big block valve wsprings

[William F.]

I've read in previous posts about weakness of '65-'69 BB valve spring design-single spring with inside damper vs. later design using 2 springs per valve. Are reported breakages limited to higher hp higher redline (6500-7000rpm) engines or has anyone had a first design spring break in a lower hp-5500-6000 redline 390-400 hp engine? What about if engine has 60-70K original miles on it?
Thanks

[Clem Z.]

Re: big block valve wsprings

I've read in previous posts about weakness of '65-'69 BB valve spring design-single spring with inside damper vs. later design using 2 springs per valve. Are reported breakages limited to higher hp higher redline (6500-7000rpm) engines or has anyone had a first design spring break in a lower hp-5500-6000 redline 390-400 hp engine? What about if engine has 60-70K original miles on it?
Thanks

you are lucky as i had one break on my 1965 396 on the way back to Pa. from the factory pickup in St Louis. i had 2 more break before i got my 66 427. i carried tools with me to change them on the road and i changed one in the carolina's on a trip to myrtle beach. maybe i ran mine too hard.

[Jerry G.]

Re: big block valve wsprings

What about switching to modern Beehive springs? I use them on race car they are great , long life and great performance.

[Michael H.]

Re: big block valve wsprings

William,

If your engine still has the original single wire valve springs, you are very lucky. While the single coil design did become more durable in the next year or two, it was still a very bad design and if a spring happens to break at a bad time/RPM, it often leaves you with one good cyl head and an intake manifold with a few good piston/rod assy's. The rest is scrap.
As far as I know, GM/Chevrolet still sells a great replacement dual spring under part number 3970627. (verify part number as that's from memory) I highly recommend replacing all of your original springs.

[Carl N.]

Re: big block valve wsprings

After breaking several on my L78 in the first few years I went with aftermarket on springs, guides, rocker arms, studs & nuts and never looked back.

should the car ever be judged and the valve covers removed it will be a full deduct lol

[William F.]

Re: big block valve wsprings

Clem,
Your 65 would have been 425 hp with hot cam and high redline. I'm asking specifically abour any problems or not with valve springs in the hydraulic lift big blocks.

[William F.]

Re: big block valve wsprings

Sorry if I repeat, but I'm asking about the lower hp haudraulic lifter cam big blocks, NOT the 425, 450,435 hp etc. solid lifter high redline big blocks. Anybody have valve spring problems in a HYDRAULIC lifter big block with first design valve spring/damper ?

[Joe R.]

Re: big block valve wsprings

Bill,

It doesn't matter which BB version you have. The original design springs are bad news. I would recommend getting rid of them ASAP. Unfortunately, I hear the 3970627 springs are no longer available from GM. I don't know what to recommend using.

Joe

[Clem Z.]

Re: big block valve wsprings

the bad retainers had a "O" on them and the later ones have a "T" on them. the better keys were "green" in color

[Joe L.]

Re: big block valve wsprings

William,

If your engine still has the original single wire valve springs, you are very lucky. While the single coil design did become more durable in the next year or two, it was still a very bad design and if a spring happens to break at a bad time/RPM, it often leaves you with one good cyl head and an intake manifold with a few good piston/rod assy's. The rest is scrap.
As far as I know, GM/Chevrolet still sells a great replacement dual spring under part number 3970627. (verify part number as that's from memory) I highly recommend replacing all of your original springs.

Michael------


Unfortunately, the 3970627 was discontinued about a year ago. Actually, GM #3970627 was not a valve spring but a valve spring unit. This consisted of a valve spring, retainer and integral umbrella-type seal.

[Michael H.]

Re: big block valve wsprings

Michael------


Unfortunately, the 3970627 was discontinued about a year ago. Actually, GM #3970627 was not a valve spring but a valve spring unit. This consisted of a valve spring, retainer and integral umbrella-type seal.

Thanks. Sorry to hear that. That is/was a great spring, especially for the money. I think I still have a set in the boxes.

[Bill M.]

Re: big block valve wsprings

Sorry if I repeat, but I'm asking about the lower hp haudraulic lifter cam big blocks, NOT the 425, 450,435 hp etc. solid lifter high redline big blocks. Anybody have valve spring problems in a HYDRAULIC lifter big block with first design valve spring/damper ?

I worked at the Tonawanda dyno lab in 1969. We ran a lot of hydraulic lifter 396s. We did break the first design valve springs and did not run the engines to redline. They ran peak torque rpm to peak HP rpm.

[Joe R.]

Re: big block valve wsprings

Sorry if I repeat, but I'm asking about the lower hp haudraulic lifter cam big blocks, NOT the 425, 450,435 hp etc. solid lifter high redline big blocks. Anybody have valve spring problems in a HYDRAULIC lifter big block with first design valve spring/damper ?

Bill,

It doesn't matter whether it's a Corvette, Chevelle, or Chevy EVERYBODY had problems with the first design HYDRAULIC lifter BB springs. You need to replace them NOW! Either that or you will be putting a SLEEVE in a couple of cylinders of your original block. And looking for someone to weld up your head!!! The 3970627 valve spring assembly was certainly the way to go but I just checked GM trax and it's gone! Check with some camshaft manufacturers as they will know the replacement for that spring.

JR

[Clem Z.]

Re: big block valve wsprings

http://www.summitracing.com/parts/NAL-12371061/ try here to see if they still have any

[Duke W.]

Re: big block valve wsprings

Michael------


Unfortunately, the 3970627 was discontinued about a year ago. Actually, GM #3970627 was not a valve spring but a valve spring unit. This consisted of a valve spring, retainer and integral umbrella-type seal.

Like most replacement parts for vintage engines I doubt if GM actually manufactured these parts. Rather it would likely be Federal Mogul or Dana Corp. and they sell the same parts under their own brands and part numbers, so there is no need to go to the GM dealer and pay their premium prices.

When this issue first came up a few years ago I tried to cross reference both the individual spring assy. no. and the 16-piece kit part number, 12371061 but came up blank.

It's inconceivable that an OE replacement valve spring is not available when just about everything else is.

You big block guys should get together and determine once and for all if these OE equivalent parts are available in the aftermarket or find an aftermarket design that has the same specs.

Duke