Hardened Valve Seats or Not?

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There is one risk not mention thus far concerning the installation of hardened valve seats.
I had hardened seats installed on my 65 273 and 2K miles later I had a cracked cylinder head at a seat.
I ended up replacing both heads without hardened seats and now just use lead additive.
Maybe bad machine shop work caused the crack, but seat installation can create stress that may lead to a cracked head.
 
Yeah - that's machinist error for leaving the press fit too tight. They should have bought you a replacement head.
 
what year are the heads? check casting date on top, 1972+3 had hard exh seats, 1971 maybe. engine is assembled, and in a not heavy car - run it. heavy loads and boats need hard exh seats. my 1970 Duster 340, 1.625" manley valves, flat solid cam .555" lift and .022" consistent lash street and strip all good since 1995
 
toolmanmike said:
Let me think about this a second. As the seats go away the valve lash tightens. Correct?
Click to expand...
It's happening to me as I type this. Head needed work, unemployed. Took it to my engine guy and told him to budget freshen it up. He said you need hard seats. I know, but not in the budget, can you buy me 10k-15k miles and then we'll do it right?

Guess what? I'm about 8-9k into those soft seats and it's acting like I need to loosen the valves up some.

The first valve grind on an induction hardened seat will probably go thru the induction hardening. It's only .005" to .030" deep. I don't see any point in scrounging for a late model set of heads if that's the only reason for them.
 
Found this in a parts dart I had. :)

unleadedfuel.jpg
 
If there is enough money in the budget, do it. You will sleep better at night knowing you won't have to worry about it. I did it for that very reason. Today's fuels are terrible and don't have all the good stuff these engines needed back when they were new. I am assuming that when you had the heads done years ago that they did a valve job. If that is so, then as stated earlier the induction hardening that was done by the factory has been tampered with. If cut deep enough depending on how well or poorly the hardening was done then the exhaust seats will be soft and ultimately fail.
 
I know this is an old thread:
Running without hardened seats long enough and you could drop a valve and destroy your engine.
You end up with less and less spring pressure and run the risk of pounding the valve through the retainer.
I can provide pictures but don't have the pictures here.
Valve fell, hit the piston, broke off the valves head, destroyed the piston and cracked the cylinder wall.
Also bent the rod and damaged that journal of the crankshaft (bearing welding) though I could clean it up and re-use the crank and I was also able to re-use the camshaft.
Owner thought they had a lifter noise for about 5000 miles before it let go.
 
j&l-motorheads said:
I know this is an old thread:
Running without hardened seats long enough and you could drop a valve and destroy your engine.
You end up with less and less spring pressure and run the risk of pounding the valve through the retainer.
I can provide pictures but don't have the pictures here.
Valve fell, hit the piston, broke off the valves head, destroyed the piston and cracked the cylinder wall.
Also bent the rod and damaged that journal of the crankshaft (bearing welding) though I could clean it up and re-use the crank and I was also able to re-use the camshaft.
Owner thought they had a lifter noise for about 5000 miles before it let go.
Click to expand...

oh yea lets see some pictures.
 
Remember that you only have so many valve grinds on the valves before the seat area is too thin.
Did they replace the valves when the heads were done years ago ? If not you may already need some new valves when you repair the seats in the heads.
It is always more expensive to do a job twice than to do it right the first time.
Whenever you are short of money, re-adjust your priorities and wait 'til you can do it correctly.
 
IF it was a huge problem every old cars seats would be so bad you'd have replaced them.
 
The lead Does NOT go a way...........break in your motor with some "leaded race fuel". add a gallon to a tank every so often. Valves/ seats will be happy.
or spend the money on hardened exhaust seat and be happy. Motor should be happy either way.
Just my 2 cents.
 
There are plenty of good lead substitute additives on the market that actually work.
 
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