With the Spartan tappets of the past we had some failures. This tappet was a stock Cummins chilled iron tappet that was modified and coated. The problem was many of the tappets were just not hard enough to avoid wear from the steel camshaft we have. Many came in under 55 HRC and the cam was 62 HRC. With the higher spring pressures, any tappet under 58 was a problem for us.
The new tappets address this hardness issue by a HUGE margin. They are at least 3 times harder and have lived in testing under extreme conditions so far. The tappets can be used over and over and even switched from cam to cam without issue. The new tappet is at 65-67 HRC, but only on the wear surface. The rest of the body is 51-55 HRC through induction hardening of the forged steel.
All tappets come with an inspection report of hardness, surface finish, a micrograph at 100X and 500X showing the martensite structure. All 33 surfaces are tested. i.e. Push tube cup, stem, etc, etc and listed on the test of EACH tappet. Any rejects are scrapped.
Mahr equipment is used for the testing:
MarSurf XP - Mahr Metrology
They are not a cheap date, but a step up past our silicon carbide tappets that cost 1200 a set with a 50K minimum order per production run. These are less than half that price and work just as well and wear just as well.
More to come with lots of photos and wear data for the last 6 months or so.
