KENT ENGINE REBUILDING

The complete rebuilding of a Formula Ford engine was traditionally an annual exercise. At the end of each season and after something like 12 to 15 hours of running time, the engine was dismantled, inspected and rebuilt as necessary. "Rebuilding" means different things to different people. At the least, the engine is taken apart, key parts are magnafluxed and, if nothing major is found, new rings and bearings are all that's really needed - plus a 'valve job'. At the other end of the spectrum the approach is to do a complete rebuild with the goal of returning the engine to absolutely top condition, with no compromises. This involves replacing anything that is even slightly out of spec which may include the crankshaft, cam & lifters and pistons. The block might even be sleeved to achieve optimum piston to wall clearances. 

Formula Ford has always had room for every imaginable approach and that includes those who want to have their engine completely rebuilt professionally every year, those who are satisfied with a "freshening", as well as those who would rather do the work themselves, replacing a minimum of parts. A 'casual' Regional competitor might simply disassemble their engine, have the major parts crack-checked and re-assemble it with new bearings and rings. But there are factors which might effect a different approach entirely. National runners will often do a rebuild and/or swap out their engine mid-season, as soon as they detect that performance has fallen off. So if the usual top end touchup does not bring things back to peak power, a leak-down test will likely confirm that the rings are no longer sealing well, for example. Since that’s a critical part of the FF horsepower equation, it’s time to pull the engine out and freshen it if peak performance at every single event is the goal and there is no room for compromise.

In Regional racing, almost everyone runs a full season on the bottom end unless there’s some signal that it needs serious attention – either bearing material is showing up in the oil or a leak-down test yields really poor results. Naturally, it all depends how much time is put on the engine and whether it's been run past the red line excessively. A guy who does, say, eight events a year is unlikely to put more than ten or twelve hours on an engine, perhaps fifteen hours maximum if a few test days are thrown into the mix.

The timetable for the yearly re-build was, in great part, dictated by the necessity to take a look at the OEM crankshaft. Better to magnaflux the original Ford crank annually and avoid the big blowup which could result from a failed crank. Several years ago then, the standing advice was never to put more than twenty hours on an engine before tearing it down and magging the crank. Some engine builders literally recommended that an OEM crank be retired after as few as ten hours running time!

But things have changed. Now that the newer, stronger aftermarket cranks are prevalent, the annual rebuild of the bottm end is not absolutely mandatory but is, instead, elective surgery based on two main factors: first, the need to do what is required to maintain peak performance – good ring seal, low piston/wall clearances, good valve seal, good oil pressure via tight bearing clearances and so on; and secondly, the desire to assure the engine’s longevity and reliability by doing a complete teardown to allow magnaflux inspection of the crankshaft, connecting rods and even the cam. Rod bolts are critical too but now the pretty much standard use of super high-strength 12 point bolts eliminates most concerns in that area.

Annual disassembly, magnaflux inspection and replacement of rings and bearings is still the typical regimen but bottom ends can now last up to fifty hour so a rebuild can be restricted to top end work only. But as in many aspects of this sport, it’s a question of three key issues - goals, expectations and budget. A full-blown rebuild – involving cylinder sleeving – is only called for if absolutely top performance is the main priority. But there are other approaches too and a decision about when to take any given route requires ‘taking stock’ – in more ways than one!

EXTENDED ENGINE LIFE  -  Engines fitted with one of new new, stronger SCCA/SCAT crankshafts, the new forged aluminum pistons and SPS or ARP rod bolts can now be considered to have a bottom end life of over 50 hours before any major rebuild work is required. This assumes, of course, that the major components have been magnafluxed, balanced and properly assembled. One other point: some of the engine builders do further work on the SCAT crankshafts. Jay Ivey, for example, shot peens them and rechecks for perfect balance and clearances.