92RSFivePointSlow

I'm getting a pair of p&p, rebuilt heads sent to me, he says it just came from a running 305, I want to double check all the parts before bolting them on though. Obviously there are the valve stem seals that can dry up, what else can go bad in a set of heads, as far as oil seepage? I've got new springs I'm putting on, and the valves are less than 5,000miles old(the heads were modified to fit bigger valves). Do valve guides wear out? Are there seals on the valve guides that are replacable? Is this easy and are the parts expensive? Am I being paraniod or is this reasonable preventative maintenance? In other words, what would YOU DO when you get a pair of used heads before bolting them on? Thanks in advance

RB83L69

Yes, the guides wear out. Guides are pressed into the head after casting. Stock guides are cast iron. Better ones (such as are often found in aftermarket heads) are bronze, and you can repair worn cast-iron ones either by drillign them out and pressing in bronze ones, or with bronze bushings.

Seals are cheap and easy to replace, especially if you're already going to replace the valve springs.

My ideal standard HP head workup for junkyard heads would include:

• new guides, or sleeves, as described above
• push rod guide slots enlarged
• stud bosses cut for screw-ins and guide plates
• spring pockets cut for 1.45" springs
• guides machined to either .530" or .500" outer diameter, for Teflon seals; and shortened by about .150"
• the usual porting and polishing
• new valves with undercut stems
• seats replaced or hardened
• milling a few .001"s off the deck for flatness and sealing

And it could go on from there.

You can easily see that by the time you buy some junkyard castings and do all that to them, and then buy the other parts (studs, guides, springs, retainers, keepers, seals, etc.) you'll have almost as much in them as you would in a set of aftermarket ones, except you'll still have some old junk iron castings.

92RSFivePointSlow

But that is the beauty of it- someone ELSE already paid all that money, and I was able to pick these heads up at a good price. I just don't want to put these heads on my car and find out they smoke and then realize I should have examined them more closely while they were off. Any suggestions to this? Thanks

RB83L69

While you're swapping valve springs and putting on new seals, check the side play the valves have in the guides... if it's less than .005 or so, it should run OK for a while; less than .002 and it's pretty good for a long time to come.

92RSFivePointSlow

Side play is the amount the whole valve can move horizontally, or is it the amount one end can wiggle? I assume there's no seal in the guide, just metal to metal? And one last thing- he says the seals are just put on- when I switch the springs, if the stem seals are still pliable, is it ok to reuse them, or should I just get new ones, and what kind? Thanks alot for all the help

RB83L69

Right, side play is how far they can move side to side... basically, how far the guide is worn.

As cheap as valve seals are, and as much of a PITA they are to change, I'd just change them if I was already there anyway. Use the Fel-Pro positive ones, that have the metal bands to clamp them to the guide.

Vader

If the heads are aluminum (or even some cast iron heads) you should remove the valves when you change the springs, then inspect the valve seat inserts for signs of looseness. The seat can have carbon buildup, oil, or physical gaps around the base area. If the seats are pressed in and have worked loose, you could be in for some more machining time (and cost).

If you're not planning to machine the spring pockets for larger springs, at least inspect them for stress cracks and wear from the spring coils. Of course, a MagnaFlux check should reveal and such stresses, cracks, and loose seats.