Valve Springs - Time to replace?

Guys,
I wanted to get some opinions on a decision that I need to make.
My A-headed 605 developed a slight high speed miss during the last 2 or 3 passes.
Timing, plugs, mixture all seem fine.
I could not see any evidence of broken valve springs, but decided to test them anyway.
Using an LSM on-engine tester I found several springs in the 240-250 lb range.
The PSI #1224 springs all averaged 295-300 when installed. I think that it is time for springs.
I am just wondering if anyone has experienced a 55 lb. loss of (seated) spring pressure causing a miss. The miss was noticeable above 7100 rpm. The engine has titanium intakes and stainless exhausts.
I am trying to rustle up a new set of springs today so I can get ready for the Div. 2 points race in Atlanta nex weekend. Last minute thrashes...grrrrr.
Thanks,
Keith

Have you got enough room to put a .030" shim under the weaker ones ?

Lem Evans wrote:Have you got enough room to put a .030" shim under the weaker ones ?

Yeah. I will save that for "plan B" if I can't get a new set soon enough.
I hope to find a set tonight or tommorrow. Checking with other shops and racers around here....
Thanks!
Keith

is there any trend....intakes or exh being the lesser ones ?

Lem Evans wrote:is there any trend....intakes or exh being the lesser ones ?

The exhaust are lower than most of the intakes.
Thanks,
Keith

what presser did it tak just to get them off the seat, which tester are u using?

Keith,

I looked that PSI1224 spring up and it has 275lbs. on the seat as you said. It's rate it 594 lbs. and it's open pressure is750 lbs. @ 1.200. It is supposed to be good for .800" lift. In all honesty that is not quite as good of a spring, as the one that comes on the new style assembled TFS A-460 heads. Lem has those springs in stock, and they are referred to as the Manley NexTek -424 spring, or the Sig Erson spring. They have a higher rate and more open pressure. You could call Shawn or Lem, and they would go out to you on Tuesday/Wednesday from the dealership.

Furthermore, IMO it is time for new valve springs. In your situation the exhaust valves are heavier than the titanium intake valves, and it is common for the spring used with the heavier valve to "go away" first, in a drag race engine. In a circle track engine, we generally always see the exhaust valve springs go away first, because of the heat encountered with the extended running.

As a last resort, swap your weakest springs over to the lighter intakes and shim them as Lem suggested. Use your strongest springs on the heavier exhaust valves, and you may be able to get a few more passes out of the set.

Hope this helps,

Charlie

BOSS 429 wrote:what presser did it tak just to get them off the seat, which tester are u using?

"I could not see any evidence of broken valve springs, but decided to test them anyway.
Using an LSM on-engine tester I found several springs in the 240-250 lb range."

Boss,
It was an LSM tester, that uses a hydraulic cylinder with a pressure gauge on it. The numbers that I posted (240 to 250 on the weaker ones) is the "seat" pressure and is recorded just to get it off the seat.
I am going to verify the accuracy of the tester (with a bench test) when I change the springs, but the LSM tool is reportedly pretty good.
Thanks,
Keith

c.evans wrote:Keith,

I looked that PSI1224 spring up and it has 275lbs. on the seat as you said. It's rate it 594 lbs. and it's open pressure is750 lbs. @ 1.200. It is supposed to be good for .800" lift. In all honesty that is not quite as good of a spring, as the one that comes on the new style assembled TFS A-460 heads. Lem has those springs in stock, and they are referred to as the Manley NexTek -424 spring, or the Sig Erson spring. They have a higher rate and more open pressure. You could call Shawn or Lem, and they would go out to you on Tuesday/Wednesday from the dealership.

Furthermore, IMO it is time for new valve springs. In your situation the exhaust valves are heavier than the titanium intake valves, and it is common for the spring used with the heavier valve to "go away" first, in a drag race engine. In a circle track engine, we generally always see the exhaust valve springs go away first, because of the heat encountered with the extended running.

As a last resort, swap your weakest springs over to the lighter intakes and shim them as Lem suggested. Use your strongest springs on the heavier exhaust valves, and you may be able to get a few more passes out of the set.

Hope this helps,

Charlie

Charlie,
Thanks for the input. I spoke with Lem last night also.
I think that I have a plan. I will report the results.
Thanks!
Keith

Keith, is that the straight or slant handle LSM model you have? I've been wanting to buy one so I can see how things are on my engine, (16 dyno pulls and 18 track passes). I would like to get the one Buxton Eng. has, but that price is way over my head right now.

Doug Rahn wrote:Keith, is that the straight or slant handle LSM model you have? I've been wanting to buy one so I can see how things are on my engine, (16 dyno pulls and 18 track passes). I would like to get the one Buxton Eng. has, but that price is way over my head right now.

Doug,
It is the PC-100 straight handle model. http://www.lsmproducts.com/pc100.htm
It works fine on my car except for the very last valve on the driver's side. (stock firewall)
I have T&D 1.8 shaft rockers on A-heads. You have to patiently wiggle the "foot" of the tester into place in the intakes. They are a little tight fitting.
I actually borrowed this one from a buddy, just to see if I should buy one.
I need to buy one! Summit has them for $229.
If you started out with good springs, you are probably just fine. Mine as 150 - 160 runs and a bunch of dyno runs. I just need to get out of cheapskate mode.....
Later...
Keith

Doug Rahn wrote:Keith, is that the straight or slant handle LSM model you have? I've been wanting to buy one so I can see how things are on my engine, (16 dyno pulls and 18 track passes). I would like to get the one Buxton Eng. has, but that price is way over my head right now.

Douglas, I have the LSM tester too...when do you want it ??

QtrWarrior wrote:

Doug Rahn wrote:Keith, is that the straight or slant handle LSM model you have? I've been wanting to buy one so I can see how things are on my engine, (16 dyno pulls and 18 track passes). I would like to get the one Buxton Eng. has, but that price is way over my head right now.

Douglas, I have the LSM tester too...when do you want it ??

Before we go to Silver Dollar Dragway, just to get a baseline and see where everything is at and to give me peace of mind .