RicocheT

I thought with the hyd lifters you can't run but so much spring pressure before you run into problems?

vette40th

Thats true, but people have experience with higher pressures, and havent had any problems with the Comp R's.

SStrokerAce

Depends on the lifers really.... stock ones can run into problems, aftermarket ones are a different story.

To Quote Billy Godbold of Comp Cams....

"We've seen a spring with 100 pounds at the seat and 300 pounds over the nose on an ovate beehive work better than something that's 180 on the seat and 400 over the nose..... buy reducing the springs own mass, it reduces its workload significantly and doesn't need to be as strong."

Food for thought.

Bret

vette40th

That goes along with a lighter valvetrain needs less spring pressures. So , instead of killing HP/TQ with heavy springs with lots of pressure, get titanium retainers, titanium valves, but keep high tensile strength in Rocker Studs, pushrods and rocker arms. Yes, Titanium isnt cheap, but neither is going fast. How fast do you want to go.
There is a new beehive, I think the last number is "20" that just came out, and I think with those, they are ideal for this guys cam. My 918's retainers are the same weight as Titanium retainers for the 978 springs. So, I have less spring pressure, not much really, but a light spring and retainers. I use a XE cam which is pretty aggresive on the ramps.

SStrokerAce

It's all the system really....

The weight is a big factor but lobe design is the other part of it.

The 26120's have more mass in the spring but 60lbs more rate and more seated pressure.

bret

JustNO

I couldn't understand.. People go with 987 springs for cc306 cam (230-244) 987 springs have 121# pressure.. But I asked specs of springs for 236-245 cam ,and you said it should be minimum 165# pressure.. Why is that?? Can any body explain this?

vette40th

It seems Bigger is Better here, bigger injectors, bigger springs, and bigger cams. Thats why. The manufacturers make recommendations based on there testing on engine dynos, and other machines to test durability etc. People here think it is necessary to overkill everything and put more, cause they feel better. The dyno's will show that a spring with too much pressure you will lose power, because it takes more power to squeeze them. Get the new Beehives that comp cams has, and you will do just fine, not the 918's but I believe the 920's. they are rated for a 600 -620 lift cam, easily, and will handle your rpm requirements as well as durability.
My 2 cents worth, and 20 years experince, not as much as some, but more than others.
http://www.compcams.com/information/...ID=-1373872784
http://www.compcams.com/Information/...%20Spring2.pdf

Mindgame

You sir, are comparing an apple to an orange. Your cam is a far cry from anything called a cc306. Seems we've missed something here so I'll say it again....
The spring rate necessary to control valvetrain is the product of many variables. Most importantly....

1) valvetrain mass
2) valvetrain acceleration/deceleration

Stronger springs will also require stronger valvetrain components...

1) stronger/stiffer pushrods
2) stiffer rocker arms
3) larger/stiffer rocker studs or a shaft mount rocker system
4) stronger billet camshaft for less torsion

Now, do you still believe a catalog recommendation takes all of these variables into account?

This is why a really top notch valvetrain is chosen to work as a system of components.

Your camshaft has similar duration to the cc306... but it has a great deal more acceleration because of the lift. Some .060 more than the cc306. We don't know all the specs but from the looks of it, this is a hydraulic cam with solid roller cam type acceleration. If you look at the Comp XR274R solid roller (12-770-8) it's a better cam for your comparison. It has advertised duration of 236/242 with 1.5 rocker lift of .564/.570 on a 110º lsa. The recommended spring is a 977-16 which has 155 lbs @1.85 height. Hey, it looks like the cc306, so why does it need 34 lbs more pressure?

So you don't want to run that much spring pressure. How do you get around the delima? Either go to a solid or spend the money on the right compliment of valvetrain components. If you run conventional round-wire springs, hefty sever duty SS valves and clunky aluminum rockers, you're going to need to have ~155-165 lbs after the springs take a set. You DO NOT want to start out with a marginal 140 lb spring that loses 20 lbs after a few trips down the 1/4 mile. You're now sitting with 120 lbs of pressure and I promise you this.... it's all downhill from here.

If you could use a hollow stem Ferrea valve like the ones I used in a buddy's 355, along with the beehive spring and a light but stiff rocker with less critical mass... you could get by with a lot less spring.

So the answer to your question is... it depends. If you can go light, then start with a 150 lb spring and you'll likely be fine. If you are going with a more conventional valvetrain setup, then you'd better settle on more spring pressure being your friend.

I see this all the times where guys should have just went to a solid roller cam. If you plan it out right and buy the right parts, you can run a cam like yours but if you don't... you'd better be ready to run a bit more spring and keep an eye on them.

I don't run into these kind of problems on the stuff I put together because I learned this a long time ago.

-Mindgame