Toasted Head - help me stick it to the man

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AbeFM
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Toasted Head - help me stick it to the man

Post by AbeFM »

Ok, so like... After quite the adventure making my own valve shims just a bit thinner.... to go on a run, then pull the head later, I found.... METAL SHAVINGS. Damnit.

First I thought the oil pump was spewing them, but 1) they were all alum, and 2 running the pump didn't do much.

So I look closer, find this:

Image

Pull the guides out, about half are so afflicted:
Image

And it corresponds to damage found here:
Image

Overall, here's the look:
Image


My question is, a while ago, a shop worked on this head, put in biggie valves I'd bought, new guides, etc. They'd line-bored the cam journals with half the caps on backwards. I was livid since I have a lot of money into this head, they gave me this and sent me home:

Image

Does anyone think I have a leg to stand on for getting a new head out of these guys?

The long version of the story is in the next post.
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Re: Toasted Head - help me stick it to the man

Post by AbeFM »

Backstory. A while ago, I overheated the head when one of the water lines broke. Nothing seized, but it wasn't too pretty. I bring it to a shop, the only one in town I found to do good work, it was recommended to me by a friend who runs a BMW shop.

Unbeknownst to me, they were under new managment, and also, the guy I specifically brought it to since I liked the work he did gave it to some new guy.

Well, since I needed new valves, I got some "plus 1" (really only about 0.5mm over) valves, which were still cheaper than mazda ones. They say it'll be a couple of days. I call them up 4 days later, they say one of the cams won't turn, they have to line bore it. What? I don't think so, I remember stuff looking ok. I tell them to double check it.

Two days later, they call, say they need to line bore it. I ask if they took it all apart, etc, and put it back together, lining up the little marks. They say yes. I say check it again.

Another couple days (now two weeks without a car, or more) they say they are basically just storing my head, waiting for permission to line bore it. I tell them to please, double and tripple check it, I know it's fine, but if they are SURE it needs it, do it.

So, they line bore it. Charge me for it as well. When I get there, half the caps on on backwards. They used the cast marks not the stamped ones for orientation. MAN am I pissed. After lots of arguing (they offer to give my $200 back or whatever, on a head with $850 in work on it, $500 of intrinsic junkyard value, and $300 or more in new guides and big valves I just put in. Oh, fuck them, you know?

So they give me this warranty.

I check the cam clearance. In one dimension, it's right on - factory spec, as tight as it would be new (only ~50k on the motor). In the other (kinda 10 o'clock?) it's right at the wear limit. I mean, RIGHT at it. So the cam can wiggle in one direction and the factory manual is staring me in the face with "replace head".

So I put it together. The valves, I find, are tight, way tight, in places. I have to tap the valves to get them to come up fully. Ok, new shims. This happens a few times, over the year or so it's been (1.5) since I had them work on it. This time I needed a shim thinner than mazda makes. So I make a shim, thinking I'll have to pull the head next week.

So, yeah - the valves don't close, so they burn. That's where I'm at. I'm sure the seats are toast too, but I don't have them off yet.
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Re: Toasted Head - help me stick it to the man

Post by Fred »

Firstly, I'd have been way more than livid. That is a really shit story Image

http://abefm.smugmug.com/photos/348829583_n9FMn-L.jpg

Those marks fit with my theory in the other thread. Are there any on the uphill side of the exhaust lifter bores?

When you say "guide" about a head, those are the brass things your valves go through :-p Lifter, cam-follower, Lash adjuster, tappet etc refers to the thing with the notch out of it.

Speaking of which, Are those notches sharp on the edge? Do they have a burr? If they are smooth then the only way it could even make appreciable contact would be by being smaller than the bore or by large side loads.

Still, a strange issue any way you look at it.

You said the cam journals were line bored, but your cams are stock, how can this be? If you bore, you surely need to either retrofit shell bearings like the bottom end or get a cam with a larger journal size.

Secondly, you said they bored it with the caps on backwards? Are they still on backwards? Or did you correct them? If the latter, that could make the bearings worse than what they had them at backwards. Still, that probably wouldn't manifest itself like this, rather it would just chew up the cam and journals more.

That kid who did the work must have been a proper noob to put the caps on backwards... the first clue is that they don't fit and they used to...

I'm left wondering why you didn't go down there pre boring and check it yourself? So many negative things to talk about. How can I end this post?

Image

Poor bugger :-(

Fred.
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Re: Toasted Head - help me stick it to the man

Post by MotoFab »

Image

What are the shavings from? Are they steel or aluminum? If you fit a new cam, maybe the shavings are wear-in asperities from the cam lobes.

Maybe not though, one of those shavings looks to be the same 'length' as the notch in the shim bucket to help with removing the shim.

If the shavings are aluminum, something caused the shim buckets to scarf the side of their bores. Did you fit a cam with much higher lift? Or maybe, did the line bore job moved the centerline of the cam? Perhaps away from the center of the motor?

It is an occasional practice on a race motor with high profile cams to relocate the cam centerline. Sort of like how the crank CL to cylinder CL is located for the best advantage.

The shows that the buckets do their damage as the valve is closing. During valve closing, the cam lobe is in contact with the 'scarfed side' of the shim/bucket, tilting the bucket in that direction against the force of the valve spring.

Whatever it is, good luck sorting it Abe.

- Jim
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Re: Toasted Head - help me stick it to the man

Post by Fred »

Great post Jim, his cams are stockers though. I wonder if you are right about the centre line of the bore, it's certainly a possibility.
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Re: Toasted Head - help me stick it to the man

Post by AbeFM »

Facts!
Yes, everything is stock save for the valves themselves
Yes, I reinstalled the caps in the facotry orientation (no reason they should be looser? In fact, to the extent they are looser, perhaps there'd be more cam slop that way?)

When I measured (plastiguage) the cam-caps, in on direction, they were tight as can be - right on the factory spec (I forget the numbers, but if it's 4-6 thou nominal, 12 wear limit), I got 4.5-5 in the tightest spot around the bore, and 12 perpendicular to it (90* around) - right on the limit.

Yeah - the shavings were alum, and mostly in that little notch in the bucket.

The "guides" I spoke of replacing were the brass valve guides, the buckets are, well, the buckets.

The centerline argument is the best I can think of... Anyway, if you have any good ideas, let me know. If they are sticklers for it seizing, I guess I could run it with a drill motor till they freeze. :-)
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Re: Toasted Head - help me stick it to the man

Post by Fred »

8InchesFlacid wrote:Pull the guides out, about half are so afflicted:
Image
OK, but that is the caption for that photo. One would naturally assume that the thing in the picture was the thing being talked about in the caption. I guess you were tired or I've missed something?

Good luck.

Fred.
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Re: Toasted Head - help me stick it to the man

Post by AbeFM »

Oh, yeah - you're right, I did say guides there and didn't mean it. :-)

I noticed that the cams don't have the same nice smooth polished surface on the backsides of the lobes. Kinda chattery. I noticed it before the connection, so I didn't see if it's only on the bad valves.

The holes are messed up on both sides, though, some all the way around. It does seem to *start* on the leading side, then directly opposite, but I think the ones which were doing it the longest look smooth again (and actually, probably catch less).

I'll put more pics up at http://abefm.smugmug.com/gallery/566621 ... 8486_43eBC soon, so you can look at holes with the tops chewed off to your heart's content. :-)
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