ok...i read an old post and tried this to check for bad timing chain:

pulled cap, marked balancer pulley, turned balancer and watched the rotor to see how much slack it has.

anyway, i have heard 5 degrees (and from someone else 6 degrees) is enough to justify changing the timing chain. well, mine had 4 degrees. should i change the timing chain/gears?

i hae heard its pretty easy, but also have heard that dropping the oil pan a little is necessary, and the oil pan gasket is a PITA. any tips would be helpful.

NOTE: this is a 91 3.1v6 auto w/140K miles.

 

are you having any problems or just think you do? if no problems i'd leave it alone. timing chane isn't my favorite thing to do but it isn't bad job either. never did one on a v6 in the car, but it'd be lot like a v8 i'd think. read your manual and it'll give you good idea what's involved.

 

dont forget about the fact that there is play in the gears that drive the dissy. If the timing doesnt jump all over the place then id say leave it alone. No need to replace it unless its causing some trouble. Nother thing to keep in mind is i think some of the v6 engines have autotensioners or something on the chains wich would make it impossible to see the slack in the chain so turning the crank to see play would accomplish nothing.

 

There's no auto-tensioner on the 3rd gen 2.8/3.1's, just a V-shaped block of rubber-coated-metal between the crank gear and cam sprocket. You can still see slack, the tensioner is meant to keep the chain straight & tight between the "pull" side of the gears. So the chain will be against the tensioner on the passenger side of the motor, but a bit loose on the driver's side of the tensioner. Watched a buddy's MX3's timing belt get done, he had a spring loaded tensioner on the timing belt that busted, $170 later and he had a new tensioner.

I didn't have to drop the oil pan when I did my timing chain, on my 2.8. Only difference I can think of between my '86 and your '91 is that you've got a one-piece rubber oil pan seal, where I have a two piece cork/rubber seal. Rubber is used at the back of the crank, cork is used for the rest of the pan.

The timing chain cover rests against the "top" of the oil pan, at the front. So on my car, when I pulled the chain cover, it ripped the gasket at the front of the pan. My FelPro gasket kit came with a stupid little cork oil pan segment for the front of the pan. I was supposed to cut the old pan gasket where the oil pan met the block, put this little segment in, dab some RTV where the segment met the oil-pan/block/old-gasket junction, and put the timing cover back on.

I said screw that, and just laid a blob of blue RTV down in that area. Haven't had any leaks.

So with Your one-piece rubber oil pan seal, the books might recommend dropping the pan to salvage and re-use that seal. (Yeah, they say it's reusable, and "expensive", if you consider $7 expensive. ) In fact, now that I think about it, I don't believe you have any front oil pan bolts, to bolt the front of the oil pan to the timing cover, do you?

Like ede said, a manual is the best spot for info; if you can get your hands on the real GM service manual thru http://www.helminc.com , or maybe someone on the v6 board can scan the 3.1 info in for you, it'll tell it all.

Overall, the job was technically easy, but was a pain to do because of scraping old gaskets away! Remember the timing chain cover on our cars is aluminum, and when you use a metal scraper on it, you can gouge the aluminum and turn that finely machined sealing surface into swiss cheese. I use Permatex Hi-Tack Gasket Sealant (metal can, brush-in-cap, Pep Boys, $3) on those gaskets. Plus too, unlike the v8 guys, our water pump fits completely onto the timing chain cover with a huge gasket, and that's extra work. (V8's just have two little gasket areas that go right into the engine block, not into the timing chain cover.)

 

With 140,000 miles I'd replace it. On my 3.1, the chain stretched and had so much slack that at 1500-2500 rpms it would "slap" the idler very loudly. Eventually it slapped it so many times that the idler broke and fell apart INSIDE. This was at about 145,000 miles BTW.

Also, you DO NOT have to loosen the oil pan on a 3.1L. The job is fairly easy. The hardest part was getting the harmonic balancer on and off by hand ( no air tools at home SUCKS).

Dimented, our RWD 2.8/3.1's don't have "tensioners". They're officially "idlers" because they don't maintain any real firm tension on the chain. The FWD 6'ers may be different.......