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My First Engine Build - Ever - Cam Question


MrSharky

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Okay - so it's happened.  Betty is going to get a new engine.  Not that there's anything too terribly wrong with what's in there - I'm guessing it's all pretty much what came with her from Germany, 32/36 Weber.. nothing too fancy.  

 

What I've got now is a reconditioned block, bored for new IE pistons for 9.5/1 compression, a 121 head which has been cleaned and pressure tested - it's disassembled now, and I'm gathering all the parts and bits to put it back together.  I've got the stock crankshaft that's been checked out by a machine shop, micro polished and "magnafluxed".  I've also got the original stock cam. 

 

So - first things first - this is my first engine build ever - I've never done this, but I'm pretty sure I can do it - I've got a lot of big brains that I can lean on (like yours) 

 

My first decision is the cam, I think.  I'm pretty sure I need to upgrade the stock cam to something a little hotter.  I'm not building a race car - this is still going to be a driver, so I've landed on a 292 of some sort.  I have narrowed it down to the Ireland new billet 292 that goes for about $300, or I've got a line on a used Schrick for approximately the same money.  What would you go with?  I like the idea of running a Schrick, but I'm a little worried that it's used.  It looks okay in the pictures, but I have no idea what i"m looking at, or looking for as far as problems.  I like the idea of a new cam, and the IE seems like a pretty safe bet.  I'm going to probably end up getting the rest of my parts from them.  I can post the pictures in a few minutes, but what do you think?  

 

New IE or used Schrick??

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There is nothing wrong with a used cam, but I would factor in the time and expense of having a machine shop check it out and polish it, if needed. In the end though, no one really cares whether you have a real Schrick cam or not. Ireland makes a quality product so I would be comfortable in letting price be my guide here.

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The Schrick might actually end up being a little cheaper, if it doesn't need work (as advertised) if I can just put it in, it might be a better deal.

Has me thinking about the other parts that I have - rockers, valves, etc. one part of me says to do it all new, and then another side of me says these parts are probably just fine. What can i safely reuse? Like - do I need new valves? Do I need new rocker arms? I'd like to only have to do this once.....

Matt

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The machine shop that does the head work will decide on the valves- they are usually reusable, with no penalty whatsoever

(as in, they don't get 'used up') You'll need new valve guides, I'll bet,

 

and if you're putting in a used cam, you 'should' re- use the rockers that were mated to it,

as in, #1 to #1 and so forth.  Or use new ones.  But not rockers that have mated to a DIFFERENT cam, unless you have them re- faced.

Old rockers, however, are probably better than new, in terms of quality- do a search, but what's floating around now really should be

sunk- it's pretty poor.  Thus, the Ireland heavy duty rockers, more for quality than anything else.

The break- in of a cam has become difficult- search 'ZDDP' on this board for some opinions, but I strongly recommend an additive.

 

I always check the valve springs for pressure and height.  They're invariably ok.

 

I subscribe to the 'warm it up and get combustion pressure on those rings' school.  Haven't had any real problems that way.

 

hth

 

t

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Thanks Toby - that does help.  

 

I'm not sure what I'd do if I got the Schrick, as I don't think the rocker arms are being offered for sale, so I'd either be using the used rockers I have now, or new rockers on the used cam.  I really don't know.

 

Kind of leaning toward the Ireland cam and rockers & valve springs - all new, reuse the valves I have.  But then part of me says to get it all new. 

 

Didn't think I'd have problems getting out of the gate.... 

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TobyB has got it right. A used cam with new followers or a new cam with new followers. The used cam will need to be closely looked at to make sure the hardened coating is intact, if it has even 1 spot of wear into the softer base material it cannot be used. New followers are always the best bet due to used ones have been "worn" in to the old cams lobe profiles and can cause premature lobe failure on a new cam. My vote is for the IE cam, followers, and springs.

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I'm doing a top end on my 2002 as well. Maybe a complete rebuild if I have time. Lots of good info in the thread I started here on the FAQ.

http://www.bmw2002faq.com/topic/143658-updated-carbs-cams-ignition-etc-geting-the-mix-right/

I've rebuilt a few 2002 heads and I would suggest finding someone who has the tool to remove/install the cam and see if you can borrow it. It's not absolutely necessary but it does make the job MUCH easier.

post-39742-0-08541100-1377111555_thumb.jpost-39742-0-95749000-1377111658_thumb.j

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ya - I'm following you on that thread as well - think I'm making some decisions based on info there.  Think I'm going to end up going with the "all new" route - new IE 292 cam, new IE heavy duty rockers, new valves & springs...  

 

I'm not familiar with that tool - I'll have to look into it.  Is that it pictured on the left? 

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hardened coating is intact

There is no hardening on a BMW cam.  The rockers are quite hard, the cam quite ductile, the 2 mate, oil keeps them together and yet apart.

ZDDP greases the skids considerably.

 

Wear is inevitable, but slow if things are working right.

 

t

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ya - I'm following you on that thread as well - think I'm making some decisions based on info there.  Think I'm going to end up going with the "all new" route - new IE 292 cam, new IE heavy duty rockers, new valves & springs...  

 

I'm not familiar with that tool - I'll have to look into it.  Is that it pictured on the left? 

The pic on the left is the tool.  The pic on the right is the tool mounted on the head.  The tool holds ALL of the rockers down simultaneously so the cam can slide in or out.  Without the tool it can be tricky.  Once the cam is out you can work on getting the rocker shafts out.  CLEAN, CLEAN, CLEAN the rocker shafts as they can be quite difficult to get out. Don't be tempted to use anything other than a soft brass drift... a LONG one. I polish mine in a lathe before reassembly.

 

post-39742-0-50560000-1377127637_thumb.j

 

I'll try to make the time to update my blog (In my signature) to include rebuilding the head in my 2002. You may find something useful.

 

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aha!! I see it now (was looking on the phone before) - I didn't notice the tool installed in the second picture.  That's awesome.   As it stands now, my head has been disassembled, so I don't need to worry about getting the rocker shafts out - will need to worry about getting them back in though, I guess.  

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aha!! I see it now (was looking on the phone before) - I didn't notice the tool installed in the second picture.  That's awesome.   As it stands now, my head has been disassembled, so I don't need to worry about getting the rocker shafts out - will need to worry about getting them back in though, I guess.  

Be careful with those shafts... It is quite possible the end of the shaft was enlarged when removed.  Look for scoring in the old rocker arm bushings and/or in the head.  Be sure to measure the shaft diameter carefully, especially at the ends, before you reinstall them to avoid potential damage your rebuilt head and/or new rockers.

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There is no hardening on a BMW cam.  The rockers are quite hard, the cam quite ductile, the 2 mate, oil keeps them together and yet apart.

ZDDP greases the skids considerably.

 

Wear is inevitable, but slow if things are working right.

 

t

That is very interesting comment. If BMW doesn't harden the lobs they must be the only manufacturer left since the 1930's that doesn't. The cam should be 40 - 45 Rockwell and the lobs should be induction hardened to 60 - 65. If I am wrong I would love to see some documentation on this.

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This was according to Delta Cams in Tacoma.  If you have a hard cam and a hard

lash pad, the wear and galling is immediate and terminal.  I am no material scientist, but I've

seen what happens on sliding surfaces when they're similar.  The lash pad and the cam

on an M10 or M20 are very different in composition, and the pads ARE quite hard.

 

From cutting up cams for fun and no profit, the lobe's not harder than the base, and there

is no evidence that the cam has been locally hardened.  It's a casting, of a unique color,

so there's no way to tell if the whole thing's been hardened or not, but it's uniform. 

Also, there's no avalanche when it starts to wear- it wears progressively, and if lash is 

kept close to correct, a cam that's worn .20mm will last a stinking long time.

 

I had a cam that was welded up and reground (to get more duration at real lift) and 

THAT was hardened- and when it failed, it DID avalanche- 3 lobes were competely wiped,

1 showed some wear, and 4 looked perfect.  

 

Without a hardness tester, however, I couldn't tell you what the hardness of the pad or rocker is.

 

Just what I've found,

 

t

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