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Old 10-09-06, 09:02PM   #1
Gach
 
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Default Darin Morgan On *Valve Springs*

Question, this was so good I had to copy it here.

Quote:
I have a question about valve spring selection. My engine is a 598cid with Big Chief heads. The cam
I am using is a 288/300@50, 114ls, 810/782 gross lift. According to the cam spec card I should be
using a spring(comp cam) #998. This spring sets up at 1.950@194lbs and has a spring rate of 677.
The springs I have been using are a Crane spring, #99878. 2.100@238lbs, 816@1.200, spring rate of 642.
My question is, Why the huge difference between what the cam company represents and what my engine
builder uses? I do not have any complaints about the performance of the engine, but trying to figure
out why use a spring that is so much more than comp recommends?

Valve train design and tuning is a science all its own and has a little touch of mysticism as well.The Kinematic motion of a valve train is extremely complex. Simply stating that a spring needs "more" or "less" pressure is overly simplistic. It overlooks the finer tuning aspects of the system and especially the spring. The spring can encounter many different problems; float being just one of them. The spring can encounter Resonance, Coil surge, Float or simple Fatigue due to excessive heat or use. Float is the term most often used to describe the spring not controlling the valve train and in most cases people are correct in using this term because Float is the predominant valve train problem in most racing engines operating at moderately high engine speeds in the 7500 to 8000rpm range. This is due to either the builder not using the correct spring to control the valve train or the springs being used have fatigued with time and or heat.This is where the valves can bounces off the seat as much as .020 bleeding off the rising cylinder pressure back up the intake tract effectively shutting the engine off or keeping it from accelerating any further.Having two or three valve bounces of about .005 at the valve is a normal but albeit unhealthy occurrence in high rpm racing engines. We would like to have zero bounce, but that just doesn’t happen. 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. Resonance is a killer but I find it a rare occurrence with the Super Series engines or other engines that operate at or below 7500rpm. In the big Block Chevy engine there are two distinct points within the rpm range that present a problem. 7600to 7800 and 9800-10000. 7600-7800 is usually just before the cam goes into loft (not float) and the 9800+ range is where the loft goes Bozo for a lack of a better term. The 7600-7800rpm point has been shown to excite certain types of springs that are considered to be "better" because of there increased rate and pressures. I put a set of PSI 048 style springs on a truck puller engine with the Raptor heads. I mistakenly thought that the “better" spring would lend some protection to the valve train because this guy revved the engine to 9600rpm+ and at time free revved the engine to 9500rpm+. Well he called me the after a week and said that he had broken six valve springs and the rest where Jell-O. They had lost 100lbs of seat pressure. I instantly knew to ask him one question. Do you hold the engine at or around 7600-7800rpm for any length of time? He reported that that is exactly where the engine dropped back down to when the sled came in. BINGO, resonance! I sent him A set of Comp 048 springs and told him to change them when they dropped below 285lbs. He has over 100runs
on the engine and going strong. He replaces the valve springs about every 25 runs. This is the point I was trying to make. Just because a spring has more pressure or rate does not mean that it is a good match for the valve train system you are using them on. On a Drag racing engine that goes to 7600-8000 or 8500rpm on the shift, you won’t generally encounter this problem because the spring goes in and out of resonance so fast its of no consequence. If you just go to the point of resonance or just past it and back down through it, you’re generally ok. It’s when you “hang" there for any length of time that the damage becomes evident.
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Old 10-09-06, 11:10PM   #2
JEFF W
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Default Re: Darin Morgan On *Valve Springs*

Good stuff.:cool:

I'm glad my race engine don't see over 6500 so I don't have to worry about those things as much.
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Old 10-09-06, 11:39PM   #3
Gach
 
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Default Re: Darin Morgan On *Valve Springs*

Yeah really, that would drive me crazy, don't think I'd be building anything
like that any to soon.
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Old 10-10-06, 10:50AM   #4
Mb125
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Default Re: Darin Morgan On *Valve Springs*

See.... big heads and big cams mean you better have a big bankroll to pay for the maintenance or else it will be sitting collecting dust.
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Old 10-10-06, 05:10PM   #5
Gach
 
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Default Re: Darin Morgan On *Valve Springs*

When I went to VMP their was a guy there checking his valve springs
after every run...I guess it's the price you pay for fame. But I also look
at it this way too, if I could afford it, I'd be doing it too. What's 25 grand
when your making over 100 and single, god bless them that do have. If
you want to be top dog that's what it takes.
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Old 10-10-06, 07:23PM   #6
Strelka Built
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Default Re: Darin Morgan On *Valve Springs*

You have to love the internal combustion engine. As John Force says, "it tickles my tinckle". LOL
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Old 10-10-06, 08:25PM   #7
huge496
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Default Re: Darin Morgan On *Valve Springs*

There are guys out there that do change valve springs after every run. They are going through $2000+ worth of valve springs a weekend (only 6 runs). When you are running 1.10+ lift with valves that are 2.60+ and over 6 inches long trying to control them at close to 8000 rpm does get very expensive!
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Old 10-11-06, 12:14AM   #8
Gach
 
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Default Re: Darin Morgan On *Valve Springs*

It's good info huge496, I don't think most of us even had a clue what the
cost is to run those numbers. I say if they can afford it god bless them, if
I had the bucks, I'd be right out there running right beside them. I'd be
calling uncle Tony...hey is my motor ready.
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Old 02-08-07, 10:25PM   #9
DINO
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Default Re: Darin Morgan On *Valve Springs*

check out www.mid-lift.com
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Old 02-08-07, 10:32PM   #10
Gach
 
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Default Re: Darin Morgan On *Valve Springs*

That's a good price Racer Net $946 & Up.
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Old 04-05-07, 10:12PM   #11
ANDY MITCHELL
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Default Re: Darin Morgan On *Valve Springs*

Quote:
Originally Posted by Gach View Post
When I went to VMP their was a guy there checking his valve springs
after every run...I guess it's the price you pay for fame. But I also look
at it this way too, if I could afford it, I'd be doing it too. What's 25 grand
when your making over 100 and single, god bless them that do have. If
you want to be top dog that's what it takes.
Gach on our 650ci 05 Grand Am i check the springs every run for lash and seat pressure,its hard on springs with the 5 speed Liberty,we operate between 7500-8900 through the gears,our engine revs to 8900rpm with a cam 288/323@050 118 LSA and .989/958 lift. we used to use Comp Pro-Pacs but found they did not suit our application as well as the Manley Nextek's,with the Comps we would have to change 3-4 springs every race and the full set every 20 passes and if we blew the tyres off on the start line 3-4 inner springs would break so we would have to change the full set,we changed to the Manley polished Nextek's last year and have not looked back they are much more suited for our engine and outlast the Comps by 2 1/2 times seat presssure is 360 and open is 1075 and we run them 070 from coil bind ,any body who tells you if you only use your spring to 75% of its capabilty it will last longer does not understand how a spring works it will actully shorten the life of the spring & may cause premiture failure of the spring or engine, springs are engineered to be worked to a certain compressed hieght and will not have the corect rebound rate if not fully compressed,they will only perform correctly if used to the compressed hieght they are designed for,we have had no valve train failures ever due to closely monitering the springs and changing when nessasary cost per set of Manley Nexteks polished is $820 a set but far cheaper that the alterative!!! We also change the Jesel keyway lifters at $2000 a set and 5/16 titanium 2.550 int/1.88 ex valves every 6 months at $2400 a set,Glad i only have to keep it running and not pay for parts.lol.Joking aside we have had no valve train falures since i joined the team 3 years ago.
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Old 04-06-07, 01:39AM   #12
Gach
 
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Default Re: Darin Morgan On *Valve Springs*

Good info Andy. Now I know what the mean when the say if you want to play
you have to pay. Well I guess we all do what we can afford.
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Old 04-06-07, 02:49AM   #13
gtofreek
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Default Re: Darin Morgan On *Valve Springs*

Just a fun side note:

We have an old worn out valve spring off of Warren Johnson's Pro-Stock and I tested it. I didn't know what WJ's spring installed height was but I tested this spring at a 2.300 installed height with 1.000" lift. It had 450 lbs. on the seat and over 1400 lbs open! Now that's a spring! The handle on our spring compressor almost wasn't long enough as I could hardly compress it to coil bind. When you try to compress this spring by hand, it feels solid.
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Old 04-06-07, 12:47PM   #14
Gach
 
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Default Re: Darin Morgan On *Valve Springs*

WOW! I had to pull one of my springs ( 800 lbs open pressure ) off my head man! it took to guys just to hold the head, and a long bar on the spring compressor, I can imagine what it took with 1400 open spring.
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Old 04-07-07, 02:27AM   #15
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Default Re: Darin Morgan On *Valve Springs*

I run the NexTek Manley's on my engine and have not had an issue other than cracking rocker arms. I really need a shaft system if I keep that set up. I am .065" from coil bind. There is power to be found or lost in valvesprings too. Most people want to try too light of pressure imo and then have valvetrain problems such as float and beating the tar out of the locks, retainers and valvestem grooves. Look at it this way; The Navy teaches you that if you are on deck and in high waves, get everypart of your body and head against the nearest bulkhead wall. Why, because if you are not against it completely and you get slammed by a wave, you will be hurt. You only have to hold on when against the wall. You get slammed, your natural reaction is a "sting" that opens your hands, there by lossing your grip to hold on with. When the water recedes guess what is going with it? Hope you don't drown because no one is going to get you out of the water in time otherwise. Thanks future Mr Admiral for those you can make it or die speeches!
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