• Registered: 2010-05-23
  • Posts: 1

Topic: what is better dual port or single port

hi new here

i have a(1970) 1600 with single port heads
i was wondering what the advantages of using one or the other (heads)
i sure the dual port heads allow for more horse power
the heads on my engine need to be replaced and was pretty much wondering if i should put dual heads back on or go back to the single ports heads
i would really appreciate your feedback
thanks

  • From: City of Roses
  • Registered: 2004-03-29
  • Posts: 793

Re: what is better dual port or single port

Hiya luvs,

Welcome aboard!

Interesting that you should bring up this topic.  I'm a little predjudiced.  Let me explain.................

I have a 1970 Bus and a 1970 Bug.  The Bug came into my possession with a dual port engine in place.  And, as of course you already know, the original engine for this application was a 1600 single port.  I ran with the dual port for quite a few years.  And in that time I did quite a bit of reading concerning the dual port versus the single port.

Here's how it came down for me.  If you are interested in increasing performance from stock, dual port is the way to go.  The increase in air/fuel flow is a definite advantage here.  Interestingly though, you'll find the total horsepower difference between a "B" series single port and an "AE" series dual port (the "B"s successor on the production line) is only 3 hp.  And that got me to looking at stock set-ups.  Single ports are generally more reliable in that the heads are not as prone to heat cracking around the spark plug holes.  Then too single ports are said to have a bit more lower end torque which makes them a great candidate for pushing a Bus around.

So........when it came time for me to do a rebuild I went with single port engines for each of my rides.  Truthfully, I've never looked back.  The Bug seems faster (or at the very worst just as fast) than with the dual port - and that dual port was in pretty good shape when I first got it. 

One thing I would definitely recommend................ if you decide to go with a single port set-up, think very hard about setting that engine up with a dual port (doghouse) fanshroud and cooling system.  It's a big improvement over the single port fanshroud.

Mike

1970 AS Bug
1970 Bus - The Ruptured Duck
  • Registered: 2009-06-25
  • Posts: 554

Re: what is better dual port or single port

From a racing background - Yep, single port heads will be more reliable and usually have more torque. Reason for the torque is the flow velocity is higher (same air pulled through a smaller opening). With the dual port manifold, the flow velocity is disrupted at the split, and this also affects the intake pulse resonance in a negative way for low end torque. The tables turn at higher RPM's because the dual port will just flow more air. The improvement is not very significant in stock motors because the type 1 intake manifold flow capabilities are poor, and it's a restriction at high RPM. Swap in even a single barrel aftermarket intake to remove that bottleneck, and the increase in power of a dual port above 3000 RPM becomes significant.

In a nutshell...
Stock engine or low RPM use: single port is better.
Reliability: single port is better.
But in an engine modified for improved breathing and higher RPM, dual ports have an advantage in terms of power potential.

Paul

  • From: Vancouver Canada
  • Registered: 2004-04-28
  • Posts: 441

Re: what is better dual port or single port

Altema wrote:

Reliability: single port is better.

What makes you say that?  What do you think is unreliable with a dual port head?

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,585

Re: what is better dual port or single port

Bruce wrote:
Altema wrote:

Reliability: single port is better.

What makes you say that?  What do you think is unreliable with a dual port head?

He didn't say dual ports were unreliable, he said single ports are more reliable. There's a difference.

But I'm curious too. Why Paul?

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • Registered: 2009-06-25
  • Posts: 554

Re: what is better dual port or single port

jamesdagg wrote:
Bruce wrote:
Altema wrote:

Reliability: single port is better.

What makes you say that?  What do you think is unreliable with a dual port head?

He didn't say dual ports were unreliable, he said single ports are more reliable. There's a difference.

But I'm curious too. Why Paul?

jim

Perhaps I should have used the term "Durability" instead, as it's nothing that will leave you stranded on the side of the road. Just like Mike said, dual port heads are more prone to cracking around the plugs, and I've seen several that have hairline cracks between the intake and exhaust valve seats. It's so common that some shops don't bother replacing cracked dual port heads unless it's more significant than a hairline.