Alan C.

When I rebuilt my RSA I put a cam in 180 degrees out. I feel for you. :-(

dasael

Man... It is tough journey! I wish you gather strenght and patience!

Tom@TPC Racing

Thank you very much for your sentiment and for your words of encouragement. On the bright side, I am just glad this happened on my car not a customer's car.

Tom@TPC Racing

Picking up from Super Bowl Sunday, it was getting late after replacing the Bank 1 hydraulic chain tensioner. There wasn't more I could do that night so just called it the night. The following day I called the dealer to order chain guide rails, And both Bank 1 & 2 tensioners for good measure(using tax refund money that was going toward roll bar & seats). The original Bank 1 tensioner from my engine and the "borrowed" one from the spare engine passed the squeeze test but like I said, for good measure knowing the engine need to come out again. The tensioners are expensive at $400+ a pop! Probably because their part number begins with "959". It is neat that our engines have 959 DNA.

A week later the parts arrived and the engine was back out that night. The following work was done- remove alternator, AC compressor, waterpump, housing, PS pump, intake manifold, valve covers, hydraulic chain tensioners, intake cam actuators, exhaust cam sprockets. With these parts removed I was able to inspect the chain guide rails. To my surprise and confusion the guide rails are fine. Before and after getting to this point I've turned the engine over by hand numerous times, didn't feel anything abnormal and no noise. So what next?? Against all odds I blamed the tensioners(yes, both) for bleeding down causing the chain slap and took comfort to replacing the Bank 1 & 2 tensioners with the new ones from the dealer. Cams timed again, everything went back together, and engine went back in the car. Took a few nights to do especially now that I'm even more **** retentive than before. You are probably thinking I'm an idiot, no way for two tensioners to be bad... if you are thinking that, you are right. All that work for nothing. Still makes the chain slap noise. Out it comes again.

To be continued. Again.


Here's a photo of removing the Bank 1 exhaust cam sprocket. One the .1 engine only the intake cam has variable timing actuator. More details to come on the actuator in general; torque value, etc.

monk46

Not that you really have much choice, but I admire your perseverance. Thank you for sharing - very educational for me, without all the headaches.

Tom@TPC Racing

Thanks for following. Glad you get something out of it.

Tom@TPC Racing

Putting the engine back in without finding the absolute cause of the problem was indeed a bad decision that I won't forget. Not to mention a huge waste of labor, materials and sleep! So out the engine comes again, for the third time. This time, I am going to disassemble as far as it takes until I find the cause of the problem.

Few nights later Bank 1 cams are exposed, again. Actuator and sprocket removed, getting ready to remove the cams and here it is... ready for this?... the intake cam oil guide(item #5 in image from PET) was not seated to the cam housing. It was moving off its seat only by about 0.5mm(yes, less than a spark plug gap). You see, this part is the oil distribution to the vario-cam actuator. Below is the photo of the actual part, see the tiny hole inside the bore that feeds oil to the tiny hole on the front section of the intake cam? These holes on the cam then feed oil to the vario-cam actuator. With the oil guide not seated to the base, which is the source of the oil, the vario-cam actuator was not "loaded" and caused the chain slack during decel. That was it.

The reason the oil guide was not seated was my fault. Going back 5 weeks ago when I was removing it the first time a small bolt(about the size of tic tac) holding the guide to the base came out taking a Heli-coil with it. I really think the threads were stripped out at the factory and they put a Heli-coil in it in an effort to save the cam housing bridge(see photo) which is machined paired with each cam housing. Whoever installed that Heli-coil tapped deeper than they should have leaving me not much material for a Time-sert. Thankfully I was able to go deeper into the bridge with a Time-sert and a 5mm longer bolt. Consequentially I didn't want to strip out the other two holes so I was being "gingerly" installing the oil guide. Which didn't turned out to be tight enough even with the use of Blue Loctite as specified by the factory. Also, the guide to the base is a very snug fit so there's the possibility that it wasn't seated when I tightened the bolts. Again, this happened 5 weeks ago, my only thought then was to save the bridge(and the machined paired cam housing) and not strip out the other holes and didn't think anything of it after the accomplishing this task. This time I tapped guide to seat on the base using a wood hammer to make sure is it fully seated and then used Red Loctite instead of Blue and gave bolts a good tug. Personally I have not had good experience with torque device less than 7 ft-lbs so I just went by feel. They snugged up just fine. Even though the noise was isolated to Bank 1 here's no way wouldn't take Bank 2 apart and redo this. I have also replaced both the vario-cam actuators knowing one was starved of oil and replaced the other one as a pair and both oil guide for extra good measure. This blew the roof off my budget! Even though the engine ever got above 2000rpm and was not driven I needed to do a cylinder leakdown test again to make sure none of valves got bent since the vario-cam actuator is capable of 52 degrees of valve timing variance(which to me is scary for it to have this range of control). If my car didn't have vario-cam(like Cup cars and 993's) I wouldn't have had this problem but I do like the better mid-range rpm performance vario-cam produces. Its a love-hate thing I suppose; Love the flexibility of the torque band but hate the complexity of the number of parts that could fail.

So leakdown was good, back in the car the engine went. No more chain slap noise!

I have learned a lot about the GT3 engine from this experience and became very proficient at timing cams and R&I the top end. I don't want to make this post longer than it already is so in future posts I will highlight and provide details on things I've learned during this experience and hopefully other Rennlist members may benefit from.

Spyerx

wow. love this techy geeky stuff... i can sit at my shop all day bugging the crap out of their engine builder just watching this stuff. So cool. Glad you found the issue and it wasn't a "big" issue and was solved.

Wondering what lead you to replace the tappets? Whats the mileage on your car?

I've almost 40k on mine now and it runs very smooth and quiet compared to many gt3 I've heard. Last oil test came back super-clean.

Tom@TPC Racing

Engine has been installed in the car. No more chain slap noise. Pressure checked the cooling system- no leak. Everything good so far. I drove the car home for the first time in 5 week. I drove with the radio off paying very close attention to every sound. Two blocks away from home I hear a tapping sound. Ugh. This is from Bank 2 now, it sounded like an exhaust leak but with a little more metallic pitch to it. My first thought(and hope) was exhaust leak for header gasket, since the same gaskets has been on and off a number of times. That'd be a very easy fix. Parked the car for a week due to snow. That week of waiting was torture BTW!! Once the snow and salt cleared drove back to the shop to have the header gaskets replaced. And guess what, the noise was still there! I then checked the spark plugs to make sure they were tight- they were. I remember checking them 3x before putting the engine back in the last time. The thought going in head was must be a lifter not pumping up, do an oil change to see if it pumps up otherwise engine out again.

I proceeded to do an oil change, didn't help. I then listened to the noise some more while the car was idling on a lift. It sounded more metallic than exhaust leak from underneath and coming from Bank 2, cyl #6, inside the valve cover. At this point I was praying for mercy. It took a minute for me to accept the fact and get myself together and a plan. I was prepared to take the engine out again. Well, lets pull the spark plugs to read if cyl #6 looks different then others by the combustion. And HOLY MOLY, there it was. See video.

https://www.youtube.com/watch?v=2XcK...ature=youtu.be

I have been in the business for a while, this is the first time I've seen a spark plug like this on a GT3. So six new plugs went in. Drove 50 miles so far so good.

Tom@TPC Racing

Thanks. Read my last post. Thought I had to take the engine out again.

I had a noisy lifter since I got the car last year with 46k miles. Has 51k now. During the disassembly couple of the old lifters have partially blocked oil holes.

Since you like techy stuff, these photos are just for you!

Photos
1. New lifters- small but expensive.
2. Soaking the new lifters in thin oil before installation.
3. Each time I take the engine out it takes couple hours to thoroughly scrape off the sealant.
4. Inspecting each oil feed hole in the lifter bores and testing fitting each one for smooth movement.
5. New lifters in and oiled up.
6. I also replaced the rear main seal because the old one was leaking. I opted to use the part # 999 113 264 40 seal. This seal was OEM on GT3 street car, GT3 Cup and GT3 R up to model year 2003. Good enough for me. Now its known as the 997TT seal.

Cloudspin

Here's hoping this is the last engine related issue you'll face for the next couple years!

dasael

very impressive job you been doing, I feel overwhelmed by so many setbacks! Im glad it is finally coming along!

Spyerx

Very cool. I have same rear seal in mine (its all my shop will use). Knock on wood not a drop since I got the car almost 2 years ago.

Tom@TPC Racing

Thank you. Hopefully that was the end of my bad luck streak and I can get on to more fun mods.

Tom@TPC Racing

Have more techy photos and info to come from this experience.