Things to improve for over 350Hp

[Gabriel30]

Hello everyone, I have an M20B25 with an 8.8:1 compression ratio. I want to build a turbo setup with a stock bottom end, but I’m aiming for a bit over 350 HP. I already have a GT35 China turbo from some time ago and a large intercooler (600 / 300 / 76).




My plan is to gather all the parts first and then start the project. The engine will be refreshed with new piston rings, and I will also install a waste-spark ignition system.




My question is: what really makes the difference when trying to make a bit more power, just over 350 horsepower? I’m thinking maybe doing something to the cylinder head? I’m also considering a slightly thicker MLS head gasket to reduce the compression a little more.




If you have any advice for me, I would really appreciate it. Thank you!

[Gabriel30]

Nobody ??

[hasa]

You need a standalone engine management like Maxxecu or similar. Then +400cc / 40lb injectors. Sachs 618 clutch. Good tune on a dyno. Then you have 350hp.

[Gabriel30]

What head gasket should I use?? Thank you !

[hasa]

I would try normal head gasket. You don't need more than 1bar / 14psi boost. If it fails, then add cut rings and still use std gasket.

[Gabriel30]

Do you know where I can find those rings? I’ve looked but nothing.

[hasa]

Look this article about "Fire rings": https://5150autosport.com/blogs/prod...26gFFf5HBXDyrh

Tool for machining the rings is Isky Groov-o-Matic for example (this is what I've used). They probably supply also the wire that is used to make the ring.

[It's Soda Not Pop]

Also not sure of how much you have read through this forum. But there is a lot of knowledge that has already been posted on here. Do a little digging and you'll find your answers.

[varg]

Nobody jumped in quickly because in 2026, such basic questions are unnecessary after doing basic research. There have likely been dozens of pretty good turbo M20 build threads at this point. Easy mode, you could pick a build thread where someone did what you want and just copy it. There's no need to reduce compression, you'll just kill your responsiveness, there's no need to use an MLS gasket, there is questionable value in having head work done because it's expensive. If your chinese GT35 is a journal bearing knockoff of a 30 year old design you'd be better off with a decent properly sized ball bearing turbo than buying a well ported head and using a cheap turbo. You'd feel better gains out of a quick spooling and not oversized modern turbo than the best head work money can buy with a chinese GT35 knockoff.

[Gabriel30]

I did research, but there are so many opinions out there, and a lot of builds went one direction and then ended up having issues with head gaskets or later switched to a more powerful setup. That’s why I made a post — to find out, now in 2026, what the most proven build for an M20 would be and to try to avoid other people’s mistakes.




I’ve read dozens of pages, and even though at first I was focused on a specific setup, the more I kept reading, the more unsure I became. I’m sorry — I know this question is somewhat basic, but I was just looking for some proven and constructive ideas.