Slalom4me

Friend of mine has a ZZ4 and needs help re-timing it.
Please double-check my suggestions to him and offer
your own.

With the EST disconnected, he finds that the mark
on the damper will not come into view as the timing
light shines and the dist is moved to advance/retard it.

I have asked whether he can see the harmonic damper
mark by shining the timing light further back or
forward of the mark on the timing cover. (A low
vacuum situation suggests retarded timing.)

I've told him that if the damper mark is on the
- driver's side of the cover mark, the timing is RETARDED
- pass side of timing cover mark, the timing is ADVANCED

I proposed that the distributor gear was mis-aligned
with the cam gear by a tooth when the distributor
was reinstalled.

I've told him that the distributor rotates
clockwise, so to allow the marks to align:

- if the timing is RETARDED (mark on driver's side)
. turn the distributor 1 tooth COUNTER-CLOCKWISE

- if the timing is ADVANCED (mark on pass side)
. turn the distributor 1 tooth CLOCKWISE

I do not know yet whether the ZZ4 harmonic damper is
degreed or has a single mark. Can anyone here answer
this?

If the balancer has a single mark, what is the timing
supposed to be when the damper mark and the cover
mark are aligned?

Thanks,
Ken R.

mseven

I agree with everything aside from the distributer can move clockwise and c.clockwise. Moving it clockwise will retard the timing, c.clockwise advances.
My suggestion would be to first look it over well before puling it and moving it a tooth. Getting the t.light in from the front of the alternater a little will allow you to see the mark on the ballancer up to the 12 oclock position and about as low as 4-5. If possible trying to time it w/out pulling it, at least at first to determine the timing.

Slalom4me

I am describing movement of the distributor shaft.
Are you talking about rotating the distributor housing?

If so, then we are both right.

But if the gear is off a tooth, I maintain that the rotor and thus the
shaft needs to move one tooth counter-clockwise to resolve the issue.

Yes, no, maybe so ??

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mseven

Ken,
If I understand this correctly the mark is visble but very low? I am guessing that he has run out of room to turn the distributer in the direction to bring up the timing.
In that case the timing showing very low, moving it one tooth counterclockwise would advance the timing. This would then allow the distributer body be in a location to time it correctly and not having the cap run into the firewall or intake.
If there was nothing in the way to turn the distributer enough to time it, there would be no need of moving the gear. Cosmetically, and space really become the only need to move the gear position. Mick

Slalom4me

My information is he can see the mark(s) on the damper when
the engine is stationary, but when he operates it & trys to time it,
the damper mark can not be seen in the strobe light.

I believe he has already used up the range of adjustment rotating
the distributer housing in the normal manner in an attempt to bring
the mark into view and - no joy.

You and I are on the same page, just approaching from different
angles.

Thanks!
Ken R.

.

Aggravated4life

If this engine was installed in a corvette,theres a good chance the timing makrs wont be the same as the stock corvette L98 locations.Im not for sure,but I do remember the ZZ4 having a larger balancer,8 inch while the stock L98 motors had a smaller 6 3/4 inch balancer.The ZZ4 has a plastic timing cover and was suggested to use the stock L98 Corvette timing cover in place of that.I think the marks would be in different locations.
If this ZZ4 was given the smaller balancer,chances are,the timing marks dont align up.This isnt gospel,but a suggestion to check before driving yourself crazy.

If the ZZ4 was left alone,and everythings stock,then theres a good chance the timing area is off by the distributor being installed wrong.

Can you shed light on what car,mods or balancer,timing covers have come into play where this motor is installed?

Slalom4me

The ZZ4 is in an '86.

I know he has the OEM ZZ4 plastic timing cover, I'm not sure if
there are different generations of this cover. Here are examples
of two composite covers - is one a change-up to the other (is
the second image of an SBC)?

12562818 Timing Chain Cover (GMPartsDirect)



A different composite cover (Posted by PhotoVette1)


It is uncertain whether the OEM ZZ4 damper is still in place or if this
was changed out for a different unit. I believe the ZZ4 has an 8"
- I know from my own damper questions recently that an 8" is said to
require cross-member mods to fit - whether they did this or swapped,
don't know, yet.

I am interested in the remark suggesting there are differences in the
locations of the timing marks. There is a post in C3 Tech that lists
damper diameters and mentions at least one damper which is said
to be at 10º. With this possibility, along with a chance of an outer
ring that has slipped, it would be worthwhile to follow suggestions
made by you and others earlier to pull #1 plug and verify where the
damper mark lines up when the piston is at TDC.

A degree tape like the one shown in the picture above could be
added at the same time. He should get one for the correct diameter.

.

mseven

Agreed, I didn't suggest slipping because I thought it was a fresh install. Finding TDC would be a good place to begin along w/timing tape.
What seems a little strange is if the car is firing rather quickly, no kick back on the starter along with other symtoms associatted /timing, outer hub slipping could be possible.
One thing that I would try would be to put a dial back timing light on it to see what it shows. (a scan to see the total advance wouldn't hurt either)

CFI-EFI

All L98 engines have a mark on the damper and a timing tab on the timing cover, that indicates the amount of timing. It is becoming increasingly clear to me that the ZZ4 has a mark on the timing cover and a degreed damper. Look at the second picture:

You can see that damper is degreed, "TDC", 10°, 20°, etc. Since the friend sees nothing, *I* am pretty sure he has changed dampers, as he might for clearance. He is either going to have to see if he can adapt a timing tab to that timing cover, install a timing tape to the "new" (old) damper, or swap back to an L98 timing cover.

RACE ON!!!

Carl Johansson

Guys - It's my ZZ4 - there has been a miscomunication as to the issue. The issue is:
I can see the timing mark on the timing chain cover when I look in under the fan belt.

i can see the timing marks on the damper when I look in from the side - but right now i can't find a line of sight that allows me to see both the damper and the timing mark on the plastic cover at the same time.
(this may be an unintended result of eliminating the air pump and rerouting the serpentine belt!)


1: the car is running quite well idle is spot on no rolling etc. rapid spooling up into high RPM - no popping flat spots etc. even with the ECM or whatever disconnected it runs great -
(I can't go back and look up the electrical 1 wire connection abreviation because I'll lose the post )

regardless - this is what I really need to know - short term.

what should I be expecting if the timing really is off? shouldn't it be running rough or some other indication?

what would timing being off do to engine temps? what about the cats etc?

If I ear time it - rotate the dist till the RPM stops climbing - then back off a little - then plug in the sensors - would this be a safe way to run it up to the braintrust (I've got to run 800 miles - but it's 1800 RPM all the way - loafing!)

I am thinking that it's not a real big issue - but I don't want to make a beta mistake!

Carl Johansson

Carl Johansson

This is the cover I have - you can see the timing mark is just a molded in ridge with a V in it - Obviously others have had a problem also - as you see the other version has a much more prominant and user friendly tab! I don't have an 8 inch damper - It is the original one from the 86 (I think)

Slalom4me

I don't know - but it has been more than 12 hrs since you
posted and no one else has spoken up, so here goes ...

While it goes against my inclinations; in a pinch, timing
by ear for an 800 mi cruise seems ok. I would prefer to
have tjwong, Alvin or others comment. I used to ear-time
point ignitions for optimal advance but I don't know how
directly this correlates to electronic ignition and I can not
hear well enough to trust any longer. (I also know now
how little I knew back then.)

Those 800 mi are over at least one mountain range, right?

If the problem is that the accessory belt obstructs your view,
is there any possibility you could simply re-route a different
belt (longer/shorter) and get a visual on the timing marks?
Probably not enough time to hunt for different belts before
leaving, I suppose. I considered suggesting to run the engine
cold with no belt - the thermostat doesn't open for a while
so I feel there's no difference if the water pump is not turning.
But the engine might not idle down low enough.

Here is what I can offer on timing symptoms

Too much advance
- More effort to crank on starting
- Pinging or detonation under load

Too little advance
- reduced power
- reduced fuel mileage
- increased emissions
- incompletely burned fuel continuing to burn in the exhaust
- plugs carbon fouling(?)
- reduced manifold vacuum

My vote is that a properly functioning cooling system
would cope with a fair amount of ignition retard but that
the cat could suffer from heat caused by fuel burning after
combustion in the exhaust.

Incidently, timing tapes like the one illustrated above are
available to add to the damper for under $5. Here is a sampling

- #1588 Mr Gasket - 6.75" dia
- #8985 MSD - 5.25 to 8" dia (8 tapes)

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