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Tue Mar 12, 2013 8:30 pm

What are the differences between a single port and a double port engine?
What types uses each of them?
A 1974 VW 1600 is a single or double port?

Tue Mar 12, 2013 8:32 pm

A stock '74 should be a 1600cc dual port

Tue Mar 12, 2013 8:43 pm

Here's a comparison of the intake ports between single port and dual port.

Tue Mar 12, 2013 9:27 pm

Something like 48 horse power vs 60 horse power. The Single port engines were also a different case with a single oil pressure relief. The Dual port engines were dual oil pressure controlled engine cases, better! The single port engines had a much less robust oil cooler on them and it was in the air flow to the left bank of cylinders VW had to retard the ignition on #3 to keep it from overheating due to the placement of the oil cooler. The dual port engines had a much better more robust oil cooler and it was off-set so it did not block any air to the #3,#4 cylinders and head. Better! The dual port engines had a much better designed fan shroud with a little box on the back for the off-set oil cooler. They call it the doghouse fan shroud engine. Better! The single port engines had a smaller flywheel and had a 180 mm clutch. The dual port engines had a 200 mm clutch flywheel. The single port engines had generators as well as some of the early dual port engines but the later dual port engines have an alternator. Some early single port engines were 6 volt. Dual port engines all generated 12 volts. Single port engines had at most a 32 mm carburetor. Dual port engines had a 34 mm carburetor.
What have I missed?
P.S. http://en.wikipedia.org/wiki/Volkswagen_air-cooled_engine

Tue Mar 12, 2013 9:50 pm

Your off on a couple of things there, take what wiki has to say with a grain of salt, they are usually way off with a lot of things.

1500 and 1600 single port engines also had 200mm flywheels and dual port 1300 engines had a 180mm flywheel.

the 1300 dual port engines also had a 31mm carb too (31pict3)

the dual port oil cooler wasnt known as doghouse by VW, just the public has given it the slang name.

Tue Mar 12, 2013 11:21 pm

Also, dual relief oil system came out in 1970... on the 1600 single port.

Danwvw wrote: Something like 48 horse power vs 60 horse power.

That's wrong!!!! Horsepower ratings changed from SAE-gross to SAE-net in 1972, the 2nd year for the dual port - and also the year that VW dropped the compression ratio a little bit and thus, the SAE-gross rating from 60 to 58. By comparison, the 1970 single port was rated 57HP SAE-gross.

Here's a full comparison of the engine ratings in the 60s and 70s.

Wed Mar 13, 2013 3:00 am

Non-USA Aug '70- May '75 (1302-Aug '70-Aug '72, 1303 Aug '72-May '75) 1285cc Dual Port 44ps@4100, 8.8mkg@3000, 7.5:1, 180mm clutch, 31PICT-3 - Oct '72, 31PICT-4 from OCT '72

Wed Mar 13, 2013 1:14 pm

Yeah, non-USA, so that's why it's not on that chart. Outside the USA, dual ports are often referred to as "twin port" engines.
If you want the expanded worldwide version of that chart, it's here:

Thu Mar 14, 2013 12:59 am

glutamodo wrote: Yeah, non-USA, so that's why it's not on that chart. Outside the USA, dual ports are often referred to as "twin port" engines.
If you want the expanded worldwide version of that chart, it's here:

Great stuff. Thanks.