1961 Dino 156 1.5-litre V6
1961 Dino 156 1.5-litre V6: Enzo Ferrari took the obvious opportunity of preparing a smooth transition into the next formula 1 of 1961, he remained faithful to V6 engines but in a new format. The previous V6 was raced in both front and mid-engined chassis, but Carlo Chiti wanted a shorter and lighter more powerful engine that would be better suited to a new mid-engined chassis. Chiti and Franco Rocchi had assigned the task to a young newcomer at Ferrari by the name of Mauro Forghieri.
Chiti “At first there was open disagreement between Ferrari and myself, as he preferred the 65 degree bank angle engine, I was however determined and all the engines I set-up were 120 degree bank angle” the new 1.5-litre engine weighed 25kg less than the 65 degree bank angle one and had even firing with a much shorter crankshaft with shorter I-section con-rods with a reduced big-end bearing diameter. They still had 2-bolt bearing cups.
The pressure and scavenge oil pumps were driven from the front of crank, the right cylinder bank was offset forward. Chain drive to cams was still used, but between the cam sprockets the chain ran straight across, as on the Lancia D50 V8, instead of being pulled down around an additional idler sprocket, each bank had its own double roller chain system driven from 2 half speed gears on nose of crank.
These gears also drove the 2 Marelli ignition distributors splayed out at 120 degrees in front of block, sparking 2-plugs per cylinder. Each cylinder head had 8 hold down studs instead of 12 as the 65 degree Dino had. Wet cylinder liners were installed in a Silumin block.
Wide cam-lobe camshafts worked on broad mushroom tappets of Jano design that screwed directly onto the valve stem for both guidance and clearance adjustment, coil valve springs were used. For this new engine Weber produced an in-line 3-barrel unit, the 40IF3C, with 40mm throttle bodies.
Inlet valves were angled at 28 degrees from vertical. Exhausts were angled at 32 degrees, giving a total included angle of 60 degrees. Only 1 exhaust valve size was used but 2 different inlet valve sizes to produce different power curves as desired were used.
The first 120 degree wide angle engine after 50 hours of dynamometer testing lived-up to its expectations and developed 190BHP@9500RPM with a red-line of 10000RPM, against the previous 65 degree 180BHP@9200RPM with a red-line of 9500RPM.
At Zandvoort which was an unique GP where all starters finished and non made a pit stop the 120 degree V6 placed one-two. In Belgian GP were Phil Hill won, the 120 degree V6 filled the first 4 positions with the 4th position taken by a 65 degree V6 driven by Oliver Gendebien, victories in Britain and Holland for Wolfgang Von Trips followed.
There is a very interesting testing data and comparison chart with other engine as regards results of using different inlet valve sizes and a combination of bore and stroke sizes done with this engine by Mauro Forghieri as regards the importance of gas velocities.
Stroke/bore ratio 0.81:1.
Compression ratio 9.8:1.
Con-rod length 98mm.
Rod/crank radius ratio 3.3:1.
Main bearing journal 60mm.
Rod journal 43.6mm.
Inlet valve 38.5mm.
Exhaust valve 34mm.
Inlet pressure 1Atm.
Engine weight 120kg.
Peak power 190BHP@9500RPM.
Piston speed corrected 20.4m/s.
128.6BHP per litre.
0.63kg per BHP.