Re-building Top End of Motor

[johnrob]

My '74 3.0CS has a worn cam lobe and I'm unable to set the proper clearance for the rocker. For a person that has never re-built a complete head; how difficult is it, and are the tools need to drive in the guides etc. readily available. I would do a complete re-build new valves, seats, guides, etc. if this is feasible or worthwhile. The alternative is to have a shop do it for me. I've heard from others to forget the 3.0 and move up to a 3.5 for a 735i. Options welcome, but this upgrade will be a tough sell with my wife due to $$.
John

 

[jmackro]

johnrob:

It takes some pretty specialized equipment and knowledge to rebuild a head. I wouldn't recommend attempting it at home with common tools. Now, you might remove the head, take it to the machinist, and then re-install it. But, pressing in the guides, grinding the valves, and re-surfacing the head is tough for an amateur to do.

On the other hand, doing a complete engine swap to a 3.5 liter will almost certainly cost more than just having your 3.0 head professionally rebuilt. And, even if you were to do the transplant, you would probably rebuild the 3.5 head while you're at it. So the "engine swap vs. head rebuild" question is sort of "apples & oranges".

If budget is the issue, why not just replace the worn cam and be done with it? Unless you have compression issues, what leads you to believe that the head needs attention?

 

[x_atlas0]

Considering the costs of having someone rebuild a head, a 3.5 swap isn't much more.

Head- 1-3k, depending on work done.
M30B35- engine itself, <1k. Getting everything to work, well, that is largely dependent on how much of it you want to do yourself.

 

[AndyM]

I agree with Jay -- you probably don't need anything more than a new (or good used) cam, new cam follows, new valve seals and maybe a quick lap job on the valves. I've never had a BMW head that needed all new valves, seats and guides. The most cost-effective option may be to find a good used head from an early 3.5 and have a leak down done on it along with a basic rebuild. Chances are you can get it done for under $500. Throw in a Schrick cam and new followers and it still should only be around $1k if you do the head R and R yourself (which is a very do-able job with basic tools).