Solutions to the great compression/engine rebuild dilemma

[Jonathan Sacks <jwsacks@xxxx>]

Hi all,

Okay, so most (hopefully all, but we'll see) of the
hard miss/compression problems have been worked out of
my newly-rebuilt 413 in my '66 300. You all might
recall that it was the topic of numerous emails around
Christmas on the network. I promised I'd let everyone
know how it all worked out. So here goes...

First order of business was to address electrical
issues. For some reason, I'd changed the whole
electrical system except for the coil. I guess it
seemed to be working fine, so I left it. Anyway,
changing that and the resistors made a bit of a
difference in the run in the engine.

Next, addressed vacume issues. Specifically changed
the brake booster, and that of course had a huge
effect on the run of the engine, as the old booster
was bleeding quite a bit.

But still, compression problems remained...

So we pulled the valve covers and had a look at the
rockers and the pushrods. Noticed that two of the
pushrods (cylinders 4and6) were not spinning like the
others, and the tops of those two cylinders appeared
to be slightly higher than 2 and 8. So we had a chat
with the gentleman who machined and assembled the
engine and he said there's a very good chance he had
to grind those two cylinders more than the others, as
they were particularly badly worn. Also, as was
pointed out by the club, the push rods were old while
the lifters were new, which could present a problem in
itself. So...we decided to take a little off the two
offending pushrods - somewhere in the neighborhood of
.020 - and sure enough, after installation of the the
two new rods, the engine smartened right up.

As regards new versus old pushrods in a rebuild, we
went to the book and it appears that the new pushrods
are exactly the same as the old in height. Still, I
don't know if I trust the book and it's measurements.
Something tells me that new pushrods might end up
being a little shorter. And so my question is...can
anyone weigh in on the pushrod question? If I've got
new lifters, would it behoove me to replace the old
push rods, or if, after shaving the two offending push
rods the engine seems to be running okay, should I
just leave it be?

And speaking of the engine running, the idle is
perfect, she's got plenty of acceleration, but for
some reason the top end just feels like it doesn't go
as high or as smoothly as it used to. Maybe it's just
me. Or maybe it could be the transmission (it wasn't
rebuilt). But she seems like she's working too hard at
70. Could this be related. Again, it could just be me,
and the engine's not supposed to go much past 80. 

As for thanks, credit goes to the whole club, as this
was a complete group effort! Naming the individual
members who's advice was particularly helpful would
keep me here all day. Almost every email I recieved
was carefully considered and most turned out to be
spot-on. I can't thank the club enough for it's help.
Suffice it to say my membership was the best $20 I
ever spent!

Until next time,
Jonathan

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