2.7i Pros and Cons

[jeffnhiscars]

The machinist I trust completely so am thinking to bring it home after the guides and valves are done and decide what's next from there

[digger]

note that this was the 885 , the 731 has different bowl shape and short side apex so is going to require a little more work especially with an oversized valve. check out the guys work when you drop it off and decide from there

[jeffnhiscars]

here is a flow test done by E21JPS of stock 885 with osvat valves i brought to his workshop when he was playing around with his new flow bench a few years back

the osvat valves have a noticeable lip

BLUE: Stock Osvat
RED: Stock port, osvat backcut
DK BLUE: a few of select grinding, osvat backcut valves

so in total a few mins work but targetting the right areas...when you look at where the material was removed it was mainly shortside work very subtle. run your finger over the short side of stock port and a massaged one its much nicer by feel

Talk about being right on point lol....thank you for the graph and yes, I noticed the lip right away.

Rama was kind enough to provide me with some detailed guidance for ports, cuts etc which I have shared with my machinist. He will be doing a back cut and a 5 angle seat.

I'm undecided about whether I let his son do the port work or do it myself now that it makes so much more sense to me plus I get the feeling he may be a bit grind happy.
No cam decision yet.

[digger]

here is a flow test done by E21JPS of stock 885 with osvat valves i brought to his workshop when he was playing around with his new flow bench a few years back

the osvat valves have a noticeable lip

BLUE: Stock Osvat
RED: Stock port, osvat backcut
DK BLUE: a few of select grinding, osvat backcut valves

so in total a few mins work but targetting the right areas...when you look at where the material was removed it was mainly shortside work very subtle. run your finger over the short side of stock port and a massaged one its much nicer by feel

[jeffnhiscars]

Btw I got these little puppies today




They're in for a 30 degree back cut

[2mAn]

howabout no. I always get a good chuckle at M52 kids (exception being Simon).

a man after my heart :giggle:

[jeffnhiscars]

i've heard mixed reviews of new febi cams, someone must have a good stock one around

If I was going to install a used cam I'd stick with my "known used" b23. It's not at the end of its life but given the goal of not forcing a head pull til they bury me, I should explore my options.

Is a re grind "as good as new" ?

[digger]

i've heard mixed reviews of new febi cams, someone must have a good stock one around

[jeffnhiscars]

My machinist tells me I can get by with my b23 cam but should look at replacement options. Based on diggers cam profile post it looks Like a b25 cam is almost identical. Given that new ones are $130 is that a decent replacement ?

[jeffnhiscars]

HAHAHAHAHAHA

No, but the exhaust ports on all M20 heads are the same. b25 has larger downpipes. b27 b20 and b23 have identical exhaust manifolds (same part numbers), b25 is the only M20 with a different part number.

My 2.7i runs very strong with the stock eta exhaust. I had the pinched section under the rear subframe replaced with a round section of pipe, otherwise it's stock. Silent at idle, quiet under 3k, muted but delicious BMW wail above that.

I half expected someone to take my 4wd comment seriously so thanks for that.

As long as all the ports, manifolds and pipes play well together I'll stick with stock for now and see how that goes since again, the goal is to do this incrementally so the results of each step are not disguised.

At some point ill be tempted to try a b25 dual pipe and will report back on any before and after differences.

Thanks for the input.

[modernist]

Is an IX harness suitable or will it turn the ETA into a 4wd ?

HAHAHAHAHAHA

Does anyone have side by sides with b27 and b25 exhaust manifolds ?

No, but the exhaust ports on all M20 heads are the same. b25 has larger downpipes. b27 b20 and b23 have identical exhaust manifolds (same part numbers), b25 is the only M20 with a different part number.

Should I just mate a stock b25 to the ETA manifolds ?

My 2.7i runs very strong with the stock eta exhaust. I had the pinched section under the rear subframe replaced with a round section of pipe, otherwise it's stock. Silent at idle, quiet under 3k, muted but delicious BMW wail above that.

[jeffnhiscars]

Speaking of which :)

Is an IX harness suitable or will it turn the ETA into a 4wd ?

[SkiFree]

Because typically it's doofuses who don't have money for anything better (swap wise) and haven't driven a decently built M20.

Perhaps someone should start another "which swap" thread for us to all have a jolly time in and let this one remain being about rebuilding Jeff's M20?

[agent]

I always get a good chuckle at M52 kids (exception being Simon).

Why?

[SkiFree]

If youte gonna go through the trouble of pulling the engine, might as well go 24v. They are dirt cheap now.

howabout no. I always get a good chuckle at M52 kids (exception being Simon).