How much spring pressure do I need

[oldhead]

How much spring pressure do I need on a SBC-400? It a Comp Cams Custom solid roller. The # are cs4875/4877 248/260 at .600 Maxhp on the dyno is at 6250 just like CC said, they redline it at 6700...So how much pressure? Now the the truth I go 7300 rarely, but 7000 alot.I drive it some days 150 miles... I have Elite rollers,,,,,,I presently have 240 seat and around #600 open. yes has boost,needs no extra pressure for boost...A friend is thinking about using #300 on the seat on his street car, I told him that won't last ? Oldhead

[oldhead]

I can't believe it, 87 views and not one answer Oldhead

[user-30257]

I can't believe it, 87 views and not one answer Oldhead

Base circle?
Why 300#?
I run less than that in big blocks with more lift.

[GARY C]

How much spring pressure do I need on a SBC-400? It a Comp Cams Custom solid roller. The # are cs4875/4877 248/260 at .600 Maxhp on the dyno is at 6250 just like CC said, they redline it at 6700...So how much pressure? Now the the truth I go 7300 rarely, but 7000 alot.I drive it some days 150 miles... I have Elite rollers,,,,,,I presently have 240 seat and around #600 open. yes has boost,needs no extra pressure for boost...A friend is thinking about using #300 on the seat on his street car, I told him that won't last ? Oldhead

I can't speak to a boosted app but on SBC 2.08 valve 7000/7500, 7700 on dyno we usually ran 200, 220 max. this was 267@ .050 680 lift stuff.

[oldhead]

I can't believe it, 87 views and not one answer Oldhead

Base circle?
Why 300#?
I run less than that in big blocks with more lift.

Because he does not know what he is doing.Won't this cause very rapid wear???

[oldhead]

How much spring pressure do I need on a SBC-400? It a Comp Cams Custom solid roller. The # are cs4875/4877 248/260 at .600 Maxhp on the dyno is at 6250 just like CC said, they redline it at 6700...So how much pressure? Now the the truth I go 7300 rarely, but 7000 alot.I drive it some days 150 miles... I have Elite rollers,,,,,,I presently have 240 seat and around #600 open. yes has boost,needs no extra pressure for boost...A friend is thinking about using #300 on the seat on his street car, I told him that won't last ? Oldhead

I can't speak to a boosted app but on SBC 2.08 valve 7000/7500, 7700 on dyno we usually ran 200, 220 max. this was 267@ .050 680 lift stuff.

So you say 220# in max. Would the 240# that I have cause rapid wear on a car that sees 5000 miles? Oldhead PS: Boost needs NO extra pressure Buick GN has under 80# on seat with 14# of boost

[Warp Speed]

How much spring pressure do I need on a SBC-400? It a Comp Cams Custom solid roller. The # are cs4875/4877 248/260 at .600 Maxhp on the dyno is at 6250 just like CC said, they redline it at 6700...So how much pressure? Now the the truth I go 7300 rarely, but 7000 alot.I drive it some days 150 miles... I have Elite rollers,,,,,,I presently have 240 seat and around #600 open. yes has boost,needs no extra pressure for boost...A friend is thinking about using #300 on the seat on his street car, I told him that won't last ? Oldhead

I can't speak to a boosted app but on SBC 2.08 valve 7000/7500, 7700 on dyno we usually ran 200, 220 max. this was 267@ .050 680 lift stuff.

So you say 220# in max. Would the 240# that I have cause rapid wear on a car that sees 5000 miles? Oldhead PS: Boost needs NO extra pressure Buick GN has under 80# on seat with 14# of boost

Then if you already know, why are you asking oldlib?!?

[GARY C]

How much spring pressure do I need on a SBC-400? It a Comp Cams Custom solid roller. The # are cs4875/4877 248/260 at .600 Maxhp on the dyno is at 6250 just like CC said, they redline it at 6700...So how much pressure? Now the the truth I go 7300 rarely, but 7000 alot.I drive it some days 150 miles... I have Elite rollers,,,,,,I presently have 240 seat and around #600 open. yes has boost,needs no extra pressure for boost...A friend is thinking about using #300 on the seat on his street car, I told him that won't last ? Oldhead

I can't speak to a boosted app but on SBC 2.08 valve 7000/7500, 7700 on dyno we usually ran 200, 220 max. this was 267@ .050 680 lift stuff.

So you say 220# in max. Would the 240# that I have cause rapid wear on a car that sees 5000 miles? Oldhead PS: Boost needs NO extra pressure Buick GN has under 80# on seat with 14# of boost

That would depend on the components, most of mine were 200 except one set that was 220, I would shift for quickest et so if it didn't run faster I didn't rpm it higher. I never had any sign of damage but I did not street drive either with the exception of testing on the back roads, in the pits and staging area.

What did comp recommend?

[oldhead]

Waited 30 minutes on the Comps.phone.no answer....It seems no one here has used a cam like mine (3/4 cam )in a 1000miles a year car.....I try to make the questions that I ask on here simple and I get realy odd answers from some....I thank you Oldhead

[oldhead]

I can't speak to a boosted app but on SBC 2.08 valve 7000/7500, 7700 on dyno we usually ran 200, 220 max. this was 267@ .050 680 lift stuff.

So you say 220# in max. Would the 240# that I have cause rapid wear on a car that sees 5000 miles? Oldhead PS: Boost needs NO extra pressure Buick GN has under 80# on seat with 14# of boost

Then if you already know, why are you asking oldlib?!?

I would not ask if I knew. I thank you for you reply But find it to be no help Oldhead

[user-30257]

I can't believe it, 87 views and not one answer Oldhead

Base circle?
Why 300#?
I run less than that in big blocks with more lift.

Because he does not know what he is doing.Won't this cause very rapid wear???

I have guys with stainless spreadports 400seat 1100 open out 1000+ miles on a set of springs.

If your geometry sucks, or lash is too loose, not enough oil to cool the springs etc... that is where the west will come from. The other extreme will be valves making love with pistons.

I wouldn't sweat 240lbs in your application. Just check the geometry.

[F-BIRD'88]

These are (mechanical) STREET roller lobes.. The net valve motion is not extreme like a radical racing roller cams lobes are. The spring loads you have now is plenty for 7300rpm with SBC valves and rockers.

Keep the valve lash setting a bit on the tight side ( aluminum heads set COLD .010 to .014".)
(The lash increases a bit as the engine reaches operating temperature.
These XR street rollers seem to like that... Is yours custom ground on a wider LSA for supercharging? is the camshaft a steel cam -9 or a cast cam core -8 ??

You may take a hit on long term wear if its the -8 cast camshaft core with those spring loads.
At any rate you want to avoid excessive valve lash . This is bad.

Visually inspect the roller lifters bearings and roller rockers and pushrod tips for wear annually..
Rebuild or replace as needed. It will run a long long time.

[oldhead]

T BIRD & Headguy...., You are great pair with GREAT answers..You gave me the answers I needed....My cam is steel with a cast gear, has a 114 CL, the geometry is right....I set the valves at .012, calls for .014 THANK YOU Oldhead

[1972ho]

Just curious but why would someone want to ride around town with a cam that has 400# of closed seat pressure and over a 1000# open.Are they driving around at 10000 rpm all the time, during those 1000 mile trips a year.Just Curious??

[user-30257]

Just curious but why would someone want to ride around town with a cam that has 400# of closed seat pressure and over a 1000# open.Are they driving around at 10000 rpm all the time, during those 1000 mile trips a year.Just Curious??

Opening and closing a near 1" lift 2.40"+ stainless valve requires pressure.

Some of these guys street race with serious gearing. And 20+ gallon fuel cells. Ever heard of drag week?

I'm sure I'm not the only one that has customers that want 1100+HP NA Big blocks to drive on the street.

remember what's streetable to Jeff Gordon is most likely too roudy for Grandpa.

As a builder sometimes it's safer to error in the stiff side. Sure he could maybe get away with 340lb seat. But if he loses 20# is rather it stop be a safe value.

These guys know what they are getting themselves into.