Help with a 1.8 rebuild or convert to a 2.0

[NJTom]

Hello other Porsche enthusiasts I'm hoping to get some advice and guidance. I really have two questions. First, I have a 1974 1.8 that was back firing and wouldn't start. We dropped the motor and it had 2 broken rocker arms, still don't know why. We've had a heck of a time finding top dead center. Based on the mark on the fly wheel if the TDC is correct when the one piston is up,the valves on the number 1 cylinder are open, which I'm told shouldn't be the case, they both should be closed. We haven't opened the crankcase yet to exam the cam shaft, the piston look good. That leads to my second question, moving forward any suggestions on rebuilding. Rings and a gasket sets are inexpensive, my friend did read where you can convert a 1.8 to a 2.0, has anyone done this and what would be the approximate cost? At this point it looks like we will rebuild and if we are going to do that why not go the extra and convert to a 2.0 any suggestions would be greatly appreciated. Below are pictures of the heads Thanks!

[Dave at Pelican Parts]

Remember that the flywheel (and fan) will show TDC twice for one complete cycle of the engine. It will show once when #1 is at TDC, and once when #3 is at TDC. That could be your problem there.

I'm not sure what would cause broken rocker arms; ours are pretty stout and not easy to break! From looking at your photo, though, I would suspect the second valve from the right has a dropped valve seat. The tip of the valve (actually the spring retainer) appears to be further down than the other three, which may be because the seat is no longer in the head and is holding the valve open slightly. Or it could be my imagination.

There are lots of things that people think of as "converting to a 2.0". Most do not address all of the differences between a 1.8 and a 2.0, though.

The easiest would be to use a set of 96mm pistons and cylinders. That gives you 1911cc displacement, which isn't as much as the 1971cc of the stock 2.0 motor but is more than you had. The 1.9 evidently can be a revvy little motor, too.

To get the actual 1971cc displacement, you would need the crank and rods from the 2.0 (71mm stroke and rods to compensate versus the 66mm of the 1.7 and 1.8 motors), plus the 94mm P&Cs from the 2.0. Or go with 96es there for 2056cc displacement.

Of course, you'd still have 1.8 heads. Which are good heads, but not quite as good for power/torque as the 2.0 heads. You can have the valve sizes increased to the stock 2.0 sizes, and you can have the ports re-shaped, but it's a whole 'nother level of work to re-locate the spark plug holes to the 2.0 position for a more efficient burn.

Still, all of the above can be very viable motors. With a stock-type mild cam, they can even use the 1.8's L-jetronic fuel injection, which is convenient.

--DD

[NJTom]

Thank you sir! The information was very helpful and much appreciated!