L79 Cam Replacement

[Joe L.]

Re: Thanks Joe

Joe-----

As long as you accept the fact that the '142' valve springs will reduce the longevity of the cam, I think that this will work out just fine. As you say, in your case the issue of camshaft longevity is not important, at all. So, you have everything to gain and nothing to lose by using these springs. Furthermore, I didn't mean to imply that the use of the '142' springs is going to drastically reduce the life of the cam; even if you drove the car fairly regularly, you'd still likely get more use out of the cam than you're ever going to need.

[Joe L.]

Addendum

Duke-----

Something that I stated incorrectly or, at least, neglected to mention is that, as you stated, a different exhaust valve spring was used for some 73-77 small block cylinder heads. This spring, GM #6263796, is the same configuration as the GM #3911068 except that it has a shorter free length. It was designed to be used with the exhaust valve rotators. When installed with the rotators it produced the same open and closed pressure as the 3911068.

After about 1977 the rotators continued to be used. However, the exhaust valve spring pockets in the heads were machined differently so that the 3911068 springs could be used on both the intake and exhaust valves. Of course, then, with these heads, the exhaust valve rotators MUST be used or an equivalently thick shim(s) MUST be used under the exhaust valve spring.

[Mark F.]

Thanks Clem & Joe. 151 it is. *NM*

[Duke W.]

Re: Addendum

Thanks for the rundown on valve springs. I admit I ASSUMED that the 381 spring was discontinued and am surprised it is still available.

From my '63 Corvette Shop Manual the specs on this spring are 78-86 lb. @ 1.66" and 170-180 lb. @ 1.26". From my neighbors '77 Chassis Service manual the inlet spring (068) is speced at 78-86 lb @ 1.70" and 194-206 lb. @ 1.25". The I-6 spring specs are the same at '63 V-8s, so it appears that the 381 spring continued on the six.

Duke