quick question for the folks out here. I have an evo IX with cosworth cams and recently purchased the cosworth springs to go along with them (not the titanium set). I was told that I can rev to 10k with just these parts, however, being cautious, I'd like to get a few opinions around this. What are your thoughts on where you can safely rev to with cams & springs?

This would be on stock valves & retainers.

 

sure you can rev to 10k on those springs and cams, however, i dont think your rod bolts will be able to take the abuse...

the safe rev limit would be 8k without having to change your rod bolts.

 

Rods and rod bolts won't take much abuse. Its usually the boost in the upper rpms that cause the problem. Compressive load is very high on the big end of the rod when VE is high as speed increases. The head will not flow ANYTHING past 8000 rpm. So just stick to about 7200 rpm tops. Stay within the power band.

 

Thanks for posts!

 

8k max---you wont make power unless you have a big turbo.

 

How can 8000rpms be the limit when evo's redline at 7800 rpm's. Im sure the rod bolts could handle more than 8000rpm's.

 

With my mods, which include dual valve springs and ti retainers and the rest of the Jackson Auto Machine stage I, on a IX with cossies I was told by JAM that 8000 was a good redline. I'm sure it can go higher but like someone else said I don't think the head and stock turbo will flow very well beyond that. Therefore there is no point in putting the extra stress of going beyond that on a regular basis.

 

Try it and let us know

 

They are completely correct. Again why shift out of your powerband? Have the car dyno'd and see where torque and HP fall off conciderably. You should shift 100 RPM before that point.

 

from all the mystery "spun rod bearing" threads i have read, that mostly occur on the #1 rod juornal, ~95% reported spinning their engines in excess of 8500 revs.

However, i am certain there are many people spinnig their stock bottom end evo's past 8,500 revs without issue too.

the oem bolts are skinny, so my guess is the big end moves around a bit @ high revs = becoming oval @ times, wiping the oil film off the bearing resulting in a scuff, then the bearing just eats itself from there.

the oem rods can take the power, but cannot take revs.

i havent heard / read any "spun bearings" while running arp replacement bolts, but then again, not everyone post's their problems either.

i dont know what revs the oem piston can handle either.

 

Stress and heat are the biggest problems. ARP Bolts or stock they will still develop the same amount of stress and heat. The DIFFERENCE is that the upgraded hardware is able to deal with the two factors a bit better.

 

Redline is 7000rpms and the revlimiter kicks in at 7606 i believe. So an extra 1000rpms is pretty decent of a stretch and some press their luck and go a little past that. Most people have the limiter set at 7800rpms to be safe.

 

What turbo are you using, any dyno sheet? Kind of an important factor

 

Why do people get so obsess with high rev? The higher you rev, the more abuse you dish out on your poor engine. At 10,000 rpm, you are swinging about 10 tons of weight on those poor rods. So rev away!!

 

r u running a 40R or 42R that u need to rev that high?