[DeTomaso] Techno Question: 351C lifter bore diameter

[Daniel C Jones]

> I have the numbers from the bores and wanted to compare them to what is
> considered factory spec. At this point it looks like the bores spec out
> to: 0.874--.875". Now, to check them against my measurements and the actual
> diameter of the new lifters......

We're going to bush the lifter bores on one of the dyno project engines.
Dave McLain has measured a number of bores (in used blocks) and they measure
0.876" to 0.877" diameter.  When fitted with bushings and honed for oil
control, they had 0.0015" clearance.  With Comp roller lifters, the diameter
ended up right at 0.875" diameter.  With no other oiling system mods and a
stock volume and pressure oil pump and bushed lifter bores, the engine held
very good oil pressure (60 psi hot @ 6000 to 6500 RPM).

When bushing the lifter bores for oil control reasons, McLain uses a 1 inch
self piloting reamer that's been "sharpened down" to a diameter of 0.996".
The reamer has a pilot on the end that's 0.875" diameter and is secured with
a set screw so it would be possible to use it for repair work on other size
lifter bores if needed.  This allows the use of a press-fit 1 inch OD bushing.
The bushing is 0.875" ID with a length of 1.5 inches drilled with the hole
size of your choice (depends upon hydraulic, solid, flat or roller lifters).
McLain does this on a Bridgeport mill with a 4 inch riser which is needed to
give enough vertical clearance for the block and the fixture that he uses.
once the block is set up, he uses an air float table from a seat and guide
machine on the Bridgeport, so the lifter bores are vertical. This set-up
makes it easy to go from one bore to the next by simply floating the block
with air pressure.  McLain charges $150 to bush the lifter bores.  The 0.996"
reamer (and maybe 0.001" wobble) makes for a tight fit on the bushing when
you knock them into place.  McLain finishes the ID to 0.875" with a Sunnen
hone and says it's important to put a very slight chamfer on the end of the
bushing and also to take a couple of minutes with a cartridge roll to deburr
around the galley hole.

Be aware this process does not correct the lifter bore positions like the BHJ
fixture does but, if your purpose is to provide better oil control or fix a
damaged block, it works just fine.  BTW, are you using a bore gauge or a set
of calipers to measure the bore diameter?

Dan Jones