From: Daniel Neuman <dneuman@stars.sfsu.edu>
>Hello All,
> Need some collective wisdom here.
> How exactly is the best way to shim up a timing chain?? My chain
>is not shimmed up at all. After the shimming and the rattle on cold start-up
>is eliminated how much longer is it safe to drive the car?? How much shimming
>is okay??
> Daniel 69 2000
Hi Dan-
Shimming the upper tensioner is accomplished by removing the tensioner,
pulling the tensioner foot out of the tensioner body, and putting [something]
around the shaft of the tensioner foot to prevent it from retracting all the
way into the tensioner body.
That [something] can be steel washers (ground for clearance), plastic
spacers, someone suggested corrugated wire loom. Just about anything durable
should be fine... I like the idea of plastic, as it's less rigid, but what
do I know... opinions?
It depends on how much shimming you have to do, how long the fix is good for.
If you have to shim it 1/4", you're probably okay for a while. But if it's
more than that, your timing set is probably sufficiently trashed that prompt
replacement is in order.
It also depends on how bad the rattle is. Obviously, if you're just getting
a touch of it on start up, you're better off than one that grinds and rattles
at idle and deceleration.
If you have a mild case of rattle, which it sounds like you do, you're
probably good to go.
IOW, heck yeah, enjoy the summer. And come up to Santa Rosa and give me a
ride around the block - it's been SEVEN months than my 2000's been down, and
I'm having major withdrawal pains... LOL.
Since your cam is starting to degrade, IIWY, I'd start saving up for a
complete rebuild... a new set of chains for an otherwise sound engine is an
okay repair, and ditto for a worn cam... but when the top and front are both
tired out, chances are the innards are ready for freshening up as well...
And if your cam is starting to fall apart, guess where those little pieces
are going- into the pan, into the bearings :-(
On to the cam - AFAIK, cam grinding is accomplished by grinding down the
"base-circle" (IOW, the non-lobes;-) to effectively restore the lobes to
their proper height relative to the base-circle. I'd assume they heat
treat it or otherwise harden the new surface when they're done. The problem
with grinding the base-circle down is that the rockers need to be adjusted
higher to keep the lash at spec. I'm not familiar with the U heads, but on
the L heads, the need arises for thicker lash pads (underneath rocker tips
and valve stems) to take up this slop. The U's may have enough adjustment
range that this isn't an issue, YMMV.
BTW - what's the cost of grinding the cam? Are you going to get your rockers
resurfaced? I'd be interested in knowing what the cost is... I hear my evil
side telling me to put a hotter cam in my SU 2000:-)
TTYL
Kyle
____ Kyle Hagemann, Born-Again Grease Monkey From Beyond
_.;(____\____ 72 240Z, L28/E88/SU, 5sp, all poly - Z Beast
| _ | | _'@`, 71 PL521, LZ22, SUs, 2" exh, 4spd - The Hulk
`-(#)------(#)-< 69 2000, engine/trans out, making a big mess
------------------- 84 Maxima, Tokicos/ST springs, 238K - Mr Max
http://www.sonic.net/~kyle http://www.sonic.net/~kyle/cars.html
|