having second thoughts on using a S52 crank in my M52

[2mAn]

Im in the process of building up a M52 motor with S52 cams and a S52 crank. Its a daily driven street car. We have 92 octane fuel up here, but Im worried it still may be too much for a street car. Tried searching but not finding what I am looking for.

Any thoughts?

Not sure if it matters, but its an alloy block also

[knuklehead92]

if anything you'll want more power...

if you want power buy a s52? it will be worth it in the long run.

[luckysnafu]

How much power is too much power? I have an M52 with S52 cams and a tune in my e30 and it's plenty of power for a daily driver (200 rwhp dyno before the tune). I can light up the tires in 1st and 2nd gear easily if I want. I don't daily mine but could if I put the interior back together.

If you already have the M52 alloy block I would just build that and enjoy. My M52 is the standard iron block. Yours will give you better weight distribution. Hope this is helpful.

[wazzu70]

The alloy block will have a hard time containing the horrible "harmonics" of the S52 crank. Just look at the M54b30. For a street car you are probably OK if you keep the rev limit below 7k. If you use the S52 crank, plan on getting an ATI damper.

Personally I would stick with the M52 crank to reduce issues with crank "harmonics" and block stiffness.

Why would the fuel octane have anything to do with S52 crank and cams? Are you planning on raising the compression to 12:1 or something?

[2mAn]

Thanks for the responses guys. Im not trying to build the fastest car out there, just a fun daily. The reference to the Octane is because the S52 crank would raise compression pretty high (over 11:1 from what Ive read) and combine that with a low grade fuel and you have a recipe for pinging. I think Im going to stick with the M52 crank. I never knew that the harmonics of the S52 crank were bad.

[ZekeTheSneak]

If you have the crank and want to sell it lmk

[wazzu70]

Thanks for the responses guys. Im not trying to build the fastest car out there, just a fun daily. The reference to the Octane is because the S52 crank would raise compression pretty high (over 11:1 from what Ive read) and combine that with a low grade fuel and you have a recipe for pinging. I think Im going to stick with the M52 crank. I never knew that the harmonics of the S52 crank were bad.

Gotcha. I didnt think you would reuse the factory M52 pistons.

The S52 crank is pretty bad, which is why that bottom end never made it into a "race" engine. For street use its ok, but constant use in the upper RPM range is bad news. This is why most of the M5x engines have oil pump issues.

The M52 engine is a very good engine for street use. Use that engine with the S52 cams and it will be a nice engine!

[2mAn]

Im convinced! Love the square setup (84mm Bore & 84mm Stroke). Im convinced, thanks everyone