Is there a good source for engine build specifications? I do not have a Boxster factory manual.
I need the cam bearing clearance range.
Thanks,
Stan

 

I had a Boxster factory manual and it didn't list any bearing clearances/tolerances.

Jake Raby of Flat Six Innovations:

http://flat6innovations.com/

I believe has worked out the clearances but I do not know if he shares this info. He came by the info the hard way and understandably could be reluctant to share it. There was some talk about him writing a book on these engines and if he did maybe the info is in the book? I have not really kept up on all this stuff. But I posted the link FWIW.

The "cam bearing" is the aluminum of the head and the aluminum of the cam shaft cover. If this diameter is worn it makes bringing it back to spec difficult. As an ex-machinist I could cover some solutions but they are not something done in one's drive way. You might be better off replacing the head/camshaft cover with an assembly obtained from a suitable donor engine.

 

Macster is correct. Porsche heads (and a lot of motorcycle) are line drilled to get the bearing surfaces. If your head dies from oil starvation, it can be repaired I suppose by drilling it and fitting replacement clamshells (not from Porsche) for bearing surfaces or a skilled machinist probably could tig weld and redrill the surfaces. Tough, precise work--the sort of skill needed to do it requires a pretty sophisticated machinist and shop. Expensive work for a 20+ year old engine with good used parts available at reasonable prices. I know a guy in San Diego who successfully did a few Kawasaki KLR heads. Really not cost effective.

You would be better to just replace the entire engine.

 

^^
Thanks for your inputs.
I checked the clearance on all the cam journals. They all have .003 inch clearance. The one journal
that has signs of wear was also at .003. So I think that is the expected original factory clearance.
This engine has only 47000 miles. The journal with signs of wear is the one closest to the IMS timing chain.
I suspect the wear is due to the prior owner not changing and/or keeping the oil level at the top. Just in case
I am replacing the chain tensioner on that chain.

 

I hope it turns out okay. Usually oil starvation on one side means oil starvation on the other side too. Have you checked the condition of the other cam and journals? 47k is a relatively new motor, it might be worth looking for a pair of heads, cam covers, and cams. When you put the cam covers back on, be very careful with sealer, when I had mine off to replace a variocam solenoid, I messed up on the sealer the first time. Pressure builds high enough to pop the cam end seals off and spew oil everywhere. BTW, Dirko sealant is available at Amazon. Hateful stuff, it's thick and tough to squeeze out of the tube.

I think I'd certainly pull the sump cover off and inspect the crank bearings, too. Do you have the engine out of the car? On an engine stand? The one sold at HF will do the trick and makes life easier if you're working on the engine. Easier, even than doing work on a bench.

How did you happen to discover that there was bad stuff happening in your engine? I think I hate the car's previous owner!

Btw, while you're in there, if you can, replace the RMS and the IMS bearing.

 

^:
Yes the engine is on a engine stand. I will open the 4-6 cam cover and inspect lifters and cams, replace the vario cam guides, and
time this bank. I have the LN IMSB kit and RMS.
I installed a set of hoists in my garage. My plan was to replace the IMS and the clutch assembly.
Turns out the floor slab was too thin to support the hoist. So instead of a week install, it took a month. All the while
the car was not driven. I started the car and drove it to get fresh gas. On the way back It made one slapping sound.
Started it the next day to put it on the hoist. It miss-fired and put out a fuel smell and a puff of white smoke. Drove it into the garage to
fit the hoist arms to the lifting points. The next day started it to leave the garage. Again had a puff of smoke and while backing out the oil
warning gage came on and the lifters started clicking. Immediately shut it down. It hasn't been run since.

At the time, I was not sure if the IMSB failed or what. Removed a perfectly smooth feeling bearing, replaced it with a temporary plastic bearing
inorder to trouble shoot the cams and engine timing. I have to put the engine on the bench to install the LN IMSB.

 

Sounds a bit like my experience. For me, changing out the engine was like a series of puzzles. I recently did a Dodge Ram V8, in about 5 days total. Working on the Porsche took me weeks.

Really destroyed my level of energy related to Porsche projects.

 

I removed the 4-6 cams and vario cam assy. I found the failed parts. Three lifters on this bank are not like the rest of the lifters in either bank.
They are solid, while the rest have about .15 inch of spring return motion. I tried to free up the solid lifters. I pressurized them to no avail.
The consensuses, from four mechanics, that I have been able garner is to replace the lifters. Additionally, I removed the oil pump. It is in very
great condition, no appreciable wear. So I ordered 24 new lifters.

Since the bad lifters are next to each other, I will remove the lifter housing, from the head, and make sure the lubrication passages are clear. They all share the same feed.

 

Ref: https://rennlist.com/forums/boxster-...grade-fix.html
So I bought 24 new lifters from Pellican parts.
I thought they would be the -50 lifters. They turned out to be the -72 newer version. When I received them
I tried to compress the piston from the bottom. I put approx. 100 pounds on the lifter. It would not compress.
The existing old lifters compress with finger pressure. These act like solid lifters. Is this the norm? There are no
install instructions that came with these lifers. I plan to put them in oil and install and put assembly lube on the cam
top surface.

I will rig up a force test tool to measure the actual force to compress these new lifters.

 

There should be no reason to measure the force to compress. Either the lifters are the right ones or they are not. Besides the amount of force necessary to compress the lifter, actually the zero lash adjuster, depends upon if the zero lash adjuster is full of oil or not. It is possible the lifters you can't compress just have the adjusters fully charged with oil.

I'm not sure the fact you are able to or unable to compress the lifters is sufficient to either accept or reject them.

The lifters if not the same part number as the old ones should be the proper part number for your car's VIN. That is the lifters maybe different but still work when dropped into the lifter bores.

 

Macster:
Thanks for your reply. After posting yesterday, I found a description of how these lifters work. I concluded the same thing that force test would not be relevant.
I concluded that they are shipped with no oil except to prevent corrosion. They have to be pumped by the oil pump at start-up.
As for the correct part number, I called a local Porsche dealer and requested a quote. They quoted the -72 part. BTW their price was 2.5 times higher.
Thanks again, Stan