Twin Carbs On 4k

[Jono.B]

Hi all could someone please tell me if Getting twin carbs (not sidedraft) for my 4k is worth it, ive had mixed opinions on this,

 

it is for a twin weber setup, my mechanic uncle says itll just waste gas.

 

Also could someone please tell me how to rejet carbs suitable for a 4k preferably with pics.

 

Thanks all

[WinKE55]

I am told that you should only need twin carbs if a single one can not supply enough fuel to the engine. Twin carbs require a bit of stuffing around to do to get them both mixtures right.

 

What are you doing to your 4k? Are you going to use it for economy? Or power? You can not have both.

 

 

All I am going is one 34 ADM downdraft (Found on old Falcons) on my 4k. Though my 4k is going to be pretty worked.

[KE ping it real]

I have twin sidedrafts on my 4k but i think you'll find you should do other things aswell not just put the twins on

 

You should also have extractors exhaust and at least a cam preferably some headwork aswell to get everything flowing well

 

If you just put twins on you'll have to dial down the mixtures so much that it wont be worth it

 

However, in saying all that if you do a couple of those other things you should see a descent increase in power aswell as agood increase in responsivness. They will use more fuel but more fuel generally equals more power

 

And as for tuning and jetting twins, this should be done by someone who knows what they are doing as twins need to be in balance

I just spent $1000 getting mine repaired, rebuilt,balaced and tuned........And i haven't stopped smiling since

 

I hope that helps

Edited June 4, 2008 by KE ping it real

[philbey]

As said, running twins is more than just slapping them on and you're done. All you'll see on a stock motor is bad consumption, poor driveability and some fully sick induction noise.

 

You''ll need at least a cam and extractors to get the benefit from them. Yes, you will use more fuel, whether its a worked motor or a stock motor.

 

As far as Rejetting etc, google it. I found all the info on rejetting and setting up Dellortos with google. Not to dispute with KE_ping about getting a pro to do the work, but I bought a book on tuning Dellorto's and I'm confident I will be able to rebuild, rejet, setup and tune them to a driveable level.

 

Research, read, understand, find out the prices, do the numbers then see. My 5K Rebuild will be run cam, extractors, minor head upgrades and twin DHLA's and I plan for it to run well. It'll set me back about 2 grand total, which is cheap, and that includes ready jetted dellortos at a bargain price.

 

You'll likely to need to spend 700-1000 bucks to get a set of twin sidedrafts setup for your 4k.

Edited June 4, 2008 by philbey

[Jono.B]

just had the extractors exhaust and ignition done, so would it make much diff to that?? i want power. Also by cam work do u mean a lumpy cam??

[KE ping it real]

Yes a lumpy cam and a cam grind would be the go. If you go to the faq section they give you a couple of suggested grinds to go for

This will definatly help with the fuel flow and power :dance:

Edited June 4, 2008 by KE ping it real

[KE ping it real]

And oh yes, as Philbey said ' Some fully sick induction noise'

 

Loooove the induction noise :dance:

[coln72]

Try and dig up a set of 3kb carbies. These are a factory fitted twin set up and will work well with a cam and extractors. If you are lucky you can pick them up cheap (have got them for $25 for a complete set and $0 for a manifold only). Noticable difference on a 5k. It actually ran better with the twins and still could get over 30mpg on the highway. When you got up it though.........

[philbey]

From my reading, a tuned set of sidedrafts will still be reasonable on the fuel consumption as long as you can take it easy on the throttle....

 

There are lots of guys running the factory twin carbs, and rave about them. Bolt on, no hassles with fitment (Factory!) like you get with sidedrafts. At the moment, I am going through the rigmarole of trying to find filters that fit my Dellortos into my car without hitting the strut tower.

 

The factory twins come up regularly on ebay for around 400. Make sure you get all the linkage gear you need, as these bits usually seem to be the first parts to disappear.

 

SU's generally come up around the same price. I only have DHLA's over these options because I got them cheeep like the budgie.

[corolla_nut]

we recently put a set of twin SU's on my car after a few months of it being off the road. Because they are su's we had issues with sourcing parts for linkages etc to set them up on my 4K. We also had issues with the needle and seat being shit, causing the float bowls to overflow onto the extractors. we took it to a speed shop to fix that, but everything else we did ourselves as my man's a mechanic.

I agree with the whole lumpy cam, extractors and exhaust thing because i don't think my car would run without these with the su's on. Actually I think my car could now deal with a lumpier cam. the cam I have now was reground by crow cams and was the second grind up from mild, and it was very grumpy when it had the single down-draught weber on it. The twin carbs have smoothed it out heaps :dance:

hooking up a choke was a little bit of a hurdle, and we also slapped a regulator on as the car still has the original fuel pump on it.

Anyway I don't know if any of this will relate to webers, i'd say some of it will...

We've had the carbs on for a couple of weeks now, but have not got the mixture quite right, nor the ignition timing, pretty close but not quite.

anyway we're fixing those this afternoon.

Hope some of this helps :lmao:

[Jono.B]

we recently put a set of twin SU's on my car after a few months of it being off the road. Because they are su's we had issues with sourcing parts for linkages etc to set them up on my 4K. We also had issues with the needle and seat being shit, causing the float bowls to overflow onto the extractors. we took it to a speed shop to fix that, but everything else we did ourselves as my man's a mechanic.

I agree with the whole lumpy cam, extractors and exhaust thing because i don't think my car would run without these with the su's on. Actually I think my car could now deal with a lumpier cam. the cam I have now was reground by crow cams and was the second grind up from mild, and it was very grumpy when it had the single down-draught weber on it. The twin carbs have smoothed it out heaps :dance:

hooking up a choke was a little bit of a hurdle, and we also slapped a regulator on as the car still has the original fuel pump on it.

Anyway I don't know if any of this will relate to webers, i'd say some of it will...

We've had the carbs on for a couple of weeks now, but have not got the mixture quite right, nor the ignition timing, pretty close but not quite.

anyway we're fixing those this afternoon.

Hope some of this helps :lmao:

 

yeah that is helpful, whats the deal with the fuel regulator?? are they expensive, where do they fit in the fuel system???

[KE ping it real]

I don't have a regulator on my Dellorto setup, just the standard fuel pump

[corolla_nut]

yeah that is helpful, whats the deal with the fuel regulator?? are they expensive, where do they fit in the fuel system???

 

The fuel regulator cost us around $50 mates rates . they go into the fuel line just after the pump. They lower and regulate the fuel pump pressure, you can set it between 1 and 5 psi which is lower than the stock fuel pump pressure on its own.

Edited June 5, 2008 by corolla_nut

[camerondownunder88]

Just a note for reference:

 

Stock pump running specs are:

 

900cc/min

@

0.2 ~ 0.3kg/cm3

 

Cameron