Brake booster vacuum problems

[DaveSpec]

Hey guys, just doing some final tuning to my 18rg, twin 45mm webers and am having trouble with the mixtures. Any advice would be helpful, what ive got so far is as follows:

Plug 1 http://postimage.org/image/yw8bifcdx/
The plug was running rich. I then tuned it to get this white deposit. You can see where it has cleaned some of the soot off the insulator. This one has the distributor advance coming off its manifold.

Plug 2 http://postimage.org/image/5kqy975hd/ and http://postimage.org/image/pe321wiv5/
Tan colour on the insulator. Greyish on the strap. Occasionally this cylinder pops through the carby. Have got it so that it sucks a small amount of air in through the manifold because it seems to backfire less like this.

Plug 3 and 4 are the some both covered in black soot but the point where the spark jump from the top of the electrode to the bottom of the earth strap is white on both.
Was guess rich mixture but have the screws wound in as far as i can and a 8th of a turn more would ruin the idle. These two plugs have the vacuum advance for the brake booster coming off the manifold, Its bridged with one way values so it can only vacuum. Maybe this has something to do with it because i was gettin a much nicer silvery sort of colour a couple of days ago.

The problem with the car is that it backfires quite abit through the exhaust, especially around the 2800rpm. Going to try for a roadworthy this week and i dont think this would help my chances so anyhelp would be greatly appreciated!

And a bit of clarification cause it probably doesnt make sense. The intake manifold is the redline one so each intake throat is separated and each one has a port where you can connect a vacuum hose.

[ToyTA22]

Webers don,t use a vacuum advance. Connecting distributor advance to manifold gives full vacuum all the time instead of just above idle to approximately quarter throttle opening.
That could explain backfiring through exhaust about 2800rpm. That is about when engine achieves max vacuum hence max advance.
Usually backfire through carby indicates to lean or ignition too advanced, which could be possibly due to vacuum advance connection.

What region of Qld do you live, I'm lower Gold Coast. If you're in Gold Coast/ lower Brisbane may be able to meet to listen to car.

[JadeEstevez]

Could you throw some pictures up of how your vacuum lines are done, Along with the carbies and manifold? I've had issues similar with my 32/36 weber and it was due to Vacuum line problems. Hehe.

[DaveSpec]

I live in sunshine coast and the car isnt registered otherwise i'd love a second opinion. I've tried holding the revs at the mid 2000 and playing with the distributor advance to no avail. T'll try blocking off all the vacuum ports on the manifold to see if i can't stop the backfiring and check out what colour the plugs are. I'm pretty sure connecting the back two vacuums to the brake booster the has caused the plugs to foul cause im sure they were ok before. Will run the car tomorrow afternoon and get back with some pics of the set up.

[JadeEstevez]

The brake booster should be hooked up to a vacuum on the manifold, not the carbs. If there is a vac port on the carbs, it's most likely your dizzy advance =)

[DaveSpec]

Yeah i dont think i explained the set up properly. I'll post a pic today so its easier to understand

[DaveSpec]

ok so here is my manifold with each intake labelled.
http://postimage.org/image/z5j7u74nv/

As you can see the each intake throat on the manifold has its own vacuum port and is not connected to any of the other ones.
the pipes on 3 and 4 were connected both to the brake booster.
2 likes to be left unblocked, allowing extra air to add to the mixture after its been mixed by the carby. Blocking this gives a poor idle
1 was the vacuum advance to the distributor.

Now i seem to have fixed the backfiring. Turns out cylinder 2 wasn’t firing so I wound the mixture screw out and it fired up properly. (this is the one with the unblocked vacuum port). So before fuel would have been passing straight into the exhaust and exploding in there, im guessing.

So i have another problem. My brake booster...
when its connected to the vacuum advance on the intake manifold:
when the car is off the brakes are nice and firm.
when the car is on at idle the brakes quite soft. So much that when i roll down a hill and slam the brakes on the wheels would hardly skid..
Not sure if this is the brake booster or something to do with the vacuum from the intake manifold.
Any ideas?

Also, kind of unrelated. The book says NGK5EZ plugs for the 18rg:
Operating temp of 5 with extra think electrode i think the z is (can't get them easily in aus i dont think.

Im pretty sure a few people use NGK6ES, (I do to because they were already in the engine):
operating temp of 6 (this means they are for a slightly cooler engine then the 5) and s is the normal electrode thickness

Just wondering why people don't use a NGK5ES which is the 18rc plug, but it has the same operating temperature as the recommended ones for the 18rg but a thinner electrode.

[JadeEstevez]

I'm jealous, they are webers ;P They look good.

Okay, I'm no sidedraft expert, but I thought those vacuum ports were used to balance the carbies? O___o Your brake booster should only need one vac port from the manifold. Do the carbies themselves have any vacuum ports, around the base most likely?

[DaveSpec]

haha the pride and joy of my 18rg except they are a #$*& to tune
Yeah i used those ports on the manifold to tune the carbies. But there carbies themselves dont have any vacuum ports on them which is annoying, well none i know of.
The more throttle the less the vacuum in the manfold is because the butterflys are open and it can balance more with the air through the filters.
Are the brake supposed to be firm with there is no vacuum then they got softer with increased vacuum? I dont know brake boosters very well. But if this is right then would connecting the brake booster to the intake manifold be doing the opposite of what it should?

[JadeEstevez]

Well my brake booster is hooked up to my manifold on my 18R... You'd probably get alot more people helping if maybe you changed the title on the subject to more about the vac lines, because that sounds like the issue here.

[ToyTA22]

To test brake booster, push foot on brake with hard pressure, engine not running. While still holding brake pedal start engine and idle or fast idle if needed. Pedal should push in but still be hard once reached full travel, not going to floor. If pedal goes to floor then you have other brake problems.
As I commented earlier Webers don't have distributor advance connections. Advance is only controlled by mechanical advance.

[DaveSpec]

so held foot on brake. Turned on the car. Pedal started to go down further. It goes pretty far down but i couldn't push it to the floor. It feel pretty good now, will need to take it for a drive and see tomorrow. I did remove the check value and check it so maybe it needed to be reseated.