Just had the springs checked at our installed height of 1.950", measured 105 lbs! :eek: :eek: :eek:

Can`t hardly believe it.
Last track visit 2 weeks ago riding out 1`st way too long laying on the limiter hard with a 7000 rpm chip, turns around and promptly runs 10.17 ET spinning with a 1.49 60 ft!

This is no anemic small block cam by any stretch either. Big 2.25" valves and .650 lift

Wolfplace...you`ve got to love this one :D

What springs are you running? It is definitely possible to have 105# at the seat and still get 350 at the nose on your cam if the springs are short to start with. It works out to a 376.9 spring rate to get 350# at .650 lift. Most hydraulic rollers only recommend a 330 - 365 rate spring.

Damn,,, that is pretty unreal.
Even so I doubt it is making power up there.
What type lifters & how are you adjusting them?
The really amazing part is going back & runnin that good after spinnin it that tight.
What were the springs at when you put them in?
I have seen engines go up here before & it usually killed the springs after a couple of shots due to float & the things would lose a bunch of RPM.
Where does it run the best shift wise?
That cam has got to be setting the valve down very gently I would think, I'm guessing it ain't an XE lobe :D

That cam is 255 at .050, 175 at .200, and .650" valve lift.
It sets the valves down slightlysofter than a STOCK GM cam.
I like a little more pressure than that, myself....

UDHarold

Harold,

If you check back in, what pressure do you spec for a hyd roller? For comparison, the springs I am running are the Comp 925 which I think are a 398-399?? rate. At a traditional 150 seat would yield 408# at .650 lift. From my own experience, this is guaranteed death to a regular cast roller.

Wolfplace...I agree, unreal.
The springs are Lunati Pro Mod # 73021.
I set them up at 1.950"
They are rated at 143# @ 1.940

Originally they were used with a set of Comp Cams hyd roller lifters. Adjustments were just shy of 1/2 turn.
Many passes run this way, trapping 6500+ RPM.

Then, they were pulled out and a set of Crane solid rollers were put in.
These I set at .000 lash cold, that ends up to be .006-.008 hot.

This is the setup we use now.

Best shift points are 5600-5800 (1-2) then 6200-6400 (2-3)

The cam is an Ultradyne graemlins/thumbsup.gif

Originally posted by GRN69CHV:
Harold,

If you check back in, what pressure do you spec for a hyd roller? For comparison, the springs I am running are the Comp 925 which I think are a 398-399?? rate. At a traditional 150 seat would yield 408# at .650 lift. From my own experience, this is guaranteed death to a regular cast roller. i'm curious about this myself. i am going to install a 50250LUN and the springs that were in my heads seat around 140# and are at 360# on the nose with this cam. this is a little more spring than lunati specs for that cam but a lunati tech told me as long i was over 300/under 400 i was okay. does this sound right or is 360 going to be too much load for my cam?

Bill,

Did you run that number past Lunati? But from what I understand, 400 max is the number with hyd rollers, mid 300's is great. I had originally installed a cast core hyd roller and scored it with minimal running time with about 450 over the nose before I knew better. The billet core rollers can take a lot of spring. THe cast core cams are fairly durable but need that mid 300 spring pressure. I have 350 over the nose on my Comp XE series, so far all is well.

Originally posted by GRN69CHV:
Bill,

Did you run that number past Lunati? yes, the lunati tech told me between 300 and 400 would be fine. i had my machine shop check the spring load at the .612 ex height and he tells me i have 360 pounds there. dont know much about roller cams so i have been watching these posts closely. noticed your cautionary comment above regarding too much load so i just wanted to double check the info i got from the lunati tech guy. thanks for the info, i need all i can get.

Comp rollers that end in -8 use a cast core. Higher strength than regular flat tappet cores, but not the same as their -9 billet cores. I would assume Lunati uses the sames -8 core for hyd rollers otherwise they would recommend 400+. Crane apparently uses billet cores for all their hyd rollers. I also have a CamMotion GenVI hyd roller here that is made from a billet core. You can immediately tell the difference, the biller core is made from a forging and judging by the shiny finish, I assume it is a high alloy steel as well.

Cool! I dont exactly know what springs I;m running, but they measure light over the heel as well, like 115 is all. But then they go 335-340 at a .600 nose. Of course, its spin up tight. I'll worry less about those springs now , THNX! Might be that the take up ramps on the hyd profile really make the cam lay the valves down easy, huh!?

BTW, since Mike and Harold might chime back, or L72, at what interval should you swap out springs on a STREET/(strip) ride? I'm at around 20K, 10K with the Crane F304-2 and 10K with the Ultradyne 276/284F10 on these springs. Just pull some and have them checked occasionally? Reading these pages can make a guy paranoid! :eek:

Unless its L72's post! :D

Keep in mind too that those recommended over the nose spring pressures are with the hydraulic lifter in mind.
Too much and the lifter won`t function correctly, to me that`s the limiting factor, not the cam itself.
Slight tracking even in billet cams is normal.

good point. i would think the hyd function of the lifter would reduce load before you would overload the cam anyhow. of course if it does then you are in effect running a much smaller cam by default.

I recently bought a Lunati hyd roller for my truck engine and it is a steel billet core with a pressed on cast rear journal and distributor gear. Recommended spring pressure was 140 closed, 400 open.

Originally posted by 79943:
</font><blockquote>quote:</font><hr />Originally posted by GRN69CHV:
Harold,

If you check back in, what pressure do you spec for a hyd roller? For comparison, the springs I am running are the Comp 925 which I think are a 398-399?? rate. At a traditional 150 seat would yield 408# at .650 lift. From my own experience, this is guaranteed death to a regular cast roller. i'm curious about this myself. i am going to install a 50250LUN and the springs that were in my heads seat around 140# and are at 360# on the nose with this cam. this is a little more spring than lunati specs for that cam but a lunati tech told me as long i was over 300/under 400 i was okay. does this sound right or is 360 going to be too much load for my cam? </font>[/QUOTE]=
=
These are in answer to a few posts in this thread so you will have to go back to sort them out tongue.gif

I'm not Harold but for a cast core roller I would like 130-150 seat & 360-380 open if it's going to see any amount of driving.
If it's a strip only deal or very limited mileage you can run over 400 open but it will kill the cam with much mileage.
I still feel the cast core roller cams are not the brightest idea to come along, especially the solid roller ones.

As Harold eluded to in his post, the biggest issue regarding valve float is the design of the lobe & the weight of the parts not the spring pressure.
If the lobe is too aggressive on the closing side It won't make much difference how much spring you throw at a hyd roller unless you run the thing at zero lash.
The opening side is relatively unimportant as long as it slows down over the nose.
The closing side is all important in stability.

Case in point,
SB with an XE lobe, 350+ open pressure, 90lbs of rev kit which equates to around 425-430 or spring without doing the math,,, it would not rpm reliably above 6000rpm.
Same dyno, same day different cam, same adjustment with about the same specs on paper,,, same spring, no rev kit, 6400rpm & still very stable with no sign of float or pump up.
Only reason I didn't go further was it was over the HP peak but I have no doubt it had another 3-400 rpm in it.
THE LOBE DESIGN IS VERY IMPORTANT

The limiting factor with a cast cam is the cam itself not the hyd lifter in regards to spring pressure.

You will not overcome the hyd lifter with a 400 pound spring in the time it takes to open the valve if hyd lifter is a normal one.
Even the "fast bleed" stuff will not have time to bleed off much at high rpms.
You will overcome the lifter instantly if the valve floats or bounces on closure though,, just in the other direction ;)

Neither cast or billet should see any appreciable "tracking" & for the cast cams, if you see tracking the next thing you are probably going to see in very short order is a lack of lobe :D

How often should you change springs??
If you are spinning the thing pretty good you should be checking the springs very closely every time you adjust them & any time you develop a miss or hear something out of the ordinary

If you are at or near valve float, which very obviously Red has been or the springs would not have lost 30 lbs you should be measuring the springs very often & replacing the whole set if you see a loss of more than about 10-15lbs from where they settle to after a few runs.
Will you get away with not changing them, probably but not always & the price you pay if one leaves is going to be very high,,,

With a billet hyd I would not be afraid to run 450 open at all but with most hyd lobes that are designed correctly it isn't necessary. With some well known lobes, sprng pressure & zero lash are the only way I know of to get them to rpm.

These are just my opinions & I am not a cam designer so hopefully Harold will chime in here with his thoughts,,,

Originally posted by Wolfplace:
With a billet hyd I would not be afraid to run 450 open at all but with most hyd lobes that are designed correctly it isn't necessary. With some well known lobes, sprng pressure & zero lash are the only way I know of to get them to rpm.
You are correct.