Cam bearing wear, would you reassemble?

[RickHaleParker]

Publicise the spreadsheet, somebody else might find it to be a lifesaver.

[highmiles]

Rick, I have attached the spread sheet here, perhaps you could give it a once over to make sure it is working correctly before I post it to prime time.

In short:
1. Select a known size lifter to measure against (any as long as the size is known.) use the same lifter for all the positions.
2. Set lifter in place, hold down cam shaft with the short side of the lobe towards the lifter, measure clearance.
3. Enter the measured clearance in the "Reference Clearance" column. (Repeat for all 10 exhaust valves using the same lifter.)
4. Note the calculated "Perfect Tappet (lifter) Size."
5. Select the lifter you have on hand that will be closest, and enter that value under "Tappet Used."
6. Confirm that "Actual Clearance" calculated is within the desired range.
7. Repeat for the intake cam.

Note that I have entered in an example in the first row of the exhaust and intake charts.

John

[kallekula]

Thanks, good points all around.

In hindsight the engine swap would have been the right (well, more economical) choice. Though part of my reasoning was to learn about the engine rebuilding process. I do confess to be being naive about the cost of parts (not to mention the parts that were outright missing...)

I already rebuilt the bottom end with new big end bearings and new rings in the pistons, so I feel good about that assembly. I scouted out the junkyard yesterday and they have two cars with the B5244T3 motor, so I plan to go next weekend to pull a head. I don't think I will even disassemble it to lap valves and put in new valve seals, just clean up the mating surfaces and roll with it.

IMO, give the head along with any seals etc to a machine shop and they will take care of everything. Its around $250-$300 around here. Totally worth it if you ask me. It will look/function as a brand new head when you get it back.

[highmiles]

The machine shop idea is a good one. I know of a local Volvo independent who must have a good machine shop recommendation.

I still plan to pull a head from the junkyard, the next project is a 2001 S60 T5 that broke a timing belt, plenty of bent valves etc.

If I am doing my research right, the head from the T5 (B5234T3) is the same as for the 2.4t (B5244T3) so I will have parts to work with.

Thanks!

[SuperHerman]

Two thoughts: One head and cam cover are married and should remain the same in the optimal world from what I have read. (I am not sure, but the two pieces may be line bored from the factory as a unit. This means you really should not mix and match.) Two, the head and cam covers are made of aluminum and the cams are made of steel. The steel will wear the aluminum to "adjust" for the cam.

So, if the cam cover is not line bored to the head, one could put a new cam cover on, and it will self machine the perfect fit. If one puts a used cam cover on the wear may not be the same and one could have slight oil pressure issues (assuming the donor and recipient are in good working condition and the cam shaft was manufactured to very high standards and still has these properties).

From there to answer your question, which may no longer be relevant at this stage, if the head and cam cover are still true, but gouged one would be able to reuse them. Caveat, you need to knock down any ridges and have a smooth surface. The cam needs to rotate freely. The engine may have a slight change in oil pressure. The cams float on a super thin layer of oil, actually rotate/float. The new imperfections will change this, but if the imperfections are just what appears in the picture the changes would be nominal. But, if the damage actually changed the overall dimensions of the bearing surface, oil pressure issues would be a concern as the rotate/float amount would increase, not to mention you may not get free cam rotation from the start.

In a summary, think of the cam as a metal lathe, as it rotates it mills the head and the cam cover because the steel is harder than the aluminum. If everything is straight and true, no measureable milling occurs, because the oil layer for the rotate/float acts as a bearing.

When the engine was starved of oil this "oil rotate/float bearing" disappeared and the metal lathe cam shaft took it to the aluminum cam cover and head. The full extent of the damage can only be determined by measurement of all the bearing surfaces. I have gotten away with cleaning things up and making sure the the cam rotated on the head visually as intended. Don't own those cars anymore, but for the 5k plus miles I owned them afterwards I had no issues. Perfect fix no, economical fix yes.

One last item, you can test the cam cover by flipping it upside down and rotating the cam on it. Look for age/wear marks on the cam and see how they line up with the cam cover - relative to the original head.

[highmiles]

Thanks for the thoughtful reply Superherman.

I confess that I am going to chicken out on reinstalling this head for fear that I would get the same timing jump as before. My working hypothesis is that the unmatched parts are so out of tolerance that there is not good lubrication at two bearings, these overheat and then the cam locks up (not enough time running for the machining you describe to take place.) I can afford the time and the $70 bucks to pull one out of the junkyard. kallekula's suggestion to take it to a machine shop may provide the best assurance, but I am a bit of a cheapskate! Still, hoping to make this the last set of head bolts I have to buy for this car! I do have a call into to a Volvo shop to see if they can recommend a machine shop.

Once running, still need to charge A/C, fix a couple of slow windows and the sunroof. The gauges came back from the shop and appear to be working now... oh, the brake master cylinder is suspect.... Looking forward to moving past this project and on to the T5 which is a manual car.

[SuperHerman]

I don't disagree with your decision. Like I said, I don't know how the head and valve cover are made. If they are line bored, meaning the pieces are put together and then the machine drills out the holes so they match, mix and match will not work (at least very well).

Now if they are made separate, and the machining is spot on, mix and match will work. Really it all depends on how good the molds and machining are. If they are really tight the parts should be swapable.

In your situation, it may be that the "cam machining" differed so much that there was no "oil float/rotate bearing" - or the parts were too different where a sufficient "oil float/rotate bearing" could not happen. "Cam machining" means one has NO oil and pure wear. It is fine for a small spot, but for anything large it will destroy bearing surfaces.

This wear is why one keeps their lifter buckets in order.

For $70 I would do the same.

[RickHaleParker]

If they are line bored

They are line bored. That is why you do not see a part number for the Cam cover in the parts catalog.

[highmiles]

Update...
Thanks again for the guidance. I pulled a head out of a junkyard car this weekend and dropped it off at the machine shop today for cleaning, pressure testing and the block/head interface dressed as needed.

Lessons learned...
Harbor Freight 3/8" extensions are good for somethings, but not for removing head bolts. Also falling victim was a 1/2 to 3/8 Craftsman extension and a Kobalt 3/8" ratchet. I knew better, but when you are that close to getting done... Lowes honored the Craftsman and Kobalt warranty and I picked up some proper 1/2" extensions, that with a HF 1/2" breaker bar, pipe extension and 1/2" socket got the job done.
The machinist confirmed that when heads are line bored, and particularly when the head top has dowel pins that specifically locate it (making any "float" impossible,) the top and bottom must be paired. Bad things happen when mis-matched head parts are put together. He said "some people don't know this," I raised my hand... "I do now..."
Google turns up amazing things, I put in the VIN of the V70 XC I pulled the part from, in 2016 it was at Copart for an "interior fire," and included photos, how it ended up at a PullAPart 3 years on is anyone's guess.
Once back from the machine shop I will lap the valves, renew the seals and get it back in the car. Will report back then.

John

[BlackBart]

This is all very good information. Made me wonder... I replaced one cam with used, but the machined steel cam journal is an exact and known dimension, so there shouldn't be any issue with the (matched) cyl head halves, should there?

Curious, if they're line-bored, does the assembly take into account the very small amount of gasket maker goop, or is assumed it compresses to zero?

I have sheared off many Craftsman 1/2" to 3/8" adapters with too much breaker bar. I'd like to find some beefier ones, or look for 1/2" drive smaller metric sockets. Mine are all 3/8 or 1/4, the 1/2" ones are in the 18, 22, 32 sorts of sizes.

That burned car was probably auctioned to another salvage yard.