M52 Exhaust manifolds on an M54

[Herbmiester 931]

So I looked at set of M54b30 exhaust manifolds and had to wonder at how constrictive these things appear. I then looked at some M52B28 manifolds and while they are no work of art like an M3 system they would appear to offer some flow potential compared to the M54B30 manifolds. So the question is; has anyones swapped them over and what were the results?

[Michael. 2313]

I suspect there wouldn't be much difference between the two. It appears they both have their design flaws.

For the hassle of changing them I wouldn't bother unless it was a guaranteed improvement.

[Herbmiester 931]

I have read that on a M52 the standard headers above flow very well compared to S50 headers up to about 6500 rpm. Now that's all my M54b30 revs to so they could be a good option.

[polley 916]

The M52 ones look much better, and would get rid of the cats but then you may run into O2 sensor issues. (would not be reading any difference between pre and post cat O2 sensors)

[Herbmiester 931]

I think there is a fix for that, the Yanks get around it when they fit headers to their E46's.

[Michael. 2313]

Only thing to consider is with the steel welded M52 ones, how did they do the port to main runner join?

From what I've seen the hole in the side of the main runner is smaller than the pipe diameter welded around it, causing an internal lip / pressure point.

[e30ftw 410]

The M52 headers are the used on the US M3 S52B32, so they must be good for something.

That said, buy my M3 headers now that you have some flanges to weld them to.

[Herbmiester 931]

To be fair if I was looking for ultimate power production I wouldn't have bought an M54, what I am interested in is has anyone done and what issues did you come up against.

[Herbmiester 931]

Having built Chev V8s for drag racing in the 80's and 90's I became aware of the adage how much horsepower can you afford. I also learned that on my LS1 that a set of tuned length headers only gave me 11 horsepower over the standard manifolds. Now having looked at both the above headers the M52 is definitely far less constricted and as It allows me to remove the cats as well I suspect there will be an advantage and I can do it for less than $100 (Parts) while a decent tuned length exhaust will set me back closer to $1000.

So while I am well aware of the principles involved in long equal length primaries I am on a budget and the E46 is just a stop gap until the M3/335i/911 choice is made. So the question remains has anyone done this?

[Herbmiester 931]

Those so called two valve clunkers I built made more power than any N/A bmw six and replacing the M50/52/54 with LS motors is popular in the US as the HP per Dollar equation is better than a modded m54. Unlike many emotive types I try not to to use worn cliches when looking at engines. Every engine has strengths and weaknesses and the Chevrolet V8 in its various guises has positives and negatives, with the two big positives being reliability and the ability to make big horsepower from a physically small package.

The principles that relate to exhausts are the same whether they come from a single exhaust valve or two. Thanks Ron but I am after discussion on what can be done not what you haven't done and don't like.

[Young Thrash Driver 1020]

I agree pointless argument- a quick look around shows nobody else has done it. Feel like dyno-ing the two and reporting back? The internet will make you famous

[thorburn 121]

I've got some m52 headers that I'd let go for some beers. Otherwise I might cut through them and check what the merge is really like

[Herbmiester 931]

Or I can look into the headers with a plumbers camera, I can swap beer money for headers?

[zero 1162]

I doubt you willl find any one who has done it because it is just pointless for the reasons outlined above.

It is simple science but feel free to go and bang your head against something,

Fitting decent headers (m3) to my 328 released another 12 kW and 10Nm of torque - making comparisons to poorly engineered 2 valve? pushrod ? clunkers from the 1950's ?? is hardly relevant. You should look at what you have and what you can do easily not rely on cliche's from the 1980's

Dude, I think you missed the point........

[wrs 120]

M52 headers are nothing special and nor is the US M3

Whilst they may flow more they are too short and too un-equal in length there is a reason many of us have swapped from the M52 exhaust manifold to the M3 Euro exhaust manifold is that its IS a LOT better. properly designed and accurately timed headers.

The difference between your two pictures, just a different type of ugly.

Yep, exactly. These are the M52 manifolds of my M50B30 conversion - were on the engine when I purchased it. I dumped these for M3 Euro headers.

They probably won't sell - unless someone with a M50 wants to change from the cast manifold.

Can't comment on the M52 vs M54 sorry. Also, I didn't try the M52 vs M3 Euro headers to see how much difference there was either.