3Tc Side Sidedraft Carb Setup Help?

[machinegun mike]

Hi guys,

 

this is my maiden post on rolla club, so i'll start with a short intro.. i'm an r31 enthusiast, also own a '78 mk1 golf and an s13 sivia, and now also a t18 :) from sydney.

 

 

 

Question:

I recently picked up a 3tc powered t18, and have installed a single side draft manifold and a dellorto dhla 45. There is quite a lot of vacuum garbage that is no longer needed however i would like to retain the vacuum advance. the dellorto does not have vacuum anywhere on it. i have hooked up the brake vacuum to the manifold.

 

am i able to t piece the brake booster vac for the dizzy? or is that a bad idea? can i just tap into one of the manifold runners and run vac advance from that?

 

also there are 2 fittings on the dizzy vacuum thingy... do they both need vacuum? if not which one does what?

 

thanks,

Mike

Edited December 14, 2011 by machinegun mike

[altezzaclub]

Basically 'yes' to the first two, it is no problem using a T-piece in the brake booster line, or tapping into the manifold in one place.

 

I ran mine on the brake line OK.

 

However I think you would need to know what the dizzy is designed to have, manifold vac or ported vac, as at idle the manifold vac is at maximum and will give you maximum vacuum advance, while the ported vac is at zero and will give you no advance at all.

 

If it is designed for ported vac (zero extra advance at idle) when you set it at 10deg with no vac line on, and then you put manifold vac on, it will give you 20deg advance at idle, an extra 10deg on the 10 you set it to with no vac line. So you set it back to 10deg again.

 

Now you've just taken 10deg off the maximum it can give you, as the dizzy will only go to 36deg or so before the weights hit the stops, so you will only have 26deg max advance at high speed full throttle..

[machinegun mike]

great info matey. thanks :)

 

so if i were to run no vac advance i should set the timing at idle quite high so that at full revs the timing will we correct?

 

also how do i plumb up the 2 vac ports on the dizzy. i'll ty find a pic..

 

ok

 

this is the sort of setup i have on my golf

only 1 port for vac.

 

3tc has 2

not the best pic sorry.

 

 

is it some sort of dual stage vacuum or something? with 2 springs inside maybe?

Edited December 15, 2011 by machinegun mike

[altezzaclub]

so if i were to run no vac advance i should set the timing at idle quite high so that at full revs the timing will we correct?

No need to, stick to the usual 10deg or so, whatever suit the fuel you use. The weights will give you a mechanical advance out to 36deg.

 

The vac advance is to give more milli-seconds of burn time when you are cruising on light throttle or going downhill with your foot off completely. At those times there is very little fuel going into the same size cylinder as usual, but at high revs the flame front doesn't move fast enough to burn it cleanly. So their anti-pollurtion solution was to start the flame earlier & help it burn the lean mix better. Go down a hill at 100kph, say 3000rpm, and you have the weights giving you 30+degrees and on top of that the vac gives you another 10. If you went uphill with that advance it would pink, so as soon as you boot it the vac collapses and the advance goes back to where it should be. Simple but clever.

 

I don't know what your two ports do on the dizzy, but mine are both the same. Some cars have a vac advance on one side and a vac retard on the other, Fords or something I read of. Get it all running with a timing light on and hook each one up to vac in turn and see what they do, or you can probably just suck on a tube and watch it if the spring isn't too strong.

 

If they both advance & you hook both up together it should advance a fraction faster and further, you just have a bigger diaphram area under vac. I just use the outer one.

 

I retained the vac advance and the charcoal canister on the 4K. I had to start researchng vac and advance once I converted to electronic ignition and needed to re-curve the advance.

 

http://www.rollaclub.com/board/topic/42407-the-girls-ke70/

[styler]

I would delete vac advance all together, add elec pickup if not one already and recurve the dizzy.

The trick is to know what to recurve it to that is flexible...

You should be around 10/12/14 base and 30/32/34 total which is 20 deg mechanical

advance from weights and gives you a range to tune with (For 3tc hemi head).

Another factor of recurving is what Rpm is it "All in" which is the Rpm that max advance is

achieved at, 4000 rpm is a base to consider (For 3tc hemi head)

 

When sending the dizzy to the specialist all you say is delete the vac stuff,

20 Deg mechanical advance from 1000rpm all in by 4000rpm.

(don't bother trying to recurve it yourself, while possible, its such an absolute pain.)

Edited December 16, 2011 by styler

[altezzaclub]

(don't bother trying to recurve it yourself, while possible, its such an absolute pain.)

 

True- if you want to try it.....

 

http://www.rollaclub.com/board/topic/49927-how-to-fix-your-brand-new-ke-motorsport-electronic-distributor/page__pid__511594#entry511594

[styler]

^^^ Awesome writeup!

Edited December 16, 2011 by styler

[machinegun mike]

i found my way to that thread earlier. was checkig out your ke70 and ended up there. i have to say i did get a little cross eyed trying to take it all in, well done though i learnt alot!

 

This car will pretty much be driven with wide open trottle all the time (this is a track hack project). so i'm actually leaning towards deleting the vac advance stuff and having the dizzy re curved. Who would do that kind of work? engine builders? carby specialist?

 

here's the culprit btw.

 

p.s. if anyone knows where i can get a set of extractors for a 3t i'm all ears!

[altezzaclub]

Yeah for track work you won't need vac advance!

 

Chat to a few guys at the track or race car engine builders. Some will lock their dizzys, others recurve them. The best would be the dizzy specialists in Melbourne, for a hundred bucks odd they will rebuild & recurve your dizzy for whatever application you want. They will need to know what cam, compression & carbs you're using I suspect, as you will want the advance coming in early but not detonating.

 

Someone on here will know their name, I've forgotten it.

[19914afc]

Ive got some extractors off my 3t, and other bits and pieces if you need anything.

[machinegun mike]

oh yeah? how much were you after for the extractors? would need them posted to NSW 2570 as well..

 

 

 

would love to find somewhere local that would be able to do it [re dizzy]. i'll do some asking and hunting around.

 

will run without it for now. just get the a/f tested and tune the carb as best as possible, get the timing OK and start driving!