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Old 12-10-2002, 06:37 PM
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Arrow question on hardened valve seats

I have a set of 1971 heads that have excellent valve seats. I am pretty sure they aren't hardened, as they look like they are part of the head casting itself. Anyway, is it absolutely necessary to use hardened seats if the original seats are in great shape? Also, how long would the seats last using unleaded gas or would a lead substitute be just as good? Any comments would be appreciated!

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Old 12-10-2002, 06:54 PM
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No you don't need hardened valve seats, nice to have but not necessary. To be honest I have never seen a case of seat erosion caused by lack of lead, modern valves are good enough that it is not even a consideration. Actually putting seats in has many dangers especially with the thickness of modern castings today, you could say I have seen 1000 times more cracks in heads due to improper installation of seats than I have seen seat erosion.

Grind what you got and replace the valves and they will last well over a 100 K miles. Alcohol fuel is a different story.
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Old 12-10-2002, 07:05 PM
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What about the guides? They look to be in pretty good shape too!
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Old 12-10-2002, 07:16 PM
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4-jaw i see valve seat erosion on an everyday basis, once it starts (usually on the center two exhausts) it usually cracks the head from all the heat and once the seat goes ,the guide goes, the stem goes etc. only the old cars that only get driven less than about 3000 miles per year seem to get away with early heads, they aren't really worked. if you are going to use the car or truck as an everyday working vehicle you have to have hard seats, even they have problems if you have a warm running engine. if you are going to tow, you must have hard seats unless you like sitting alongside the road with the radiator steaming from a cracked head at 3 a.m. sunday etc. just because you can't see an insert in the valve seat area doesn't mean they are not hardened, the factory uses induction hardened seats which is a cheap way to surface harden the seat, not very deep. you can tell if you grind through it. the induction hardening is part of the reason the late model thin castings crack, due to the stresses put into the casting from the unequal heating process. if the head was cast before 1973 it will not have hard seats, unless it is industrial use.
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Old 12-10-2002, 07:43 PM
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They will be going on my 350 sbc which I use mainly on the weekends and one or two days through the week. I do haul heavy loads sometimes, but not that often. If I do, it is only about 4-5 miles, so no extended periods of time. It is mainly a cruise to work and play on the weekends kind of motor. Any other thoughts??
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Old 12-10-2002, 07:47 PM
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make sure the guides and springs are good, make um flat (less than .003 at any point) and usem.
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Old 12-10-2002, 11:15 PM
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I run 041 castings that have been worked 4 times, the seats aren`t hardened, I run lead substitute, the cars a daily driver, no problems as of yet. Not sure if it has anything to do with the types of fuels from different part of the states. before these heads were on the current engine, they were on a small block that I ran for 70,000 miles, also a daily driver that seen some light track use, when I had them worked they only needed guides. not saying this would be the case with everybody, and not saying i`m just getting lucky, my lucks lousy enough as it is.
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Old 12-11-2002, 12:07 AM
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I guess Bob what I should explain is my theory of valve seat erosion. See if you agree.

Valves are typically hardened using the flame process right from the factory. Not the old stuff that's got 200K on them, but the new valves. Usually these old valves are as soft as the cast iron seat they seal against, grind them once and it gets even softer inside. If the valves are replaced with a modern equivalent you get a much harder valve face which makes a much better wearing pair with the soft seat, you don't get the seat material adhering to the valve face. Now if you grind a new valve your right back to square one, thats why I don't recommend reusing/grinding valves. Besides valves are not that expensive anymore and regrinding them is almost half the price of a decent valve (sometimes equal?), I prefer to just spend the extra money and put in new. Peace of mind for this critical component is cheap to me. It doesn't matter which part is hard, the valve or the seat. As long as you have a good wearing pair they will last, soft on soft will not last...long.

So when you compare the price and hazards or putting in hardened seats to replacing the valves and regrinding the soft seats I think my method is the better value. I've seen a lot of engineering data that debunks the old myth of seat erosion caused by lack of lead in the fuel, the data just does not support it particularly when you factor in modern valves materials.

To me regrinding a highly stressed component like a valve is an invitation for disaster especially when your turning the big rpm numbers. The other factor I consider is that I have seen so many valve regrinding machines with bad chucks over the years that unless the machine is new or had the chuck replaced recently I don't trust them. Try this on your valve machine, do a light grind on a used valve...the finest you can do. Now remove it and touch on again, 99 times out of a 100 it will runout because the chuck is just not accurate enough to repeat within tenths...even new.

It's not the machine it's just a fact of life with machine tools, now with factory production tooling it is done on a centerless grinder which is far more accurate than what you can do on a common valve grinder because both stem and valve face are ground at the same time...it's also faster and cheaper to mass produce them this way. If you ever check a new valve on a surface plate they are perfect...usually (I send them back if the aren't).

Now of course with a street engine does this slight runout matter? Nah, there's enough clearance in the guide to accomodate this amount of runout and it works just fine. Where this becomes critical is on highly stressed engines like Japanese motorcycle engines, the manufacturers even state never to attempt to grind their valves because;
  • A) The valves flame hardening is so thin any grinding will ruin the valve. Margins are extremely thin too.
  • B) Even the slightest runout will not allow the valve to seal because of the tight tolerances in the guide on this small of a scale.

    and finally;
  • C) The seats on these engines are not hardened but dead soft and a similar wearing pair will result which will destroy the two in short order.

These are the things I learned from doing racing motorcycle 4 cylinder engines and I learned it the hard way, no factory sponsorship for the guys I was helping/hurting Ha Ha! Of course stainless valves need hardened seats because even the hardest stainless is not that hard and you need the hardness in the valve seat since you can't get it into the valve.

So if you can see what I am saying when you compare the dollar figures and the dangers of seat installation (when is the last time you've seen seats installed with dry ice? Thats the proper way) using a new valve with a soft seat seems to me the better value and a heck of lot safer to the head. The other thing is regrinding valves is a money maker for the rebuilder, their is not much profit in buying new valves. This is the main reason why I think the practice is so prevalent in the automotive industry.

Of course I could be wrong? It happened just last week! :p
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Old 12-11-2002, 12:23 AM
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yes chuck you could be wrong and since I don't know anything about the topic I will keep my mouth shut..
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Old 12-11-2002, 12:34 PM
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I have all new parts for the heads, including stainless steel valves with hardened tips, new Z28 .500 lift springs, new hardened locks and lightweight retainers. I also have the blue umbrella valve seals like you mentioned. So, do you think with all these parts and not running the engine that hard, maybe 3500 rpm tops I would be ok without hardened seats?
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Old 12-11-2002, 12:36 PM
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Also, what do I need to look for as far as guide wear and if I need new ones installed?
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Old 12-11-2002, 03:58 PM
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you should have no more than.002" clearance on the stem, if you can feel a lubricated valve rock sideways in the guide it is too loose, 4-jaw has some valid points but he evidently hasn't bought automotive valves for a while,(non sb chevy) regrinding say a Daewoo intake valve(just for arguments sake) i priced them today, my cost $26.00 each, eight of them in a head, regrind less than $4.00 each, less than .003" removed from the face and tip. you know what the customer is going to go for! also i do freeze my seats and guides when working with aluminum heads. and our grinding equipment is checked constantly for runout. Factory valves are far from perfect, i have had to send more than a few back.
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Old 12-11-2002, 04:29 PM
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Thanks for the info Bob, but you know, it didn't help me a bit. LOL

Any comments on the questions I asked?? Thanks!
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Old 12-11-2002, 05:35 PM
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i told you how to check for guide wear thats what you asked, if they are bad you will have to have them repaired and a valve job. the parts you have will work ok. like i said before,you got them use them. if you do opt for guides and a valve job, heres a tip, have bronze liners installed(we get about$8.00 per guide installed) if you can possibly afford it, they last. also if you are having guide work done don't let your shop talk you into a three angle valve job for exra money, whenever guide work is done the valve job you get will be three angle on the seat anyway (if its done correctly)
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Old 12-11-2002, 06:16 PM
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Well I don't know how many Daewoo motors you guys are hopping up down there but...just kidding. I understand what your saying but we haven't taken into account the cost of the seats or the cost of installation of them in the equation. When you consider that full set of Manley race valves cost less than a $100 for a set of eight and installing seats into the head are about the same it becomes a question of what do you want to do, seats or valves?

Just to clarify I do not do volume engine rebuilds only a few select people are my customers. I only do what they want and if they want to do the seats and not the valves then thats what they get, I don't do any head machining in my garage only assembly. I like this arrangement because I act as inspector/assembler and farm out work to shops that do quality work. Many people like the arrangement because I do not have any vested interest in the machine work other than getting it right. It's kinda like building a house, you have a general contractor overseeing the individual work of other job specific contractors and this helps to keep the goal in site and everyone honest.

For me it means no overhead and I only need space to do the assembly, easy to accomplish in a double car garage. I don't advertise because this is a hobby to me and I get enough work already, I charge very reasonable prices because for me it's fun. It also means I pick and choose my customers, I have been left holding the bag with Joe Blow too many times for me to want to change it. I stand behind my work 100% and the warranty is lifetime, not too many shops do that anymore because Joe Blow ruins it for everyone else, I have never had an engine go bad...yet (cross my fingers) and I tell my customers not to advertise who did their engine work, word of mouth gets me more than work than I can do already. I like the family atmosphere and my customers/friends kids play with my kids, they are my friends first...customers second. I like to think this is how it was done in the old days.

Geez look at that almost forgot you Stfinney, I think you need to invest in some seats for your heads because of the stainless valves, I think we all agree to that.

Ok, I'll shut up now. :o
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