Nothing Sucks Like Vacuum (1976 L28 Piping attached)

[Jennys280Z]

Except for a Z that isn't running great, and this time, I mean suck in a bad way. :kiss:

For people who don't like reading my long-winded questions, my quick & dirty issue is trying to size these vacuum hoses so I can replace them.

Okay now I'm going to sound authoritative: In the L28's piping there are three sizes of vacuum hoses. Small, medium and large. Looking at the "Fig. ET-1 L28 engine system piping" I attached, an example of a large hose would be #32, the 3-way connector to rocker cover rubber hose. An example of a medium hose would be #4, the Canister purge line. An example of a small hose would be #51, the 3-way connector to throttle chamber vacuum hose.

I am pretty sure these hoses are sized by their inner diameters, and I have to suppose they are metric sizes (like everything else on my car, right?) Does anyone have the sizes of these hoses?

Yup, I know what you're thinking, I could just pull them off and take them to a parts store, but NAPA doesn't have metric sizes, and I don't know if standard sizes are interchangeable enough to be an option, nor what the proper substitutes would be, even if they were! The hoses seem fragile on my car and the vacuum hose to my distributor is cracked at the t-junction and the others on that little t-junction seem to be barely hanging on. Not sure if this would effect how my baby runs, but replacing most of these hoses is a job I want to do anyway so might as well get it over with in these cold months when I don't drive much anyway!

I looked all over the forum at other threads and couldn't find this information anywhere. I Googled, even searched other Z-car forums and the best I got was a thread about this where someone was answered with a private message. Whats all the secrecy about? I don't belong to that website and I want to stay here and that thread was ancient anyway and...ok ok I'll stop ranting now

Also I'm really curious about something that doesn't make sense about my car. I have a non-California manual transmission 280Z (I know stuff too, see?), and the double-asterisk part numbers on the diagram (#13-16) are supposed to be for "Non-California Manual Transmission models only". Well that's my car and I don't have ANY of those parts on my engine. BUT, the little picture at the upper left corner of the diagram (#5, 50, and 51) I DO have on my car even though they are for "All except Non-California manual transmission models". So I'm wondering what the discrepancy is. Is the wording in the manual printed wrong? I have to admit, some of the English in here sounds somewhat roughly-translated from Japanese, domo arrigato. Or, is some weird history of my car the culprit? I know the history of my car though. The original owner was a teacher in Georgia and the 2nd owner was my ex b/f so I know this isn't some California car that got de-California-ed.

And one more curious thing. I read in Tom Monroe's book on L-engines that an easy way to check the PCV system is to start the engine and while it's idling, remove the oil-filler cap and hold a piece of paper over the hole to see if it gets sucked down into the hole. If there is suction then your PCV valve is working and unobstructed and you're good to go! Mine sucked on the piece of paper so my PCV system is good. But my Z has been idling crappily and running crappily lately, and I promise that when I took off the oil filler cap my idle speed seemed to increase and run better. I read a few people say on this forum that when you take the oil filler cap off, the engine should almost stall out?! (if your vacuum plumbing is good n tight?) Why wouldn't mr Monroe mention that in his book? (because he doesn't know I'm a NOOB I guess) and how come my car didn't start to sputter and die, but actually seemed to idle a little better (it sounded to me like a healthy 800RPM than the shaky 600-700RPM I was getting) than before I opened the filler cap?

Edited February 5, 2010 by Jennys280Z
RESOLVED

[Zed Head]

Hey Jennys280Z, here's a wordy response.

I don't know why you don't have #13 - 16 parts. But I do know what they are suppose to do. They control the vacuum advance on the manual transmission 1976 motor. For whatever reason (probably emissions control vs. performance), the 1976 models had an electrical switch on the transmission that puts power to Part #13 to shut off the vacuum advance at all times, unless the transmission is in 4th gear. In other words, if you had those parts and they worked correctly, you would see vacuum advance only while driving in 4th gear. You may have figured this out already from the FSM. It took me a while though, but I did actually confirm it on my running engine (which has all of those parts and is non-CA MT).

It looks like your car is set up to run full-time vacuum advance. I changed my transmission to one without the switch so that is how I run now. I think that it runs a little better. I have bumped my timing up a few degrees off initial also, just tuning for smooth-running.

Do you have parts 33-36? If not, maybe your car was originally a non-CA automatic and got converted. If this is the case, you may have a different distributor also, EE-27, with a different vacuum advance canister.

Love how every model year has something a little different.

[Jennys280Z]

Do you have parts 33-36? If not, maybe your car was originally a non-CA automatic and got converted. If this is the case, you may have a different distributor also, EE-27, with a different vacuum advance canister.

Love how every model year has something a little different.

Hey Zed Head, nope I don't have 33-36 or any other California stuff that I know of. I wonder if some mechanic removed my vacuum switching valve/piping on purpose? And having a transmission that expected this wouldn't mind the lack of it? This car was worked on at one point by an SCCA racer who brought the car back running remarkably well from a tuneup one day. I knew absolutely nothing about cars at the time but we were wondering how the car felt so fast. He scolded my b/f when we picked the car up to "not mess with the AFM" for some reason, though my b/f never messed with anything under the hood as he didn't know anything about cars either He would resent me saying that so I ought to be fair...he knew a lot more than I did, I'm sure...

One reason I'm suspicious now about who did what to this car while working on it in the past is my alternator. I noticed my fan belt (crank + fan + alternator belt) is loose. I can move it about 1.5" with my thumb instead of the 0.5" I'm supposed to. My battery is only getting 11.51V between the posts with the car not running. I wonder if any of this could affect how my car is running (no power, rough), if there is weaker than normal voltage in the system from the battery. So I looked at the bottom of my alternator where there's supposed to be two bolts holding it in place and there is only one bolt (the front one is missing) and unfortunately the rear bolt is seized/glued. I suspect if both bolts were present this might not have gotten so seized over the years in the first place. I had my neighbor try to break it loose for me and the socket got stuck on the bolt head! I had to get a mallet and hammer it off. The 12mm bolt is now rounded. The simplest thing to do and I can't even do it now. :mad: The belt slips in my hand just from pulling on it too so I'm surprised I didn't hear it whining before while running/driving the car. I doused the bolt in WD-40 but at this point my only recourse might be to jack it up and try to use a vice grip or failing that, take it to a garage and have someone else do it. sigh

Before my car started running bad I took the fan belt off my A/C compressor. I don't suppose how it's possible this could make my car run badly but nothing surprises me anymore. If anything I thought I'd get a bit better gas mileage and a couple horsepower from doing it but i got backfires and no power instead.

Anyhoo my clutch master cylinder was like...empty too. I filled it up (the liquid is dark now--has stuff floating in it). I never checked it after the years the car was just sitting. It's things like this that make me feel so stupid sometimes. I guess I just have to learn, the hard way if necessary.

Thanks for your help!

Jen

[torker]

Bummer on the alternator. Hopefully when you get the bolt out and readjust it will charge good. Your battery should be 12.7 even after sitting awhile. And aprox. 13.8 while running. If not, that will affect how it runs. I would just take some vacuum hose to match it up. That's really the easiest way.

Then give it some fuel system cleaner in the tank and a nice run down the hiway/backroad-your preference. That might be all it needs;)

[Jennys280Z]

Bummer on the alternator. Hopefully when you get the bolt out and readjust it will charge good. Your battery should be 12.7 even after sitting awhile. And aprox. 13.8 while running. If not, that will affect how it runs. I would just take some vacuum hose to match it up. That's really the easiest way.

Then give it some fuel system cleaner in the tank and a nice run down the hiway/backroad-your preference. That might be all it needs;)

Hi Torker, I hope you're right and it is the battery! (aside from my alternator belt grrrrr!) I knew my batt had a drain and that was one of the reasons why I didn't drive my car more often the past few months, and I would usually use a portable starter/charger to charge it up before starting it and driving it; though the last four times I've driven it, I did not do that, and it ran progressively worse. After running my ECU tests tonight, it's testing at 11.15V between the posts. Since that's >1.5V less than what I want, I suspect my voltage while running will be approximately the same difference. And perhaps ~12.2V isn't enough for my car to run good. At least, granted that the charging isn't working well, the alternator belt is probably slipping. I guess you think that some of their standard sized vacuum hoses at NAPA (1/8", 1/4", 3/8", or 5/16") will be close enough to the metric sizes. That sounds right as vacuum isn't that major of a deal but I also don't want fitment issues if I can help it. Some people talked about twis-ties or something to fasten the ends tight. Do you know something I could use like that to do a really good job?

[torker]

I know they make some small wire type clamps for vacuum hoses. Kinda like the cheapies you see for fuel line that you just squeeze with pliers. They use them a lot on motorcycles. You really shouldn't need them unless you run across a situation where one size is a little too big and the next smaller size is so tight that you take a chance of breaking off a plastic nipple by pushing too hard.

Also have you charged the battery overnight to see if it recovers its voltage? On my sons car we were fighting a battery drain problem and he was making a lot of short trips and it sooted the plugs real bad.

Once you get the vacuum and alt./battery sorted out you may have to check the plugs.

[FastWoman]

Hi Jenny,

When you take off the oil filler cap, you're introducing unmetered air, causing your engine to run leaner. If it runs better that way, it means the engine ordinarily runs too richly. You can probably smell raw fuel in the exhaust, right?

As to vacuum line sizes, you'll need to go by ID. Measure the pipe/tube the line fits onto. Do that by tightening a crescent wrench across the pipe, and measuring the gap between the jaws. You can then use approximate imperial equivalents, for the most part:

mm -- in

3 -- 1/8

4 -- 5/32

6 -- 1/4

8 -- 5/16

10 -- 3/8

12 -- 1/2

[Jennys280Z]

I know they make some small wire type clamps for vacuum hoses. Kinda like the cheapies you see for fuel line that you just squeeze with pliers. They use them a lot on motorcycles. You really shouldn't need them unless you run across a situation where one size is a little too big and the next smaller size is so tight that you take a chance of breaking off a plastic nipple by pushing too hard.

Also have you charged the battery overnight to see if it recovers its voltage? On my sons car we were fighting a battery drain problem and he was making a lot of short trips and it sooted the plugs real bad.

Once you get the vacuum and alt./battery sorted out you may have to check the plugs.

Gosh I'm the same. Just short trips, combined with my loose alternator belt. Actually, right before it started backfiring and really running bad, I started it only to back it out, then shut it off. Then started it again to pull it forward then shut it off. So that was two REALLY quick trips for sure hehe

I have a little charger I can recharge my battery before I run it again. I'll have to tighten my belt and then see how the battery holds a charge. It's still under warranty until summer so at least that's a bit of good news for me for a change.

I'll pass on the clamps as I should be able to find some hoses that fit good enough. Thanks for your help torker!! You're right I might want to look at my plugs too.

[Jennys280Z]

Hi Jenny,

When you take off the oil filler cap, you're introducing unmetered air, causing your engine to run leaner. If it runs better that way, it means the engine ordinarily runs too richly. You can probably smell raw fuel in the exhaust, right?

As to vacuum line sizes, you'll need to go by ID. Measure the pipe/tube the line fits onto. Do that by tightening a crescent wrench across the pipe, and measuring the gap between the jaws. You can then use approximate imperial equivalents, for the most part:

mm -- in

3 -- 1/8

4 -- 5/32

6 -- 1/4

8 -- 5/16

10 -- 3/8

12 -- 1/2

Wow that is very good ideas and thanks for the conversions. I remember that you can just take the fraction in inches, multiply times 25.4 and get metric mm's! I just spent over an hour digging through drawers trying to find a good metric straight edge and realize I don't even have one. But I do have a tape measure in metric so I'm saved! yippee;)

[TomoHawk]

When you select your vacuum hose, keep in mind whether it is just plain air (like for the he heater controls) in the hose or if it might contain oil or fuel fumes (rocker box or emissions system.) The latter requires an oil-or gas-proof material. Also make sure you get hoses that won't collapse from the vacuum.

[geezer]

Wow that is very good ideas and thanks for the conversions. I remember that you can just take the fraction in inches, multiply times 25.4 and get metric mm's! I just spent over an hour digging through drawers trying to find a good metric straight edge and realize I don't even have one. But I do have a tape measure in metric so I'm saved! yippee;)

I bought this electronic digital caliper ($12) that has the added benefit of doing measurement conversions as well. Just open to the desired measurement, then press the mm/inch button.

[TomoHawk]

I still have my "manual" calipers from college days. it reads in both Metric & standard, but the fine marks are hard to see. Your comment suggests that maybe a new digital one from Harbor Freight might be good to have.