spring pressure

[junior barns]

Originally Posted by Woodro Josey

Cam Profiles determine in most cases the spring pressure needed, along with the weight of the Valves, retainers and locks! Thats my story and i'm sticking to it. Merry Christmas!

So rpm is not a major factor????

[Alan Roehrich]

Originally Posted by junior barns

So rpm is not a major factor????

RPM is a factor of cam profile, which determines the RPM at which the engine makes HP and torque.

The question you're asking is extremely generalized, and the answers given are about as good and as complete as is possible.

Just to add a little. A lower RPM profile might be more radical, because there is something else limiting RPM, and it would therefore require as much spring pressure. In other words, if a given combination is RPM limited by something other than the cam profile, a more radical cam profile might be used to make more power at that lower RPM.

Clear as mud? It's hard to explain in a post on an Internet bulletin board, as there are time and space restrictions, and a proper dissertation/explanation would take up far too much of both. It is a very complex subject.

[junior barns]

Thanks all.

Bottom line then is a radical cam needs A LOT of spring pressure regardless of rpm range???

[Ian Hill]

i have been adding shims along the way this year and the motor has liked it each time i did it. F/CM 350 ci 330 hp. shift at 6500 and cross at 7200. i haven't heard the coils binding yet, so i am going to add another shim under the exhaust side for the next race and see what happens :-) i love this sport!


i look forward to the day i cross the line and the car shuts off and the parachute deploys automatically....in my stocker! LOL

Ian

[junior barns]

Originally Posted by Ian Hill

i have been adding shims along the way this year and the motor has liked it each time i did it. F/CM 350 ci 330 hp. shift at 6500 and cross at 7200. i haven't heard the coils binding yet, so i am going to add another shim under the exhaust side for the next race and see what happens :-) i love this sport!


i look forward to the day i cross the line and the car shuts off and the parachute deploys automatically....in my stocker! LOL

Ian

So, what kind of pressure are you up to???

[Jeff Lee]

Originally Posted by Ian Hill

i have been adding shims along the way this year and the motor has liked it each time i did it. F/CM 350 ci 330 hp. shift at 6500 and cross at 7200. i haven't heard the coils binding yet, so i am going to add another shim under the exhaust side for the next race and see what happens :-) i love this sport!


i look forward to the day i cross the line and the car shuts off and the parachute deploys automatically....in my stocker! LOL

Ian

So what does coil bind SOUND like?

[Bub Whitaker]

Originally Posted by Jeff Lee

So what does coil bind SOUND like?

Dink, dink, dink, dink, ......

[Chad Rhodes]

Originally Posted by Jeff Lee

So what does coil bind SOUND like?

it sounds a lot like the head of a valve coming out the header collector.

[Ian Hill]

Ahh, you have gone too far too! My "valve through the exhaust" sounded like a death rattle at 1100 feet. Ended by splitting the piston in two, one half embedded in the block, half way up the bore, the other half scattered throughout the other 7 holes!

It was actually caused by coil bind, but I'd imagine similar results if it did happen.

I have been increasing valve pressure buy .01" shims and am up to .06" intake and .03" exhaust over recommended and each time I add shims the car picks up. The next race I go to I will be matching the ex with the intake. It is a largerjump than I've done so far, but I am guessing it will be good as I did the intake first and have been catching up with exhaust with good results. I've discussed this lots with my engine builder and we decided to go with the idea that more is better, to the point we wipe the cam shaft out. This will be season two coming up, the last cam had three seasons without fail. As far as telling you what my spring pressure is, I don't think it matters. My combo likes the springs stiff. Just like valve lash, my combo runs near to zero as I dare go... I set them cold and I set them tight. But that's for another thread I am sure.

What I will tell you is at what spring pressure I wipe the cam out...if it happens. I switched Joe Gibbs oil this past seaon, this is the first time I am not freshening my engine, everything, including the cam looks good. I figure I'll get to coil bind before hurting the cam.
Ian