Steve J.

I am about to reinstall refinished cam covers but noticed that the left cam chain has 1-2mm slack on top but the right chain is tight. Is this OK? A result of the chain tensioner piston arrangement or cam position?
From the manual page 15-130 - "Chain tensioner piston on righthand side for cylinders 1 to 4 presses the chain up; on lefthand side for cylinders 5 to 8 down."
The engine performs well and I have never noticed any cam chain noise. I do not want to go back in here for a long time!

Thom1

Hi Steve,

Replace both chains and more. See the following document for ideas. Some items like the rubber intake sleeves do not apply to the 87.

Cam Cover and Intake Service Essentials:

Thoroughly clean the engine first, without removing any factory stickers.

1986 model recommended replacement parts:
Rubber Intake Manifold (Intake) Sleeves
Rubber Vacuum Elbows
Intake Sleeve Hose Clamps – New ones look better
Rubber Intake Hoses – Most of them are formed.
2 O-Rings at air flow meter
Cam Cover Breather Hoses (on one side)
Check Valves at chain tensioners
Crush Washers for check valves and tensioners
Thermostat
Thermostat O-ring
Fuel Injector O-rings
Cam Cover Gasket Set – May include the following – Verify contents:
Camshaft Seals
Camshaft cover bolt Seals
Cam Cover Gaskets
Cam Cover Seals for plugs (on one side)
Cam Cover Plugs (2 on one side)
Cam Cover Breather Hoses (2 on one side)
Spark plug hole Sealing Rings
Intake Gaskets

If removing cams, for the chain tensioner service add:
Chains
Tensioners – only if deeply grooved (in my opinion)
Loctite 574

Note: When I removed my intakes I had to replace all the rubber up there. This includes vacuum sleeves, vacuum elbows, and hoses. The rubber has been cooked so much by now that it is stuck in an inflexible shape, and it will leak after it is disturbed.

Warning: My washers, beneath the cover bolt heads, had a cushion of rubbery looking substance stuck beneath them about 1/16th inch thick. Upon investigation, none of the big 3 could find a part # or reference to this part/substance. Other 928 owners told me that a spacer is required for my model to prevent leakage at the cover gasket. Therefore, if your washers have spacers stuck to them, leave the spacers alone.

Note: The Allen Head bolts may be very stubborn. Have a good 3/8 inch socket type of Allen wrench on hand.


HTH, <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

joel roeder

good post thom, i did run into a tensioner that didnt show much wear but wound up pulling an engine thinking somthing had fallin in the cylinder and was going to get it out. upon removal we found the tensioner rubbing block had cracked and swung in under the chain and jammed the cam. thats why we couldnt turn the engine by hand all of a sudden. was glad to find this issue while hand cranking rather than at 90mph another day. i would recomend to any and all to check for any signs of weakness in this plastic when you have valve covers off. joel

Steve J.

Thanks Thom-
I also found rotten oil-soaked breather hoses and brittle vacuum connections and wiring. All rubber parts replaced. Also replaced crumbled knock sensors and impulse sender - the wiring was cracked and brittle with bare wire exposed. Same with the mating connectors on the harness. On each side, the four bottom and two end cam cover bolts had additional spacers.
Maybe I'm staring at these photos too hard, but on page 15-133 the 1-4 chain is pushed up and looks tight but the 5-8 chain appears to be draped over the guide with some slack- just like mine.
&lt;img&gt;http://www.flash.net/~ego/chains.jpg&lt;/img&gt;

Thom1

Hi Steve,

That’s a lot of work. Sounds like you are doing right so far. Something looks different in those pictures. Could be a bad spring on the tensioner. You can push on the tensioner to see if it springs back. I was advised to change the chains because I was pulling the heads. Pulling the cams is a lot more work. Perhaps someone else can tell if it is advisable to leave the chains like that. My impression is that they should be changed. If you pull the cams, you can get to the cam seals while you are in there. The timing is tricky. Devek has a video that you can rent that explains the entire procedure. Below is something that I wrote up that could be useful. Warning: You can break a cam by not using tool 9226!

* Trick for avoiding use of special cam tool 9226:
Note: I have heard that people have broken or warped cams when they did not use the tool 9226.
Remove Valve Cover
Turn to 45 degrees before top dead center (BTDC)
Remove Timing Belt
Remove Cam Gear
Remove Cam Seal Retainers (3 of them held on by 10mm hex head bolts)
Remove Chain Tensioner
Loosen all allen head bolts, and 2 middle-end valve cover bolts (10mm hex head, with threaded center) just slightly. Start in the middle, and work toward the ends. Alternate ends diagonally after loosening each bolt.
Return to loosening bolts ¼ turn each from the center to the ends.
If necessary, lightly tap the bridges at the ends to break them loose before you get too far.

Joel,

Good to know about the plastic in the tensioner breaking. I think it is the 944 that has real problems with that. It seems that the 928 plastic there is normally of better quality. I just hope mine stays good.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Steve J.

Thom-
If there exists a condition whereby the cams are pulling or pushing against each other, then that part of the chain running over the non-moving guide could be tight or slack. But, the part of the chain running over the spring loaded guide will always be tight. (OK - I just don't want to pull those cams!)

Thom1

Steve,

I don’t blame you. Perhaps someone with expertise in that area can advise you.

If you pull cams, harborfreight.com has an inexpensive dial indictor for doing timing.