This 560 SEC engine was rebuilt from our original 560 test engine that came out of the 1987 560 SEC Carobu test car. After dyno testing this original engine (9:1 compression) it made about 300 HP. We wanted to see how much power we could get out of a modified lower end so we used higher compression, forged HB Sport pistons in 98.5 mm size to give 5.8L capacity. Although the bore size is only 2 mm larger, this change helps both torque and improves breathing. Also, the stock head gasket still fits the larger bore size.

After the engine was reassembled using the stock cylinder heads and the same exhaust and intake manifolding as before, we strapped it back on the dyno to test some new camshaft variations that had more lift than the previous iterations. The camshaft durations were the same as before (300 HP). For more details, see our Face Book posts (https://www.facebook.com/Carobuengineering).

After testing both versions of the cams, we decided to use the milder camshaft version (similar in duration to the Mercedes 24/25, 300 HP cam, but with more lift). We did this to keep more torque in the lower rpm range so the heavy 560 SEC would be more responsive at lower rpm. Compared to dyno tests of engines with longer duration cams (see 560 SL, 350 HP test), we gained an extra 500 rpm on the lower end of the rpm scale of torque over 350 lb-ft. This is significant in this application.

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Power: 352-hp @ 5,400-rpm, 387 lb-ft of torque @ 4,000-rpm

Type: M117, SOHC 2v, V-8
Bore: 98.5-mm Razzo Rosso forged pistons, standard pin size
Stroke: 94.8-mm
Compression Ratio: 10.5:1
Cylinder heads: stock
Camshafts: 228/228 duration (@1 mm) and 12.92/12.95-mm lift (in/exh), 110° lobe seperation
Induction: HB Sport custom manifold/plenum. Bosch CIS injection with electronic controls
Exhaust: HB Sport headers/down pipes with dyno mufflers
Ignition: Bosch electronic ignition with HB Sport ECU control