Here's some interesting info on on the retrofit hydrailic roller lifter setups. They are currently sold by Crane & Comp Cams. They have a very large (about 1/2") oiling groove and are a good bit taller than flat tapppets. Bought a Crane set for my 340 & after putting on the heads & front end of the motor I find the pushrods are hitting the heads. The heads had to come off for grinding & I'm out $90 for new head gaskets. Then I notice when rotating the cam that several lifters are actually have the oil grooves raisng above the holes in block at max lift. This is potentially a big deal as it could cause a very hard to find oil pressure problem. After some good advice here I decided the best (cheapest) route would be to have the cam reground . Sent the cam to Crane, they say they could regrind for $202.
Crane finally called yesterday to discuss. They say there is a lot of variance between mopar small blocks regarding the machined height of the lifter holes in the block. Regarding individual cams in a product line, the cams are actually designed such that the position in the block at max lift remains constant. In other words, the base circle diameter is changed between a .500 & .600 lift cam. More importantly, the problem regarding the lifter oil ring exposure would be no better or worse with a higher lift cam. I always thought they kept the base circle constant & used taller lobes. If you had a really high lift cam, there could be a problem with the lifter oil ring being exposed on the bottom side of the lifter bore.
According to Crane, when you get a cam reground, if you use an identical profile with a smaller base circle then the duration is reduced. It's more than you might think- it amounted to 4 degrees for my cam with a .060 base circle reduction. In order for the duration to be maintained, then the profile must be re-engineered (i.e. more $$). Fortunately someone already went through this at Crane & I used their profile so it didn't cost anything extra. I took pics of the various problems & can post if anyone wants to see.
Crane finally called yesterday to discuss. They say there is a lot of variance between mopar small blocks regarding the machined height of the lifter holes in the block. Regarding individual cams in a product line, the cams are actually designed such that the position in the block at max lift remains constant. In other words, the base circle diameter is changed between a .500 & .600 lift cam. More importantly, the problem regarding the lifter oil ring exposure would be no better or worse with a higher lift cam. I always thought they kept the base circle constant & used taller lobes. If you had a really high lift cam, there could be a problem with the lifter oil ring being exposed on the bottom side of the lifter bore.
According to Crane, when you get a cam reground, if you use an identical profile with a smaller base circle then the duration is reduced. It's more than you might think- it amounted to 4 degrees for my cam with a .060 base circle reduction. In order for the duration to be maintained, then the profile must be re-engineered (i.e. more $$). Fortunately someone already went through this at Crane & I used their profile so it didn't cost anything extra. I took pics of the various problems & can post if anyone wants to see.
