What parts should I replace when having an 885 head rebuilt?

[jc1000]

Hi there, I am a newbie and am going to have a machine shop rebuild my 885 head. What parts should I replace? (I am planning on sticking with the stock cam for now.)

Am I correct in assuming that I should provide all replacement parts to the machine shop for them to use when rebuilding it?

What else should I have them check/do while rebuilding the head? Clean, check for cracks, possibly skim it if needed for flatness?

Like I said, I am new to this and invite all the help I can get.

[zaq123]

valve guides will need to be checked/replaced if needed. Most likely EX side is out of spec or close to it. It's rare to find this car with rockers/cams that are still good. Typically it is a good idea to replace cams and rockers at the same time as they wear against each other. Valve springs need to be checked, valves need to be checked. Basically everything needs to be checked and replaced as needed. If you are paying your machine shop to do the whole job, they will tell you what they find out of spec (unless you are able to see it yourself). Whatever you do, do not hammer rocker shafts out of the head (as many do and damage them). Rocker shafts need just a little force to come out once all rockers are off the valves. If the shaft is stuck, most likely it's due to a very small burrs which are created by rocker retainers when they are inserted onto the shaft (in the area of the retainer slit on the shaft). That burr gets hung on rockers or the head and if banged out the head, can scratch rocker bushings and shaft journals on the head. Loosen all adjusters, remove rocker retainers, gently go over those slits with a miniature fine file/small piece of sandpaper, release any pressure from rockers and slide the rocker away from the valve. Once there isn't any tension on the shaft and any burrs are cleaned up, the shaft will come out with a simple hand force. I wouldn't trust a machine shop to do this correctly and would do this myself. This would allow you to inspect a lot of the head yourself and dictate the shop what you want to be done. Old timing belt in the strap wrench handle is an easy DIY tool to rotate the cam/cam gear during disassembly. Make sure that the head is not resting on any opened valves and it is not on some dirty/hard surface that can scratch the aluminum gasket mating surface.

[TobyB]

Short answer: everything that's worn out. (zaq- use the enter key. That block of text is too dense for dense people like me)

Which almost always includes valve guides.

EVERYTHING else is dependent upon wear, which in turn depends on mileage, oil changes, usage patterns, production date, and phases of the moon.

On a 'good used' head, the rockers may or may not be worn out. I'd say 'usually' they are, but it's well worth looking, especially if
-is the cam still good? If it is in good shape, and the rockers are ok, using them together as a matched pair's good practice.
Likewise, for a 'do it once' job, if a rocker or 2 is marginal and the cam's a bit worn, doing the cam and rockers together is ALSO good practice.

The valve springs seem to be very durable- as long as they are all at the correct relaxed height and undamaged, they'll be fine.
The valves also usually clean up well, UNLESS the exhausts are damaged. A partially plugged injector can cause cracking around
the perimeter, and that's worth crack- checking for.

But:

Your machinist will do all this reflexively. It's well- worth having this conversation with them when you bring the parts in,
including about who supplies parts. I've had the best luck with being direct: "Here are all the parts I'm bringing to you.
If you need more, and can get them easily from a known- good source, please do so. If something comes up that you
can't find, or if the parts come in from ITM or some other questionable source, call me, and we'll figure it out. I'm happy
to do the digging if a part turns out to be unobtanium." or something equally stilted.

Most machinists want to spend as few 'work cycles' on the job as possible, and not having to come back to it over and
over saves them hassle, time, and brain space.

t

[ForcedFirebird]

Rocker arm pads can be refinished. I have a setup to do so. :)

[jc1000]

Thanks, everyone. It sounds like the process depends on some pretty good communication with the machine shop. I will give them a call and see how they tend to handle head rebuilds.

[ForcedFirebird]

Thanks, everyone. It sounds like the process depends on some pretty good communication with the machine shop. I will give them a call and see how they tend to handle head rebuilds.

Any machine shop worth thier salt will have done multiple m20 heads. ;)

[jc1000]

So I have disassembled my 885 head in preparation for taking it to the machine shop.

Unfortunately, I found a couple of concerns.

First, there seems to be some breakdown on the rocker surfaces (see pics). Does this mean they are toast? Also, I have a 2.7 eta head - are those rockers identical to these? As in, could I swap in a few if I wanted or is this a terrible idea (reminder that I am a newbie)?

Second, take a look at the scoring on the cam journal of my camshaft. It seems pretty light but does catch my fingernail just barely without a glove on. The rest of the camshaft looks to be in good shape. What would you guys suggest? Could I polish it and run with it? Or should I take my medicine and replace it? I will be turboing if that makes a difference.

[jc1000]

Perhaps an even bigger concern: are these cam journals toast?

I imagine most M20 heads - being 30+ years old - are scored to some degree? If they are too far gone, is the only option replacing the whole head?

[digger]

head looks ok to me, i'd consider using a fine dangle berry hone(s) and buzz it for a split second though.
the rockers i'd replace as they dont look like a candidate for recon as appear to be deeply pitted and thus makes sense for new cam to IMO

[hasa]

For me the journals are good. Better than mine.

[TobyB]

If the journals in the head aren't as ugly as the cam,
then polishing the cam (to a really high finish, but NOT to remove all the scoring)
has worked for me in past.
If the head looks worse than the cam, then it's time for another casting...

t
has yet to make a rig to sleeve cam journals.

[jc1000]

head looks ok to me, i'd consider using a fine dangle berry hone(s) and buzz it for a split second though.
the rockers i'd replace as they dont look like a candidate for recon as appear to be deeply pitted and thus makes sense for new cam to IMO

So if I get new rockers, do I need to get a new cam? Or can I polish and use this cam with new rockers?

[digger]

So if I get new rockers, do I need to get a new cam? Or can I polish and use this cam with new rockers?

the journals look like theyd polish fine, but with new rockers i'd err on getting a new cam as the lobes are not mint but if you find someone to polish them to then should also be ok.

[jc1000]

Thanks, digger . Any suggestions as far as a new cam? (And rockers too, come to think of it?) I am running an ETA M20B27 "e" bottom end - block, crank, pistons - with the 885 head and I plan to turbo.

[jc1000]

ForcedFirebird what are your thoughts on the camshaft scoring and cam journal scoring (pics above)? I know you work a lot with the M20's, so I would be interested to hear your thoughts.

Right now I am planning to replace the rocker arms and camshaft and have the cam journals lightly polished, allowing me to still use the head.

Also curious if B25 and B27 rocker arms are identical. I will have a B27 head lying around unused anyway. Part of me wonders if I could steal a few from the B27 head to use in the B25, then polish and reuse the cam. But maybe (probably) this is madness!