Inliners International Forums General Discussion Engines GM 4 cylinders 151 153 181

Each time the topic of roller cams for the street comes up I always ask myself the question

WHY?

I get it that its always neat to have something different from anyone else. Heck, that is one reason for running a six in a hot rod in the first place.

I have done dynamometer comparison testing on various engine components in a previous life. Car manufacturers have incorporated many design improvements in the engine to enhance its efficiency and performance, like smaller journals with aluminum bearing shells, low friction ring packs, low drag oil seals, revised piston designs and rollerized valve trains. Tests I've run on SBF engines showed around 15 lb-ft improvement at 500 RPM and as RPM increased to say, 4500, the reduction in friction vs a flat tappet hydraulic cam diminished to almost nil - maybe 2 lb-ft. So to gain that small slice of the torque pie by re-engineering the cam for roller lifters seems to me to be a large expense for a small gain. You would be better off investing that cash in a stronger piston with smaller, lighter, low friction metric rings.

Even if rollerized lifters could be fitted then the first cut at an optimal cam grind would be a rough guestimate. The big car companies have the resources to beat those cam grinds to death first on the computerized engine analyzer programs and then on the dyno before deciding on the most effective grind.

Vintage inlines are never going to be RPM champions so a good flat tappet grind will suffice in 99.9% of street rod applications.