Frank Clarici and I just aren't having much luck with our engine building
here lately.
I bought a crank kit for Big Red (77 Ford 3/4 ton - 400 c.i. - Spridget
hauler) to recify that annoying light hammering sound at speed that has
been there since after the Rhode Island towing trip over a year ago.
Pulled the engine and yanked the crank, with the heads on and pistons still
in. All bearings were down to brass but none had started to spin yet. Spun
the newly reground crank into place (yes it can be done - but V-8s tend to
be tricky) and plastiguaged the mains - came out 0.003 on all 5 mains.
Specs are 0.0008 to 0.0015. What a disappointment and waste of time.
Years ago, I assembled a Buick 455 that plastiguaged 0.003 and it always
hammered until the oil pressure came up (after starting). It bugged me so
much to have my newly rebuilt engine hammering that I eventually tore it
apart again and had the crank reground - but since I had run the engine for
some time, the original kit was un-returnable and I had to stand the price
of grinding the crank and another set of new bearings. This time the crank
kit is going back.
Moral of the story is to always, always plastiguage when assembling - and
don't settle for out of spec. Plus, never assume machine-work to be
correct.
In reterospect, I think it would be a good idea to tell machinists to give
you a list of their measurements after their machining is complete (to
compare against specs and make sure they actually take care to be within
specs) - and if a kit is purchased, it would be a good idea to have a
machinist measure the parts for you (to be sure) before going to the
trouble of assembling. You can bet I will be having this done when my new
crank kit comes in.
Once I had a 350 Chevy crank re-ground by a local machinist who actually
asked me what oil clearance I wanted - I told him, he ground the crank, and
it plastiguaged perfectly at the clearances I specified. So I know it can
be done and that there can be no excuse for this kind of bulls**t.
Les Myer
PDLJMPR
67 Sprite-
77 Midget
77 Ford pickup still in pieces
|