When my high-rpm 1300 was getting tired, I decided to go the other way towards a very driveable torquey motor with larger displacement. Maybe I'm getting old :-)

Here is what I built:

• early 1500 block bored to 86.8 mm
• 1600 crank from a Fiat Tipo (67.4 mm stroke)
• 1500 rods and pistons (cast-in valve reliefs)
• pistons milled so they protrude 0.5 mm from block
• FelPro headgasket
• PBS big-valve head based on 1118cc Yugo head with S2 cam
• CR between 11.0:1 and 11.5:1
• 2x 40DCNF12 on PBS manifold (30mm venturis)
• PBS header into Ulixpeed exhaust using Walker Super Turbo muffler
• PBS lightened flywheel
• Marelli Plex 201 ignition

More technical details later, here are some results of the current status of the engine.

These are RoadDyno curves comparing my car to Dierk's and Holgi's FI cars with completely stock engines. Each car was recorded once going north and once going south on the test track.

Horsepower curve:

Torque curve:

I am very pleased with the power of the engine. In combination with the light '74 chassis, the car could almost be described as "quick".

Things that still have to be addressed:

1. At the top end, the power drops off quite fast. 
• Currently I run only 30 mm venturis in the carbs. I want to find some 32 mm venturis and evaluated the difference. 
• The S2 cam is comparable to a euro 1500 cam, a "hotter" profile may be tried at one point
• Cam timing has not yet been varied, an adjustable pulley is installed
• Ignition timing could be non-optimal at high revs
2. The engine stumbles at revs between 2000 and 3000/3500
• I saw the same phenomenon with my 1300, it disappeared when I installed the stock exhaust system instead of the PBS header system. An IAP header will be installed and may eliminate the problem with its longer primary runner lenght.