Valve Springs

[Mark H.]

[FONT='Calibri','sans-serif']I have a question about valve springs for a '64 L75 (with 461 heads form 1966, but I don't think that matters). In researching prior posts, I see that Sealed Power VS-677 has been recommended. But, when I looked up my engine on the Federal Mogul website, it told me to use VS-521. These two springs are very close in spec, but not identical. The 521 is 8 thousandths smaller in diameter, 4 thousandths shorter in closed height, has closed pressure of 82.5 lbs (vs. 76 lbs for the 677 spring), is 56 thousandths taller in open height, and has open pressure of 193.3 lbs (vs. 194 for the 677 spring). These differences seem negligible to me, but they must matter to someone because both parts exist. Any thoughts? I've looked in my shop manual, and I can't match the spring specs to either one. Thanks and Happy New Year![/FONT]

[Joe L.]

Re: Valve Springs

[FONT='Calibri','sans-serif']I have a question about valve springs for a '64 L75 (with 461 heads form 1966, but I don't think that matters). In researching prior posts, I see that Sealed Power VS-677 has been recommended. But, when I looked up my engine on the Federal Mogul website, it told me to use VS-521. These two springs are very close in spec, but not identical. The 521 is 8 thousandths smaller in diameter, 4 thousandths shorter in closed height, has closed pressure of 82.5 lbs (vs. 76 lbs for the 677 spring), is 56 thousandths taller in open height, and has open pressure of 193.3 lbs (vs. 194 for the 677 spring). These differences seem negligible to me, but they must matter to someone because both parts exist. Any thoughts? I've looked in my shop manual, and I can't match the spring specs to either one. Thanks and Happy New Year![/font]

Mark------


The VS-677 spring is the equivalent of the GM #3911068 which was used for virtually all 1967-91 small blocks. The VS-521 is the equivalent of the GM #3735381 which was used for pre-1967 small blocks.

As you have found, the specs between the two springs are very close. However, the VS-521 or GM #3735381 would be the correct spring for your 1964 application.

[Duke W.]

Re: Valve Springs

Mark is installing a McCaw Special camshaft that has the same lobes as the 3896929, which was first used in 1967 along with the 3911068 valve springs.

So I have recommended the VS-677 to Mark. With its slightly greater rate, seat and open force, I recommend this spring for all SB rebuilds back to '57 with any OE camshaft.

With proper attention to valve spring installed height, hydraulic lifter pump up will occur at 6500+ with OE hydraulic lifter cams and OE mechanical lifter cams can rev to 7000+ before minor valve float occurs.

I'm not sure of the price of the VS-521, but I have seen online vendors that sell 16-piece sets of the VS-677 for less than 20 dollars, so it's a very economical choice, and given its use in milllions of SBs from '67 to at least the early nineties, it has proven durability.

It suprised me that GM and the aftermarket still offer the earlier spring. I think you once quoted the GM price and it was outlandish. I expect they've had them in stock for years and just keep adding inventory carrying cost every year.

GM discontinued the earlier base cam long ago and substituted the ...929 back to '57, which is a good choice because the early base cam has harsh dynamics, which is tougher on the valvetrain; and it makes sense to use the same spring that was OE with the ...929 cam - and later designed cams including the LT-1, which uses the 30-30 lobe on the exhaust side.

The L-79 cam used the earlier springs through '66, but the ...068 in '67 and '68. As long as there are no judging consequences, I usually prefer using the lastest released parts since they almost always have functional or durability improvements. Otherwise, there would have been no need to replace the earlier part.

Duke

[Mark H.]

Re: Valve Springs

Thanks. -677 it is. FWIW, the -677 is $1.00 cheeper at NAPA than the 521 spring ($2.49 each vs. $3.49 each).