Roller cam bearings

[1347]

Originally Posted by SSDiv6

NASCAR engine blocks, have closed camshaft tunnels; therefore, the roller cam bearings, camshaft and lifters were always flooded with oil. The initial idea for the use of roller bearings was to reduce friction. Nevertheless, no one expected valvetrain frequencies and harmonics to generate from its use.

Junior Johnson was running roller bearings in a stock Chevrolet block in 74. I saw a stock open tunnel block at Smokey Yunicks shop from the 70s or 80s also with roller cam bearings. Maybe Jenkins saw harmonics, but the Nascar guys were cheatin with them before with success.

[Signman]

Harmonics are probably always there it is when they magnify become intolerable would think is dependent on operating rpm. Friend had severe believe valve train issues with a Ford combination in a Late Model years ago when changing engine builders the second had him take gear away problem solved.

[SSDiv6]

Originally Posted by 1347

Junior Johnson was running roller bearings in a stock Chevrolet block in 74. I saw a stock open tunnel block at Smokey Yunicks shop from the 70s or 80s also with roller cam bearings. Maybe Jenkins saw harmonics, but the Nascar guys were cheatin with them before with success.

They were not cheating with them; it was common knowledge at the time.

The closed tunnel blocks started to show up after Mike Ege, the head of the NASCAR engine shops for Robert Yates Racing and years later, for Roger Penske Racing, built the first closed cam tunnel Ford engine block while working for Yates. Mike later incorporated the same feature on the Chevy and Mopar NASCAR engine blocks while working for Penske.

[carl hinkson]

Originally Posted by HP HUNTER

Carl

Some years back I had a contract to build Winston West 9.1 comp 390 carbed 358 engines. We were quite sucessful and won several races, every engine we built had roller cam bearings, but also were dry sump. I never saw any weird stuff going on in those engines, they made right at 600 HP. Not going to say there was no harmonics, but we never had problems. We also built some with 55 MM babbit, I never saw any difference on the dyno, I did like getting rid of the oil leaks.

The 55MM bearing you used probably had 3 oil holes = huge oil, A few years ago I had 55MM babbit bearings designed with one oil hole and a groove.

A lot of my customers have said going from Roller to babbit once the adjust the valves nothing changes in lash going to babbit which is good indicator there is less harmonics having the cam floating film of oil VS iron to iron.