Reconnected the hose to the cam cover, the noise comes back. Using a short tube to my ear, I've traced the sound to the dipstick tube/front main seal & at a guess, the rear main seal as well. Given that the noise only occurs at certain vacuum levels, it's the only conclusion I have.

 

I'd like to correct myself there, it's NOT the oil seals doing the squealing. It was while doing some idle-mixture tuning that I got distracted & did some experimenting. Then filmed it, so you know why it's so annoying.

 

In the first part of the video, I give it a little rev & as the revs die, the noise starts. This is what I have to put up with. In the second part of the video, I have the cam-cover breather hose disconnected & blocked off, I'm not sure how well you can hear it in the video but the noise coming from the breather fitting due to air going through it sounds awfully familiar. Add some strong vacuum to that & I think I have my culprit.

 

I was wrong, yet again. Drilled/tapped a thread in one of the cylinder head casting-plugs for a hose fitting & used that as a breather. Connected the cam-cover fitting to the air filters with a pcv valve inline as a fresh air return &.....the noise is still there. FFS.

 

Not being able to solve this is still less annoying than the noise itself, so I will find a solution.

Drilled/tapped a thread in one of the cylinder head casting-plugs for a hose fitting & used that as a breather. Connected the cam-cover fitting to the air filters with a pcv valve inline as a fresh air return &.....the noise is still there. FFS.

 

So, is this with nothing connected to the inlet manifold vacuum?? or rather, does this mean something that is still connected to the inlet manifold must be leaking.

 

 

Then I removed the breather hose from the cam-cover. The noise stopped. My thoughts are that it's air being sucked in somewhere as that breather hose is connected to my intake manifold & under vacuum.

 

It seems so simple... like all the hardest problems!

 

Definately a vacuum leak sound? or could it be a belt/bearing that coincidentally stopped then??

Whatever it is, it doesn't make the noise when the engine is internally at atmospheric pressure. I.e I have the cam-cover pipe open to the air. The engine idles rough as guts if I do though.

 

Did another upgrade today courtesy of the TCCAV Wrecker Run. Pathetic standard horn replaced by a SAAB 900 item.

 

hehe eeexcellent

Holy shit I'm getting one.

People seem to actually notice when you use the horn now.

 

I kinda left the squealing noise alone, trying to solve it was starting to do my head in so I left it. Turned the cd player volume up, can't hear it. However, when playing with the mixture screws attempting to richen the idle, I discovered something. The noise used to stop at about 1,800rpm, as I wound out the screws, the rpm at which the noise would stop got lower & lower. At present, the noise is pretty much constant at idle, but the mixtures are getting better.

 

I have NFI what this means/what the cause is, just an observation.

Edited March 11, 201511 yr by carbonboy

The idle mixture screws were 4.5 turns out from seated & the wideband was only just reading richer than 22.4 AFR at idle. Figuring that they were at the limit of their adjustment, it was out with the #38 jets & in with the #42 jets.

 

 

This process gets easier each time.

That didn't work as I'd hoped, the #42 jets turned out to be too large. Mixture screws were only 1/4-turn out, yet it was reading 10.5:1 - 11.4:1 at cruise, sometimes 9.4:1, even though at idle it was around 20.4:1.

 

 

So I ordered a set of #40 jets (available in Oz rather surprisingly) & while I had access to a hoist, tested to see if changing jets was easier to do from underneath (leaving the intake on), rather than pulling the entire intake off the engine. Having done so, I can testify that it's easier to pull the intake off. Do-able, just bugger-all room. With the mixture screws 2 turns out, it's reading 13.6:1 at cruise & 22.4:1 at idle. Needs some more tweaking, but I'm definitely in the ballpark.

 

I also have a theory that the air correction jets are the cause of the squealing noise, but I'm ignoring it for the moment.

Gotta love carbs... you always end up with a jet collection!

 

Literally "at cruise" my SUs are down at 16 or 18, but if its an incline or a headwind they're around 14. I can't feel myself put my foot down sometimes and I see the mixture display richen up.

 

Fun to play with hey!

I was lucky enough to have scored a jetting kit when I bought the carbs, so I had some to play with from the beginning. More importantly, a nice little container to store them in! :lol:

 

These carbs are similar, it only takes the slightest movement of the throttle pedal to completely change the mixture reading. Mine go slightly lean at first, then richen up as the load increases. At full throttle & ~6,500rpm it's somewhere in the 12's, don't really have time to pay much more attention as you're busy keeping it pointed where you want it. Solving the squealing noise & dyno-time is what I need now.

In the pursuit of the air jets causing the squealing noise, I swapped out the #140 ones for some #155 items. Made zero difference to the noise, but helped the AFR's. Since changing one thing means changing all of the things, I then had to adjust the idle, the mixture screws & gave the carbs another synch to be on the safe side. Hovering around 21.0:1 at idle, but I'm happy with everywhere else.

 

Have a new theory about the noise.....the vacuum distribution block I made. (Yes, I will keep coming up with new theories until I solve it)

Vacuum manifold V1.0, now onto V2.0. The four barbs go to the intake runners, the larger bottom fitting goes to the brake booster & the smaller fitting is for the MAP sensor.

 

P.S - Yes, that is an EFI fuel rail.

 

P.P.S - Yes, the open hole is plugged up.

 

 

Also didn't stop the squealing noise.....

It's been a while since I bothered to work this out, but Blue Things fuel economy figures with the 16/20 4A-G are in. With morning/afternoon traffic, city, suburban & freeway driving combined, 7.94L/100km.

That's pretty good! :y:

 

What's up with the squeal noise? It sounds like a belt or maybe a bearing?

Edited April 17, 201511 yr by rian