TDC issue - help needed please … - 986 Forum - The Community for Porsche Boxster & Cayman Owners

I’ve taken the camshafts out of bank one on my 2002 Boxster- to change the variocam and solenoid but I forgot to set TDC before I began did this job. Any thoughts on how to reassemble safely? I did wonder if it’s as simple as putting a breaker bar on the crankshaft bolt and turning the engine until I find TDC. My worry is that because the camshafts are removed on bank one, and the lobes are loose with no pressure on them from the camshaft, will this cause a problem/ they fall out/ something gets bent if I turn the crank with camshafts removed?

Quotes source post: 639682

Hello Colacharlie, I am Not an expert, but since you are removing the cams the valves will be closed, and rotating the crank should not cause any damage to the valve train... It would be interesting to hear more comments from people with more experience.

Quotes source post: 639684

Agreed. Without cams the valves won`t be opened. You need to pull and hold the chain aside so it won`t get jammed in the crankcase while someone else slowly rotates the crankshaft. Pull the plugs to make it easier to turn the crank. EDIT: now that I`ve reread what you wrote, I`m not sure if you replaced the camshafts. If so, I`d pull the whole assembly off, rotate the crankshaft to TDC and put everything back on.

He only has the cams out of one bank, rotating the engine in this configuration is problematic.

Quotes source post: 639687

Why would it be? The two chains are independent on each other and the other bank is intact with all the tensioners and chains I assume.

Wouldn't it pull the IMS (the shaft) out of alignment?????

Quotes source post: 639690

Because I would be willing to bet if he has the cams out, he also has the tensioners out as well (it would be real interesting to try and remove the cams on one bank without releasing the tensioners), which means the remaining long chains are slack and potentially able to slip during rotation.

Quotes source post: 639693

Only if the IMS rear flange were removed; if it is in place, the shaft cannot move.

Quotes source post: 639694

I rebuilt the engine from scratch about a year ago and as far as I remember there are three tensioners in these engines, one for the crankshaft to IMS chain and one for each of the banks. For pulling the camshafts on one bank you only need to remove one tensioner that corresponds to that bank. The other bank has a separate one on the other side of the engine and that can be left intact. The two long chains corresponding to the two banks run on the opposite ends of the IMS, so it`s very hard to mess with the other bank`s chain. So you can even pull the entire head off on one side and still can rotate the crankshaft safely if everything else is intact on the other bank. Obviously you need to hold the chain so it won`t get stuck in the crankcase. If he removed both (or all three) tensioners, then yes, turning the crankshaft over can be problematic... But if he started with removing all tensioners for no reason without setting the timing I`m not sure he should proceed with this job..

Quotes source post: 639695

Thanks for the clarification. I had some vague memory of the shaft moving out of alignment when rotating the engine. If I would have thought for a moment I would have realized it could only happen with the rear flange removed.

Thank you all for all of your excellent information and ideas. I will do as you say and get someone else underneath the car to keep the tension on the oil pick up chain (probable wrong term - my apologies) while I rotate the engine to find top dead centre. Thanks again I’ll keep you updated how I get on 🙏

Quotes source post: 639718

Just to clarify for everyone I did only remove the camshaft on bank one. Am I right in thinking that if the piston at cylinder one is at the top of its stroke and the crank is at top dead centre with the bolt to hold it in place I can replace the cams now?

If you didn`t pull the camshafts on the other bank and you didn`t touch the tensioner on that side, that`s fine, you can safely rotate the crankshaft if both camshafts are pulled on that bank you are working on. So that`s a good thing you didn`t jump on the engine and pulled apart both banks before locking the crankshaft at TDC. On the other hand, before you proceed, I would recommend to take a break and read all the available source of information regarding setting the timing on this engine. Based on the questions you ask I think you need to spend some time on understanding what you are doing. No offense. There are lots of good articles on the web, good threads on this forum that can help you. If you are not familiar with this job at all you can cause damage to the engine easily, or you can pull the engine apart again after you finish. This is a boxer (flat) engine, so timing is not as trivial as it is on an in-line 4. To answer your question: depends on which bank you are working on, 1-3 or 4-6. Crankshaft`s speed is double of the speed of the camshafts, basically when the crankshaft is at TDC, cylinder 1 and cylinder 4 are both at TDC, but in different strokes. This means that the camshafts corresponding to the opposing cylinders are 180 degree offseted with respect to each other. This also means that when you are working on one bank you need to know where the camshafts are at on the other bank, since they need to be offseted by 180 degrees. If you set the camshafts on both banks to TDC, you won`t have piston-to-valve contact but your engine won`t work. So the correct procedure is to set the crank at TDC, adjust the camshafts to TDC on one bank, then rotate the crankshaft 360 degrees, and adjust the camshafts to TDC on the other bank. So, if your crankshaft is at TDC, and your camshafts on the oppoosite side (NOT on the one you are working on) is 180 degrees off TDC, then you can lock down your camshafts at TDC. A few other notes: - using special tools is highly recommended, will make your life much easier. If you don`t use clamp tools you can break the camshafts. They are made of very rigid steel tubes. A Chinese full engine tool set is around $80 on Amazon. - torquing down the bolts to spec is critical. Most 6mm bolts need relatively low torque, which means they are easy to break. - It matters how much sealant you apply and where to avoid leaks or what is worse, getting sealent inside the oil lines. Start with these links and try to download a factory manual. Wayne`s book is free online, he has an article about timing as I recall, with lots of pictures. Good luck! Project NUTROD http://986forum.com/forums/show-tell-gallery/73917-blue-boxster-resurrection-project-3.html

Quotes source post: 639730

Hi mate and thank you for your information. I did leave it last night and came home to do some reading this morning before I set the timing up. I have bought the 101 project book which I have been using but I’m not seeing much about timing. I also have the Durometric (enthusiast edition) tool here and from some basic reading it seems it may be very useful. I’ve done a couple of rudimentary searches this morning but any links about timing will be greatly appreciated 👍

Quotes source post: 639755

Looks like you already sorted it out, just saw your other thread. Just FYI, here are the respective pages from the book: https://www.pelicanparts.com/techarticles/Boxster_Tech/16-ENGINE-Camshaft_Swap_and_Chain_Tensioner/16-ENGINE-Camshaft_Swap_and_Chain_Tensioner.htm