Difference between Single Port and Twin Port?

benny_acko Officially Full-On Dubber

253 posts · joined Aug 2011 · 21 Sep 2011, 9:26 pm

#863251

Hey
just wondering what the difference between a single port engine and a twin port is (apart from an extra port!!)
Also, what are the advantages/disadvantages between these?
Can you still have a twin carb with a single port engine?
Thanks

1967 VW Beetle Deluxe

68AutoBug Beetle Restorer - Experience over 138\% - YIKES --

11,654 posts · joined Aug 2002 · 22 Sep 2011, 1:18 am

#863314

benny_acko wrote:Hey
just wondering what the difference between a single port engine and a twin port is (apart from an extra port!!)
Also, what are the advantages/disadvantages between these?
Can you still have a twin carb with a single port engine?
Thanks

Hi
the early engines were all single port until the 1600 Dual ports came out [in Australia]

You can fit twin carburetors.. usually Kadrons..
single port engines have slightly more torque than dual port engines..

Dual port engines can rev more as they have better breathing

I have a single port 1600 engine and have never really thought about changing the heads etc to dual port..
even though I have replaced the heads..

cheers

LEE

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Sides Veteran Volks Folk

2,220 posts · joined May 2007 · 22 Sep 2011, 9:22 am

#863342

Extra to what Lee's said, here's some differences I know:

Twin port engines are usually all 1600's, though there were also some twin port 1300's.
Twin port engines used a different crank case - two oil pressure relief valves instead of just one and larger diameter oil galleries internally
Twin port upright engines have better cooling as they use doghouse oil coolers, with the different fan shroud and tinwork to suit
Twin port engines the engine bolt nearest #3 cylinder threads into the crank case, while single port engines there's a nut that has to go on

Advantages/disadvantages...well as standard there's the obvious capacity advantage and better cooling, but also a twin port crank case is a better base if you're going to build a big engine.

There's no reason at all you can't put twin carb's on a single port engine, just there are less options and kits around to do it. Think old school, with two stock VW carb's mounted up rather than twin Weber's or Dell's.

Bottom line... unless you've got a good single port on hand already, go for twin port.

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11,654 posts · joined Aug 2002 · 22 Sep 2011, 1:20 pm

#863356

all the things I forgot... lol

You can of course fit a doghouse oil cooler and fan shroud and wider fan...

If the engine is OK

You can fit twin solex or Kadron carbies..

and an SVDA distributor for better acceleration...

plus an extractor exhaust system...

Lee

- Helping keep Air Cooled VWs on the road - location: SCONE in the Upper Hunter Valley - Northern NSW 320 kms NNW of SYDNEY---

Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 · 22 Sep 2011, 1:29 pm

#863359

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