Hardened valveseats...or not?

[AKcharger]

Need some advice here guys, one of the 452 heads I brought to the shop is cracked   So here's the questions:

1) I can get another 452 but heard the hardening can be "cut away" during the valve job...is that true? Something about induction hardening"

2) I have a spare set of 906's laying around and those are my back up but hardened valve seats are $300. So question is do I need them with just limited driving? since this engine will not see 100K miles anytime soon is it worth the investment?

Thanks

AK


P.S. On the positive side I picked up the Short block today...all 470 cubic inches of it 

[chargerbr549]

Most factory induction hardened seats that I have run accross the thickness or depth of the hardness runs about 1/16th to 1/8th inch deep so if the heads haven't had a valve job before you can probably get away with just cutting the seats however with that being said it all depends on the usage of the heads I have seen alot of factory induction hardened heads where the seats are sunk deep into the head because they can't take extreme usage very well, you see it in a lot of pick-up truck motors where they pull a lot of weight or run alot of rpm or both in order to do there job.
In most of the late 80's on up to the late 90's small block chevys if it was a 1/2 ton pick-up they just used induction hardened seats and 3/4 ton on up used a hardened alloy seat insert to take the abuse.

kevin

[AKcharger]

Gotcha Sir...well on another post someone said that 452's we not induction hardened but used another process...anyone know if that's true?

[firefighter3931]

Gotcha Sir...well on another post someone said that 452's we not induction hardened but used another process...anyone know if that's true?

The 452's use an induction hardening process. The earlier 346 heads use a flame hardening method which is less durable. If you use the stock size 1.74 valve the 452's are the way to go. I would use a good stainless steel valve no matter what head you decide to go with.

The 906's would probably last for awhile with a good stainless valve and maybe a bottle of lead additive in every tank of gas.


Ron

[Challenger340]

100 ML's of top end oil, per tank of fuel, is sufficient to provide valve seat lubrication and prevent recession on non hardened heads.

Works best on "hard" material type stainless valves, and very soft "as cast" seats after enlarging for bigger valves.

Stay with non synthetic, non tcw-3, just plain old 2 stroke oil.

No, the engine won't smoke like a 2 stroke either !

TIP; start off with about 200 ml/tank on a fresh rebuild, then back away incrementaly on subsequent tanks to eventually about 50ml/tank. It is important to remember, that just like the "lead" used to, the stuff builds up quite fast on the seats and remains there, hence you can "back away" the amount used after a few tanks.

Hope this helps,  Bob out.

[AKcharger]

So Bob you're saying use 2-stroke oil in the gas? Interesting, never head that. I thought it was a heat problem as opposed to lubrication

[chargerbr549]

What mainly causes the seats to sink is the ex valve gets very hot and it basically tack welds itself to the seat ever so slightly and it pulls metal away from the head causing it to sink, years ago when they had tetraethyl lead added to the fuel it would coat the valve and seat area and wouldn't allow the metal transfer, now with the dry fuels and running higher temperatures its a tough evironment for the valve and seat. Using different valve and seat materials will pretty much cure that problem but as Challenger 340 and Ron have said using different additives will help eliminate or slow the problem down.

Kevin

[AKcharger]

OK, that makes sense...weird that I've never heard of that before.

Well I'm going to sit down and do some number crunching and see how much the difference is between getting my 906's done with hard seats and new springs and simply getting a set up aluminium's...

[Chryco Psycho]

if the heads are off having the hard seats machined in is easy to do , you could also increase valve size to 1.81

[AKcharger]

I called 440 source and their saying Feb for their heads...I'll wait for them. If they have long delays then I'll go with the 906's

Thanks!