340 hp valve springs

[William F.]

Re: 340 hp valve springs

Thanks for the PN's for valve springs but only one chimed in on whether it's necessary to replace original springs after 50+ years of service. How 'bout it? If you do replace with the GM or Fed Mogul springs, do you just replace springs, retainers, keepers and that's it or do you have to check height, etc. and bring in line somehow? Thanks

[Joe C.]

Re: 340 hp valve springs

Thanks for the PN's for valve springs but only one chimed in on whether it's necessary to replace original springs after 50+ years of service. How 'bout it? If you do replace with the GM or Fed Mogul springs, do you just replace springs, retainers, keepers and that's it or do you have to check height, etc. and bring in line somehow? Thanks

Nope. No need to check installed height, just leave any shims that are already in place right where they are. Of course, that's assuming that the spring heights were set correctly to begin with.

Remove a few springs and bring them to a machine shop. Have them checked on a valve spring checker where they are compressed both to installed height and full lift height, whereupon, the spring pressures are noted.

Stock GM 3911068 springs should be 80# @ 1.700" (installed height), and 200# @ 1.250". Spring rate should be 267 #/inch.

[Stuart F.]

Re: 340 hp valve springs

How about the burrs on the valve stems left by the keepers? Sorry, just read a build in my latest Super Chevy Mag today and i'd never heard of that before.

My 63 L-76 (340HP) has about 46k on the clock now and it's never been apart. I regularly run it up to red line when I'm out exercising it on Sunday mornings, but I"ve backed down some due to the fears about the rods noted on many threads here and the thought of loosing an irreplaceble piece of GM performance iron. By the way, I have one of Don Lowe's valve spring stickers on my bumper.

Stu Fox

[Jerry G.]

Re: 340 hp valve springs

The only thing that makes me a little nervous is what happens if you break a Beehive. Does the valve fall into the cylinder? I'm still using them but.... I broke many "conventional" springs but never a BeeHive.

[Joe L.]

Re: 340 hp valve springs

The only thing that makes me a little nervous is what happens if you break a Beehive. Does the valve fall into the cylinder? I'm still using them but.... I broke many "conventional" springs but never a BeeHive.

Jerry-----


I would say that if the spring breaks in the beehive (i.e. reduced diameter) area, what you suggest might be a slight possibility. If it breaks in the full diameter area, I don't see why it would be any different than if a conventional valve spring breaks.

[Joe C.]

Re: 340 hp valve springs

Jerry-----


I would say that if the spring breaks in the beehive (i.e. reduced diameter) area, what you suggest might be a slight possibility. If it breaks in the full diameter area, I don't see why it would be any different than if a conventional valve spring breaks.

Joe,

The difference would be that a conventional spring capable of developing similar pressures as a beehive are never single units. They are generally dual at the low end and triple at the high end, and some use dampers as well. Jerry MIGHT mean that the second spring and/or damper would act as a safety mechanism. In this regard, I'd have to agree with him, although as you know, single springs as well as beehives break and remain intact thereby holding the valve away from the piston crown.

[Robert K.]

Re: 340 hp valve springs

Any brand or part numbers for the Beehive springs?

[Joe C.]

Re: 340 hp valve springs

Any brand or part numbers for the Beehive springs?

You don't need beehive springs with any GM vintage cam running stock stamped steel rockers. Beehives are only useful when required spring pressures get to be anything more than (about) 120# on the seat and (about) 360# @ full lift. If you use a LT1, 30-30, or any "off road" cam with 1.6:1 or 1.7:1 rockers, then you cannot use a stock spring, and beehives would be beneficial.

If you have a non-stock cam, or are using high ratio rockers with a GM cam, then post the part numbers and I can recommend a beehive spring for you.

If you use a 097 cam with 1.6 or 1.7 rockers, then the stock 068 springs have enough lift capability as to not go into coil bind, and are useable.

Joe

[Jerry G.]

Re: 340 hp valve springs

Any brand or part numbers for the Beehive springs?

I use COMP CAMS 26120-1, very easy on original type stamped steel rockers. I have run an entire season on one set of rockers and they still look like new. Most of my engines time is between 4000 and 7000.