Hardened valve seats - do they really matter?

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barbee6043 said:
I asked the local small time machine shop about milling me some slant heads .1 He quickly said NO WAY!!!! Guess he did not want to wear out his machine!!
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A local shop was going to cut 0.100 off my big block heads, then in turn, have to also cut the intake manifold side. Was ~$300
 
marksmopars said:
With the cost of a motor rebuild nowdays I would think hardened seats is cheep insurance.
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Yea, as I read through the comments more, I think I'm just going to use the head as is and later when I find a 73 and up head with the factory hardened valve seats, I'll mill that one and swap them out.

I plan to daily drive the car as I have daily driven several old mopars already and I like to tow my little mower trailer around and let the car be a car and do car stuff.
 
If I go thru the effort to yank a head (or set of heads) they WILL be sent thru a machine shop before they go back on.
The last /6 I built I had OS valves put in, and milled 0.070.
I requested new seats/ at least for the exhaust side, and when I got a call saying the head was done I asked if they'd replaced the seats and they tried to tell me "it's done, oversized seats cut in, everything". I asked again if they put new seats in and was told that they didn't, I insisted they do so before I picked it up, they weren't happy but they did put them in/ took a day to get and a day to put them in.
 
And for whoever said what the CR would be on a /6 with that much head shave it won't be that much. I haven't seen one that is as high as 8:1 to start out with, even though they "advertised" 8.4:1. They're actually in the 7s.
And with it being doubtful to find an original shim steel head gasket chances are better than even that the replacement HG will be thicker than that original one which reduces CR further from stock. You basically gotta cut the head 0.020-0.030 just to make up for the thicker replacement HG
 
Princess Valiant said:
Yea, as I read through the comments more, I think I'm just going to use the head as is and later when I find a 73 and up head with the factory hardened valve seats, I'll mill that one and swap them out.

I plan to daily drive the car as I have daily driven several old mopars already and I like to tow my little mower trailer around and let the car be a car and do car stuff.
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You used to be a traveling mech. , did you not ?
I noticed you may have a lawn business now ?? Pretty industrious girl ...
 
Ill just say that when getting the head done price it out. I don't think any of it is cheap not in my experience. But other parts of the country prices my vary. In my case I am a weekend cruiser not a racer,i have 3 sets of heads 2 J one X 340 etc. If I were to sink valves Id toss another set of heads on I have enough engines and heads to last my life out. Throwing blanket statements like "all heads need hardened seats " and "when you get on it youll sink the valves?" well if I was racing id have the hardened seats most likely set into aluminum heads...
 
Dartswinger70 said:
I think it comes down to what you want to spend. I had 2 sets of J heads and i think I mentioned this in another thread but, I sent the 1.88 set out in 2013 it cost high 400 and some change may as well say $500 dollars because I think it was 496 or something plus add the cost of the cores. Cant sell em for that, then this year I sent a 2.02 set of js out and that set needed more so it was high $600 and some change may as well say $700. I'm definitely not breaking even on that set but. They are good to go on an engine that will be low mileage cruised. Id take the chance ifand did to save some money also Id run some lead additive top cylinder lubricant etc. Maybe not every fill up but every other month or so. I think if it is a 70s truck or van id put the seats in but a 70s truck or van should already have them no?
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Really!?! Had mine gone through in 2020. New valve guides, valves, springs, and hardened exhaust seats for $300. Of course was having the engine done too. Cleaned and painted the block. Cylinders bored .40 over, new pistons, rings, rod and main bearings, cam bearings, stock cam, timing chain and sprocket, crank polish and a gasket kit. It came to just over 900 for everything. I did the reassembly. They did a great job. Sauer's Machine in Central Point OR.
 
Well that was around the start of covid if I remember correctly.
Jobs we had to farm out at work back then that were $3k, are now $7k for the same job at the same vendor. Prices have gotten stupid.

When I had my /6 done, about 3 years ago now, they bored it, polished the crank, shaved the block 30-thou, hot tanked it, put the cam bearings and freeze plugs in (I didn't ask them, I was gonna do that myself) and pressed the new pistons on the rods. (I'd found a set of NOS rods so no rebuild of them was needed) and shot peened/x rayed the block. Block work was $400.
Then they got the head. I had already done some port work on it, as deep as I dared. They touched it up and finished my work.
Shaved 70-thou. Cut in for oversized valves which I furnished. Put in new exhaust seats which they furnished. Plus a crack check.
Head was $400 labor, just like the block.
They'd had my block 9 mo before they got it done, and the head another 3 months. I picked up the block and dropped the head. So a year to get done.

Fast forward a year to year and a half I took them a single cylinder cast iron Kohler off of a Cub cadet.
They did the valves, bored it 10-over, cut the crank 10-thou, deck d the block just enough to make sure it wasn't warped and the same for the head. THAT was $300. Not including any parts.
800 for an inline 6, $300 for a single cylinder air cooled small engine. Doesn't seem right.
They'd done another Kohler for me before the /6.
It was about half of the money they got from me for the most recent one.
Took them a month for each Kohler.
 
volaredon said:
And for whoever said what the CR would be on a /6 with that much head shave it won't be that much. I haven't seen one that is as high as 8:1 to start out with, even though they "advertised" 8.4:1. They're actually in the 7s.
And with it being doubtful to find an original shim steel head gasket chances are better than even that the replacement HG will be thicker than that original one which reduces CR further from stock. You basically gotta cut the head 0.020-0.030 just to make up for the thicker replacement HG
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I have several NOS thin steel head gaskets. They are hard to find too. You're dead right about the compression, too. I measured mine that's in the car now after I pulled the head and it was 7.8xxx. lol Of course since I had about .180 milled off I'm at 10.2.
 
weaverjsnw said:
Really!?! Had mine gone through in 2020. New valve guides, valves, springs, and hardened exhaust seats for $300. Of course was having the engine done too. Cleaned and painted the block. Cylinders bored .40 over, new pistons, rings, rod and main bearings, cam bearings, stock cam, timing chain and sprocket, crank polish and a gasket kit. It came to just over 900 for everything. I did the reassembly. They did a great job. Sauer's Machine in Central Point OR.
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No, I'm lying... :thumbsup:
 
When it comes to cars and trucks (at least my own) and engine work I'm almost never "not" working on something from Mopar. The same machine shop mentioned above has told me more than once that Chrysler couldn't do a concentric valve seat if their lives depend on it. Almost every one he gets in is eccentric to start with.,. Not saying yours are cuz I can't see em from here but if there's that chance, then simply lapping them in won't help
 
even if they were adequate to start with, castings move and change shape for years until they "season" or Work Harden. especially when vibrated or heated or machined or all 3 or any combination


small block connecting rods on the other hand.....
the small end is often not in the middle of the casting for the small end... why? center to centre fine, the holes need to be the correct distance apart but variance in either direction perpendicular to that in the small end is just shoddy unless there is some bizzare balancing reason....... Ho Hum.

Dave
 
I bet right now the people in this discussion thread are the last ones to ever rebuild any of this 60s 70s mopar stuff whatever we leave behind will be it. It doesnt matter if you put hardened seats in and it will "last forever" it will end up melted down in 20-30 years anyway...its truth there will be dwindling demand over the next few years...LS swap modern engines will be shoehorned into the bodies. Noone will rebuild or machine anything. I know its negative but its also reality.
 
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Fark the LS anything. Been a die hard Mopar guy since I knew what cars and trucks are, want no part of LS anything
 
Trends.
I remember when the "clone" aka "tribuite" showed up at BJ, Mecum. 69 383s Roadrunners being cloned out of sport furys/ I asked myself WHY? They made what? 85,000-95,000 of just the 69 mode. Real 69 383 RR where top be had, easy and not that man y $$.
Trend/
3000s, 40s classic made into Good Guys street machines or what ever you call them. Look at what the few that sell at Mecum bring in general.
Trend,
Them comes the resto mod/"protouring" type animal. The guys into the reto mod want the old style bod on a modern driving auto. Why?????????? (yea I knpow!) BUT.. Why not just drive your modern hemi powered 2000 Charger or 2002 HellCat??????? if you need modern? OK so I am OLD.
Trend////////
 
Times are changing for sure. Not as many people rebuilding these older engines. The newer stuff LS for example runs longer then the entire vehicle is scrapped.
I typically took a few heads of whatever I was building to the machine shop. They would take the best ones and install hardend seats. Not sure I would have noticed the difference. Cost wise I did.
It is interesting how far some of the old heads valves would sink though. Well pass the hardened surface. Wonder how much better a hardened seat head would hold up under the same circumstances.
Regardless of wether you choose hardened seats are not it's nice to have the option. A few machine shops in my area have closed. A bit of a bummer as it may be an indicator of times changing.
 
AJ/FormS said:
You'll know when you take your head off, by how far the valves have pounded themselves into the seats. It takes thousands upon thousands of miles to get to be like that.
If it has mechanical lifters, you might notice it, by more often lash adjustments.
My opinion is that if yur gonna put 12,000 miles a year on it, ok, get hardened seats.
But if just an occasional cruiser , then I wouldn't bother. The car will rust out before it needs a valve job.
But
if the head needs a valve job now, there is no better time to install hard seats.
Plus, I know that you're always on a budget, so, it's cheap enough to do a valve job 6>10 years into the future.
But
you'll know by looking at the installed valves, if it needs to be done, and once the valves are out, it will be obvious.

Oh and BTW, hardened seats will not make it run better of themselves. Just a lot longer at the same good, lol.
But, .100 of the head is a heckuva thing.
If my math is right, that will take an 8/1 225slanty to 9.5Scr. With a stock cam, the pressure is predicted to rise from 140@sealvel, to 175 with a stock cam. I imagine and hope, that you're gonna cam it up to drop the pressure down into pump-gas territory.
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One of the things to remember with /6 heads is that Chrysler often just milled them flat and didn't give a damn about the combustion chamber volume. I've milled two heads, both '79s. Both had complete valve jobs. Both had grossly oversize combustion chamgers Once done the two end combustion chambers were checked for volume. On the first, I forget the result, but took .100" off of it and it only brought the CR up to about 9.1:1. The other one had milled to bring the combustion chamber into spec. This time the shop took .035" to get me to the mean of the spec.

If you start with a combustion chamber that's in spec, then yes, you'll get a fairly high CR and need to proceed accordingly. But I recommend measuring volumes first to find out how far oversize the chambers really are before you mill anything.
 
Yup I put a '77 peanut plug head on a 74 short block and before a 0.070 mill had 60cc chambers. After I had 1at 48, 1 at 49 and 1 at 50cc
I had the machine shop CC it and it came out at 60. I was driving when I got the call and did a quick off the top of my head guess when I told him I wanted 70-thou off.
Had I known my pistons were still 0.180 in the hole after a 0.030 block shave i'd have had them do a deeper block shave.
I wonder how much +/- tolerance they had for block deck height and/or head thickness after they were cast and before assembly on the line and how many were actually spot checked on that line when they were new
 
Princess Valiant said:
Ok. This is all some good info.

A lot to digest. Now that I have a visual of what a valve seat failure looks like, my 68 slant head is definitely a good head. So I think I'll just mill it and use it.

Milling a head these days is a couple hundred bucks so I just wanted to be sure.

I do plan to daily drive the car but if it's made it this far, 56 years later, surely it will take more than me to kill it.
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My understanding on installing exhaust seats is, if you drive a lot (long distances) at a high rate of speed or hot rod a lot (drag strips or light to light racing) you should install the harden seats. As some say here, putting around town or just cruising, you should be fine with the heads as they are. Removing the heads should tell you the whole story. I don't play cheap with my motors. For the minimal cost of installing harden seats, I would do it, though you may not need or have to.
 
On the head in question that I brought up in this thread that I had insisted they put hardened seats into at least on the exhaust side I did put oversized valves in. And my understanding was that with surface hardening, they'd have machined thru the surface hardening. Which was why I wanted new seats put in.
But on the other side, the valves I put in were stainless, of which from what I understand in itself goes a long way towards preventing valve and seat burning. So there's an argument right there on each side of the fence....but given the money already spent on the overhaul, the amount extra it cost for the hardened seats vs not putting them in, was cheap insurance the job wouldn't go sour
 
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