S54 Stock Headers on M20?

[AWDBOB]

I've always wondered if these could be welded to an m20 exhaust flange. 1.5" primaries, cylinder distance is the same. Would be a great header option if they could be made to fit easily/done in a batch.

M20 exhaust port ramp is more upward facing, s54 has a flatter exit.

Won't fit at all with b25 oil cooler setup. Would require a short filter b27 mount style or oil filter relocation.

Couldn't find any info on it so I wanted to take a few photos while I had a set on hand.

Engine block tab hit the front most head flange so I couldn't get the front flat. This orientation was the closest fit.

Untitled by bimmertown, on Flickr

Untitled by bimmertown, on Flickr
Untitled by bimmertown, on Flickr

[AWDBOB]

Flipped the oil filter housing, cut the flanges off that were hitting the block, and this is looking quite feasible. Flipped oil filter likely isn't serviceable in the current position but retains A/C. With it flipped down and forward it would take the place of the a/c bracket but become serviceable.

Front header hits the engine mount arm but would clear if it was cut back before the pipe expands for the cat. I know some efficiency is lost this way but not make or break.

#5 runner hits the block coolant drain, but making 3d printed stainless adapters like hoveringuy did with the s54 to n52 headers would allow me to design them so they clear everything.

Untitled by bimmertown, on Flickr
Untitled by bimmertown, on Flickr
Untitled by bimmertown, on Flickr

[2mAn]

Amazing & Interesting!

I love that ~40 years later there are still innovations being made on the M20.

[moatilliatta]

What about a euro aluminum arm?

[digger]

This is an interesting project.

[AWDBOB]

What about a euro aluminum arm?

Alloy mount arms definitely look slimmer- would be ideal to keep the expansion there for venturi if possible

I also don't think it'd be a huge deal to modify that mount arm if they fit okay otherwise.

This is an interesting project.

I definitely didn't expect the exhaust ports to be spaced the same- I'll be able to see how they fit in a car in a few weeks.

I have 3 sets- if it looks promising in car I'll have a fabricator do all of them.

What are your thoughts about where to merge them? Worth trying to keep the venturi off the collector?

[digger]

Alloy mount arms definitely look slimmer- would be ideal to keep the expansion there for venturi if possible

I also don't think it'd be a huge deal to modify that mount arm if they fit okay otherwise.



I definitely didn't expect the exhaust ports to be spaced the same- I'll be able to see how they fit in a car in a few weeks.

I have 3 sets- if it looks promising in car I'll have a fabricator do all of them.

What are your thoughts about where to merge them? Worth trying to keep the venturi off the collector?

all of the 6 cylinder use the same 91mm bore spacing sans M30/S38 and related "big sizes" so i would expect any of the headers would align once you fixed the bolt pattern issue as i dont think any of them have the odd port spacing that you see on domestic stuff like SBC etc

Do you mean where to merge the 2 collector pipes into a X, Y or H? These have short primaries so IMO you will want long collector pipes as that gives best overall powerband for a street engine

The venturi/choke is only there because it is a natural result by-product of it being a catted header. The non catted euro headers don't have a venturi so i wouldn't bother with a choke unless you are going to test various sizes

[AWDBOB]

all of the 6 cylinder use the same 91mm bore spacing sans M30/S38 and related "big sizes" so i would expect any of the headers would align once you fixed the bolt pattern issue as i dont think any of them have the odd port spacing that you see on domestic stuff like SBC etc

Do you mean where to merge the 2 collector pipes into a X, Y or H? These have short primaries so IMO you will want long collector pipes as that gives best overall powerband for a street engine

The non catted euro headers don't have a venturi so i wouldn't bother with a choke unless you are going to test various sizes

I knew the bore spacing was the same but was surprised the port spacing was the same with how much different the s54 head is- a pleasant surprise.

Re: x pipe, thank you. I was planning to go with the stock s54 merge so it sounds like that'll work well.

Re: venturi, perfect, I'll just cut the cat expansion off and make fitment easier.

As always, thanks a bunch for the great info.