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Hello everyone, I just was measuring the stem to guide clearance and noticed some of the guides are about 0.005 on the exhaust. Also, the intakes are about 0.002. I知 guessing this might be a little too loose as I can also see some side to side movement with my bare eyes.
Now, I知 wondering what the options I might have. I heard that the bronze K-line brand liners are really good as they allow oil to flow better in the guide. I guess they work by reaming the guides slightly and pressing in the liner with a air hammer.I was wondering if the seats would need regrinding to make up for concentricity issues that might occur, the seats are perfect shape with no pitting. Also, I found a great set of Elgin brand valves in standard size stem diameters on Amazon for 100 bucks. I would greatly appreciate some help.
Oh I forgot to mention I think I messed up royally, some of my old valves were badly pitted, I知 kind of green with the actual machining of valve jobs, before I always just lapped my old valves that weren稚 badly damaged with permetex.
Anyway, I bought a set of Elgin valves to do an experiment, I wanted to to see if I could see a valve seat concentric pattern from the Prussian blue ink with the valve unlapped in its new state. Well, it was hard to see anything. So then I lapped all of them and now I got an identical concentric pattern compared to my old valves.
Now, here is the messed up part, I previously measured my stem clearances and I recall I was getting around 0.002 and 0.003 on all of them. I went back to double check and now they off. I知 pretty sure I must of had a brain fart, and was not reading my micrometer correctly, my Fowler calibration gauge block is accurate as I verified it with a high end Mitutoyo digital mic (not caliper at work) that is also certified from a calibration company. Sorry, for the rant everyone, now that I lapped the new set of valves
I assume they are junk now, because the pattern will be off when the seats are recut and new guides are put in. I was surprised how beautiful and smooth the machining on these Elgin valves are. In closing I only lapped by hand with suction cups and no drill. Anyway the permetex is only like 220 grit abrasive. I feel like an idiot and I get kind of excited when building new engines
One last thing, here is some video links to k-line valve liners. They don稚 remove nowhere near the amount of material from the heads that thick wall valve guide require.
Any time new guides are installed, a valve job is required. Liners or otherwise.
And the face of the valve can be cut to eliminate any weirdness you may have imparted on it with lapping. Often a back cut is added above the seat to help with low lift flow.
Aside from using a bore gauge and miking the valve stem to determine clearance, a quick and easy pre-determination can be had buy lifting the valve approximately an inch off of it's seat and measuring the side play at the valve head. Anything exceeding .015" is considered too much and guides are needed.
I've come across this from Goodson. A general rule of thumb is that intake guides need guide-to-stem clearance of .001″ to .003″ and exhaust guides need from .002″ to .004″ clearance.
Towards the small end of those ranges is better.
Thank you for your response, so is it common for even new valves out of the box require a cut, because on the premise that the seat and valve face will not match. For instance if my guides were not worn to begin with would I be able to just take off the shelf valves and put them in by just lapping. I知 guessing only other option would be to find better set of heads from the junkyard. These were a junkyard set and I missed the 30 day return policy
It's safe to say that "it depends".
New valves, decent guides and an existing valve job is no guarantee that they'll seal. Or how wide a given seat will be or it's concentricity. Lapping will certainly give an indication. It may prove that the seats have receded into the heads and more work is needed.
FWIW, even the new stuff pouring out of places like eBay are often in need of disassembly and additional work.
Parts-store "Permatex" valve grinding compound is useless. It's about the consistency of playground sand in a grease or water-based carrier. It's not possible to get a good "concentricity" reading from the lapping pattern on the valve, because the grit is so gigantic that it'll show that the valve is lapped even when the seat isn't concentric--the grit "fills in" the low spots. Prussian Blue is better, but the real test is a concentricity gauge.
I bought a can of "Clover"-brand 400 grit lapping compound, and if I had it to do again, I'd have bought 600 grit or even finer.
Be sure your valve-stem-to-guide clearance is wear in the guides, rather than wear on the valve stems or (usually) a combination of both. As said, if you install guides or liners, the seats will probably have to be touched-up to get appropriate concentricity. This will be measured with a concentricity gauge, not by "lapping" the valve. Not everyone agrees with the process of "lapping", there's concern that the grit embeds into the pores of the metal, cannot be cleaned-out, and results in seat/valve face wear. I'm not sure that I believe that is a genuine concern.
New valves may/may not need to be touched-up on a valve grinding machine. When I rebuilt the 4-valve DOHC heads for my Lumina, I discovered that the old, original valves were more concentric than the brand-new aftermarket valves. I could grind valves on my Sioux 680 valve grinder closer/better to concentric than the aftermarket valves I bought. I needed to install two new valves, and had to "fix" them on the valve grinder before installation. The advantages I had was that 1) It didn't need guide work, and 2) the intake and exhaust seats were hardened inserts in an aluminum head, only a couple needed to be reworked, and even that was very minor. The exhaust valves were terrible-looking, intake valves not so bad. Exhaust valves cleaned-up with a .003 cut, intakes with about .001.
When I was done, I vacuum-tested the valve sealing. A vacuum is pulled on the intake, and the exhaust ports. With valve stem seals in place to minimize airflow down the guide, the amount of vacuum in the port is compared to the maximum vacuum the machine can produce. In my case, I was seeing ~88--89 percent vacuum (about 27 inches) compared to the machine's capacity of 92-ish percent vacuum. EASILY good enough.
You could buy valves with oversize stems, say .002" Then have the guides sized to get the proper clearance.
The K-line brand bronze liners will cost as much to install as cast iron replacement guides.
Anytime you do anything to the guides, grinding the seats is required.
Are oversized stems still available? I put oversize-stem valves into a 283 about a thousand years ago; but I thought the oversize stems "went away". I haven't seen oversize stems advertised in forever.
Seems to me the valves I bought way back then were .015-over. Ream the guides, kiss the seats, have fun. Downside, of course, is that you need an oversized pilot to match the now-oversized guides.
I don't have much use for "adjustable" pilots; but sometimes y' gotta use what's on hand.
How about knurling valve guides, I guess you can then use standard size valves. I hear some bad and good things about the cast iron being fatigued in a bad way. On the other hand they say the spiraling helps with oil retention.
Unfortunately, my machine shop that has been open for 55 years is an older man that just has recently had his valve and seat machine break down. It痴 made in Sweden and he is waiting for the part to come in so it could be months. Also, does knurling require the seats to be recut. I have heard about Neway tungsten carbide seat cutters to work well??
Knurling was considered a crap, bottom-feeder way to "fix" worn guides when I first heard about it in the late 1970s. It was probably OK in the '40s and '50s; lower spring pressure, lower valve lift, lower rpm, lower expectations--engines were commonly worn-out at 50 or 70 thousand miles, maybe less.
Yes, anytime you screw with the guides, you'll be at minimum checking the concentricity of the seats. Almost certainly having to kiss the seats with a stone or cutter to get them in-line with the new valve guide centers. Perhaps having to replace the seats entirely, depending on how much the centerline of the guide moved; and how worn the seats were.
01-01-2023, 07:28 PM
