I've read some on unleaded gas damaging valve seats on our older cars due to the lack of Tetraethyl Lead and it's lubrication qualities and that the only fix is to have hardened seats installed.

On the other hand I've read that there is minimal damage to valve seats and there is no need to do anything with the valve seats. Then I've read that there are other additives that can lubricate the valve seats sufficiently to prevent damage.

Talking to a guy that rebuilds old carburetors, he says that just running them richer with unleaded is sufficient to prevent damage to valve seats.

I'm a little confused but I know the truth is somewhere in all that. I really don't want to do anything to the heads on my car if I can at all avoid it. Currently I can get lead additive for it but I wouldn't mind not having to since it's an added expense.

I'm sure there is a right path to go down with a little guidance.

The last time I was at the machine shop and I had my 340 heads done they told me unless I was driving the car a lot or use it as a daily driver not to concern myself with it. It never became a issue for the 10 years or so I had the car. Then again it`s your engine and you do what makes you the most comfortable. BTW, what year engine is it? I`m not 100% sure but I think Chrysler started hardening valve seats around 73 or so.

My machinist said pretty much the same thing as mopars4ever said.For my own piece of mind I toss a can of Seafoam and 6 ounces of Marvel oil in every tank.

Back in the day when this info first came out, it was reported that some valve and seat damage could occur in as little as 75,000 miles without the lead additive.

75,000 miles is a long time in most occasionally driven cars, and then the "damage could occur in as little as" comes into play. Most read that as the damage could possibly start in 75,000 miles, not that it would, or was guaranteed to.

Funny thing is, before the mid 70s, it was not uncommon for some cars to show signs of needing valve jobs by 75,000 miles, and few motors lived past 100,000 miles.
If I had a motor apart it might be something to consider, but I'm not pulling a running motor down just for this purpose. I'll take my chances. I've driven a lot of high miles Mopars. Defective valves was of little concern, the motors often outlasted the cars. Gene

I've been running unleaded gas in my 360 with non-hardened J heads since I built the engine in 1993. Daily driving duty for long periods, long highway trips, you name it. I've probably put 150,000 miles on it.

I recently tore down the heads. Major valve seat recession, and pitted exhaust valves as expected. BUT, it was still running fine expect for the fact that I wore down a cam lobe as a result of coolant in the oil, rusting a lifter in place and preventing it spinning on the lobe as it should. No cloud of smoke etc, no dramatic loss of power.

The seat recession I attribute to a larger than stock cam and valve spring. With every valve closure it is like a tiny hammer strike on heated metal. The softer metal is going to move.

The valves themselves had the bigger part of the damage. Stock exhaust valves from rock auto cost me about 6 bucks a piece, a little lapping compound and elbow grease on the valve lapping tool and they should be set for another 100,000 miles. Compare that to the cost of installing hardened seats, which if incorrectly installed can drop out and hole a piston. I installed adjustable rockers (which I planned to do anyway) and they were able to correct for the valve seat recession. Otherwise a trip to the machine shop to trim off the tops of the valve stems and set the tips at equal heights would have been the route I took.

Is my rocker geometry perfect? No. Are all of my valve spring installed heights within .001? No. Is it what you want to do for pro stock or FAST racing? No. But for a street driven car, with a mild cam, my car is running just fine still, thank you very much.

M Ecks has your answer folks. ^^^^^^^^^^^^^
There is not yes or no answer on this topic.

We had a slant six on the road for about 40 years. A valve lash check in 2010 confirmed no valve seat recession.

Just like M Ecks, I had a big hydraulic cam pounding on 1967 big block heads. After a few summers of heavy beatings. I noticed 3 mph of trap speed missing and took the engine apart. We found half of the ex seats were sunk down. Fact is the engine ran totally fine and with 12 sec runs. I'm sure most would say making good power but the lack of lead or hardened seats definately deterioated my engine.

Seems to me there is both a yes and a no answer to this. Yes, lead will help under certain conditions and no, it really doesn't matter under other conditions.

Since I have some Tetraethyl Lead additive I'll use that until it's gone and then change my carburetor out with one that was set up for pump gas and forgo the additive.

Thanks for the input.

Depends on usage - if you are at low load most of the time (most street drivers are, even with the odd blast down the quarter) you will probably be OK. If you are at high load frequently (eg towing a trailer) you will probably get valve seat recession. If you do, is it a problem? Probably not, as per peoples experience above. Eventually if left long enough you would have to fit hardened seats, but that could be a very long time.
You do increase the size of the combustion chamber therefore lower CR as the valves recede, again on a street driver this is probably not going to be an issue.

My 2c, if the engine were torn down, it is really not THAT expensive to have the seats done, I'd get it done and never wonder again. If the engine is running fine, carry on for now!

I've often wondered if the technique of 'beating' the seats in isn't some of the problem with them coming loose later. If I ever decide that inserts are necessary I think I'd try a dry ice chill and try for a shrink fit rather than a press fit. IIRC, for the same interference, a shrink fit has 3-4 times the holding power of a press fit.

Amoco, Esso and Atlantic Richfield all introduced unleaded gasoline in 1970. Beginning with the 1971 model year American car manufacturers started introducing engines that could run on unleaded. I assume that meant hardened valve seats. My 1972 Satellite owners manual specifically mentions it could use unleaded gas. In 1975, most cars started using catalytic converters and were required to use unleaded gas. The Honda Civic with the stratified charge engine was one of the few that met pollution requirements without a converter.
Craig

My dad's 71 challenger with a 318 burned exhaust valves. I remember pulling the heads off a few times and lapping valves with compound and a hand drill. He used a lot of lead substitute. What a giant pain in the ass. Why we didn't swap in newer heads... I don't think he trusted them being interchangeable. I'd find a way to get the motor updated.

Unleaded gas predates WWII.

Lead was not put into gasoline for valve seats or lubrication.

It was put there for octane boost.

The valve seat bonus was a side effect discovered later.

Doesn't take much to fix the seat recession issue, Chrysler simply induction hardened the exhaust seat. But it was cheaper for Chrysler, and others, to not do this when they could let TEL solve the problem. Wasn't till the ban on TEL in gasoline that they started doing it. Save a nickle, kill millions.

Carburetors don't change for leaded or unleaded gasoline. The mechanic's claim of avoiding valve seat recession by running a richer mixture is pure unadulterated hogwash. Adding Marvel Mystery Oil or whatever does NOTHING for the exhaust valve seats. It does make you feel better because you have "done something" but you might as well have paid a medicine man for a special charm to hang on the rearview mirror.

Chrysler didn't start induction hardening seats until I believe 1973. I think GM did it one year earlier.

If you are lucky enough to have a real hot tank around, when you get your cast iron heads back there should be a blued area around the exhaust seat, maybe both. This is the indicator.

If you are using a Neway or similar seat cutting tool, the hardened seats have smaller chips. It's quite easy to tell. If you're using a stone I don't know you'd see a difference.

If you are spending big money on your heads for sentimental reasons, then install the hardened seats. I learned something new today...I had thought the seats were always installed by cooling them before installation. I would agree that using mechanical force could be more problematic.

My '64Dog's Poly 318 ran well over 130K miles on unleaded fuel with no valve seat recession, but it had the stock springs and camshaft. It has on occasion run for miles wide open pulling up a mountain,, which is the hardest on the exhaust valve seats. But those mild lobe ramps and soft springs were easy on the parts.

With any cylinder head work, get a firm written quote before the work starts, and compare with a new set of aluminum heads. Many times the cost difference is small. In some cases the aluminum heads may cost less than reworking your old heads.

R.