Is what the machine shop told me true?

I was going to take a set of heads to be checked for leaks awhile back. I asked the guy on the phone if it would be easier for him if I
removed the valves and everythign at home. He said if anyone reoved the valves from their cylinder head, that the head would have to have a valve job because the valve will never line up exactly right or in the same spot.
Those heads tested as cracked. (Magnaflux). I have a set of salvage heads that I was going to lap the valves myself and take everything off. Will I have a problem as long as I put the valve back in its origional hole?
One other thing, I am going to replace the valve seals while I am at it. Is this hard top do? It looks like they are just rubber gromets that you push down on the valve stem.
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On Fri, 24 Apr 2009 05:25:26 -0700 (PDT), stryped

Think about the valves for a bit. They go up and down as the engine runs, right? So why not take them out? No difference other then this time they went a little further up....
I suspect what the guy was talking about is if you take the valves out and DON'T put them back in the holes that they came out of they might not seal well, but what most shade tree guys do is get a shoe box and poke holes in the cover. mark each hole with the valve you put in it - #1-Exh, #1-in, and so on. Then when you put the engine back together the valves all go back in the right holes.
The valve "seals" aren't really seals, they are just rubber caps that keep oil from leaking down the valve stem - as you say, just rubber caps. Shoot, my grand daughter could change them if she didn't mind getting her hands dirty...
Cheers,
Bruce in Bangkok (bruceinbangkokatgmaildotcom)
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wrote:

Bruce is exactly right, although she might have a little difficulty with the valve springs:-))
To handle the springs ie. to get them on and off it is best to beg, borrow, or buy a spring compressor which is a clamping type device.
When we did the valves on our 92 Toyota Tercel we removed the springs by compressing them in the drill press with a little adapter plate fitted over the springs. Doing it this way was a 2 man operation.
Replacing the valve stem seals was easy.
Wolfgang
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by compressing them in the drill press with a little adapter plate fitted over the springs. Doing it this way was a 2 man operation.
Now that's a cool idea. I can see why its a two man operation with a drill press since there is nothing to keep the chuck from flying back up, but now that I have the idea in my head I can adapt it to other things. Maybe use my hydraulic press, or if I have to use a drill press set up a chain and hook to hold the handle if I am working solo... Good idea. I will apply it somehow some day. Maybe Tuesday.
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Bob La Londe wrote:

You can add a bathroom scale to the setup and check spring tension also. I have checked everything from oil pressure relief valves to 1911 recoil springs
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How can you check spring pressure with a bathroom scale?
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wrote in message news:322712e0-8c03-404f-ae2e-

How can you check spring pressure with a bathroom scale?
Easy...
...put the scale on the table of your drill press
...place spring ON said scale
...put a 6" scale along the spring
...compress spring with the drill chuck
...when you have compressed the spring the correct amount...which varies from spring to spring...read the weight on the scale
...OR when you have the weight reading that you are looking for, read the distance travled with the 6" scale
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On Fri, 24 Apr 2009 06:16:49 -0700 (PDT), snipped-for-privacy@hotmail.com wrote:

Nah. Even at six she is smart enough to get a male to do the heavy lifting. Probably get Grampa to squeeze the springy things...

Cheers,
Bruce in Bangkok (bruceinbangkokatgmaildotcom)
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wrote:

What I thought was maybe the valve wont be oriented the same way? Maybe 180 degrees turned from the position it was taken out?
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wrote:

What I thought was maybe the valve wont be oriented the same way? Maybe 180 degrees turned from the position it was taken out?
They rotate slightly each cycle, so angular position is not important - at least thats what I was told.....
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That is how it is supposed to work. Each valve wears differently in the guide, so when taking a head apart stick each valve into a hole in cardboard or wood, numbered to go back to the same hole. If the guides are worn beyond tolerance this does not matter, but you didn't know that yet unless you checked it with a dial indicator. Worn guides burn oil, tight ones can sieze. Also if you change the head, the guides need to be done, and consequently the seats need to be ground. The head also needs to be flat within a few thousandths, specs vary. Lapping valves is a touch-up for good seal, but is not a substitute for having the valves and seats ground to match. You have different heads, a good machinist will recommend new guides and exhaust valves, he may opt to grind the intakes, and the seats are replaced if worn too bad. Once that is done the stem height needs to be corrected. There is a lot to it, and it takes automotive machinery not found in a general machine shop.
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Why do I need to redo the the guides if changing the head?
WOuld I be better off not taking the valves out?
I had planed on taking them out, cleaning everythign up, Do a light lapping putting each valve in it's origional location, new seals etc. Checking for platness with a straight edge. (My manual says no more than .002 per 6 inches).
Before assembling standing on end and filling with kerosene to check for leaks, also maybe putting air in it and placing it in a water tank.
My main thing is to just get this running. I hope to trade it in or sell it as I am needing an economical car.
Should I use the rocker arms off my old head or the salvaged head?
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Rocker arms should be kept as sets and used with the same valve and pushrod, on the same lifter. Guides need to fit the valves, look up the specs and see what you have. As I stated, too loose burns oil and to tight will sieze and cause damage. Did the "new" head come complete or bare?
What are you working with? An old Ford 292 iron head would be a lot more forgiving than a Porsche 911, but the priciples are the same.
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On Fri, 24 Apr 2009 06:55:19 -0700 (PDT), stryped

Valves rotate. Some passively, while some have "positive rotators"
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On Fri, 24 Apr 2009 06:55:19 -0700 (PDT), stryped

Nope. they are supposed to spin round and round. Some even have "valve rotators" built in.
Cheers,
Bruce in Bangkok (bruceinbangkokatgmaildotcom)
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wrote:

Modern aluminum heads typically have hardened seats. Hobs of hell hard.
What is interesting/amusing here is theat this is a conversation about spending a hundred hours to salvage a $200.00 head. The OP is in North America, not Africa.
JC
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On Fri, 24 Apr 2009 18:43:18 -0700, "John R. Carroll"

and IIRC it is on a, at best, $2000 Dakota Pickup???? And that's when it's PROPERLY fixed. About $300 as is.
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On Apr 24, 9:43pm, "John R. Carroll"

Kentucky, right?
The last time I visited my relatives in rural Alabama one of them was still farming with his first 1936 pickup truck. Every single inch of the sheetmetal was dented but the engine and the oil, which he never changed, were surprisingly clean. My father sure came a long ways from well water, no electricity and plowing behind a mule. When I was a kid some of them still lived that way, and honestly I liked the slower pace, self-reliance and friendly, non-competitive people, after I got used to Southern bugs and snakes and dead animal parts hanging all around the house.
jsw
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On Fri, 24 Apr 2009 19:57:42 +0700, Bruce in Bangkok

Some are caps, some ARE lip seals. Can't make generalizations. Lapped valves GENERALLY do not last as long or seal as well as properly ground valves. I'd pay the machine shop to grind the valves and seats properly. You do NOT want to have to take it apart again in a few months, do you? Let the moths out of the wallet and do it right.
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What everyone said. However, if you're just trying to get it to run, you could try lapping the old valves into the "new" head. If you can get them to seal (check with prussian blue), the engine will run. Not the best procedure - you'll end up with a wide mating surface and low seat pressure, and maybe really time consuming, but it will get a running engine.
You don't want to replace the guides unless A) they're worn way out of spec (remember, you're getting rid of this car) AND B) you're going to cut the seats - the new guides never line up exactly perpendicular to the seats. If you replace the seals and sell the car reasonably soon, you could most likely leave the guides alone.
p.
p.
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