Limitations of Super Coupe Internals

I understand the rpm limitations of the SC engine in stock trim. Peak torque at 2,000rpm and peak HP at 4,000 keeps most SC owners shifting below 5,000rpm. Even with major upgrades to the engine, the M90 seems to have efficiency limitations at high RPMs. I also understand that many of you fine gentlemen have made obscene power and torque below 5,500rpm.

However, if one wanted to make a street/strip car with high flowing heads (with appropriate valve train upgrades) and a cam designed to push the power band significantly farther to the right; maybe using a centrifugal, twin turbo, nitrous, etc. What maximum RPM would you estimate the stock Super Coupe rotating assembly (stock forged crank, forged rods, hypereutectic pistons) capable of winding up to before having to upgrade to scat rods, forged pistons in order to stave off disaster?

Any other considerations I should be aware of?

Thanks for the help,

Jay

my set-up withheld 18psi and 397hp/509tq to the rear wheels, stock spec rebuild with hyper pistons....that's probably getting close to pushing it. Going to nearly 6,000RPM too, but the power band fell of a little shorter than that due to the size of my turbo.

they were built to handle a good amount of torque, but if you want to run any sort of upgraded power adder, its good insurance to build the bottom end

Ive seen mid 400rwhp with a good tune. I think if you limit rpm and hav ea good tune youll be very safe at the mid 300rwhp range

The main limitation internal wise with the motor is the valve train, mainly springs. So a stock motor shouldn't really go much above 5200 or so.

I'm running upgraded springs with roller rockers and a good tune, and I can safely rev the motor up to around 6200, with the limit being the aggressiveness of the ramp rate of my cam.... ie short duration high lift. Thats with the stock rods and FACTORY pistons... I would not do this if I had those junky powerseal hyper's as I've seen first hand how junky those things really are.

BTW this is with an MPX setup. I've determined that the MPX with its high rpm efficiency can be run at 15% OD to the above rpm and still make power. Any more OD and my peak rpm drops off, almost with 5% OD taking away 500 rpm of usefulness. You can OD more if you want and rev high, but because the inlet plenum to the MPX is way too small, it starves for air and starts to really heat up which robs power.

If your not after strip/track performance too often and prowl the streets, you can run higher OD and keep the rpm down and still have a killer car that most cars can't touch off the line so to speak. But if your after endurance and high speed, then better performance is had with less OD and higher rpm.

Fraser

Any other input? Employing valve springs with 100-125lbs of seat pressure, guide plates, hardened push rods, etc., could the stock rotating assembly wind to 6,500? 7,000? to take advantage of a high peak HP application?

Thanks again for the help!

I am making 440+ rwhp @17psi with stock internals (rods and pistons) shifting at 6400. Some day with another spring swap and minishaft rockers 6800+ is achievable.

jet74 said:

Any other input? Employing valve springs with 100-125lbs of seat pressure, guide plates, hardened push rods, etc., could the stock rotating assembly wind to 6,500? 7,000? to take advantage of a high peak HP application?

Thanks again for the help!

Click to expand...

Your going to have to spend $1-2k on valvetrain parts ALONE to safely run those kind of rpms. If one was willing to spend that kind of dough, why chance it with a stock short block?

I think the stock bottom end is pretty stout if you can keep the detonation away. piston weight is a bit heavy for crazy rpms. I measured 669 grams for the piston and pin. 662 grams for a stock rod.

Here is a thread with a motor which broke one of the main bearing webs. Not specifically due to RPM, but definitely due to use.
http://www.sccoa.com/forums/showthread.php?t=120915

durability will not be there spinning the factory motor to 6000 plus rpms. Thats considering good valvetrain componants that will get you there.

Stick to under 6000 rpm's make sure you put new valvesprings and youll be good.

My opinion.

jet74 said:

Any other input? Employing valve springs with 100-125lbs of seat pressure, guide plates, hardened push rods, etc., could the stock rotating assembly wind to 6,500? 7,000? to take advantage of a high peak HP application?

Thanks again for the help!

Click to expand...

Those spring pressures are only good for 5800rpm max so you'd need to rethink that. But on the other hand, no SC engine (rotating assembly) has failed from RPM related causes.