Big Cam Power!!!!!
Whats the difference between a small cam cummins and the big cam cummins engine?
Lobe size and injector plunger drive rates were a byproduct in afterthought of the original fix which was updating and repairing the ever-so-prevalent cam bearing spin in small cams. When big cams started having the same issues, tho later in engine hour life, they dropped the running oil pressure from 54/60PSI to 38/42PSI thru II and III series noting it was not tube load but wash out load that spun the bearing. Easy argument fix in cam size isWe should look more at the camshaft itself to differ the 'small' verse 'Big'. This has nothing to the cam being big in lift or small in lift. It pertains to the physical SIZE of the camshaft as a whole. If you see an older 855 series Small cam you will notice the camshaft itself has a smaller diameter journal which entails smaller lobes, opposite is true for a big cam, large journals equals larger usable lobe size which do tune differently however the large journal cam can accept higher rates of acceleration at the lifter. The cam follower plates are also different in size where you adjust your valve timing.
I had a slight argument with some older co workers on this when I told them there was no such thing as a "big" cam or "small" cam at which they were thinking on a whole different perspective as I was.
Thanx Fest. :thumbsup bike didn't go so well... :bangtube load " pressure excerted on cam follower by lift of injector lobe thru injector tube" parasitic shock. injector plunger bottoming out. bearing washout " high oil pressure washing out bearing's, small cam including the 743 series ran 55 to [email protected] rated speed but held together, bc cummins 35 to 45lbs @ rated speed ran forever
Are the bearings in a race engine smaller in surface area compared to a diesel engine? I guess my reasoning is psi is force based on area so if a bearing surface is larger you get more force at the same oil pressure.This brings me back to the rule of thumb of oil pressure in a racing engine, 10psi per 1000 rpms. Could a performance diesel be used under the same thumb? Granted heavier parts but still....