magnesium valve covers

[Clem Z.]

question for joe

joe i am not used to working with mag parts for corvette but i have worked with mag parts for mine and my sons motorcycles and every mag part has the word "MAGNESIUM" cast into the part and i would guess that was because of the fire hazard of the material. does the mag corvette valve covers have the word cast into them? PS welding mag is a real art as i have had some work done and it looked fine but the next day the item was in pieces as it just exploded.

[Joe L.]

Re: Did you try asking this on the C3 CF?

Geoffrey-----

Vallejo did used to be a "big time" Navy town as a result of the Mare Island Shipyard being located there. However, and a great misfortune, Mare Island was a victim of the "Base Closure and Re-alignment Commission". This base had a storied history going back well over 100 years, but it's gone now. It was once the only base on the west coast where nuclear submarines could be re-fueled. Now there are NO such facilities on the west coast, as far as I know. However, the west coast is home to one "auspicious" facility related to submarines. That facility is the Puget Sound Naval Shipyard at Bremerton, WA. That's where ALL US submarines go to die. They enter drydock, the reactor section is cut out of the hull intact, and the remaining portions of the submarine are cut up to be recycled into Corvette frames, Toyota Corollas, Kias, or whatever. The reactor section is sent up the beautiful Columbia River on barges to be buried, all in a row with their "brethren", at the Hanford Reservation or the Idaho National Engineering Laboratory.

[Joe L.]

Re: question for joe

clem----

Yes, they do. At least, the 80-82 covers did. The word "mag." followed the part number. However, most of the covers that I've seen had the dual sets of part numbers that I described. So, at least with these, there was no real way of telling which valve covers that you had in hand.

I'm not sure about the 84-92 covers, though. I've got an NOS set of 92 covers [not for sale]. I'll check them when I get a chance.

[Warren S.]

Re: I can't look away

Jerry, does my 67 chassis service manual have a misprint in it or am I reading it incorrectly? For 8 Cyl.-327 Cu. in. Corvette (300 H.P.) Auto. Trans w/RPO K-19 the ignition timing is 4 deg. ATDC? That is AFTER top dead center isn't it.

[G B.]

It may not be a misprint

But it certainly is a bad idea. The shop manual also says the '67 CA smog Holley carb uses #63 primary jets rather than the regular #65 jets. If you set up your car using these specs, it will be a pretty weak sister at low speeds.

I'm sure there are many who take satisfaction in having their Corvette tuned exactly as GM originally recommended. My hat is off to you Warren, if you are one of them. However, in this case, I would prefer to have my Corvette to run like the 48 state 300 hp cars.

[Mark G.]

[John H.]

Re: It may not be a misprint

Yes, those are the correct original specs - retarded base timing was THE key ingredient in making the air injection system work, as it dramatically increased exhaust gas temperature, which promoted a more complete "burn" of hydrocarbons in the exhaust stream when fresh air was introduced from the A.I.R. pump (it also caused them to "run hot" at idle as a result). It also reduced peak combustion chamber temperature, which tended to reduce formation of oxides of nitrogen (NOX) emissions. You'll also note that the corresponding distributor for that engine provided a whopping 40 degrees of centrifugal advance (at 5100 rpm) in order to "buy back" some WOT performance in spite of the 4* ATDC base timing; that 40 degrees, minus the 4* ATDC, provides the normal 36 degrees total timing that most small-blocks like. These engines also had "ported" vacuum to the distributor, which rendered the vacuum advance totally inoperative at idle to maintain the 4* ATDC retarded idle timing; "ported" vacuum was simply an early/crude emissions strategy to maintain retarded idle timing for A.I.R. system effectiveness - period.