S38B36 & S38B38 differences...

tomson · 13th April 2010, 20:15

Hi,

I have done some checking on realoem and can see the two engines have different cylinder heads from the part numbers but is there a visual check I can do ? The engine is built up so I cant measure the intake valves either!

Thanks !

tomson · 13th April 2010, 21:00

Another one then, will the B38 head work with the B36 bottom end?

tomson · 14th April 2010, 11:15

Quote:

Originally Posted by tomson

Another one then, will the B38 head work with the B36 bottom end?

I'm starting to think this is what I've done, with a 3.6 head gasket.

Does anyone know if the combustion chambers are different sizes ?

Lantz · 14th April 2010, 14:36

I am pretty sure that a 3.6 bottom end can work with a 3.8 head as this is often the setup used when the S38 is tuned. The 3.6 bottom end is regarded as more durable as it has less stroke than the 3.8, and therefore the bearings tend to last longer.

I am not an engineer and could very well be wrong though, so i'll let others chime in.

Lantz

tomson · 14th April 2010, 16:25

Thanks Lantz.

The engine has timed up fine and spins over without any interferance by hand ok.
What I'm worried about is if the compression ratio will be dropped by what I've done?

I dont even know this for sure but its looking like thats what has happened...

When I bought my M5 the engine was out and stripped and there was a spare engine with it which the previous owner told me he bought for the head and this head he fitted to the cars engine. I removed it to inspect everything and refitted the same head after cleaning everything up. I have looked at the leftover bottom end more closely yesterday to find the pistons are marked S38B38

The last of the parts I need to try and start her arrived from BMW yesterday so I'm hoping to get her running on Saturday, until this which is worrying me now ...

GoneAgain · 14th April 2010, 16:28

Aren't the blocks stamped with the displacement?

tomson · 14th April 2010, 22:37

Quote:

Originally Posted by GoneAgain

Aren't the blocks stamped with the displacement?

Yes, I can see there are markings on the block, now, its the head I need to identify...

MM-5 · 15th April 2010, 13:49

Hi

Check the intake port diameter, if throttle bodies are not mounted. S38B36 diameter is 28 mm and S38B38 has 29,2 mm diameter intake ports. You can also see the difference from the exhaust side front end covers (cam gear covers). In 3.6 there is cover for distributor and in 3.8 there is camshaft trigger cover/sensor.

I hope this helped You

.

Best Regards, Janne.

tomson · 18th April 2010, 22:51

Hi Janne, the intake post sizes is most helpful, i'll be measuring them this week, thanks very much !

The cam trays are the same on 3.6 & 3.8 but as you say the 3.6 has a distributor and the 3.8 a sensor but these mount in the same way to the cam tray so it doesnt give me 100% confirmation, the intake port sizes do though . . . .

Thanks again