restoring my 645csi help!

hello everyone,

i have a 1985 635csi i have owned these past 8 years, i have put on a total of 388,000 miles on this car, bought it from the orifinal owner, a doctor i worked with when it had 178,000 in 1997...

i want to restore my 6 to the highest performance mechanical condition possible. i have perused the net, familiar with several websites, my 6 still runs but wont pass smog, still hits 80mph on the freeway as though it doesnt know it is 20 years old!

where do i start? should i re-build engine? buy a new engine? install performance dinan chips? gut the whole mechanics? any info appreciated,
thank you, john

If it were mine I would completely rebuild the original engine. Keep It as original as possible but use simple upgrades if you can find them and afford them. Most all the performance chips wont allow you to pass very many smog tests (legally). I dont know how hard it would be to find oversized pistons and valves if you need to rebore and redo the heads. All I mostly see are direct replacements, maybe BMW figures that after 300,000 miles you dont need to bore. If you do, by chance, find performance parts, please let me know where.

hi,
thanks for response,

i hear this in discussions, the choice to rebuild or purchase a new engine but i am concerned the new engine would not be a true 6 series engine with the stainless stell timing belt.
folks who tell me to get the new enging route insist the engine is just old and can tolerate being rebuilt, this doesnt make sense to me unless the engine core was cracked or somehow warped from age or heat, in this area i am really ignorant, so you think rebuild engine. this would entail pulling it out, having new head, pistons etc, installed and possible reboring? anything else that goes with rebuilding an engine, and then do i need to rebuild or get a new transmission to keep up with the new engine and all the other mechanical ancillary stuff like water pump, power steering etc..
any help is appreciated, thanks, john

folks who tell me to get the new enging route insist the engine is just old and can tolerate being rebuilt, this doesnt make sense to me unless the engine core was cracked or somehow warped from age or heat, in this area i am really ignorant, so you think rebuild engine. this would entail pulling it out, having new head, pistons etc, installed and possible reboring? anything else that goes with rebuilding an engine, and then do i need to rebuild or get a new transmission to keep up with the new engine and all the other mechanical ancillary stuff like water pump, power steering etc..
any help is appreciated, thanks, john

Not necessarily all new parts, pistons, maybe but the crank can be turned and oversized bearings installed, the head can be shaved and maybe a few new valves, this engine can be rebuilt from anywhere from $10000 to whatever depending on condition. Since it is still running and dont use a lot of oil or leaks fluids past the head gaskets, you can probably get by for around $1000 or so. When you take it apart and take it to a machine shop they can give you a fairly good idea of valves, boring new pistons or oversized rings etc. From past experiences do not reuse the old cam, oil pump, freeze plugs, waterpump, hoses etc. Alot of the cooling system parts need a good cleaning at a rad. shop, just dont rush anything, if done right it will last as long as the original. As far as the trans, if it aint broke dont fix it, a good transmission place can remove the covers and feel and look and tell you what, if anything needs done. While you have it all out be sure to REALLY clean uunder the hood and check every hose and fitting, especially thos that are hard to replace when it is asembled like the hose from the master cyl to clutch master cyl and heater hoses etc.