Twin 32/36 Down Draught Webers?

[agius]

Hey all! :wink:

 

ok so here's the deal...

 

so when we normally hear about twin carbs on a k motor we think twin side draught 40 DCOE webers right?

 

now ive already got a 32/36 weber on my 5k runs good i only bought it for $250

 

I'm prety sure i can find another 32/36 for a similar price.

 

if i do something like theese guys but on my 5k twin 32/36 down draught

 

do you rekon its possible to get the same performance or even better than a twin side draught 40 DCOE?

 

reason i brought this topic up is because twin DCOE plus the manifold are so pricey..

 

plus i love to muck around with things and make them work haha! :)

 

thanks in advance guys. ;)

[parrot]

a) where are you going to get a manifold from, at a price cheaper than a side draft manifold.

 

b) downdraft carbs are never going to be as infinitely tuneable. Side draft carbs are easily tuned specifically to your engine on a dyno, that's where the power gains and driveability are really found

[colonel]

Just find a set of the twin aisan down draughts.

They pop up on here and E-bay frequently and you'll get em chesper than what you're willing to pay for two webers

[tojo2]

do you rekon its possible to get the same performance or even better than a twin side draught 40 DCOE?

 

 

No, not by a log shot . The thing about twin dcoe is that you get independent throttles to each cylinder so you can run a big cam with overlap (long duration) without getting revertion problems. Your setup will be more of a 3k-b thing. One carb feeding cyl.1+2 and other one feeding 3+4 isnt ideal either.

 

A crossover manifold feeding 1+4 and 2+3 would be better but don't see how on a K.

 

If you want twin down draught carbs with similar potential to dcoe Id look for idf style carbs. Have seen maifolds for them but rare. Would be fairly tall as well... na, stick to the single downdraught unless youre chasing big hp.

 

Just my 2c and I'm no expert.

By the way, what else have you done to the 5k ?

[colonel]

Here's another option

 

 

http://www.rollaclub.com/board/index.php?showtopic=36821

[agius]

a) where are you going to get a manifold from, at a price cheaper than a side draft manifold.

 

b) downdraft carbs are never going to be as infinitely tuneable. Side draft carbs are easily tuned specifically to your engine on a dyno, that's where the power gains and driveability are really found

 

I was going to mock up my own manifold like the link i posted

 

No, not by a log shot . The thing about twin dcoe is that you get independent throttles to each cylinder so you can run a big cam with overlap (long duration) without getting revertion problems. Your setup will be more of a 3k-b thing. One carb feeding cyl.1+2 and other one feeding 3+4 isnt ideal either.

 

A crossover manifold feeding 1+4 and 2+3 would be better but don't see how on a K.

 

If you want twin down draught carbs with similar potential to dcoe Id look for idf style carbs. Have seen maifolds for them but rare. Would be fairly tall as well... na, stick to the single downdraught unless youre chasing big hp.

 

Just my 2c and I'm no expert.

By the way, what else have you done to the 5k ?

 

mmm you make alot of sense..i didnt think of it that way i guess.

and to your question just the single 32/36 at the moment ill be doing extractors exhausted port and shave the head change valve seats and a nice big cam.

 

Just find a set of the twin aisan down draughts.

They pop up on here and E-bay frequently and you'll get em chesper than what you're willing to pay for two webers

 

from my knowledge twin asain carbs are the factory carbs the came with...

if i were to buy 2 carbs i might aswell go with the twin side draft webers.

 

Thanks heaps every body for all your help...

 

from all what you are saying i came to figure that twin side draft webers are the way to go

a) there easy to tune

b) can buy a manifold that fits straight on

c) better performance for less effort

d) its what 40 DCOE are made for! haha

 

if any one else wants to give there opinion feel free I'm still listening because it will be a little while till i change over the carby

and I'm open to new ideas and learning more I'm still quite new about this stuff.

[Felix]

3K-B manifold with a couple of weber adapter plates.

 

If you wanted twin downdrafts you can't go past 28/36 DCD Webers. They are more

tunable than sidedrafts over a much wider rev range. You can change

venturis (19mm - 28mm in 1mm increments for both primary and secondary

throats), and everything else is tunable. Coolest thing about them is

you can change the idle jets and main jets without even removing the

aircleaner. :)

 

Probably won't be cheap though as they are rare, orig fitment to MK1 1500GT Cortinas.

[altezzaclub]

Quads off a bike!!!

 

The manifold is just 4 bent pipes with a flange on the engine end!

 

15,000rpm on a 650cc is the same airflow as 7,500rpm on a 4K, so anything from 650cc upwards is more than enough!

[agius]

3K-B manifold with a couple of weber adapter plates.

 

If you wanted twin downdrafts you can't go past 28/36 DCD Webers. They are more

tunable than sidedrafts over a much wider rev range. You can change

venturis (19mm - 28mm in 1mm increments for both primary and secondary

throats), and everything else is tunable. Coolest thing about them is

you can change the idle jets and main jets without even removing the

aircleaner. :)

 

Probably won't be cheap though as they are rare, orig fitment to MK1 1500GT Cortinas.

 

that would be prety crazy easy cruising with the 28mm and when u punch it a massive 36mm opens to say hello ahhaha

 

hrrm your probably right about 28/36 being the biggest twin down drought but by the time i do all this ill have a bit of head work done = more compression so maybe ill be alright with the 32/36.

 

to come to think about it the side draft DCOE are twin 40mm isnt that way to huge then?

 

 

 

Quads off a bike!!!

 

The manifold is just 4 bent pipes with a flange on the engine end!

 

15,000rpm on a 650cc is the same airflow as 7,500rpm on a 4K, so anything from 650cc upwards is more than enough!

 

ahhaha thats crazy ive seen that thread

 

its quite awsome having 1 carby per cylinder

 

might have to have another look at that one i kinda liked the idea from the start

 

hrmm so many ideas going around I'm loving it!

[agius]

Oh and with the side draft DCOE do the primary and secondary open like a 32/36

primary being 1/4 way before the secondry starts to open

 

or do they open at the same time?

[philbey]

no such thing as a primary or secondary on a sidedraft. One butterfly, one jet per piston, unlike a downdraft.

 

If you can get the factory manifold as mentioned, adaptors on that will be the easiest way.

 

You wont get the tunability cheap, while Felix mentioned the hard to find 28/36 that will cost a bomb to not only find but I hazard that getting all the goodies for them will be pricey too.

 

And remember, you'll always get a bigger pressure drop which equals flow restriction in a downdraft manifold.

Edited February 21, 2010 by philbey

[agius]

ohh that makes sence about the side draft u can just tell by looking at the manifold it was right under my nose... :)

 

yeaaa ;) nay on the 28/36 the whole reason i brought this thread up is so i can work out the cheepest way to have twin carbs hahaha!

 

alredy got a 32/36 so just needa get one more and yeah.

 

my old mans great with welding has 2 lathes and a milling machine so making my own manifolds etc wont be so hard

 

i still feel inside that i can pull this thing off

 

hrmm maybe i just have my hopes to high

 

maybe i gota include some maths with this work out cfm etc etc.

[agius]

And remember, you'll always get a bigger pressure drop which equals flow restriction in a downdraft manifold.

 

sorry man can u explain that further i didnt understand it.

[philbey]

All I'm trying to say is that there is more restriction in a downdraft carby manifold than there is in a sidedraft. That makes it harder to pull lots of air through it.

[agius]

ahh i see :) makes sence..