Porsche Cayman – Full Engine Rebuild – Machine Shop Selection

As previously discussed in articles here, here, and here, I am performing a full engine rebuild on my 2007 Cayman S with the M97 engine. Based on my inspection of the dis-assembled engine components, the most pressing item that would require the services of a machine shop was the ovality of the piston bores, with the scuffing of the piston skirts being a probable offshoot of the cylinder bore wear. The other area that I would contemplate “while I am in there” is any general degradation of the cylinder heads, in particular the valve guides and valve seats.

Dealing with the cylinder bores is certainly the most technically complex part of the job. There are many good articles out there about the cylinder bore process that Porsche used on this engine. To quote from an article at the LN Engineering website “The Boxster, Cayman, and 911 from 1997 through 2008 utilized a hypereutectic engine block casting technology called Lokasil.” See the full article here. There is also a lot of info at the Hartech Automotive website and Facebook page. The long and the short of it is that you cannot just bore out the cylinders and fit oversize pistons. What you can do is bore out the cylinder and install a sleeve. This restores the cylinder bore to it’s correct profile and gets you a brand new wear surface. Also as discussed by LN Engineering and Hartech is the fact that not all sleeves are created equally. For instance, an old school steel sleeve can be problematic in an aluminum block. Both LN and Hartech have come up with a proprietary sleeve process for these engines. Both have their merits. I guess what personally won me over to the Hartech process was reading some of their technical papers. I’ve been reading technical papers all my life and some just resonate with me. Not to downplay the technical documents that LN Engineering have developed but I really liked what I read at Hartech. Frankly, there were a few days when I was all fired up to ship my block overseas to the UK, where Hartech is located. My initial enthusiasm cooled as reality set in. Overseas shipping in an era of supply chain issues? I think not!

It was about this time that a friend mentioned that Hartech’s Facebook page was touting a US collaboration with Slakker Racing Development in Oklahoma City, OK. Not exactly right around the corner from NC but no boats or airplanes would be involved in the shipping. I looked up Slakker on the internet, called their number, and got right through to the owner, Brandon Clark. We had a good initial conversation. He was very informative and more importantly, patient. The gist of it was that he also likes Hartech and had reached out to them. One thing has led to another and he is now set up to implement their cylinder sleeving process here in the US. I have made a 50% deposit with Slakker to get “my place in line”. I have finished tearing down the engine and will be building an enclosed shipping pallet suitable for truck freight to Slakker. I also decided to send my cylinder heads to Slakker, where they will be evaluated, tested, and rebuilt as required. This means I can just lightly assemble the block halves and attach the cylinder heads for shipping.

When you embark on a project like this, you should probably look at your bank account and set some goals. An initial question is whether the engine that is making very bad sounds even rebuildable? Fortunately, I was not in this position but if there is a hole in the side of the block with a piston rod sticking out, I’m not sure there is anything a machine shop can do for you. You are probably looking at getting a replacement engine. But if the engine is rebuildable, then there are several decisions to be made. Put it back together with new bearings, rings, and gaskets might be a route I would have taken when I was a college student. (I actually had a rod or main bearing start knocking on my 356 Super 90 in college. The car got towed home and utlimately sold, as I had no money to fix it) More likely is that you will want to repair/restore/replace critical wear items such as rod and main bearings, cylinder bores, pistons, rings, valves, and valve guides. Then the list can expand if you look at reasonable “why you are in there things” such as the clutch, flywheel, water pump, AOS, rubber and plastic hoses. And then we get into a grey area of reliability improvements. Since this is going to be a track car but also a road trip car, I have two good reasons to be breakdown adverse. I plan to be aggresive on replacing items that have some chance of becoming problematic over the second 100K miles of this cars life. My list includes timing chains, chain guides, chain tensioners, and all sensors. I am replacing the engine wiring harness, to preclude issues with degraded wiring and wonky connectors. In a cost is no object world I would replace the air mass meter, oil pumps, throttle body but will not as they are just too expensive with not much evidence that they randomly fail. Also while I am in there, the car will get new motor mounts and new struts at all 4 corners.

So finally there are performance upgrades. I am likely in the minority here but I like to keep the car mainly stock. This is just a track day car and being the top dog at any given track day is a ship that has long past sailed for me. Frankly, with the equipment that shows up at track events these days, my 15 year old Cayman is definately 2nd tier. So although it is readily available from Hartech and LN, I am not going with a displacement increase. Or fancy plenums. Or trick exhausts. Or someone’s vision of a GT3 clone engine. I am going to add a 3rd radiator to keep temps down on hot track days. I understand a coolant thermostat with a lower temperature than stock has been postulated to help with bore scoring so I am going with that. One Hartech upgrade that I am going with is a wider “big end” rod bearing shells.

Subsequently to working with Brandon to set up the machining order, both our minds turned to parts. He has a standard parts package that he can sell with the cylinder work as required to perform basic re-assembly of the engine. BTW, the package includes proprietary Hartech pistons, rings, and pins. Rod bearings, main bearings, gaskets, AOS, IMS bearing, water pump, etc. He also offers a Premium package. My personal list as discussed above includes those items and many more. Brandon says he is happy to fulfill my custom parts order as a discounted package.

So things are moving along. I am taking the opportunity of having all the engine parts dis-assembled to get to know the layout of the engine. My article 944 Oiling System Explained has always been a popular view at my website so I am currently working on a video version for the M97 engine. Then I will clean everything up, bolt the heads and cases together, and package everything for truck shipment to Oklahoma City. Stay tuned.