hardened valve seats---how? [Archive] - Chevelle Tech

: hardened valve seats---how?


baddbob71
Jan 4th, 04, 8:42 PM
G.M. started using hardened valve seats when unleaded was introduced. I was wondering if anyone out there new how the factory actually did it? I was once told they were induction hardened meaning? The exhaust seats on the old 462 heads I just rebuilt sure seemed hard on the surface but from what I've been told the factory never hardened seats back then. Are seat inserts the best way to go? Two of my friends have had problems with coolant leaks with the inserts-is this common? My 454 049 heads have about $700 and 40hrs. tied up in them----I'll be crying the blues if they end up leaking.

BillK
Jan 4th, 04, 8:59 PM
Bob,
Induction hardening is done with a magnetic induction coil that heats the valve seat area without touching it. Any good machine shop should be able to install hardened seat inserts without hurting the heads however .... on Big Block heads I always tell my customer that there is a possibility of breaking into the water on the exhaust seats. Especially if you are trying to put in larger valves. It has only happened twice in 15 years to us, but thats enough to warn them up front. You can usually tell if the seats are hardened when you start to cut the seats with carbide cutters. The non hardened ones cut a lot easier.

Wolfplace
Jan 4th, 04, 9:00 PM
Bob,
I have installed way more exhaust seats then & can remember & I always warn the customer that there is a posiblilty of getting into water.
In 20+ years I have had ALMOST no problems in both rat & sb applications.
But castings being what they are I would recommend that in your deal you just run a lead substitute in your fuel.
Unless you are working the sucker to death, towing, motor home etc You will go a long time without problems this way.
My basic understanding of what happens in heavy duty service is the valves get so hot that when you turn the engine off the valve microwelds itself to the seat. The next time you start the engine the valve actually pulls cast iron out of the seat. Eventualy you can kind of guess where your valve seat ends up :D

Wolfplace
Jan 4th, 04, 9:02 PM
Hi Bill,
Happy New Year.
Musta been typing while you was postin ;)

BillK
Jan 4th, 04, 9:04 PM
Hi Mike,
Glad we both think alike !
Happy New Year smile.gif

baddbob71
Jan 4th, 04, 9:11 PM
Thanks guys for shedding some light on this for me. I always wondered how the factory hardened the seats. I'll cross my fingers on the bigblock heads. The 462 fuelies I just did for my son didn't get the inserts, hopefully He will get 10k or so out of them before the seats go away.

Daves70SS
Jan 4th, 04, 9:51 PM
Originally posted by BillK:
Bob,
Induction hardening is done with a magnetic induction coil that heats the valve seat area without touching it. Any good machine shop should be able to install hardened seat inserts without hurting the heads however .... on Big Block heads I always tell my customer that there is a possibility of breaking into the water on the exhaust seats. Especially if you are trying to put in larger valves. It has only happened twice in 15 years to us, but thats enough to warn them up front. You can usually tell if the seats are hardened when you start to cut the seats with carbide cutters. The non hardened ones cut a lot easier. Why are the machine shops not doing the induction hardening instead of installing inserts? Is there induction hardening equiptment available to the engine rebuilding industry?

Dave

baddbob71
Jan 4th, 04, 9:57 PM
Dave there must be alot more to it than what I picture or the shops would be doing it I would think. Especially considering the time invloved with installing hardened inserts.

jakeshoe
Jan 4th, 04, 10:02 PM
New car manufacturers use induction hardening because everything is new and fresh. And it is fewer machining operations, and potentially more reliable. Also costs less, the all important profit...

In a automotive machine shop we aren't dealing with new stuff usually.
Usually 35 year old worn out stuff for the hot rod crowd.
So induction hardening a seat that is sunk 1/8" is not a possibility.

You have to cut the old material away, install a new seat, then cut it.

The stellite seats are harder than anything the factory does. If properly installed they are great.

10K shouldn't be a problem on even a non-hardened seat.
A little lead additive, even if not every tank will help but isn't mandatory.

Sometimes they last a long time, others they seem to go quicker..
if the guides are in good shape, they'll last probably until the motor is in need of an overhaul.

MonteMan454
Jan 5th, 04, 12:29 PM
Would there be any reason someone would shift from hardened to non-hardened? I think up here in Canada all lead gas including racing fuel is banned.

pdq67
Jan 5th, 04, 1:15 PM
I have mentioned this before about adding half a bottle of good old Marvel Mystery Oil to both your tank and the oil b/c the stuff is imho, darn good top-oil!!

It should help the seats as well as the valve stems..

pdq67

Busted Knuckles
Jan 5th, 04, 2:54 PM
Anyone have experience with installing larger valves in the new big block Vortec (7.4L) heads (heart chamber, swirl ramp in intake port)? I have a set that I'll be putting on a 496 for my 1-ton dually and don't want to take a chance on seats if GM has started making big block castings thinner/weaker - I'll just go with factory valve sizes and give up a few ponies. Thanks!

MonteMan454
Jan 5th, 04, 3:02 PM
I think I figured out why leaded might be used.

When you are using high octane fuel with high compression the lead acts as a cooling action in the combustion chamber. This will reduce pre ignition.