cylinder head home job

guys,
i've recently had some bad news about my 240D cylinder head. the machine shop has come to the wallet wrenching conclusion that my valves are too thin to regrind, therefore new ones are in order as well as guides and stem seals. the shop wants 540 bucks to do this all themselves (in which case i would rather buy a new one for 595). their parts their laybor their warranty. i can shave off 120 bucks if i use my own parts (less expencive parts) and their laybor, no warranty. now, here is where the question lies. i was thinking (dangerous, i know....): what if i bought my parts, installed the new valves, stems and seals myself, and then had the shop mearly grind and seat the new valves for 100 or so bucks? here is where you all come in. please let me know if this can or cant be done as a home job. all i should have to do is install new valves guides and stem seals. if anyone has ever gone this route before, please let me know. awaiting you vast knowledge,
william gum

Bamboo,

I certainly understand your desire to economize. First of all, my machinist told me that these valves are now available on the aftermarket and are much less expensive. You might start calling some foreign car supply houses and see what you can come up with there.

Secondly, the majority of valve reconditioning labor is grinding seats and valve faces.

Also, my machinist took a lot of time to remove the prechambers and resurface the head. I expect that this short, cast iron head is not prone to losing its flatness. Get them to check it for straightness and skip that step if you can.

Summary: It seems that most economic way would be to check for straightness, find aftermarket valves and pay the machine shop for guide replacement and seat grinding. With new valves you may get by without grinding the valve face. I'm not sure, but it may be standard procedure NOT to face new valves. Hooking up the valves yourself would save very little.

Let us know how it turns out.

Good luck,

larry,
thanks for the speedy reply. i'm not sure what EXACTLY the shop is wanting to do to the head that makes thier price so high (i will find out on monday when they reopen). but, my question is, if all they want to do is put in new parts (no mention of resurfacing) and grind the valves, i would like to do the installation myself (which it sounded like you were in favor of) therefore saving a lot of cash. the only mention of things wrong with the head other than the valve parts was what the machine shop called some nuts that the injectors screw down into. they said that a few of them were stripped? i thought that the injectors threaded right down into the head. i'm confused with this nut thing. if you can shead some light, thanks.
william gum

[cth350]

When in doubt, let somebody else drive. If you think this shop is charging too much (and they probably are), find another shop. Ask yourself if this is really the right time for you to learn how to do this yourself? Just how expensive will it be for you to get it wrong the first time.

I don't work on my wife's car, because she'd kill me if I screwed it up and had to spend the extra time to fix it. My friend Howie works on her car and charges me well for the privledge. I keep my own cars afloat because I can always walk when I make a mistake; it keeps me on my toes.

Have the shop do all the "work", you supply all the parts, including the guides, seals and valves. The guides should be under 10$ each, the valves under 20$. Be sure your supplier is selling OEM guides, not aftermarket. Have you asked these guys (mercedesshop.com) how much they'd charge for the parts?

Let the shop lapp the valves and grind the seats. No doubt, they've already diassembled the head, so you can't install the valves yourself anyway. If you interfere with their job in progress, not only will they not warrentee the work, they probably will refuse to do it. Nobody wants to do half a job, especially if they're being paid. On the other hand, you may not want then to complete the job, that's your right. They'll still charge you for the work done so far. Taking it apart and checking the components is most definitely work and it does take time.

I have it easy, my machinist services all the local dealerships (3 mercedes, several acura, lexus, etc), so he's very well acquainted with the mercedes engines. He knows I'm easy to work with (and almost know what I'm doing), so he gives me the jobber's price 'cause I don't get in his way, don't blame him for my own mistakes and I pay cash.

-CTH

I Would like to reply to the post by Wm. Gum.
The pre-chambers can be removed by removing the collar. No special tool required. Use a flat head punch to remove the collars. Turn the head over and knock the pre-chambers out using a soft metal hammer. I use a large diameter brass rod. Remove the nuts on the valves, remove springs and other parts.I Use duct tape to hold the valves in their respective holes. Have the machine shop to do the same after the valves are lapped in.
If you need some numbers to check for parts, let me know.
I understand that this web-site sells parts, so check with them.
Bill Lewallen Lex.Ky.

wm lewallen,

i'm always open to new parts suppliers that may have lower prices. let me know what you've got. and if this site frowns upon advertising for other distributors, you can reach me at: wrgum@juno.com thanks
william gum

If the injector threads are stripped, remove the prechambers like Bill instructed, examine them and order the necessary parts from Parts Shop or the best source you can find.

The reason for the valves being shot is that these are 30 degree seats, and they tend to cup the seats to a point where if faced will be too thin.

I'm sorry I can't point you toward the aftermarket valve supplier. I would suggest that you Email the Parts Shop and see if they have such a source.

Good luck,