e12 6 series question for the experts

[bgriff]

Hey guys, I'm going to do "something" to the original power train on my 1979 633csi and I'd really like an opinion from someone who might know more than I do about swaps. I thought I wanted to swap in an m30b35 engine with a chip and a 5 speed od manual, car now has the original 4 speed manual and original motor with 140k on it. In talking to Truett at the Shade Tree Garage in Raleigh, he's suggesting I just refresh my motor and put in the 5 speed instead of spending the money for the m30b35. I really don't need to be able to outrun everything in the county, but I do want more scoot when I play with the gas peddle....any thoughts or opinions?? Thanks.

Bob G

[JodyStevens]

B35s aren't expensive, not sure where you live, but even where I live I can grab a b35 for a few hundred. Since it sounds like you're paying someone else, it could get expensive if they're unfamiliar with this particular swap. Electronics will take some time to sort.

[Mike W.]

I'm not sure what "freshen" amounts to, a valve job? Rings? Bore to 3.5 and new pistons? It's possible to take your block and achieve an equal or greater output to a B35, but it would cost a lot more. He may be apprehensive about doing a conversion or getting a bad engine and having to do the work twice and bill you for it twice. But just the numbers, 174 to 211HP is a big jump and worth it IMO if you want a bump in power.

[RonDwyer]

Engine rebuild
Bump compression a bit
Schrick street cam
port & polish the head (Extrude hone?)
Free-flow exhaust


5 speed...Is only going to give you lower RPM's on the expressway.

You already have a lambda sensor, is it working?
What is your current compression across the 6?
How old is your cat? If really old it's partially plugged. 15 years or more, replace it now.

You can hide upgrades amongst a stock underhood appearance. Your call.

[Mike W.]

You already have a lambda sensor, is it working?
What is your current compression across the 6?
How old is your cat? If really old it's partially plugged. 15 years or more, replace it now.

A 79 E24 would not have either an O2 sensor or a cat. That would have been thermo reactors, air pump and EGR if it's all still there.

[RonDwyer]

That's a grey area in my working knowledge, 3.3 would indicate to me a later engine unless its a 630. Oh well. A quick look under the hood confirms it all!

[Mike W.]

That's a grey area in my working knowledge, 3.3 would indicate to me a later engine unless its a 630. Oh well. A quick look under the hood confirms it all!

On E24s, 77 was 3.0, 78/79 was 3.3, all with about the same engine management, thermos etc. 80/81 was L jet with Lambda, both 3.3s were 8:1 CR.

[franky2fingaz]

What's the budget?

[tlake]

Miller & Norburn, H&B etc used to offer bolt on turbo kits that worked really well with stock compression ratio.