You run yours at +2/0 right? Isn't it more dangerous to do this for cars not running alky or water?

 

Not with proper tuning and adequate knock protection.

 

i wanna bring this thread bad because it appears that the max lift on the jun and hks are the same at least on teh exhaust side so why do people insist on the valvetrain with the jun cams?

would advancing the 280 intake by 2 degrees make for a horrid idle? is there a way to offset this? say advance both or advance and seperate both by 2 degrees?

 

I had similar questions about the Jun 272 cams.

Here is a link that may provide some more information.

https://www.evolutionm.net/forums/sh...&highlight=Jun

 

The upgraded valvetrain isn't necessitated strictly by lift, but by the ramp rate.

 

Thats how these cams build the power earlier. That fast ramp rate equates to the valve opening faster and earlier as the piston is traveling in the cylinder to allow more air to enter. This is also the reason that an upgraded valve train is needed to cope with that fast ramp rate. If you didnt have the upgraded springs and retainers the cams would open the valve so fast that is would not keep up with the cam lobe. Same thing when closing the valve, the lobe would lead the valve going down because the spring pressure is not enough and would hit the seats very hard.

At least this is my understanding of it.

 

That's pretty close. Bascially, you want enough valve spring pressure such that the valvetrain action accurately follows the cam lobes timing. Without sufficient pressure, the valvetrain will be lagging bahind and bouncing around.

 

AKA; valve float at high rpm's=possibly having valve to piston clearance problems

 

Would there be any advantage to adding valve springs with the hks 272/272 cams?? I was looking to get the Crower springs and down the road a 50 trim turbo kit.

 

spragueevo - if you are planning on revving your motor higher than the limiters usually programmed by your typical reflash, then yes, you'll absolutely want to run springs. If you plan on a conservative redline, then it's not necessary, though doing a set of springs and ti retainers may reduce some weight vs stock

 

What is the down side of the reduced weight? I am planning towards a higher rev engine than stock.

 

No downsides I can think of, in fact, just the opposite. The lighter you can make a rotating assembly, the less force it takes it get it moving, and the less inertia it takes to keep it moving. I've never sat down to weigh the stock springs vs a performance single or dual setup - one of the engine builders (AMS, Buschur, etc) might be able to address that though. Not to mention the increased spring pressure and the stronger nature of the aftermarket ti retainers vs the stock ones (I don't think stock ones are titanium) is another benefit.

 

Maybe it was me but it seemed as though the weight was a bad thing from reading you post. My bad!! I do not know much about he internals of the engine and learning as I go. what is the major difference between the dual and single setup. Is it the spring pressure??

 

I personally did not have good results in terms of spool with the 280's. I tried a number of different cam settings including 2+ in, 0 ex with the same result of weaker spool. swapped in a 272 intake cam and my spool/low end was greatly improved. Right now, I am running cosworth m2's which make excellent tq and spool up. the high lift may be too much for the top end though, but my tq and hp numbers are still very similar.