[DeTomaso] Hydraulic lifter pressure hole location

[Daniel C Jones]

> What's the recommendation on how close the pressure hole on a hydraulic
> roller lifter can get to the top of the lifter bore and still be safe?
> As you go with a cam with taller lift, the hole gets closer and closer to
> coming out of the bore.  I talking about how close the hole can safely get
> to the edge of the chamfer at the top of the lifter bore where pressurized
> oil will just begin to leak.  I want to check this on my new stroker motor
> to be safe.

It varies from block-to-block and depends upon the size of the chamfer
at the top of the lifter bore but, on many blocks, the oil feed is exposed
at maximum lobe lift.  Some manufacturers (like Comp) will reduce the
base circle of the cam so the OEM type lifters can be used.  As a rule,
irregardless of how much lift that a camshaft has, the lifters generally
all stop in approximately the same location at the top unless the base
circle is deliberately reduced which can cause problems at the other end
of the lifter bores.  With a reduced base circle cam, the OEM lifters
will usually be safe at maximum lift but some blocks will have interference
problems with the dogbones.  A local shop has a fixture to machine the
block for clearance but it can also be done by hand.  Comps link bar
lifters have the oil feed (and associated band on the lifter) in the same
place as the OEM lifters so have the same problems at max lobe lift.

The Crane/FRPP link bar retrofit hydraulic roller lifters have the oil
feed placed lower on the lifter body and do not have the max lift problem.
Erson also makes a couple of link bar lifters (one a less expensive street
version and the other a more expensive race version) but I've not been
able to verify them for fit.

Dan Jones