Exhaust cams in used set of heads won't turn

[ElementR]

I have a used set of heads at a reputable cylinder head shop. They are testing them out and intent is to do a valve job and install all new Supertech valvetrain. They are telling me that the exhaust cam in both heads won't turn. Mind you that they are trying to turn them by hand, but that sounds odd to me. They admit that they are not experts on these particular heads so they are raising it as a potential issue before proceeding any further. I know the valves were bent on these heads, but does anyone have experience with the exhaust cams binding as a result?

I can always get another set of used heads, but that's more $$ and not sure I won't run into the same issue.

[okkim]

Maybe the cam caps are not from that head? Or they are mixed from each other. That can lock the cams.

[ElementR]

I gave the shop the detailed Audi manual and pointed out how to assemble the caps by number, but they were in a box so it's definitely possible and quite likely that they have them mixed between heads. Is there really that much tolerance between heads? It would be nice to head over to the shop and swap the caps, but are they stamped in any way that I could know which goes to which head?

Previous shop disassembled them... yeah, I got a box of parts back from them when they supposedly were getting evicted for not paying rent. Like a present that I never wanted.

Oh, and there are stripped threads in the heads for the cam caps. So they would need to get repaired at a minimum. I'm at the point of either pulling apart my current engine (something that I didn't want to do since it runs fine) and taking those heads to the shop or trying to salvage what I got.

[okkim]

The caps are machined in the head, so that's why they won't work in the other head. I have tested that, and my cam locked. If you have very good luck, caps from the other head might work.

If you know that all caps belong to these heads, it is quite easy to test which goes where. Those are numbered, so you know in what position to test it. Remove all lifters, put the cam in the head and just one cam cap. If the cam rotates, put the next cap and so on until all the caps are installed in both heads.

[ElementR]

Sounds like a good approach. I'll give it a shot. Thanks.

[NOTORIOUS VR]

Always, always, always keep bearing caps with it's other half.

A reputable cylinder head should should have told you this from the get go what the (likely) problem is.

[ElementR]

Easier said than done when the first shop tears down the engine, then gets part way through and tells me they are getting evicted from the building (likely BS) and hands me a box of parts and a partially completed job. So, now the new shop is running through the heads and trying to make sense of what they were given. I never expected such tolerance on cam caps from head to head...main caps, yes, but I'm an old push rod guy so these are not my usual forte. Appreciate the advice and hoping it's as simple as moving caps around.

[NOTORIOUS VR]

Easier said than done when the first shop tears down the engine, then gets part way through and tells me they are getting evicted from the building (likely BS) and hands me a box of parts and a partially completed job. So, now the new shop is running through the heads and trying to make sense of what they were given. I never expected such tolerance on cam caps from head to head...main caps, yes, but I'm an old push rod guy so these are not my usual forte. Appreciate the advice and hoping it's as simple as moving caps around.

I understand how it could happen... It's just when people say reputable shop... for me if a shop is reputable, that to me means they're better than the rest. Installing a set of cams in a set of heads and using random cam caps from a box that weren't labeled and cause the cam not to spin after assembly makes me immediately think that the caps are not from that head/journal. That they didn't even think of it or mention it to you makes me think otherwise of a shop. Going to a good shop means you should have to turn to the internet for advice

Aluminum heads distort (between heat and head TQ, block distortion, etc), and the caps "wear" into the journals in a certain way... mixing them up doesn't work.

I'm not an engine builder, but experience and common sense goes a long, long way. Don't mind me, I'm just thinking out loud.

[JVD]

Ya, your second "reputable shop" should be experienced enough to know you can't just throw caps on the head at random.

[ElementR]

Around here in the big 3 land, reputable shops are used to domestics... so think largely pushrod engines. Overhead cam engines, although finding their way into the domestic performance car world, are still very new to these guys. I wish there were better options, believe me.

All said, I do wish these guys caught the miss-matched cam caps from the get go. Hope the rest goes smoothly.

[NOTORIOUS VR]

Around here in the big 3 land, reputable shops are used to domestics... so think largely pushrod engines. Overhead cam engines, although finding their way into the domestic performance car world, are still very new to these guys.

I see what you mean... to me, that's scary lol

[MTV2002]

if the caps are installed wrong, they have a tendency to crack. make sure to check them.

[ElementR]

So, the shop said that the caps are in fact marked LH and RH so the previous shop apparently did have the foresight to mark them. They have them installed correctly and the exhaust cams are not turning easily by hand (no springs/valves in place). This shop is far from my house so I haven't had a chance to stop by there. I want to do that and check them for myself, but does anyone have first hand experience with turning these cams by hand and do they spin easily without springs/valves in place?

I find it hard to imagine that the cams/caps could be damaged from a valve crash. A warped head, perhaps, but that still seems like a stretch to me. Something is not right with this picture.

[Nichtknicken]

Either the cam caps are in wrong ( position in head OR facing the wrong way in the correct position) or the previous shop could have thrown in caps from another set of heads ( a little unlikely but who knows). I think your only choice it to go inspect them for yourself. The little arrows on the cam caps point toward the plug wells on both cams, numbers are right side up looking from the intake side of the head.
I would expect damage to the cam bearing surface at the very least if they were tightened all the way down, but they may have gotten lucky.
And I will say I would have very little confidence in a shop that couldn't figure this out without calling the customer. This is basic stuff.

[ElementR]

Agree, unless something is truly wrong with the parts. I'll put my hands on them and see what I can determine. Thanks for the feedback.

P.S., previous shop had no other Audi engines on hand so highly unlikely that they got them mixed with another set.

[Nichtknicken]

It occurs to me that the cams could be bent from the first shop improperly removing the cam caps. Just another possibility.
I just tried out putting the cam caps on backwards in a junk head I have. Someone would have to be seriously ham handed to cram them down over the locating dowels. Cam should spin by hand, a little drag but smoothly on my head. I grabbed where the timing belt pulley would normally be.

[NOTORIOUS VR]

So, the shop said that the caps are in fact marked LH and RH so the previous shop apparently did have the foresight to mark them. They have them installed correctly and the exhaust cams are not turning easily by hand (no springs/valves in place).

Again, this shop you have your heads at worries me if this is what they're telling you because no one, not the previous show or the shop you have the heads at now seems to know what they're doing.

Just because you have the cam caps on the right sides (RH & LH), that's only part of the problem. You have to have the actual cam cap from it's mating journal. Meaning you can't put cap from cyl 1 on to cyl 4 or 5 or 2. All cam caps have to go back on the same cam journal that they came off of.

I would highly suggest you take the heads from this shop and either drop everything off to a real quality shop that have great experience w/ multi-valve DOHC heads.. maybe they will have a way to measure each one to figure out which cap goes with which journal, or maybe they will line bore them.

Or you just should just look for another set of heads and don't have them disassembled unless it by a pro shop that knows what they're doing.

[ElementR]

The cap sequence is understood. In fact, I provided them the Bentley manual for this and they installed them per the order in the manual. Given that I only have two sets of cam caps and there are only two heads, if the caps are labeled LH and RH, it should be a no brainer. Unless someone miss-labeled or damaged something, I don't understand the issue.

Yes, this shop has suggested a line bore to resolve the issue but then they haven't touched it because it doesn't seem right to them as well. If the cams are bent, the line bore wouldn't solve the issue anyway. My other option is another complete set of used but functional heads. I know where I can get a set for $400, but before I spend another $400 I need to understand what's wrong with these ones if that's possible.

I'll inspect myself... hope to get out there tomorrow. Appreciate the feedback.

[NOTORIOUS VR]

The cap sequence is understood. In fact, I provided them the Bentley manual for this and they installed them per the order in the manual. Given that I only have two sets of cam caps and there are only two heads, if the caps are labeled LH and RH, it should be a no brainer. Unless someone miss-labeled or damaged something, I don't understand the issue.

Yes, this shop has suggested a line bore to resolve the issue but then they haven't touched it because it doesn't seem right to them as well. If the cams are bent, the line bore wouldn't solve the issue anyway. My other option is another complete set of used but functional heads. I know where I can get a set for $400, but before I spend another $400 I need to understand what's wrong with these ones if that's possible.

I'll inspect myself... hope to get out there tomorrow. Appreciate the feedback.

That's a crappy situation.. unfortunately since everything was apart it's possible something was damaged previously... does seem extremely odd though if the caps were in fact labeled (and checking google images, it seems the journal caps are indeed marked 1-2-3-4 as well... Hopefully you get it sorted.

[Nichtknicken]

Yeah, the cam cap marking from the first shop is definitely suspect, especially if they didn't mark the heads left and right as well. Who knows which one they thought was the right or left head anyway. Crap situation for sure. Sounds like you did what you could to avoid problems and problems found you anyway.

[ElementR]

It's just the luck of the Irish, but fortunately not the sort of luck that lands your car into the hands of a thief who crashes it...could be worse all things considered. Gotta stay positive. I want to get this engine together sooner than later.

[ElementR]

OK, I've put my eyes and hands on them now. There is definitely something wrong with the intake (not exhaust) cams or caps. The caps do not have any signs of being damaged. I removed all caps and inspected them. The cam journals are also clean and I did not notice any axial binding either with the caps in place. The exhaust cams turn like you'd expect with little drag. The intake cams have to be turned with significant force. Keep in mind springs, valves and buckets are not in place so they are not a factor.

All caps are installed with the proper direction (arrow pointing towards plug holes) and number sequenced per the Bentley manual. Also, the caps are clearly stamped LH and RH. I'd be guessing as to who stamped them, but despite trying to play with moving the caps around between heads, it did not solve the issue. And a few bolts holding the caps in place are clearly cross threaded as well.

So, I'm throwing in the towel with these heads. The shop can line hone them, but for the money, I'm better off getting a set of heads that are known to function and come with a warranty in case something's wrong. Moreover, if the cams are bent, the line hone will do nothing for me. Sucks, but this is reality.

FWIW - The owner of this shop even went to an Audi dealer and asked their techs to take a look and see if everything looked correct as far as the assembly sequence of the caps and such and they said yes...

[okkim]

It is quite easy to see if the cams are bent. Just put one to it's place without cam caps and turn it. If it doesn't turn well and wobbles, it is not straight.

[NOTORIOUS VR]

That's unfortunate, but I agree best to just start with a new/working set of heads.

[ElementR]

If the cams are bent, it's very difficult to see it. The problem arises once the caps are put into place whether they are torqued down or not. Still seems very odd to me, but it is what it is unfortunately.

[ElementR]

Just to confirm, the following heads from an A6 2.7L are the same as used on the S4, correct? Want to be certain before I purchase them. TIA

078 103 373 AE Right Hand
078 103 373 AF Left Hand

[hibiscusS4]

the heads in the 2.7 a6 were the same yes

[ElementR]

Thanks. I thought so, just wanted some reassurance.

[hibiscusS4]

its cool. good luck with this set