hey guys.

i've decided to have a go at making my own twin su inlet manifold (aluminium of course). I'm able to make one at work being a sheetmetal apprentice and i also have access to a TIG and plenty of material.

I'm basically after some design advice.

Do the carbs have to have a pipe joining them? I don't plan on running a booster or PCV.

Any other ideas you guys might have would be great.

Cheers, Cameron

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72 Clubbie - Current project - Vauxhall C20XE 2000cc 16v 150hp.
78 Clubbie - Future project.

Yes they do, as they are SUs- a constant depression carb which have a vacuum operated piston.. and the vacuum level in each port goes `high/high/zero/zero' with the induction pulses.

If you try and do it with NO balance pipe, the pistons in the carbs will flutter and the mixture will be all over the place.
I would look at the Maniflow steel one (arguably the best flowing design right now) and put the balance pipe as shown.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

there is lots of design advice in Vizard's "tuning BL's A series engine" - including Vizards own design which he reckons was 99% efficient - the VS1 manifold, but I believe it never went into production

got access to a flowbench?

Pic of Maniflow manifold,which I got posted out from UK.
Shows the equaliser tube.

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thanks for the info.

so, a balance pipe is definately needed.

LS1380 - what's the diameter of that balance pipe on the maniflow?

skssgn - unfortunatly no access to a flowbench

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72 Clubbie - Current project - Vauxhall C20XE 2000cc 16v 150hp.
78 Clubbie - Future project.

you could have a look at the VS1 manifold as well if you want something a bit more challenging.

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no time to finish me bleedin car ..
1982 Blue-White Roof.

http://aseriesmodifications.wordpress.com/

The maniflow one is done originally in mild steel.

This pic shows mine:


The balance pipe is around 7/16" to 1/2" internal diameter, the bores of the manifold itself are 1 1/4" at the carb face (as I wanted one for twin 1 1/4" carbs, natch ) and match the port size at the other end (12g940 inlet ports.)

It is curved, not straight, so no easy task I reckon. (tapered curve pipe)

If doing this yourself, make the pipes longer as it will increase torque, but make sure the carb face is still on close to the correct angle. (The doc will know this one) Make sure you won't hit the bulk head!

Good luck!

Matt

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68 Deluxe.... it's shiny..... I like shiny!!

Correct angle for twins on a Mini is 30*.

I made a 15* steel one years ago for a pair of Amal Monobloc bike carbs on my 1220,
I kept the pipe straight and put the flanges each end at 7.5*.
It worked well, but putting them at 15* each end to get 30* total will be too much, IMO.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Motorbike Carbs-Is that anything like these?

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Like this, but a LH and a RH, as used on original Bonneville.
I used the Bonny 2-1 cable link too.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Please post pics when you are done, i am interested in making one also

Cheers kiwiinwgtn

I found the invoice from when I purchased the manifold from Maniflow.
Purchased in 2004 for 95.00pounds plus postage 15.00pounds.
Total 110.00pounds-so just a thought,could you make one cheaper or better than?

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LS1380 - will definately be able to make one cheaper, don't know about better though as i don't have access to a flow bench. I will definately give it a go.

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72 Clubbie - Current project - Vauxhall C20XE 2000cc 16v 150hp.
78 Clubbie - Future project.