Date: Thu Jan 2 14:24:08 1992   
Subject: re:next project: timing chain replacement

>	My last advance of cam timing moved the timing from very horrible
>to the low side of marginal, using mark #3.  Now, when I start the car,
>I can hear the chain rattle (against the spray bar I assume) for a second
>or two until the oil pressure gets up.  My guess is that it is time to
>put on a new chain.

If the teeth on the cam gear are not worn excessivly and the chain does
not have too much lateral play (<3/4" or so), you can simply adjust
the guides.  The guides bolted to the front of the block have enlogated
slots that permit the tension to be adjusted.  Getting to these bolts
is almost as much trouble as changing the chain but not quite.  The problem
is that the front timing plate has to be removed which just about
requires at least loosening the oil pan.  TFM has a pretty good
description of how to adjust the chain tensioners.

>	My question is, "any pointers, do's/don't, or while you are at 
>it..."?  I'll probably be dropping in a new oil pump while I'm at it.
>Would getting a competition pump be worth it if I don't intend to add
>any more oil outlets/spray bars?

You have to go back and ask the question "What problem are you trying
to solve?" in considering a new/larger pump.  If you currently have good
oil pressure there is no need for a new pump.  And if you have good
oil pressure with a new stock pump, all a racing pump will do is 
waste power pumping oil through the pressure relief.  And it will
increase the chance of breaking the pump/distributor drive shaft.
If it ain't broke, don't fix it.  

If you want to determine the need for more oil capacity, one way of
doing that is to evaluate how much oil is going through the pressure
relief valve.  This is a test I always do when installing a turbocharger
because of the increased oil demand.  Remove the cap on the pressure
relief valve (the large bolt on the top of the oil pump.  Remove the
spring and install a rod cut to length to hold the valve on its
seat.  Install a pressure gauge in place of the oil sender.  Do NOT
rely on the built in oil gauge.  too slow.  Start the engine and
cautiously spool the engine up until the gauge hits 60 psi. (That's 
where most pressure relief valves start to lift.)  Do this cautiously
because your oil filter is now the only oil pressure relief device
in the system and when it "operates", it's a mess!  Note the
RPM.  If the RPM is at or below your normal operating range (~4-5000
for street cars), you have more than enough oil pump capacity.  Any
additional capacity would be wasted pumping oil through the relief.
Remove the block and reinstall the sender and drive away.

If you don't have enough capacity, the most common solution is to simply
blueprint a stock pump.  All that requires is a piece of glass and some
waterproof sandpaper.   disassemble the pump and using a straightedge
across the cap mating surface, measure the clearance between the cap
and the end of the rotors.  If this gap is too wide, sand the housing
and/or the cap to reduce the clearance.  Use the glass as a backing
for the sandpaper, use it wet and sand away.  If the cap shows wear
marks from the rotor, sand it first.  Then sand the mating surface on
the housing to bring the clearance down.    Before you do this, of course,
check the lobe clearance between the gear and rotor to make sure it
is not worn.  The only way to bring this clearance in if it is wide is
to select  parts for proper clearance.  Helps to have a box of old
pump parts :-)

Recommendations on changing the chain:  This might sound radical but if
you have a lift, pull the motor.  With the proper lift, this is only a 
couple of hour job and it will save you endless grief working in the 
cramped area around the front of the engine.  Pull that sucker out
and put it on a stand and THEN change the cam chain in the comfort of 
your shop.

You probably know to change the chain and sprokets as a set but I 
thought I'd mention it.  If you don't remove the head, be sure to
tighten the two little 6mm bolts that attach the head to the
timing cover BEFORE you tighten the block bolts.  If you don't, you're
guaranteed an oil leak from  under the head gasket.

Drop the oil pan before starting the work.  You'll release all kinds of
debris as you remove the cover and scrap gaskets and all this crap
ends up in the oil pan.  I've seen some "mechanics" try to stuff
the hole full of rags.  All this does is push the stuff in faster.
You'll want to replace the pan gasket anyway for a good oil seal
on the timing cover do just do it.  Yet another reason to pull the motor.

>	Also, should I use genuine NISSAN stuff, or are there better
>aftermarket gasket/chains/etc?

Stick with Nissan parts, especially on gaskets.  I've used aftermarket
parts and not been terribly happy with 'em and I paid just about as 
much.  Nissan cam chains seem to be a bit harder (The De Armond
hardness test:  does it scratch with a file :-) than the aftermarket
ones I've seen.

>	Does Nissan make a chain replacement kit?

Not that I know of.  Just buy the chain and the two sprokets and a 
gasket set and away you go.

John

Date: Fri Jan 3 09:23:37 1992   
Subject: Re: Agree-Pull the engine...

>A friend of mine went to adjust his chain and lost the tensioner
>(fell out of the hole) and we ended up spending a great deal of time
>(well over 8 hours) getting the front pulley and other items out of
>the way so that we could remove the front cover.  It would have 
>been much easier to pull the engine.  If you have done it before,
>you might be able to get by, but it is well worth the expierence
>to pull the engine.

Yep.  Someone else mentioned in Email that he thought fuel injection engines
are more difficult to pull.   Not really if you know the tricks :-)  So
here's the next trick.  If you work on a Z much and especially if you
are working on a FI engine, you should build a cowl shelf.  This is 
easily constructed from a couple of pieces of 1X12 lumber and a few 
hinges.  Cut a piece of wood wide enough to cross the car at the cowl
(in front of the windshield.)  It should clear the sides by 6 inches or so.
Measure for legs so that the legs will hold the shelf a couple of inches
above the cowl.  Cut these legs from 1X12 and fasten 'em to the shelf
piece with piano hinge so that they'll be able to fold up for storage.
Next make diagonal braces and mount them with hinges and latches so
that the shelf can be braced when open.   If you get flimsy wood, 
a couple of 1X2 strips can be screwed along the wide side to the bottom of 
the shelf in order to stiffen it.  Glue or staple some heavy
carpet to the inside surfaces to protect the paint.

For normal work, you use this shelf to hold tools, oil cans and whatnot
that you don't want to lay on the body.  When you're pulling the 
engine, simply unbolt the intake manifold/fuel injection 
assembly, loosen the cables from the tiedowns on the body but don't 
unhook any.  Then just pivot the manifold up on the shelf.  No wires 
to unhook and only a couple of gas lines.  Use a motorcycle tiedown
strap to secure the manifold to the shelf so it won't fall.
This one trick will save at least an hour plus it will preserve your
resevior of curse words that you invariably use when you're trying
to get those damn injector cable retaining clips off!


>John, 
>
>I really enjoyed reading your recommendations on tuning up
>the oil pump.  Sounds like an excellent proceedure.    The only 
>thing that I would like to add is to mic the housing to make
>sure that you dont get it somewhat lop-sided.

yeah, forgot to mention that.  Don't think a mike would work since
the side that mates to the engine is not guaranteed flat enough to gauge with.
I use a machinist's steel parallel and feeler gauges to check trueness.
Simply lay the flat across the pump housing and feeler the clearance
between the rotor and the parallel.

For those unfamiliar with the term, a steel parallel is an object that
should be in every mechanic's toolkit.  it's a hardened and ground square
steel rod whose flatness is typically guaranteed to better than 0.0003"

These things are cheap.  Example:  Enco catalog lists a 6"X3/8"X3/4" 
parallel for $17.30.  800-873-3626.  Plastic accepted.  

John