How many sub 4K rpm street trucks did NOT upgrade valve springs

Good call regarding the drive pressure balancing things out.

I think, atleast in 12v, the problem is the lack of over the nose pressure with stock and 60lb springs not necessarily the seat pressure. Not sure if this is the same problem with 24 heads or not. An interesting topic either way.

I plan to add a nice set of beehive springs to replace my 60lb springs in the near future anyway. Hoping to find a bit of power above 3000rpm and hopefully everywhere!
 
UNBROKEN said:
I tend to agree but I think the boost pressure comes into play at some point.
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bosshogg said:
Think about this mathematically for a second. Boost is measured (and drive as well for that matter) in Pounds/Square Inch
Spring pressure is measured in Pounds
So when boost reaches a pressure that pushes on the exposed area of the intake valves that is greater than the pressure the spring puts on the valve, it is going to crack open. I'm not sure of the area of the valve that boost is going to push on, or I would run the numbers. Once that valve cracks open though, math gets real crazy because you will also have to have enough flow to keep it open and maintain increasing pressure to open it further.
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Joesixpack said:
You have to account for the pressure on the other side of the valve as well. Compression-combustion-exhaust stroke....all high pressure conditions relative to boost.
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paulb said:
Exactly. Drive pressure will push the exhaust valve open when the intake valve is open.

Paul
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I echo what these guys said and add: This would seem to be possible to effect both valves. Anytime the differential pressure on the back side of the valve vs the combustion chamber exceeds the spring pressure*surface area of the valve... when the valve is seated.

How inertia of the valve as it travels at a given RPM minus the spring force and velocity of air as it moves past the valve once open effect it... that makes my head hurt any my eyes cross involuntarily. :hehe: But I'm sure it does.
 
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On a CR (seat ~78lbs., nose 140-ish) reversion is as likely to be from a narrow LSA's overlap as anything else, since drive/boost ratios are almost always over 1:1
 
Im going to ALWAYS upgrade my springs from now on.....lesson learned the hard way.

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RJM06590 said:
I dont see whats in the picture? Broken spring or something?
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Broken spring looks like...look at other spring, there is a gap between coils and on said spring there is no gap...looks compressed.
 
RJM06590 said:
Not sure about float, but I know 12 valve springs will start to pull the locks through the retainers after 4400 rpms. Ask Nick about it haha I tried to tell him.
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when you start throwing pushrods is when you need to upgrade your valve springs locks and retainers :lolly:
 
XLR8R said:
On a CR (seat ~78lbs., nose 140-ish) reversion is as likely to be from a narrow LSA's overlap as anything else, since drive/boost ratios are almost always over 1:1
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Yeah I think its overlap more likley then floating valves that cause reversion.
 
Increased boost slows the the intake valve closing...more boost...slower response. Even if the spring can overcome the boost...it may no do it fast enough to avoid piston contact...its worse at high rpms.


I picked up a bunch of power in the higher rpms with my springs...the truck just runs better.
 
i had to hammer out the retainers out of a few trucks with 4k kits. springs got changed when i did the ti retainers.
 
I think it's much more rpm based than boost. The pressure in the engine is going to be more than the boost in most cases and guys with 3 to 1 drive pressure and low rpm's arnt getting valve float are they?

Hmm took to long to post that there are like 15 more posts in the thread lol
 
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Just read through some of this thread. I am very glad to see some very good discussion on this topic. The knowledge about valvetrain components has greatly improved among comp d members in the last year or two. A few years ago this thread would have looked a lot different.

A few things to add. Issues with float mostly apply to 12valves especially if there is a performance cam with higher lift. 60lb springs have much higher seat pressure that OE's but have the same pressure over the nose of the cam as the stockers. Another issue with them is that the OE retainers weigh in at 38-44 grams and they separate easily over 4k. Haisley Ti retainers address this and weigh in at 24 grams. They are a good option if you are just wanting to address the retainer and run 60lbers. Although a bit more expensive than just retainers we designed a new beehive spring that addresses the spring pressure issue and an 11gram retainer.


We bolted a a plate on the intake of a 12v and a 24v and pressured up the intakes. 12v's blow open around 32 +/- psi and 24v's blow open at 50psi +/- this does not paint the whole picture as there are other forces to consider in the engine so that does not mean they can not be used over 50psi or 3500 rpm just that your valvetrain is not being controlled at all times.

I talk to pullers that run 55psi and 90+lbs of drive pressure all the time. This will allow major reversion with stock or performance springs due to overlap. MOst of them have large cams with a lot of overlap so they see more reversion than a street truck might. You can buy all of the best parts in the world and have low power. At some point the tuners intelligence level is the deciding factor in wins not his credit card buying power.

I see trucks (24v's and cr's) that have great power with stock springs all of the time but at elevated boost numbers they are giving up power. The main place on a 24v where you would benefit would be when the piston is on it's downward travel and the intakes valves are open filling the cylinder(at say 60psi boost and 80+psi drive) there is a negative pressure in the cylinder at points that also acts on the surface area of the exhaust valve plus the drive acting on the opposite surface area of the exhaust. This creates a situation where a large amount of exhaust can enter the cylinder and act as an inert gas which slows combustion. At high rpm this is an issue. Yes there will be reversion on overlap but it is greatly increased in this scenario. If your engine is setup and drive pressure is kept in check, the reversion will be all but eliminated on the overlap stroke. On our economy cams we give a little bit more overlap by using a narrow lsa this opens the exhaust later(pressure acting on piston longer in amount of crank degrees) and at overlap at highway speeds (1-6 psi)the exiting exhaust helps pull ion fresh air. This is a great cam if the truck has the correct turbo and is tuned correctly. If not it is a horrible setup. I find I have to design cams based on how they will be used not how they should be used so some of our products are dummed down for the end user, not all but some.

On 12v's. if you are revving over 3500rpm then 60lbers are not afequate pressure wise over the nose to control the valves and keep all of the parts of the valvetrain in contact. I have seen people put springs in and loose power on hot 12v's. They were opening and closing the cam off of boost pressure partially and launching the tappet off of the opening ramp and it might not touch the lobe until the base circle at higher rpms. This greatly exagerates the intake profile and allows moreflow. THis would be a case for a bigger cam. On the exhaust side of things blowing open would dirty the intake stroke with inert gasses.

I thought I would inject a few bits of information. By no means am I trying to tell people their business or how to setup their trucks. Yes you can run a 24v above 4k with a 99.9% chance of no failure just reduced efficiency. If you are reving a 12v above 4k you have much greater chances of reduced efficiency and catastrophic damage, mainly due to the stock retianers poor quality.
 
Stock springs and stock cam here, up to 3200 RPM, 45psi boost, 62psi drive, could be floating I don't know but no catastrophic failure or piston/valve contact.
 
UNBROKEN said:
I'm sure someone knows, I can't remember ever seeing that info though.
60lb 12v springs are 110 total IIRC so that would be 50 stock I suppose.
I could be wrong on those numbers too....not a big 12v guy. I like electronics. LOL
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Timebomb said:
A stock 12v spring is 90psi on the seat (closed pressure) open is much more. Your not gonna blow a valve shut with boost. The issue is rpm and not so much boost.
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so what is the stock 12v spring pressure? what is a 60lb spring?

Garrett
 
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