Replacing 427 Valve Springs

[Gary F.]

I am rebuilding my 1967 aluminum heads for my L71 engine. I want to replace my valve springs with the better Sealed Power V-708 springs. My problem is finding the correct valve retainers, GM part number 3964264, or an equivalent. I plan on using Sealed Power viton valve seals, part number MV-912 with GM 3947880 valve keys. Are these the latest/best parts to use and what are my options for the valve retainers. Thanks for any help.

[Joe L.]

Re: Replacing 427 Valve Springs

I am rebuilding my 1967 aluminum heads for my L71 engine. I want to replace my valve springs with the better Sealed Power V-708 springs. My problem is finding the correct valve retainers, GM part number 3964264, or an equivalent. I plan on using Sealed Power viton valve seals, part number MV-912 with GM 3947880 valve keys. Are these the latest/best parts to use and what are my options for the valve retainers. Thanks for any help.

Gary------


I think you mean Sealed Power MV-1912; I know of no MV-912. In any event, the MV-1912 umbrella type seals will not work with the VS-708 valve springs as the diameter of the inner spring is not great enough for the seals to remain free of the spring when in operation.

The GM #3964264 retainers are equipped with an attached umbrella seal which is designed to work perfectly with the VS-708 valve springs. Replacement seals are available from Federal-Mogul. Sealed Power advises that the VS-708 valve springs must be used with the GM retainers, although Sealed Power or any other manufacturer I know of has ever offered the GM style retainers. These retainers sometimes come up on eBay.

The VS-708 or discontinued GM #3970627 springs are, in my opinion, the absolute best valve springs for your application. As far as I have been able to determine, the valve springs in the GM #3970627 unit are identical to the VS-708 (except for paint stripe on the GM springs). I also favor the GM #3947880 valve stem locks.

[Mark E.]

Re: Replacing 427 Valve Springs

As Joe suggests, good option is to reuse your valve retainers or find an NOS source. Following Joe's advice, I replaced the springs on my LS5 using new VS-708 springs, new OEM type umbrella seals from Fed-Mogul, and my original retainers. That worked great. I used the opportunity to measure and shim valve spring installed height. It's surprising how much this can differ from valve to valve.

[Joe R.]

Re: Replacing 427 Valve Springs

Here's a picture of the GM 3970627 valve spring and I do not have a set. This is the valve spring to use in my opinion. Used them for years and never had a problem with one.

JR
IMG_0307[1].jpg

[Gary F.]

Re: Replacing 427 Valve Springs

What was the part number of the OEM type umbrella seals that you got from Fed-Mogul? Thanks for your help.

[Joe L.]

Re: Replacing 427 Valve Springs

What was the part number of the OEM type umbrella seals that you got from Fed-Mogul? Thanks for your help.

Gary------

I can't answer for Mark. However, I can tell you that the Fel-Pro (Federal-Mogul) OEM equivalent valve seals (available as a set) is SS71152. The OEM seals from GM are GM #460527. However, regardless of Mark's apparent success, I do not recommend using these with the VS-708 valve springs for several reasons:

1) As I previously mentioned, the OD of the above seals is too great to be used within the inner spring which is part of the VS-708 valve spring. In time, the spring will destroy the seal. The OEM umbrella seals are designed to be used with the original 1965-E1969 valve springs which are an outer spring with flat wire damper. They are not designed to be used with the dual valve spring VS-708. Federal Mogul specifies that the VS-708 are to be used with the GM #3964264 valve spring caps ("retainers");

2) The GM #3964264 cap is configured to center both the inner and outer valve springs of the GM #3970627 or VS-708. Earlier caps will not accomplish this. Will the earlier caps fit the VS-708 springs? Yes, they will but they will not center the two springs.

[Gary F.]

Re: Replacing 427 Valve Springs

What is the inside diameter of the inner and outer VS-708 springs that the valve spring retainer must locate on? If I had the retainers is there a valve stem seal that will work with the VS-708 spring? Once again thanks for your help.

[Gary F.]

Re: Replacing 427 Valve Springs

If the VS-708 spring will not work for the above reasons what spring would you recommend to replace my fifty year old springs which have a bad reputation for failing?

[Chris H.]

Re: Replacing 427 Valve Springs

Here's a thread that may be helpful........

https://www.forums.ncrs.org/showthread.php?115471-69-L71-Valve-Spring-Retainer-Recommendation&highlight=hewitt

[Gary F.]

Re: Replacing 427 Valve Springs

I could not open the above thread. What about using a Sealed Power VS-657 spring with a MV-1912 viton umbrella seal? This is a single spring with a damper like the original spring? Is there a better aftermarket spring to use since the VS-708 spring will not work.

[Joe L.]

Re: Replacing 427 Valve Springs

What is the inside diameter of the inner and outer VS-708 springs that the valve spring retainer must locate on? If I had the retainers is there a valve stem seal that will work with the VS-708 spring? Once again thanks for your help.

Gary------



The inside diameter of the VS-708 inner spring is 0.797" with an OD of 1.07"

The inside diameter of the VS-708 outer spring is 1.087" with an OD of 1.501"

You can cut-and-paste the link that Chris posted into your address bar in order to read that thread.
It has a LOT more information on this subject.

[Mark E.]

Re: Replacing 427 Valve Springs

Gary------

I can't answer for Mark. However, I can tell you that the Fel-Pro (Federal-Mogul) OEM equivalent valve seals (available as a set) is SS71152. The OEM seals from GM are GM #460527. However, regardless of Mark's apparent success, I do not recommend using these with the VS-708 valve springs for several reasons:

1) As I previously mentioned, the OD of the above seals is too great to be used within the inner spring which is part of the VS-708 valve spring. In time, the spring will destroy the seal. The OEM umbrella seals are designed to be used with the original 1965-E1969 valve springs which are an outer spring with flat wire damper. They are not designed to be used with the dual valve spring VS-708. Federal Mogul specifies that the VS-708 are to be used with the GM #3964264 valve spring caps ("retainers");

2) The GM #3964264 cap is configured to center both the inner and outer valve springs of the GM #3970627 or VS-708. Earlier caps will not accomplish this. Will the earlier caps fit the VS-708 springs? Yes, they will but they will not center the two springs.

I misspoke. I used Fel-Pro "Valve Stem Seal Set SS 72513" which is a box of sixteen 90763 seals; see:

https://www.rockauto.com/en/parts/fel-pro,SS72513,valve+stem+seal,5800

They snap onto the original retainers like the original seals. I started a thread a few months ago about this, and I believe these are the seals Joe recommended to use with the dual spring VS-708. No interference noted between the seals and springs.

[Joe L.]

Re: Replacing 427 Valve Springs

I misspoke. I used Fel-Pro "Valve Stem Seal Set SS 72513" which is a box of sixteen 90763 seals; see:

https://www.rockauto.com/en/parts/fel-pro,SS72513,valve+stem+seal,5800

They snap onto the original retainers like the original seals. I started a thread a few months ago about this, and I believe these are the seals Joe recommended to use with the dual spring VS-708. No interference noted between the seals and springs.

Mark-------


In your case, your 1970 should have originally had the 3964264 valve spring caps so all you had to do was replace the seals. In Gary's case, his 1967 did not originally come equipped with the 3964264 caps, so to use the VS-708 springs he would need to acquire those valve spring caps.

GM never sold the springs without the caps. In fact, GM #3970627 was not a valve spring. It was a UNIT that consisted of the dual spring + the 3964264 cap. The spring, alone, must have had a different part number but I don't know what it was since, as I say, it was never available separately. The valve spring cap, GM #3964264, which was part of the 3970627 UNIT, was once available separately.

[Joe R.]

Re: Replacing 427 Valve Springs

Mark-------


In your case, your 1970 should have originally had the 3964264 valve spring caps so all you had to do was replace the seals. In Gary's case, his 1967 did not originally come equipped with the 3964264 caps, so to use the VS-708 springs he would need to acquire those valve spring caps.

GM never sold the springs without the caps. In fact, GM #3970627 was not a valve spring. It was a UNIT that consisted of the dual spring + the 3964264 cap. The spring, alone, must have had a different part number but I don't know what it was since, as I say, it was never available separately. The valve spring cap, GM #3964264, which was part of the 3970627 UNIT, was once available separately.

Check out #4 above and you will see what Joe is talking about! That is if the picture came thru!

JR

[Gary F.]

Re: Replacing 427 Valve Springs

I have ordered VS-708 springs which were hard to find because they have been discontinued. What is the installed height of the VS -708 spring? I plan on machining for positive seals to replace the umbrella seals but I need valve spring retainers. Does anybody know of an aftermarket retainer that will work? Does anyone have a 3964264 retainer to measure the heights of the 3 steps? I have the OD's as 1.401 bottom flange, 1.081 first step, and .417 at the top with a flange thickness as .115. Thanks for any help.