Hardened valve seats, iron head

[Lucas]

Please excuse my lack of experience. I'm diving in deep to learn.

I'm finally taking my extra head for my 615 in next week for a valve/seat grind and new guides. This motor will live a long time so I got a little OCD and am match porting and polishing it. I know I know, silly. People claim a 5hp gain, that's close to 10%!

I saw someone working on an old gas motor with an iron head. They got a valve job and had hardened valve seats placed in it, as opposed to seating right on the head. They said the iron seats were designed for leaded fuel, and required an additive to run unleaded and not burn them up.

I know this MB steel is tough, I've never broke so many tools in my life. I snapped a snap-on 1/2" breaker bar tearing the motor down.

I'm wondering if this application would be beneficial to my head, having hardened valve seats installed?

Is unleaded fuel a common problem for iron heads?

Less interval for valve adjustment, and longer head life in general. I know the FSM says that if seat height is beyond spec they grind it down and install a new seat, but not sure if anyone does that or just find a new head.

[junqueyardjim]

NO Lucas, you do not have to do that. The valves on you 615 engine are totally adequate. The reason they do it on old gas engines is that before we went to unleaded fuel, I think in 1975, the lead in fuel gave a lot of protection to valves and valve seats. Now there is no lead in gas, so the manufactures have all had to toughen up their valves. It took a while but they are all up to snuff now. But you are or will be running diesel, also a lead free fuel, and your diesel engine does not require lead or hardened valves and valve seats.

[OM617YOTA]

Diesels run at a significantly lower temperature than gassers, which greatly increases valve and seat life. MBZ also knew their biz, I'd be pretty surprised if you don't already have hardened valve seats. Regardless, these engines go a LONG time the way MBZ put them out from the factory, I'm sure whatever's there is fine.

A machine shop may disagree, but a barber would disagree when you tell him you don't think you need a haircut, too.

[Lucas]

Lol. I honestly should be more worried about getting a hair cut.

Thanks. Thats a good reason for asking here.

With them grinding the seats, should I harden them when I get it back? I believe I still have some materials for that type of operation. Not sure if it's the same as hardening the mechanisms in a trigger assembly for a gun.

This motor is before 1975 was my concern. Before unleaded.

[OM617YOTA]

Hardened valve seats are installed in a head by machining out the head and pressing in an insert of a hardened material, and then grinding that hardened material into the appropriate shape. The material of the head itself isn't hardened.

I've done some hardening at home with a torch and a dunk in water or oil, but like you that was always smaller parts and nothing cast. Attempting that with a small portion of a large cast iron assembly would be disastrous.

Lead was never added to diesel fuel. It was added to gasoline first as an octane booster and had a secondary benefit of creating a coating on the valves and valve seats that prevented wear. It wasn't so much a lube as preventing the red-hot valves from welding to the seats in little tiny spots, and then breaking those welds and having a bit of the material fly away out the exhaust every time the valve was opened. Our diesels, not needing octane, never had lead added to the fuel. They also don't get anywhere near as hot as a gasser, which also greatly adds to valve and seat life.

You'll be fine.

[Lucas]

Ok ok. Last question, if I were to put on hardened seats would it beneficial. Like if I won the lottery and was just crazy?

And would valve adjustment interval increase?

I've put in stainless seats and titanium valves on a dirt bike to avoid valve adjustment intervals. They were like every 600 miles initially.

Edit: maybe it was the other way around. Or completely different. Can't remember.

But if I made the seats harder would I need to do something about the valves?


This motor has changed direction. And now might go in my dads 49 Chevy truck. Turbo is too complicated for him. Guys taught me everything I know with farming, so kinda going all out.

[leathermang]

It would not do any harm to have Stellite valve seats installed....
You are not able to harden that area yourself.... trust me on that one...
If you want to get trick... put in the sodium filled valves at the time of the valve job...
and I know you are doing springs, rotators, and stem seals...

[Lucas]

Still haven't figured out those rotators. Lol. I'm anxious to see if you are pulling my leg. Going in next week.

Are the stock valves sodium filled? What's common in aftermarket? This thing was pieced together, how do I tell them apart.

Thanks for the metal type. I'll look into that.

[leathermang]

The turbo needs and has sodium filled ... at least the exhaust...
I am not pulling your leg about rotators...... surely you have seen them on your old tractor engines......
some small engines have them.. and the keep the valve and seat ROUND... and can greatly increase the life of an engine...

[leathermang]

Remember... the valve seats are a three angle cut....

[Lucas]

Lol. I just don't understand what makes them rotate. The cap is notched into a slot in the valve which seems different. I probably would get it if I wasn't focusing on 5 problems at once.

I was reading about that. This machinist is supposed to be good. But I'm bringing him the FSM printed out and seeing what he says.

I looked into metric motors. They were $520 but didn't include springs. So it was about $120 more plus a drive to LA. If I don't feel comfortable with this guy I'll head down there.

[leathermang]

Ratcheting.

[BillGrissom]

All gas engines w/ aluminum head (most common today) have hardened steel valve seats. Some cast-iron heads made in the no-lead days had "induction hardening" in the area of the valve seat, instead of separate steel seats. The Chrysler "Magnum" engine is like that (V-6 & V-8 5.2 & 5.9L, used in ~1989-2000 trucks & some Jeeps). Not the best choice, since those heads have big problems with cracks between the valve ports.

[Lucas]

Interesting. I'll see what the machinist says and report back.

[leathermang]

The FSM shows doing this.... I think the hole made for the Stellite valve seats is slightly dovetailed..... and then the valve seat is PEENED several places around the edge to keep in place... then a three angle grind is.....