Cam and Valve spring

ChrisU · Post by **ChrisU** » Thu Mar 02, 2006 12:12 pm

Yep.. you don't know your limits until you go beyond them.

fredo11 · Post by **fredo11** » Thu Mar 02, 2006 6:44 pm

I appreciate all of the input.There have been several comments along the way that have pointed me in directions to help in the future. I have often followed the stiff spring theroy.I can see there will be lots more to learn in this area alone.
I have a better grasp now on the relation between the valve,valve stem,valve length,set up height,spring rate, and all else that I will find with the quest for more on this matter.I do believe that we are all looking for a better way to have just enough and not to much in just this one area, with lots of different ideas to get us there.
Guess its back to the rimac, garage & track.

Keith Morganstein · Post by **Keith Morganstein** » Mon Mar 06, 2006 8:30 pm

Coil surge is a scenario that takes place when the spring is set up to far away from coil bind giving the middle coils room to bounce back and forth from top to bottom as the spring is closing. This usually takes place with a highly energized spring (fast ramp rate) at high engine speeds. Having a spring with not enough rate can exacerbate the problem and having a spring with both to little rate and not enough seat/nose pressure in conjunction with being set up to far from coil bind is down right deadly. I have seen springs turn blue, shatter and literally melt due to this scenario. This will cause valve bounce similar to floating the system and letting the valve hit the seat.

Darin, I've read your post several times and thank you for the info.

Above you are explaining coil surge.

A question I have is how far from away from coil bind is too far ?

Darin Morgan · Post by **Darin Morgan** » Mon Mar 06, 2006 8:50 pm

Max Effort wrote:
Coil surge is a scenario that takes place when the spring is set up to far away from coil bind giving the middle coils room to bounce back and forth from top to bottom as the spring is closing. This usually takes place with a highly energized spring (fast ramp rate) at high engine speeds. Having a spring with not enough rate can exacerbate the problem and having a spring with both to little rate and not enough seat/nose pressure in conjunction with being set up to far from coil bind is down right deadly. I have seen springs turn blue, shatter and literally melt due to this scenario. This will cause valve bounce similar to floating the system and letting the valve hit the seat.

Darin, I've read your post several times and thank you for the info.

Above you are explaining coil surge.

A question I have is how far from away from coil bind is too far ?

Depends on the rpm range of the engine and the springs and valve train components being used as well as the valve train design. there is no pat answer to that question although tighter is usually better. .050 away from coil bind is generally excepted as the norm and any more than .080 in a high rpm engine is probably asking for trouble unless you know exactly whats gong on in your particular valve train and you have the spin tron data to tell you how much is to much. Some people tune the valve train with a little heavier components to loft hard and give up some top end power at the very upper rpm range in doing so. Some run closer to coil bind with lighter components and loft easier making a lot of power in the upper rpm range but not getting that burst of power in the middle. Its a give and take. You look at each system with a clean sheet of paper and a lot of R&D time as well as spin-tron time. Its 80% trial and error and 20% frustration.

ItsA68 · Post by **ItsA68** » Mon Mar 06, 2006 11:12 pm

Don't even TRUST the cam companies' catelogs, OR the guy on the phone. Read it all twice, and then look at the parts themselves to see whats going on. I have been doing a lot of research into what cam I want to run in a motor I'm building, and I was lookin' really hard at the comp cams extreme energy street rollers. What I found didn't make me happy. I ended up ordering from Crower! (other factors too, the biggest being only cast steel cores at comp, with no billet option with everwear gear)

Here's an example from the comp cams catelog. They recommend the 977 spring for all of the solid roller extreme energy grinds.

If you pick from the bottom of the page, and get the 12-773-8 cam, and get the springs they recommend, and install them at the recommended install height, you'll be running within .034" of coil bind IF you are running 1.6 ratio rockers. I knew about the .050 from bind limit, so that seemed a bit tight. 1.6 rockers seem like what you'd want to run, and what would be common to me. I think that these guys have a problem, and they need to look really hard at their recommendations. When I called their so called cam help line, and pointed this out to them, they seemed somewhat surprised...

specs for 977 spring, are 155lbs @ installed height of 1.850, and 419lbs @ 1.250, with coil bind coming at 1.195. The 12-773 cam has .388 lobe lift on the intake, and .392 on the exhaust. With 1.6 rockers on the intake, that puts your lift at .621" if my calculator is right. Coil bind comes at .655" lift at the recommended install height. If you drop down to 1.5 ratio rockers, you're OK, and at .073 from coil bind.

I guess I'm just a techno dweeb, but I CAN read a catelog. Unfortunately, I end up spending a lot of time only looking at stuff while I wait for the $$ and time to put plans into action.

~~fred

airflowdevelop · Post by **airflowdevelop** » Mon Mar 06, 2006 11:20 pm

hey fred...what about lash? You can get anything from comp ground on a billet.

Post by **ou812** » Mon Mar 06, 2006 11:30 pm

Yes, comp will grind anything you want...on any core you want (within reason).
I just built a blown BBC with an extreme energy solid roller grind on a steel billet core so I know they will.

Brian

ItsA68 · Post by **ItsA68** » Tue Mar 07, 2006 12:31 am

they do have billet cores, but all require the bronze dist gear. at least that's what they told me. didn't make sense to me. I was looking for the billet core with the pressed on cast "everwear" gear like what you get from lunati, crane, crower etc....I'd imagine they may make it, but the guy on the phone either didn't know what I was talking about, or something.

there is lash. forgot about that. Its .016" intake, and .018" exh. Wouldn't the quoted lifts include the recommended lash?

Wolfplace · Post by **Wolfplace** » Tue Mar 07, 2006 1:44 am

ItsA68 wrote:they do have billet cores, but all require the bronze dist gear. at least that's what they told me. didn't make sense to me. I was looking for the billet core with the pressed on cast "everwear" gear like what you get from lunati, crane, crower etc....I'd imagine they may make it, but the guy on the phone either didn't know what I was talking about, or something.

there is lash. forgot about that. Its .016" intake, and .018" exh. Wouldn't the quoted lifts include the recommended lash?

=
Don't know who you are talking to there but you can get any roller you wish with the "ever-wear" gear from Comp.
BTW, they don't make the cores

And no, the quoted lift does not include lash, just do the math.

lobe lift x rocker ratio - lash = advertised lift.
Your results will vary depending on a number of things including geometry, spring used,,,,,

And the reason for the 977 is because you can't put a real spring on these cast core POS cams,,
In my opinion, anyone who would put a cast roller in anything is just plain nuts,,, I don't even know why they make these damn things.

Did I mention I don't care for cast core cams

70MC · Post by **70MC** » Tue Mar 07, 2006 10:17 am

Wolfplace wrote:
In my opinion, anyone who would put a cast roller in anything is just plain nuts,,, I don't even know why they make these damn things.

Did I mention I don't care for cast core cams

Wolfplace, would that statement hold true only with solid roller cams?
Or do you also mean hydrulic rollers?

Wolfplace · Post by **Wolfplace** » Tue Mar 07, 2006 12:44 pm

70MC wrote:
Wolfplace wrote:
In my opinion, anyone who would put a cast roller in anything is just plain nuts,,, I don't even know why they make these damn things.

Did I mention I don't care for cast core cams
Wolfplace, would that statement hold true only with solid roller cams?
Or do you also mean hydrulic rollers?

=
To this point, I no longer use cast core rollers period. Hell, even GM doesn't use a cast core

Now with the Beehive springs this may change with a hyd roller as they seem to be showing some promise controlling things without excessive pressures.

I have a customer with two street engines & both picked up RPM substantially with the Beehives with less pressure than what he was running before.
Only "tests" I have as I haven't tried them personally.

I know there are exceptions but I haven't found much of anything that liked more than about 6000 with conventional springs & hyd rollers.

I think it goes back to part of what Darin was saying about certain combos liking a different spring than you would "expect"

SStrokerAce · Post by **SStrokerAce** » Wed Mar 08, 2006 1:10 am

ItsA68 wrote:they do have billet cores, but all require the bronze dist gear. at least that's what they told me. didn't make sense to me. I was looking for the billet core with the pressed on cast "everwear" gear like what you get from lunati, crane, crower etc....I'd imagine they may make it, but the guy on the phone either didn't know what I was talking about, or something.

there is lash. forgot about that. Its .016" intake, and .018" exh. Wouldn't the quoted lifts include the recommended lash?

Yep Comp makes it with that gear. It's $50 more, which is basically the cost of the bronze distributor gear

I was pissed that they switched over to not having this standard on billet cores. The cast cores are fine with the beehive springs since the pressure over the nose is not as high with them. Probably done well over 100 of those cam/spring combos and they work fine.

Bret

jacksoni · Post by **jacksoni** » Wed Mar 08, 2006 3:02 pm

Darin (and the others) your posts about valve train design, harmonics,dynamics etc seem to say that your valve spring package plus the other parts of the system determine cam design more than other factors(HP, rpm etc) . In other words, in a high rpm application, the lobe and rocker ratio have to get you within your .050-.080 of bind or likely problem (I understand no pat answers) and so you are picking the lobe to match the valve train rather than the head, flows, displacement, intended application etc. Am I way off base here?

I am working on an engine which will need >9000 for 1-2 minutes (Bonneville) with a big head on a small displacement. I had wanted a modest cam (Pipemax and EAPro show no big help with bigger lifts). Cam designer sending me a very dear ($900) custom billet with a .460 lobe, 276/286 @.050 cam (1.85 RR) for about.850 lift. Springs are Manley Nextec triples with 350seat, 1050 at .900. This fits your above apparent recommendations but scares me. Anybodies thoughts?

BRENT FAY · Post by **BRENT FAY** » Wed Mar 08, 2006 10:31 pm

I believe some where I read a bulleitin on the Nextek springs that you want to run them close to coil bind to help eliminate spring surge but I cant place it. But in your application I would think about spring oilers. Nothing worse than going a bazillion mph like you and Bill Jones do and have a catostrophic failure of some nature. Dont second guess on any thing!

Brent

jacksoni · Post by **jacksoni** » Thu Mar 09, 2006 6:34 am

BRENT FAY wrote:I believe some where I read a bulleitin on the Nextek springs that you want to run them close to coil bind to help eliminate spring surge but I cant place it. But in your application I would think about spring oilers.

Nothing worse than going a bazillion mph like you and Bill Jones do and have a catostrophic failure of some nature. Dont second guess on any thing! Brent

Thanks, I do have oilers in this one.

Last time I ran out there was going about 260 when lost a rod through side of block. Small fire.

Yes I am really trying to get everything right.

Don Terrill’s Speed-Talk

Cam and Valve spring

Springs

catelog example....