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First 550 to 63amg conversion in USA (M278 to M157)
Hey y'all, thought I would share my build. It is a 2013 GL550 with 110,000 miles that developed a misfire on #1. After a relative compression test with an oscilloscope it was time to pull the engine. Pulled from the top, no bumper pull, no lift.
so upon tear down we see the ring seizure and oval piston.
so I decided to go with the Darton MID sleeves to close the deck and get better cooling with a wet sleeve. They only make it in the 98mm for M157. After research the M157 is almost identical to M278 with the exception of the bore and stroke, rods and pistons and head gaskets. A few of the pistons have oval shape so instead of the crappy stock rods I'm doing Italian rods and pistons with ARP bolts that are 10% stronger than 300M rods and 2618 double bridge forged pistons.
I'm working with Gulf Performance in UAE for the rods and pistons as they have done a ton of these 63amg rebuilds. This will be the first conversion of a 4.6 to 5.5 liter. If you want you can follow the build on my IG account rolleymotorsports.
Are you using the M157 crank? If you don't increase your stroke and run the same piston as the M157, it will yield less than 5.2L. You would either need to run a 100 MM piston with same stroke or increase your stroke and run the 98 MM pistons in the M157. Why not go with a used M157 and just drop it in?
The 63's tranny is also different. Will you rebuild your 7 speed to make it stronger like the MCT in the AMG?
A 105MM piston and your stock crank will yield around 6L. If you go with a 105mm piston and use the M157 crank, you would have a true 6.3L engine. Keep in mind, make sure there are existing rings that will fit. Custom rings are very expensive.
Going with the sleeves, really opens up a new world for piston sizes. I would go with a JE or Weisco piston. You can send them your stock piston so they can properly cut and size everything. Wonder what the max piston size you can use? In the end, the sleeved engine, if done correctly, will be stronger and able to handle more boost than the stock M157. Should be fun if everything is done correctly and it sounds like you are doing it right.
Are you using the M157 crank? If you don't increase your stroke and run the same piston as the M157, it will yield less than 5.2L. You would either need to run a 100 MM piston with same stroke or increase your stroke and run the 98 MM pistons in the M157. Why not go with a used M157 and just drop it in?
The 63's tranny is also different. Will you rebuild your 7 speed to make it stronger like the MCT in the AMG?
A 105MM piston and your stock crank will yield around 6L. If you go with a 105mm piston and use the M157 crank, you would have a true 6.3L engine. Keep in mind, make sure there are existing rings that will fit. Custom rings are very expensive.
Going with the sleeves, really opens up a new world for piston sizes. I would go with a JE or Weisco piston. You can send them your stock piston so they can properly cut and size everything. Wonder what the max piston size you can use? In the end, the sleeved engine, if done correctly, will be stronger and able to handle more boost than the stock M157. Should be fun if everything is done correctly and it sounds like you are doing it right.
157 crank, 157 bore and stroke. JE or Weisco I would have wait as they don't have them in their catalog. I would rather go with something that has been installed dozens of times by Gulf Performance.
So, Joel. How did it all work out? I'm in the same boat with bad compression on my #5 cylinder and the borescope reveals badly scored cylinder walls. Probably have an oval piston now too. Also, would you happen to have discovered during your research where to pick up a nice used block? My vehicle is running great with no codes/CEL yet, so I'm thinking about keeping the vehicle in operation while I build the longblock portion of the M157. If you completed it all, did you have it tuned or get a custom tune by RennTech or a similar tuner?
So, Joel. How did it all work out? I'm in the same boat with bad compression on my #5 cylinder and the borescope reveals badly scored cylinder walls. Probably have an oval piston now too. Also, would you happen to have discovered during your research where to pick up a nice used block? My vehicle is running great with no codes/CEL yet, so I'm thinking about keeping the vehicle in operation while I build the longblock portion of the M157. If you completed it all, did you have it tuned or get a custom tune by RennTech or a similar tuner?
I was wondering how ECU going to handle it. Are you going to have custom tune?
Yeah old topic I know but I had to reply this. I'm runnig drop-in-M157 in my '14 E500 Coupe with original 278-loom and ecu. No dtc no nothing, all works.
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