Dyno Session at Bob Homewood's Ford Escort Twin Cam

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When I rebuilt the engine it was initially dynoed and tuned to make sure nothing was amiss. At the time it was felt that the cams were more than likely retarded - ideally they'd be dialed in. Shortly after this Bob Homewood bought a new dyno where the cars's driving axles/hubs are bolted directly to the dyno. As Bob is very experienced with Lotus Twin Cams, I wanted him to do a double check on the previous dyno work. This finally happened a short while ago (three years later) - he's a very busy guy !!. To make life easy I purchased a pair of vernier Cam Sprockets (from Burton Power in the UK), so we could quickly alter the cam timing (these appear to be very professionally made). The car was duely bolted up to the dyno. The original cam sprockets were swapped with the vernier style ones. The engine was retimed and the ignition checked.The first run gave a figure of 100.2hp at the rear wheels. Whilst not to bad the cam cover came off and we started retarding the exhaust cam, then advancing the inlet cam. After further dyno runs it soon became apparent that with the relatively mild cams in the engine little power gains could be expected by any further changes to the cam timing. Cam specs are 266 degrees duration at 0.012 lift, peak lift 0.358" inch. The ignition was then checked. It was soon discovered that the distributor could do with reconditioning, as a slight flutter was apparent on the scope. Despite this we found that the engine ran better by retarding the ignition by a couple of degrees. This one change reaped a power increase of 10hp at the wheels. The carbs were then checked and the jetting scruitenised. We soon discovered that a mechanic from the previous dyno session had fitted a different size jet for no. 4 cylinder. Initially we tried a larger jet size on all four - but this resulted in a power drop. Four jets of the original size were fitted. This gave good power and the lamda sensor indicated that this was a good compromise. All dyno runs were done with the engine running on PULP pump gas. By the end the power was up from 100HP to 112HP at the rear wheels. Not to bad given that the original Escort Twin Cam was rated at only 108HP at the flywheel, and the engine in my car is still pretty standard ;-). I think the increase in performance has come from the head being uprated to Lotus Big Valve specs and ported to suit, valve seats being multi angled, Carbs rejetted and larger venturis fitted, fully balancing the engine, evening up the primary lengths on the factory extractors, as well as a 2" exhaust being fitted. For me to get more power from my engine will involve a lot more work. We feel the cams and carbs are now the limiting factor. In order to go to bigger cams the head would need to be removed and spring seats checked/modified. Also the inlet tracts would need to be modified to accept bigger 45mm side draught carburettors. It will have to wait. I will update this page later with pictures detailing the Vernier Adjustable Sprockets.

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Video Movie of my Escort Twin Cam During a Dyno Run at Bob Homewood Motorsport

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