'70 head rebuild.

[Ol' Geezer]

Geezer here. I have a '70 350/370 w/ '78 L-82 heads (I suppose for more cc's, lower CR, gasoline availability, and perhaps lead-free tolerance.) The original heads came with the car. I have just now opened the boxes and found two 3927186 heads, with reasonable date-codes. These are the double-hump fuelie heads with 2.02" intakes. The heads have only the valves, screw-in studs, and push-rod guides. I plan to have these heads rebuilt. In the old days, all I needed to do was ask a good machine shop for a valve job and perhaps PC-Seals. But, I don't know what to ask for now. Seat hardening for no-lead fuels? Any better seals out there? And what spring-sets, caps, keepers, etc. should I get from my handy parts guy?


Thanx in advance.

[Joe L.]

Re: '70 head rebuild.

Geezer------


Now, you're not going to sell this thing off after I offer advice on it, are you?


Anyway, here's what I'd do. Have the machine shop install hardened exhaust seats. Many machine shops don't like doing this on Chevy heads with 2.02/1.60 valve size. But, it can be done. I've talked personally with the owner of Valley Head Service in Pacoima, CA, which is one of the west coast's leading cylinder head servicers for 30+ years. He told me that they do them all the time. But, if you get any resistance from your machine shop, I wouldn't force them into it. I'd take them to a shop that is comfortable and experienced doing it. Valley Head Service would be one, if all else fails.


Second, don't use PC-teflon seals. I've had poor luck with these for street use and I don't recommend them. I've also spoken with many others that have had the same experience as I. Instead, I would use the Viton valve seals that GM switched to in 1981. These are GM #460483 and currently GM list for $3.05 each. You only use them on the intake valves. The stock 0-ring seal is sufficient for the exhausts, or you can use a rubber-type umbrella shield which fits on the valve stem(like some big blocks use). A seal kit, which includes 8 of the 460483 intake seals and exhaust seals used to be available under GM #14003974, but I don't know if it is still available. An alternative to these are the seals used on late model Corvette LT-1 engines. These use positive type seals on the intake and exhaust and they are a specific type for either. I don't have the part numbers handy, though.


As far as retainers and locks go, I would use stock GM. These are very reliable and economical and will work well within the limitations of a street performance engine. The retainers(caps) are GM #14003974 which list for $1.95 each and the locks (key) are GM #3947770 which list for $0.74 each. Also, I highly recommend using the stock GM metal umbrella shields if you use stock or near stock diameter valve springs. These are GM #10007818. Some folks like to eliminate these; I DON'T.


For valve springs, there are several ways to go. I wouldn't use a high pressure valve spring for street operation, especially if you are going to use a stock-type cam(like the LT-1 cam). Use stock GM valve springs GM #3911068. These were also used on original LT-1 engines. For a better spring with somewhat higher spring pressure, use GM #10134358. Both of these springs are of "stock" diameter. Don't use any spring with a greater pressure that the 10134358.


If you valves are good as to face and STEM, you can re-use them. They will live very well with unleaded gas. But, if the stems are worn even a little, you'll need to replace them. Replace with high quality, American made, stainless steel valves.


If your valve guides are worn, DON'T EVEN THINK ABOUT HAVING THEM KNURLED. Replace the guides with CAST IRON valve guide inserts. Do not use thin wall bronze. Thick wall silicon-bronze guides are ok, but they're more expensive than the cast iron and won't serve you any better.

[Ol' Geezer]

Re: '70 head rebuild.

Geezer here. Joe -- thanx for your very detailed and complete response to my inquiry. I have printed it out and will hie myself down to my friendly Chevy parts man tomorrow. (Side-note to John -- yep, it still prints yellow, but that is expected)


As far as selling the car?, I don't know. 'Tain't too much fun to work on anymore. When I stick my noggin under the hood, it takes about 67.83 seconds before my eyes get acclimated to the change in light level. Then, any idle-screw, etc., is always in the wrong plane of my bifocals, meaning that I adjust by Braille. Finally, my arthritis is acting up so I can't properly grip a wrench or screwdriver. BUT, when I get behind the wheel and feel the car get legs about 4500 rpm -- makes up for a lot of grief.

[Joe L.]

Small Correction to Above Post

I made an error when I provided the part number for the valve seal KIT. The part number was GM #14033547 NOT 14003974. Anyway, I researched the 14033547 and found that it became GM #10132715 which later became GM #12511980. That part was superceded by GM #22636288 which was, itself, superceded by GM #22636289. Then, the GM #22636289 was discontinued. So, the short of it is, you can't get the kit anymore. But, you can get the GM #460483 individual seals (which come in a package of 4).