Re: [Chrysler300] Solutions to the great compression/engine rebuild dilemma

[Mike Apfelbeck <moparmike@xxxx>]

Jonathan,
There is a spec in the shop manuals for valve clearance for hydraulic 
lifters.It is measured between the rocker arm tip and the end of the valve 
stem(with that cylinder on the firing stroke, of course).The valve lifter 
has to be completely collapsed to do this(you have to put steady pressure 
with some kind of pry tool against the rocker arm long enough to squeeze 
the oil out of the lifter so that it slowly goes down).I believe the 
acceptable range is something like .060 to.120 of an inch.An old Chrysler 
mechanic told me once that you want to get all of them as even as possible 
to get the smoothest, quietest idle.If you are going to buy push rods, you 
might consider a set of adjustable rocker arms to go with them, then you 
can set things exactly right.One thing you have to keep in mind about 
adjustable rocker arms on a hydraulic cam is that Mopar hydraulic lifters 
are .050" taller than solid lifters and need shorter pushrods to keep the 
geometry correct.All that stuff is readily available through the 
aftermarket if it can't be found at Chrysler.
If you ever have to pull the front cover off the engine(to fix a leak or 
whatever)you might consider installing an offset bushing in the timing 
gear, to advance the cam timing a few degrees. That will build a little 
more cylinder pressure & give a bit more mid-range torque(and maybe a 
little more mileage).

Mike

At 09:37 AM 2/4/02 -0800, Jonathan Sacks wrote:
> 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.