Extreme Engine Tech: Building a BMW S52 - Part 2: The Cylinder Head

by Nick Betz

If the engine as a whole is the heart of a car the cylinder head would be all the supporting parts that make the heart pump. Without the opening and closing of certain valves the heart wouldn't be able to get blood to flow into the atriums and out the ventricles. Just like the heart, a cylinder head has multiple valves, that need to open and close at specific times, to get air in to, and exhaust out of, the combustion chambers to keep the engine pumping.  

In order to keep Project E36 323is’ high compression bottom end from cardiac arrest we need to make sure the cylinder head matched the needs of the bottom end. If you remember from part 1 of our S52 build the only cylinder head parts we had from our original purchase of a used S52 were the cams and cam trays, due to a crack in the original S52 head we returned it with the valvetrain to the original owner, this quite literally left a few holes to plug. With the help of Supertech, Pelican Parts and Pure Performance we’ve managed to build a head with a lightweight valvetrain while maintaining OEM reliability. 

The first step into building our head was to plug the holes, specifically the 24 holes left vacant from the lack of valves, for this we turned to Supertech.


For the exhaust side of things we went with Supertech Inconel valves. Supertech exhaust valves are made of heat resisting one piece inconel forgings.  Many valves use two piece spin welded construction.  Two piece valves tend to loose their heads under pressure so a once piece valve is the only way to go for a performance application. 
The benefit of Inconel exhaust valves is their resistance to high temperatures. Inconel is an aerospace alloy developed specifically for operation in extreme high temperatures and pressures.  Inconel is an alloy primarily composed of nickel and chromium.  The exhaust valves are not cooled by the intake charge on every cycle like the intake valves are. High performance engines run hotter on the exhaust side as well so inconel is the wise choice for materials here.
For the best heat transfer and strength at high temperatures the exhaust valve stem is only minimally reduced near the valve head. The valve heads have a tulip shape for best exhaust flow. 
For our intake side we chose Supertech standard Black Nitride valves. The intake valves are made from stainless steel.  Like the exhaust valves, the intake valves are made from one piece forgings.  it is common for valves to have the shafts spin welded to the heads which is inherently weak. Forging ensures proper grain flow and a homogenous super strong valve.
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Dusty Duster
Dusty Dusterlink
Tuesday, June 16, 2015 5:03 AM
Sound. I need video with sound of this thing running!
Tuesday, June 16, 2015 7:21 PM
Did you guys stroke the bottom end? I forget.

Also.... do the Euro S52 ITBs work on this? Or are you guys gonna run an M50 IM?

Nice build. I do wish you went aggressive on the cams and got solid lifters though.
Nick B
Nick Blink
Wednesday, June 17, 2015 7:27 AM
@CTK - you could say we stroked and bored the original 2.5 out to 3.2 but it's just a stock S52 crank in a bored 2.5L block.

The euro S50B32 (not S52) ITB's won't fit on the US head, we wish they did though! We will be running the M50 IM but that will be discussed in the article after the cooling upgrades.

We're still debating solid lifter/cam vs hydraulic upgrade. We'll end up doing one or the other later down the road.
Thursday, June 18, 2015 12:13 AM
Which valve stem seals did you use? Supertech or Corteco or Goetze or BMW?

I believe the Supertech valve stem seals are viton on the exhaust side only.
Thursday, June 18, 2015 8:22 AM
If I had money I'd love to do a full build of my S52 but at 115k I'm hoping to not open it up for a while.

The S52 is such a great engine. The mid-range torque really makes the car fun to drive. I got to drive mine back to back with a stock S2000 which has the same quoted factory BHP. It is fun to truly notice the difference in the torque curves. The BMW pulls from 2000 while the Honda doesn't really start to move until 6k where the BMW is pretty much at redline.
Thursday, June 18, 2015 5:34 PM
Agree, I had my 98 M3 since brand new. It has 230k miles on it. I have 2 cylinders w/ >15% leakage on leakdown test. So I am going to rebuild soon.

I changed the exhaust, got rid of the restrictive factory cats and put HJS Hi-Flow 200 cell cats, went from 2 in pipes to 2.25, a merge pipe, CAI, but stock headers. That alone inc the acceleration and power, (or unrestricted it). I am using Lucas Synthetic Oil Stabilizer, which definitely cuts down on the oil burning (otherwise can easily go through a quart in less than 200 miles,) and it definitely inc the compression,

See my exhaust pics:
(I replaced the ITG filter w/ AEM oilless)

For my rebuild I plan: CP pistons and rings, Calico Bearings, OE BMW gaskets, valves - Supertech inconel or just replace the bad ones w/ CRP valves which are made in Germany and a bargain at $10 for intake and $15 for exhaust at FCP Euro) or just keep the original valves and springs? - That is the dilemma.
Supertech valve stem seals or BMW ones - I read somewhere that Supertech can cause leakage since the exhaust ones are Viton and can't expand and contract like the OEM Rubber.
Yes new timing chains, tensioners, (lower tensioner - replace the whole thing or just the spring), Stewart water pump, Evans waterless coolant, etc.

Nick B
Nick Blink
Friday, June 19, 2015 4:16 PM
@buzzboy - with only 115K on the clock your S52 has PLENTY of life in it if you've been maintaining it properly. You should easily see another 100-150K with no problems. The M52 that was in this car had 190K on the clock when we pulled it and it ran like a clock, just didn't have any power.

@hjsna - the next article will cover all the cooling stuff you talked about, stay tuned.
Sunday, October 04, 2015 8:23 AM
When will part 3 be out? Looking forward to it since I own the same and have 235K on my S52 that is still running great but consuming 1 quart every 700 miles. I've already replaced the entire CCV system and the oil filter housing gaskets and there are zero external leaks or oil wetting anywhere.
Nick B
Nick Blink
Monday, October 05, 2015 11:51 AM
@97M3 - Part 3 should be out by month end. It's going to cover the cooling upgrades just FYI. Part 4 will be install/clutch/tune and dyno numbers.
Friday, February 12, 2016 10:09 AM
Dudes, where are the other parts?? I own an 323i much like the one on this Project and im just dying to see de rest of this article.
Sunday, February 28, 2016 9:09 AM
What ever happened to this series? Did it ever get done and is the write up coming any time soon? Last reply I was sent said the next installment was going to post months ago. Trying to decide what to do with my S52 and want to see how this one came out to pull ideas from.
Sunday, February 28, 2016 10:01 AM
Hi I sent my 98 M3 S52 engine to RL Engines in Dover, NH.
Just got it back and waiting on my tech to install. Mine has 230k miles. I went with CP pistons 11.5 compression vs stock 10.5. I got regular Ferrea 6mm valves. Also Glyco bearings that are calico coated. I got stock BMW parts including gaskets, valve stem seals, etc. The labor alone came to about $4500, thats with them building me a crate and priming the engine w/ 7qts of Gibbs break in oil.
I did go a little overboard, they told me my oil pump still looked new and so did the lifters and 3 chains, but I decided to replace them.
Sunday, February 28, 2016 10:04 AM
Sunday, April 10, 2016 3:59 PM
Still anxiously waiting for the next installment. Any updates as to when that might be?
Anonymous User
Anonymous Userlink
Wednesday, September 07, 2016 11:23 PM
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