BGIII

Most people say to switch cams if using a crate GM 502 in a boat. Can the factory GM roller lifters be used w/ a Crane hydraulic roller cam or do you need to switch to Crane roller lifters also?

Thanks

Dennis Moore

All camshafts have lobes that are just large enough to fit inside the cam bearings. Lift is the difference between the bottom of the lobe and the top. A high lift camshaft will have a smaller bottom, known as a smaller base circle. A very high lift camshaft may drop the lifter down too far into the lifter bore when it is on the bottom of the lobe. With such a high lift (small base circle) the stock roller lifter may fall out of the guide bar. A high lift/small base circle camshaft needs taller lifters, which Crane makes. So, it depends on the amount of lift, or stated another way, how small the base circle has to be made to get a high amount of lift. A high lift/small base circle camshaft also needs longer push rods to maintain rocker arm geometry.
Hope this makes sense to somebody!
Sincerely
Dennis Moore

Ratchet

Definitely makes sense.

My recommendation - - Give the cam mfr (whoever you chose, crower, comp, isky, whoever) your intent when doing up the engine. Let them know that it's a marine application, and that you want a cam that won't destroy your valve train in 10 hours (instead of just throwing a drag race cam in there). All of the fore-mentioned will be able to recommend a cam & the correct lifters for the cam.

Just my thoughts............

blown1500

If you get any cam that is not a true race part and very radical, the BASE CIRCLE of the cam is pretty much standard, therefore the lifter drops to the same depth in the lifter bore with any cam you are likely to use in a normal application. The high lift cams can make the lifter rise enough to contact the bottom of the OEM guide and cause a problem. Lifts of .650" or less should not be a problem, but ALWAYS CHECK to make sure. Post the cam you are considering and I can tell you how much trouble you might have.
Beware of the crate engine bearing and piston clearances-We ALWAYS check and often find problems that could destroy a boat motor, would probaboly not be a problem in a car!!!

bobby daniels

It would make good sense to Warren Johnson or some I H R A ,pro -mod engine builder whose cams lifts from 800 to 1 inch
The common roller that you would run in a dual purpose boat or hot street car this would not be a problem at all!!
Crane does make tall rollers for mk-6 and certain other engines with stock merc. cams ,the bosses in the block ,(lifter bores) are taller with some mk5&6 blocks
This small base circle is only for special apps. ,boy o.t.
let us know the cam number and I'll try and help

PROSTOCK guys today run 1.140 ect LIFT now thats big

just pick a good cam and 99% of time lifters work great !!!


not trying to argue just don't want this to be a big deal

liquid lounge

Blown- not my experience...I'm with Denny on this one....I had a relatively tame .601"@1.7 Ultradyne and the lifters dropped below the top of the lifter retainer [Gen6]...didn't like the looks of that so I bought the Cranes.

bobby daniels

thats what they were made for gen.6

Dennis Moore

If you lay a straight edge across the cam bearing journals, the lobes will not exceed the height of the straight edge. They will be equal to the height of the cam bearing journals. This is true of all camshafts. I have never seen a camshaft that has lobes higher than the bearing journals. If the lobes exceed the height of the bearing journals how do you install the camshaft? Even a stock, low lift, camshaft will have the lobes the size of the bearing journals. Am I wrong on this?
Respectfully
Dennis Moore

blown1500

Mr. Moore, what cams have you been looking at??
Almost all cams have lobes noticably smaller in height than a straight edge would be between the journals. Am I misunderstanding what you are saying?? I have seen cams with lobes larger than the journals used in overhead cam engines that have removable caps like main bearing caps. The lobes on cams that are installed like chevy V-8s must be smaller than the journals, but they are almost always considerably lower than the straight edge would be.
Liquid lounge, was your Ultradyn cam a small base circle design? I would like very much to know what the deal is here.

Dennis Moore

My point is that you do not increase lift with a taller cam lobe, (like you seem to be saying). You increase lift by starting at a lower lift point. You seem to be saying that a high lift camshaft raises the lifter higher in the lifter bore. "The high lift cams can make the lifter rise high enough to contact the bottom of the OEM guide and cause a problem" It doesn't, even a low lift camshaft raises the lifter to the maximum point in the lifter bore. The only way lift can be increased is by making the base circle smaller and adjusting the rocker arm to have the correct lash with a smaller base circle. The difference in the lift between a high lift and low lift cam is not the height of the lobe (they are all the same height just small enough to fit in the bearing journals) but the diameter of the base circle and a lower starting point (for a high lift cam) for the lifter.
Hope this makes some sense to somebody!
Sincerely and Respectfully
Dennis Moore