After an extensive testing regime of bolt-on parts that yielded over 300 HP (see our FB page for extensive details), we rebuilt the 560 engine using HB Sport 98.5mm high-compression, forged pistons. The stock crankshaft, connecting rods and cylinder heads were used. Added to the mix were our HB Sport modified intake manifold (same as on the 300 HP version), high-lift camshafts and our engine control units (FrankenCIS/Microsquirt/MSD) with a modified distributor.

Here are some takeaways from the dyno-testing.

First, the stock cylinder heads are capable of supporting 350+ HP. We will experiment with cylinder head modification on a later project.

Second, the intake manifold modifications work even better with more displacement and a higher compression ratio. In the future, we will be adding more flow to the intake manifold.

Third, The camshaft with more duration (300 HP +10°) and lift definitely likes the added compression.

Fourth, the headers seem to be fine for this power level. We will see if they can sustain more power increases.

Fifth, using the stock CIS fuel injection with electronic controls is good enough to produce this output. On the next phase of development, EFI will be compared to the CIS system to see what different that makes to airflow. We don’t expect to see much difference just from changing to EFI alone.

Based on some preliminary road testing of a 560 SL that we did, the acceleration is vastly improved even with the bolt-on version of the engine (280 HP with cats).

See more detail on this 560 SL engine build here.