~400HP M52 Turbo Build - Plenty of questions

[JRHemmen]

I'm diving into the world of FI for the first time with the M52 I just bought last week. My goal is ~400HP on pump gas, OBDI. I want this engine to be reliable (i.e. won't need anything other than routine maintenance for years to come). The engine has 155,xxx miles on it. I've been doing a ton of research but I still have some questions before I start throwing money into this build.


Is it worth buying forged pistons and rods for this HP goal?

What's the general consensus on the copper HG spacers offered by CES? That should get me to a 9:1 CR on stock internals.
How necessary is it to pull the crank, polish, and replace bearings at this mileage?

Do I need to deck the block/head to properly seat an Athena cutring head gasket?

Is there any benefit to replacing the valve springs if I switch to S52 cams?

Am I going to immediately destroy a Getrag 260 with HP/Torque numbers in the 400 range? I'm not going to be launching the car all the time but I do want to drift it.


My current plan is to do the following:

Seals
Gaskets
Timing/Vanos/Oil Pump chains
3 angle valve job
New hoses/water pump/thermostat
S52 Cams
M50 Intake Manifold
Single Scroll Turbo (unknown size for now)
Possibly new crank/rod bearings (if necessary)
Athena Cutring head gasket
ARP head studs
GoodNTight topmount turbo manifold

Is there anything else that I should be replacing while I'm in there? I haven't had any chance to look at the engine since I bought it, as I put it in my warehouse 3 hours south of where I live currently. I'll be able to get more info and take pics this weekend.

[SGT StudMuffiin]

I'm diving into the world of FI for the first time with the M52 I just bought last week. My goal is ~400HP on pump gas, OBDI. I want this engine to be reliable (i.e. won't need anything other than routine maintenance for years to come). The engine has 155,xxx miles on it. I've been doing a ton of research but I still have some questions before I start throwing money into this build. Is it worth buying forged pistons and rods for this HP goal? What's the general consensus on the copper HG spacers offered by CES? That should get me to a 9:1 CR on stock internals. How necessary is it to pull the crank, polish, and replace bearings at this mileage? Do I need to deck the block/head to properly seat an Athena cutring head gasket? Is there any benefit to replacing the valve springs if I switch to S52 cams? Am I going to immediately destroy a Getrag 260 with HP/Torque numbers in the 400 range? I'm not going to be launching the car all the time but I do want to drift it. My current plan is to do the following: Seals Gaskets Timing/Vanos/Oil Pump chains 3 angle valve job New hoses/water pump/thermostat S52 Cams M50 Intake Manifold Single Scroll Turbo (unknown size for now) Possibly new crank/rod bearings (if necessary) Athena Cutring head gasket ARP head studs GoodNTight topmount turbo manifold Is there anything else that I should be replacing while I'm in there? I haven't had any chance to look at the engine since I bought it, as I put it in my warehouse 3 hours south of where I live currently. I'll be able to get more info and take pics this weekend.

Stock internals are fine for 400whp. CES HG combo is a good idea. I’d personally do the bottom end bearings at that kind of mileage. I only skimmed the head when doing the HG with no sealing issues. Stiffer valve springs are a good idea for a more aggressive cam. Realistically you should just get some new springs at that mileage. 400whp has been no issue for my 260 with lots of abuse. Sent from my iPhone using Tapatalk

[JRHemmen]

Stock internals are fine for 400whp. CES HG combo is a good idea. I�d personally do the bottom end bearings at that kind of mileage. I only skimmed the head when doing the HG with no sealing issues. Stiffer valve springs are a good idea for a more aggressive cam. Realistically you should just get some new springs at that mileage. 400whp has been no issue for my 260 with lots of abuse. Sent from my iPhone using Tapatalk

Thanks for the good info. If the general consensus seems to be that stock pistons and rods are fine, I'll leave them. Should I replace the pins or anything? I assume the rings should be replaced at the very least with a hone. Sent from my OnePlus 7 Pro using Tapatalk

[SGT StudMuffiin]

Thanks for the good info. If the general consensus seems to be that stock pistons and rods are fine, I'll leave them. Should I replace the pins or anything? I assume the rings should be replaced at the very least with a hone. Sent from my OnePlus 7 Pro using Tapatalk

I mean there are guys who turbo junkyard M20s with more miles that hold up, but if you’re willing to do it, rings are also a good idea. They’re old and they’ll be seeing fairly high cylinder pressures. Sent from my iPhone using Tapatalk