I read an Article, maybe it was here that all Heads will fit on All blocks.

Looking at a chart it seem that solid Lifters stopped in '79. and the Hardened Seats started in '73. Soooo for my '70 engine I guess I'm looking for a '73-'79 head for best match?

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1970 Valiant.. my sons Daily Driver
1975 CJ5, fiberglass body,350/345Hp chevy
1985 chevy stepside pickup, Original Owner
1989 Volvo 240: Original Owner
OTHER TOYS: http://home.no.net/ebrox/Tony's%20cars.htm

1980 was the last year for solid lifters. 1973 was the first year for factory induction-hardened exhaust seats, but that's not really too relevant when picking a head to build up, for you'll want to have real hard seat inserts installed. With the exception of '60-'62 heads originally used on cast-iron engines not being compatible with the '61-'63 aluminum block, all slant-6 heads are compatible with all slant-6 blocks—there's no need to shop for a particular year head just because you have a particular year block. The combustion chamber was slightly revised for better combustion in '67. That's desireable. Some heads got air injection passages starting in '72, and I'm pretty sure all heads had air injection passages starting in '75. Unless your vehicle needs to run air injection because it has a catalytic converter, this is not desireable because it makes the head heavier. The spark plug tubes were deleted and miniature taper-seat spark plugs used starting in '75; if you find yourself unable to cope with spark plug tubes, the later head becomes attractive, but there are more spark plug options with the up-to-'74 heads (w/spark plug tubes).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

72 was the first year for flame induction seats.

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

If you get a head with induction hardened seats in it there is no reason to replace them with new seats. The induction hardening goes deep enough that it will even be good for oversize valves.

Yes, I have 2 heads with oversize valves and induction hardened seats. Neither one has ever seen leaded gas and neither one has had a seat issue.

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Official Cookie and Mater Tormentor.

Mmm...the induction hardening goes only to a depth of about 0.05" tops, per factory specs & measurements when the induction-hardening process was introduced.
Good, but remember correlation doesn't imply causation. Many of us run unhardened seats with unleaded fuel in our slant-6s for a long while without recession. Doesn't make it a smart thing to do deliberately, though.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

'72 was the first year for induction hardened exhaust valve seats in V8 engines. The slant-6 didn't get them til '73.

Also, there's no such thing as "flame induction". Flames were not involved in the hardening process introduced on V8s in '72 and Slant-6s in '73. An electric induction coil was brought into proximity with the seat, and a high current passed through it. This heat-hardened the exhaust valve seat to a depth of about 0.050" max, which is enough for initial service and maybe a valve grind or two, with stock-size valves.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan, you can take your FSM and wipe your ass with it for all I care. I had mine done by a very competent machine shop and will follow their directions until hell freezes over.

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Official Cookie and Mater Tormentor.

Do a search on Wikipedia or valiant.org and you will see that both say that '72 was the first year for hardened seats for the slant six. My owners manual says the same also.

And a hearty good day to you, too, sir!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

*shrug* As you wish. I'm going by factory engineering info. Owner's manuals are notorious for containing errors, and anybody can write anything on Wikipedia.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Common sense and good machining workmenship hold true with the factory induction hardened valve seat issue. Let's face it, after all this time it is hard to know for sure what year a head is from.

Once the head is clean, you can see the discolored area around the exhaust seats, it is pretty obvious the area has been super heated.

When you grind on the seats, you know if it is still hard, the stone or cutter just does not cut well, it just seems to "buff" the surface. Once you get under the hardness, the material cuts like cast iron should. (soft and fast)

Have I successfully "touched-up" factory hardened seats, yes.
Have I put nickel alloy seat inserts into heads, yes.
Do I know which way to properly do the valve job prior to cleaning the head and grinding on the valve seats, no.

Bottomline: both methods are acceptable given the right situation.
DD

I've got a few of those older heads (not always certain of the years or mileage) that have held up well and I also have seen a few that burnt out badly. I've also seen a few with hardened seats that had burn valves (I know the one was on a low mileage (about 80k) stock 1978 that had 3 burn valves, perhaps due to a vacuum leak) Nothing is completely fool proof.

I seem to remember that lots of factors other than seat hardness determine if you will have problems. Excessive timing, Cam duration, Fuel mixture, Lash setting, Compression, Octane rating, Quality of Gas, etc. all can play a role on how a valve seat will wear. A harder seat is a nice safety net against some mistakes.

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1980 Aspen 225 super six

My philosophy is exactly what ↑↑ he ↑↑ said.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.