Compression increase M119.974 10:1 -> 11:0

[jnes]

Hi,

Tried to search but didn't find any clear answer.. so if I want to increase compression from stock 10:1 to 11:1 how do you guys recommend to do it? Only by milling off material from heads?
If done so would that affect to alignment of intake and exhaust manifolds etc.? I bet that here are people who have done that job before.

I have understand that avoiding that risk would be combination by milling and thinner head gasket.(MLS) But to my understanding aftermarket head gaskets are not available on various thicknesses, and even if they are how they would last?

Is the M119 50 AMG (M119.98X) head gaskets same as in (M119.974)

Or is that even an issue?

Any thoughts?

Thanks!

 

[gsxr]

Factory M119's with 11:1 compression ratio use different pistons. 10:1 are flat-top, 11:1 are domed / extend above the block deck surface.

Head gaskets are different between closed-deck and open-deck engines, see the engine number breaks in the EPC. The E50 AMG uses the same head gaskets as late 119.97x with open-deck blocks.

Anyway. There's not much to be gained with an increase in compression ratio. All other things being equal there's maybe a 3% increase in power (~10hp, maybe, on a 5.0L M119). Generally not worth the cost or hassle. And, there's also a minor concern about knock / ignition retard as well with LH-SFI as the 5.0L EZL was not calibrated for 11:1 compression ratio.

 

[jnes]

Thanks GSXR for very detailed answer. I agree, it makes no sense to just increase compression. I was just thinking if I will do the headwork (CNC ported heads etc.) with regrind camshafts if it then make sense to do also this compression increase.

GSXR, do you think that you can't run with high octane fuel (RON 98) without adjusting the LH? Of course ecu needs or should be adjusted if doing performance upgrades in order to get max gains and that LH-SFI would be very tricky to adjust..

Are the pistons interchangeable between .974 and .980 engines?

If I understood correct the thickness of the head gaskets in .974 & .980 models are pretty much same and pistons do the difference?

 

[gsxr]

If you have higher octane fuel available, that should eliminate the knock concerns. No adjustment needed of any kind for LH or EZL. Here in the colonies, only 91 octane (R+M/2) petrol is available... some lucky locations can get 93, but most of the USA is limited to 91.

Good question about pistons. I think they should be interchangeable, with the appropriate rods/wristpins?

And yes, the primary difference is the pistons. The stock thickness head gaskets will not have a significant effect on the compression ratio. With camshaft regrinds, make sure there is still adequate clearance to the pistons with the increased valve lift.

 

[gsxr]

BTW - here is a photo of an 11:1 ratio piston on a 5.0L M119:

 

[jnes]

My plan was to do dBilas setup with regrinds.

 

[Markus-MD]

The Pistons are interchangeble.But i know not more exact the weight are the same.This ist important for Balance in the Crajnk
Tomorrow my wife is not here. I can took her scale and take a measurment

 

[Markus-MD]

The Batterie of the scale was the Prob .Now i have the weight
1-M119 5.0 Mopf comp 11-1 672 gramm
2-Conrod to 1 800 gramm
3-M119 5,0 vor Mopf 10-1 712gramm
4-Conrod to 3 802 gramm
5-M119.975 4,2 11-1 664 gramm this only as an example

Look the differenc both conrods 2Gramms .they are stock and equal

That was i am thinking ,you can not change easy the Pistons.Merc was change the Counterwights of the Crank to from 10 to 11.