Alright - I'm a turbo guy, but I figured this questin would be best answered in the all motor forum... so here goes.

I'm in the market to buy a set of turbo cams, and the full-race ones are looking great both price wise and performance wise. However, they STRONGLY reccomend a seat pressure of 100lbs+... but they were also revving to roughly 10,500 rpm before anything failed in their tests.

I have supertech valvesprings with a seat pressure of 70lbs and only plan to rev to 9000, 9500 max (mostly for gearing ... but the added performance won't be bad either.)

So here's the question - Is such a high seat pressure really needed if I don't plan on revving that high?

Isn't the high seat pressure used mainly to close the valves at higher rpm?

Now I know going against a companies recommendation is usually a bad idea... but i'm just curious as to whether or not this would work or not.

Also - If using a larger cam such as Crower 3 or similar, is it possible to adjust the cam gears as to get rid of any overlap, which in turn benefits the turbo application to make power like a turbo cam would?

 

I'm sure Full Race reccommends that high seat preasure for a few different reasons, and it sounds like they are giving you a pretty large gray area as far as what they "reccommend" vs. "how far you can actually push them." Just to protect themselves, and understandably so, I think if one were to go out and test their 10.5k theory, I think they would be ok, but be REAL close to the point of binding and dropping a valve. But nobody wants to spend the $$ to just blow a motor up right? Hahaha. Honestly man, I've seen comparable(to yours) valvesprings pushed to 10k on the regular with the largest of n/a cams. (i.e. S2S3/S2 Pro1/2/3 BC4) Never once have I seen/heard of those valvesprings binding and dropping a valve, and some of those cams have upto 12.8 lift with 300+ duration. Obviously you having a turbo motor you won't want a cam that large, so I would say you're ok. Are you realisticly making power to 9.5? And yes, you can dial out the overlap of a camshaft assuming they aren't enormous. Just make sure you have accurate gears, GE and Toda are a good option...though I've heard of the GE stripping out. If you want an upgrade though just in case, the RM gen 1 springs would work AWESOME. I believe they are around a 90lbs. seat preasure.

 

I honestly can't say that i'll make power to 9500 ... or even 9000. I'm fairly confident that i can make power to 9000+ because i've still got plenty of turbo to go and it shows no sign of dropping in power till 8200. The only reason those numbers were given really is as a goal to make power to, and to show that i wasn't planning on revving that high, even if it were to make power to there... although the extended powerband would be nice... ... Either way - i'll talk to my tuner about it when i see him next and see what he says, and also talk to my friend who is buying my CTR/GSR cam combo and see if he wants valvesprings too ... then i'll just upgrade to the rocket motorsports gen1's ... jsut to be on the safe side ... thanks for the help and super quick response

 

Not a problem man, good luck with that bad bitch!


Oh, and let me know if you need help getting the RM springs.

 

Talk to Dan at DPR about seat pressures. He'll talk your ear off. One thing he told me was that especially with a turbo car you want higher seat pressures at zero lift so the valves do not open up slightly when boost is in the manifold pushing against them. He recommends aftermarket springs on a turbo motor even if you are using stock cams. To get higher seat pressures you can shim the spring. But then you have to watch the spring at full lift and make sure it doesn't coil bind. Its a back and forth gamble to try and get the right amount of pressure and not bind.

 

Thanks for the replies guys ... I decided to just stick with the valvetrain i have and use my gsr ex/ctr int. cam combo instead and bought an LSD instead of the full-race cams.

thanks again