Hi!

I opened my -00 996 c2 engine because there was small pieces of black and brown plastic in oil filter. After teardown I found out that both variocam pads and IMS chain tensioner paddle were quite badly worn. There's no bore scoring and at the moment it's not possible for me to do a complete reconditioning including new liners and pistons etc. I'd just like to reassemble the engine with new chains, tensioners, and all the plastic pads and guides.

My car has 90k miles and I've understood that it's almost certain that bores are oval and tapered too much to just fit new rings because round ring in oval hole isn't good.

Questions:
Is it better to just reassemble the engine with old piston rings or fit new ones?
If new, which rings should I buy?

Thanks in advance!

 

There is not a way to change the rings unless you split the case. And installing new rings also requires measuring and grinding the ring ends to a specific gap. And reassembling the case halves requires new rod bolts and etc... and you can see the slippery slope that you are on. For whatever reasons you have, if all you are wanting to do is tensioners, pads, and some new chains (the two chains between the cam shafts), then it is best to ignore the short block, assemble the heads, cams, tensioners, pads, and put it back in the car.

 

Sounds like he already split the case.

I say just reuse the rings. Its all worn in together.

 

Have you split the case to examine the IMS chain tensioner paddle? If so, you need to replace the rod bolts as Yelcab says as they are stretch bolts.
Mark

 

Likely have to rent the piston install tool kit to re-assemble or buy from LN engineering or some others.
Your already a fair number of $$ down the path on re-assembly.

 

The decision of re-using the old rings or not, would have been easy if you had done a blow-by test ( or leak down test ) prior to dissassembly to see the actual ring performance...You will likely regret not going "whole hog" on the rebuild after a while..unless you just like doing the work...

That said,,, knowing the cylinders go oval on all of them with time, new rings will not seal well on oval cylinders....the old rings will probably seal better..

 

1 post and no response. We are wasting time.

 

What Skip said. FWIW, you're better off actually measuring the bores to see if and how much they are ovalized by. A lot of people were certain they had scored bores or other issues only to find out they did not after proper diagnostics. Trust yourself but verify!

 

Thanks for all the replies!

Yep. Already split the case and the paddle plastic was already so badly worn that it wasn't far from the chain touching metal. I already have all the gaskets, stretch bolts and other bits and pieces needed to put the engine back together.

This was kind of the the answer I looking for. Thank you. I think I'm going to put it back together with old rings. Blow by test would have been good idea. But in any case it is not possible for me to do new liners and pistons at the moment. And actually I do just like doing the work and hopefully in few years it financially possible to put in 3.4 --> 3.8 conversion nickies, ims solution, UIDS and all the possible updates because the car is a keeper. Here in Finland because of looong winters it's nice to have something to do outside the driving season also. BTW UAOS already installed last winter and it's working great .

Because of different time zones, language and the fact that I think this was the second time posting on any forum ever it takes time to response. Had to even look for YouTube tutorial on how to multi quote. But I think this wasn't my last posting. After all this seems to be the place to find answers that are based on more experience than gut feeling.

Thats true. From what I've red there just seems to be little to no hope that the bores would be round. But you never know..

 

How oval would you expect on average?

(thinking out loud) I suspect the casting stresses of the whole block and webs and stuff relieve over time and cause the oval bores. also probably causes a lot of interference conditions and bore damage. also it stands to reason there would be certain cylinders that would consistently oval worse than others.

 

Use upgraded rod bolts rather than the stock ones. They are a weak point in the engine.

 

From what I have seen, I would expect from 0.003 to 0.009 in oval in the cylinders mostly at the top 1.5 inches...The center down low remains round while the upper top ovals...Hartech used to make a "retaiining ring" that would go around the top to re-round or to keep round the top of the Lokasil cylinders....but they reciently started to replace the complete cylinders like LN does..Either they weren't making enough money that way or they were having problems with the process..anyway I don'tthink they do that any more ..

Remember the piston skirts are not round, the piston is round at the "piston head" but the head is 0.015 in. smaller diameter where the rings fit.... the skirt is "barrel shaped" in the vertical axis and is "cam ground" in the horizontal axis...all this is intentional to place the load in the middle of the skirt on the thrust sides..and to keep the "head" of the piston from touching the bore and only the rings touching the bores..

 

I have ARP rod bolts