I am measuring my existing cam (used). My service manual specifies lobe lift at .2600/.2733 +/- .002, but doesn't differentiate between as to which 350 cid.
-
-
Re:
I know those aren't the correct lobe lifts. What service manual are you looking int. I think .306/.323 is the deal. You probably have some wear. How many miles?
Duke -
Re:
the engine has about 49,000 miles, so obviously some wear. Next question, excessive wear, should I replace the cam. The was supposed to only be a head job and engine compartment detail. Arghhh!
My dial indicator was moving around somewhat, I know, I know, but it's all I had access to.
Lifters all look good and all lobe lifts were pretty consistent.Comment
-
Re:
I wish Clem were around to advise on this one, but maybe Clup or John Z can give some guidance.
I think you're okay as long as you're willing to take the engine down in another 50K or so. If the measurements were pretty equal then you probably haven't worn through the surface hardening. Once through the hardening, the lobe will go pretty quick.
As a point of reference I recently refreshed the head on my Cosworth Vega. The valve guides were WAAAAAY worn, but the lobe lifts were all in the range of .353-.355 against a .355 spec - virtually no wear. Those little direct actuated valves don't need much spring, so there is little cam wear, but I haven't a clue why the guides were so worn as the 1.4 inch diameter inverted buckets should absorb all the side load. Go figure!
Anyway, replacement nickel-bronze guides are available for about four bucks each. The cams are unobtanium.
Duke
P.S. Start using HD diesel engine oil (API service grade CF-4). That's what I recently started using in my pre-converter cars. It has more EP (zinc-based) anti-wear additive, but their exhaust by products can be tough on catalysts. That's why modern oils for SI (spark ignition) engines have a less robust additive package than the HD diesel engine oils and prior SI API spec oils. I use Chevron Delo 15W-40, but Mobil Delvac and Shell Rotella are essentially the same.Comment
-
Re:
robert-----
The GM #3972178 camshaft is still available from GM and currently lists for $160.79. This cam can be purchased, though, for about $125.00 from many GM dealers. Also, reproductions of this cam can be purchased for $100, or less, from a variety of aftermarket sources. Wolverine, a division of Crane I think, manufactures them.
However, if you replace the cam, then you'll have to replace all of the lifters, too. GM mechanical lifters, of both the piddle valve and edge-orifice type, are discontinued. So, even if you use a GM cam, you'd have to use aftermarket lifters.
I really think that your cam is ok for continued use. If all you set out to do is a valve job, then you should be looking at a 50,000 mile "horizon" before further engine work may be required. There's certainly that much left in the cam based upon your description.In Appreciation of John HinckleyComment
Comment