valve seats

[Guest JT]

Should hardened valve seats always be installed on a pre war valve in block engine when doing a major rebuild? The car will be driven occasionally at highway speed and fairly regular around town.

[ply33]

The low compression ratios of those engines mean a relatively cool flame front and pretty low valve recession problems. Also keep in mind that the regular gas of the period was unleaded. You had to pay extra to "fill it with Ethyl". So you should be fine.<P>On the other hand, the expense of putting in valve seats when everything is apart is low enough that you might want the little extra peace of mind.<P>If your pre-WW2 car is a Chrysler product, and was built in the early 1930s or later, then it already has hardened exhaust valve seats. I don't know about other manufacturers, they might or might not....

[ronbarn]

How many miles on the engine? Has it been driven recently (after the advent of lead-free gas)? Is there any evidence of seat recession? If there is not problem you may continue to use the non-hardened valve seats. However, the relative cost is fairly low, so if you need new seats, go ahead and installed the hardened seats and valves.

[1913Moline]

I would strongly recommend against installation of hardened seats. Unless you have a machine shop that really understands what they are dealing with, they can ruin your block, or head. I have seen more than one engine with an improperly installed seat which later came loose and hammered out the block. Things get really tough to fix.<P>I would also recommend against the stainless steel valves which companies like to hog out of barstock and call "better than new". The heat transfer from head to stem is critical, and stainless ranks pretty poor in this capability. Re-using good original valves, finding NOS valves or modifying other NORS valves is a much better route.<P>Good Luck

[Guest JT]

There is 60k miles on the engine with no sign of valve seat recession. I did have one burned exhaust valve and a few bad guides though. I have new stainless steel exhaust valves I was going to use along with the original intakes (reground) and I did think the SS would be superior to the original?

[ronbarn]

Just my thoughts - 60,000 on a pre-war car is pretty good. I recall a "rule-of-thumb" given by an older mechanic years ago, "40,000 huh, better be prepared for an overhaul soon." <P>After your last discription I think I will side with Kisselman. Stay with the original seats ground, and original type valves. Possibly change to Stellite valves, but stay away from the SS. How long will it take to put another 60,000 miles on the car?

[Guest]

Stay away from hardened inserts as few people can put them in properly, they should be shrunk into place not hammered. SS valves work fine with bronze liners, the heat transfer is better. Bronze and stainless steel make a better wearing pair than cast iron and stainless.<P>If possible use swaged bronze liners as they are superior. Swaging means a thin wall liner is placed in undersized into the guide, it is then supported from below and a sized carbide ball is pushed through the brass tube making a press fit of the brass bushing and at the same time cold works the liner which increases wear resistance. Fast, durable, easy to do and cheap for someone with the right tools. Not often you can say that about anything.<P>Don't worry about valve recession, you won't be running the engine hard enough to cause this problem, this is kind of an old wives tale no doubt created by the repair industry. I've cut thousands of valve of all types and have never seen the supposed deleterious effects of NO LEAD. <P>Modern fuels contains minute amounts of additives that are sufficient to eliminate this problem anyway. Lead was there for antiknock resistance-period, the fact that it lubricated the valves was a fortunate side effect.<P>This kind of reminds me of the old wives tale about not putting a battery on a concrete floor as if the electrons will somehow migrate through the insulated case and reach "ground". <P>This fallacy came about because early batteries were made out of glass and only an idiot would try to place a hundred pound piece on glass on a rough concrete floor.<P>If I were you I would be more concerned about finding a rebuilder who had a good condition valve grinder, most of these devices had little more than a glorified drill chuck mounted on the spindle for holding the valve. <P>Here's the acid test, take a scrap valve to your rebuilder and ask him to do a quick test grind on the valve. Remove the valve and then put it right back into the chuck and do it again. <P>If the valve runs out when doing the regrind you'll see it grind heavy on one side right off the bat. If you don't believe me dial it out with an indicator, even 0.0001" out is not acceptable in my opinion. <P>I can't stress enough the importance of good condition valves. Whenever I rebuild something of my own, new valves go in. Regrinding is half the cost of replacing anyway and you would be surprised at how cheap custom valves are to obtain. Contact Manley if you happen to need something special. <P>Remember, something that's going to be red hot whenever the engine is running is not the place I want to be removing metal.<P>Nearly every specialty valve grinding machine I've used has a worn out chuck on it because it has cut a million valves and they cost upwards of $800<BR>to replace!!!<P>Personally I cut my valves on a lathe and I dial out the compound rest to get an accurate 45 degrees. Your going to lap the valves anyway, what difference does it make what method is used to face the valve right?!! Besides you can back cut the valve right on the lathe with the same setup and pick up some free horsepower. <P>Also the 44 1/2 degree spec in the book was there to make up for production line variances and would ensure good valve sealing. The half degree disappeared after the first 5000 miles. You don't think there was a guy lapping valves on the assembly line do you?!!<P>This is where a good accurate work pays off, proper width seats not too far up the valve face will make all the difference. If the seat is too far up the valve it won't last long. If the valves are marginal replace them all, it's money well spent. usually the seats can be deepened to remove any burnt sections. The only drawback to deep seats is they shroud the valve and will cost you some horsepower (not a big deal).<P>Another important item is the valve geometry, if the seats needed a lot of cutting you will have to shim the springs and grind the valve where the rocker contacts to ensure you don't bottom the rocker slot on the stud and also to make sure the rocker sits at the right angle. This is another item most high volume shops don't even check. I could go on and on but you get the idea.<P>A good rule of thumb is chose a shop that has qualified machinists doing the rebuilding. The crappy shops I've worked at were full of immigrants without tickets that could care less. Most of the time the customer doesn't even notice until 50 000 miles later the engine turns into a smoker. There is no reason a well rebuilt motor should not last 100 000 miles with todays rings and honing practice. <P>Quality work is worth paying for and now is not the time to play it cheap. What I have explained is all very common sense stuff I've learned from rebuiding all kinds of internal combustion engines trying to eek the last bit of performance out of every cube. I've tried nearly every wacky combination in the search for more ponies that you can think of. <P>What I've explained is good no nonsense engineering that's reliable and sound. Anyone who tells you different is probably trying to sell you something or doesn't know from expierience.