This is what it should look like if the second vacuum line is not on the TB ?

A short three inch piece of tubing going no where connected to the advance port of the distributer. do not cap the port. This is the way they came from the factory.

Click to view attachment

Hey Pete...thats exactly the same diagram that initiated this thread because of the conflict I noticed between it and the diagram in the first post. I am told the diagram in the first post is correct, please read post in this thread. I deleted the diagram you posted because of the comments by people here who know more about it than I, to avoid future confusion.

Are you sure? I think the vacuum from the TB should pull on the advance port of the dizzy can. I'm confused.

There are some disturbing errors throughout this thread, and they need to be addressed.

MY 1974 and MY 1975 1.8 equipped 914s sold in the US were all equipped with L-jet electronic fuel injection. There were NO 1973 MY 1.8s, nor were there any 1976s. None were equipped with D-jet EFI. All 1.8 L-jet engines were equipped with dual vacuum controlled distributors, and with dual vacuum port throttle bodies. None were equipped with vented cylinder heads. As the vacuum retard function of the distributor is required for both ignition timing and control of the idle speed, none were vented to the atmosphere, and all used the vacuum advance function, as well. Because starting and running in an L-jet engine depends on ALL the intake tract air passing through the air flow meter (AKA "air mass meter" or "air box"), the system is sealed. Common leaks, which will prevent the engine from starting, are loose, cracked, or disconnected hoses and fittings, missing or damaged oil filler gaskets and o-rings, and loose or damaged valve cover gaskets. The 2.0L 912E induction system shares all the characteristics of the L-jet equipped 1.8L cars. L-jet equipped 914s are unique in that they're the only 914s to require the timing to be set at idle, and there's a specific procedure for doing so.

The Cap'n

I have seen several Ljet equipped engines with the single vacuum throttle bodies, including the one I own. I have read that sticky throttle valves were common. So perhaps replacement was often done with the more readily available single vac TB. I only say that because I found it more difficult to source a good used dual vac TB compared the relatively common single vac type.

This seems to be a controversial topic !

There are a lot of threads on this over on the Pelican Parts site too.

Here are just a few:

http://forums.pelicanparts.com/porsche-914...-necessary.html

http://forums.pelicanparts.com/porsche-914...1976-2-0-a.html

http://forums.pelicanparts.com/porsche-914...-hose-help.html

If this is the case why do so many 1.8 L-Jet engines only have one port on the TB? Were they swapped out for some reason? how do you get vacuum to both sides of the distributer with only one vacuum port on the TB??

This is interesting....

"After Jan 1 1974 the vacuum advance was discontinued "

Does this mean the advance side of the distributer should be vented to the wind or the retard side of the distributer on single port TB cars? I think that is the big question here.

We need a 'dog-chasing-his-tail' smiley because thats how I feel right now.

The question is how to plumb distributor advance/retard for the 1.8 L-jet cars? Lets sort this out, I don't have a 1.8L car so I have nothing to refer to - counting on the 914world braintrust to figure it out. "Jim Hoyland...Clay Perrine...Come to the white courtesy phone please"

We apparently have two different throttle bodies, one with only one port (#1 on non-pressure side of throttle plate) and another with two nipples (#1 on non-pressure side, #2 on the pressure side of the throtle plate).

The distributor vacuum can always has two ports: a 4mm OD advance port (away from dizz) and 5mm OD retard port (towards dizz).

I searched the tech sources I have for answers - 2 different Bosch L-jet manuals, the 1974 and 1975 914 Service and Training manuals, the factory 914 repair manual, Harold T. Glenns manual and a privately authored 912E manual (L-Jet) I found on the internet.

Only the 912E manual has a vacuum hose diagram (below). Note how the vacuum retard port on the vacuum can is shown connected to the single port throttle body in the diagram. Dr. 914 also suggests that the vacuum retard function is the hose that is connected to the throttle body. Another point of reference is the 1974 and later D-Jet cars with only a single port throttle body (which is a 5mm OD port) - the hose is connected to the retard side of the vacuum can for these cars (also a 5mm OD port).

The preponderence of evidence suggests: The vacuum hose on 1.8L single port throttle body (5mm OD) gets connected to the vacuum can retard port (5mm OD)? If so, the second diagram Pete posted would seem to be correct after all.

Can someone with a single port 1.8L throttle body verify the port OD size? Is it 5mm OD?

Does anyone have a 2 port 1.8L 914 throttle body they can check the port OD sizes?

When it is verified, I'll be sure the correct diagram is posted in this thread and on my website for future reference.

Here is a photo of my TB on my 74 1.8 L-Jet I am changing out to a Terry throttle cable at the moment and snapped a picture.

Only has the rearward port and it is 5mm.

Currently I am running the vacuum line to the retard port. I did notice when I purchased this car it would not idle very well when it was cold and it tended to ping a bit. The hose was to the advance port when I got the car and the retard port went to the manifold which I know was wrong. I replaced all the vacuum lines and AAR valve and it seems happier.

Hopes this helps solve this mystery.

Single port on throttle body to distributor vacuum advance. Vacuum retard has hose with open end stuffed out of sight. This is like schematics #1 at the start of this thread.

(If the hose is swapped to the vacuum retard, the engine runs like crap, lurches and sputters under load.)

Note the tee off to the EGR valve.

Throttle body is p/n 022 133 067C.

Click to view attachment
Click to view attachment
Click to view attachment

This is a two-vacuum-port throttle body (p/n 022 133 067A) that I was thinking of trying out to see how things go with the retard vacuum connection. This was pulled from a 1975 1.8L L-jet engine.

Click to view attachment
Click to view attachment

This is probably due to some confusion with 2.0L vacuum hose diagram. The throttle body is in a different orientation than a 1.8L engine (vertical vs. horizontal).

Here it is, courtesy of the Cap'n.

I've worked on the 1.8s since BEFORE they were on the market (prepped some at the school, and replaced a head on one before we sold it) and there have been a couple here at the shop in the past month or 2. Both had dual vacuum, and one is a '75. I don't recall any without it. Later bus engines didn't have dual vacuum, but the timing procedure is different, too.

The Cap'n

What about this statement (see above quote) from Auto Atlanta?

BTW: My engine seems to run just fine with no vacuum advance hooked up????

Here is another quote from Rennlist:

Probably referring to the 2.0L engine. No 1.8L in '76.

Check the position of the vacuum fittings on the throttle body. The retard fitting would be "downstream" of the closed position of the throttle body. The advance fitting would be just barely "upstream" of the closed position of the throttle body.

The advance fitting on the distributor is the one that points away from the distributor body; the retard fitting is the one that points back toward the distributor body.

Hook up the advance fitting on the TB to the advance fitting on the distributor, and the retard fitting on the TB to the retard fitting on the distributor. If your TB is missing one of those fittings, leave the corresponding fitting on the distributor open to the air. Or do what the factory did, which is hook up a short piece of hose and run it to nowhere.

--DD

My '75 1.8 L-Jet has the 2 port throttle body; last year, I installed the Mallory Unilite distributer I got from Tangerine Racing. The unilte does not have a vac can; and, I put rubber boots over the throttle body nipples.

Ok let me get this right, if the car came with only one fitting to the TB that would make it the retard fitting. Then the advance fitting on the distributer would then get vented to the air with a short peice of tubing. (No vacuum advance on these cars!)

That would make my diagram correct.

I think this could only be proven by looking at the position of single vacuum nipple on the TB (i.e. upstream or downstream of the throttle disc).

I kinda think the rear facing nipple is for the advance on the 1.8L. That's how I have mine set up and it runs like poo if I switch it to the retard port on the dizzy diaphragm. So mine basically follows the PP diagram: http://www.pelicanparts.com/914/technical_...4_18FI_diag.htm

I think there is some confusion with the other FI types. If you look at the 2.0L D-jet diagram http://www.pelicanparts.com/914/technical_...4_20FI_diag.htm, the rear-facing vac port on the TB is the retard.

My head hurts.

--DD

Revisiting this old thread.

I have pulled off my TB to do some cleaning and replace the mounting seal.
I also wanted to see if the single vacuum port is upstream or down stream.


It seems to be right under the butterfly when it is in closed position. Now if my TB is slightly warn and slightly over closing I would say the port would be rearward of the butterfly by a tiny bit. As the butterfly begins to open the port is on the rearward side towards the intake manifold.

So as stated it would make sense that being "down stream" of the butterfly this line should go to the retard side of the distributor.

the portion of the diagram the notes the charcoal canister lines is the simple way to vent off the gassy smell with carbs using the stock plastic lines. one would need the late, plastic, canister. you mount the canister to the engine side of the rear firewall with the stock strap and draw off to one or both carbs with T.