compression ratio

[BeeJay]

OK. I'm finally getting started on my 2 liter for my 73 914. It will have carbs, delllorto 36's to start, webber 40s when I can find a set. I've ordered the mild street carb webcam, and I'm using a set of European pistons and cylinders(8to1 CR). OK. The machine shop, which builds tons of Porsche and VW engines, and really know their stuff, insists that with the carb/cam combo, I should definitely stick with 8to1CR. My background is mostly watercooled chevy's but I'vealways thought 9 to 1 was needed for good power. Many of my new Porsche friends also think 9 to 1 is fine. The machine shop doesn't think the gas available today is good enough for 9 to 1, and longevity would suffer big time. What are your thoughts?

[Dave at Pelican Parts]

I agree with your machine shop. At least, for a street motor, I do.

The 2.0 heads are notoriously crack-prone. The mechanics I have talked to tell me that is a result of too much heat, not enough heat dissipation, and not enough metal.

If you make more power, you will make more heat. Higher compression makes more power, AND makes for higher pressures in the combustion chamber. More heat, more pressure, more stress. Think about it for a moment. It may not result in broken heads, but it sure as heck will result in more wear.

Depending on how hard you intend to use the motor, you can probably go up to 8.5:1 on premium-unleaded fuel. I would be concerned about track use (extended high-power high-RPM) at that point, though. I think I'd stop worrying if I had a 911 fan setup, but that is really serious $$$.

What I don't know about carbs is pretty much everything, but I have heard that the 40 Webers are a little small for a high-revving 2.0 (just fine for a street one). So I would think that Dell 36es would be too small, unless the numbers refer to different measurements.

--DD

[Tim Polzin]

The point about cooling heads brought up a question concerning an interesting head I saw at a machine shop. The head was obviously VW with type 2 exhaust ports, a twin port intake, but was water cooled, no fins. I thought the water cooled Wasserboxer engine used in the VW transporter was a type 4.

[Dave at Pelican Parts]

Could it have been a Subaru head? I have heard that the early Subies were more or less the VW Type I with water jackets around it.

--DD

[Tim Polzin]

Never even occured to me, could be. If it is still there when I pick up the crank for my son's New Yorker (yuk!) I'll check.

[djs]

The Vanagon water-cooled motor is actually quite a compact unit, physically smaller than the air-cooled Type IV. This is largely due to the fact that liquid cooling allows for closer spaced cylinders and thus a shorter crankshaft and motor length. If you see one installed in a Vanagon, there is no cooling sheet metal present and you can see the ground through a lot of empty space around the motor.

Additionally, the valve covers appear similar to (or are actually the same as) Type I - III air-cooled motors. I believe VW capitalized on this and other Type I-III motor dimensions and parts bin pieces to save money on their water-cooled development.