Especially if the pre-repair brake setup was vibration-free, I'd really try hard to find a local,
old-school brake service so that you can get this all sorted out to your satisfaction.
Good luck. Let us know what ends up being the final fix...
14 bolt drums
- Thread starter EKOBS
- Start date
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old-school brake service so that you can get this all sorted out to your satisfaction.
Good luck. Let us know what ends up being the final fix...
A machine shop I spoke with said they could fix the “out of round and out of balance” on new drums for $75 apiece. So, $300 on top of new drum cost. That service used to be free with US manufactured drums. I don’t begrudge them for that charge, why should they work for free? So, yeah, there’s that route too.
Big T
Newbie
Just replaced the rear drums on my ‘99 K2500 and went with Napa Fleet for $118 each (no sales tax in Montana) and couldn’t be happier.
Which axle? Semi-float or full-float? What size are the drums? 11.x or 13 inch?
What part number on the drums?
Big T
Newbie
14 bolt full float, 8 lug 13”’ with 3.5” wide shoes.
If you get a chance to do this, don't hesitate, you won't regret it. After blowing
the budget on a used flowbench, I knew I also needed the ability to do my own
valve job work. A full-blown Serdi was my fantasy (YES) ...but even used it was
way, way above my pay grade.
So, after recalibrating my internal want/need scale, I found an old gem that looked like
it had earned it's keep just as much as your brake lathe has. Picked this up awhile
ago...and I liked the way it worked so much I decided to give it a million-mile tuneup:
Black & Decker "Super Service Valve Refacer"
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Note: Still a couple of small, out of the way dents on the sides, but made sure that the forward-facing sheet metal was straight & dent-free. Also new 3/4" plywood base.
Rattle can spray job + clear coat. (And the obligatory wet-sanding, buffing, etc. No orange peel on the cab. Original paint on the machine itself.)
If I had to guess it was manufactured before I was. :0) Like both you & @HotWheelsBurban said, turning old,
tired metal work surfaces back into new condition is pure pleasure. There's a tube with pressurized cutting oil that you aim at the
valve/stone interface, and the aluminum piece catches the oil sling & it drains back to a reservoir behind the machine.
With all the spring-loaded oil cups, I make sure that it is literally a well-oiled machine. Like a vacuum tube computer, this is definitely
a trailing-edge setup...but sometimes living in the past is a great way to take a breather from all the nonsense swirling around
us these days.
Note: If I did this for a living, this machine & I proceed at a pace where I would certainly starve to death. :0)
But as a hobbyist this old school "Electric Valve Shop" is a home run.
And I find it to be very easy on the eyes. :0)
Fix up your old friend asap...and splurge for the new bearings.
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Sioux 680, bought used from second owner, cleaned-up (TOTALLY filled with metal and grinding-wheel dust) but not re-painted. Installed new rubber motor mounts for the chuck motor, got the coolant pump working. Had the local machine shop modify the valve-tip support rod to handle smaller-diameter valves, and got the chuck re-set.
I don't use it much. I still dial-indicate every valve. I can get the runout to 0.0005. If I'm careful, and lucky, it'll hold 0.0002 (sometimes.)
I just figured-out that I have no photo of the complete machine. Gonna have to change that someday.
Nice cross check with the dial indicator. That is not senseless beauty. What you are showing
is the foundation of a rock-solid idle. Once a troubleshooter realizes that valves actually rotate
(at varying speeds/degrees) during operation, and that this means that sometimes a slightly warped
or otherwise out-of-spec valves seal, but other times don't, then this can help explain how a marginal
valve can lead to a difficult to troubleshoot intermittent miss. (!)
****
Thanks to where I've been driving on the used car food chain, I've had numerous opportunities
to troubleshoot/fix rough idling/misfiring engines over the years. (As well as helping my buddies
stretch their commuter car budget.) Sometimes a straightforward full tuneup cures the problem.
(SPARK)
When that doesn't cure the issue, further poking around uncovers an air/fuel ratio problem. Whether
too lean (split hose, leaky gasket, weak fuel pressure, leaky EGR valve, bad vac brake booster, etc)
or too rich. (bad/lazy sensor lying to ECU/VCM, dribbly fuel injector, etc)
(FUEL)
And once all the ancillary bits supporting the engine operation are proven good, we finally end up
running a compression test, possibly followed by a leakdown test. And IF the issue is bad enough,
then this testing will identify the root cause.
(COMPRESSION)
But guess what? In the past I've gone through all 3 levels of troubleshooting, and even with everything
passing the test criteria, I've still had that annoying intermittent/random 'skip' during prolonged idling,
or just as annoying, a rough idle that is noticeable behind the wheel, but not bad enough to illuminate the
MIL/CEL icon? (By the way, the EPA rulebook says that the Check Engine Light doesn't have to be lit until
the misfiring will cause the emissions to rise a full 50% over the limits that the engine originally had to
meet in order to sell in the marketplace? More on this in a later post.)
Pulling this all together, I finally figured out what was going on, and why all my underhood testing wasn't
duplicating the issues I observed while driving? (This all has to do with your photo above, promise.)
The answer? Part of it is pure luck. When I compression test that cylinder, is the marginal valve rotated
to the 'bad spot', where the valve face vs. the valve seat is showing the issue? Good, I'll see the problem.
Or did the valve rotate to the 'sweet spot' where it will show up good when it's actually an intermittent issue?
Fudge, I'll get a false OK on this cylinder. Of course I'm oversimplifying, because I've never seen real
numbers on how fast the valves rotate at cranking speed...if at all.
One more testing vs driving variable. We tend to think of the force closing the valve is entirely from
the valve spring. But if you look at the compression chamber side of a valve, when the pressure in
the cylinder rises during the compression stroke, this same pressure ALSO helps to force the valve
against the seat. If we take the PSI (Pounds per Square Inch) x the Square Inches, we can actually
gonkulate this. So I decided to put a 2.02" intake valve into the following calculator, and this is
what I got:
A 2.02" intake has a little over 3 square inches of surface area in the compression chamber - this times 150psi during compression = 450+ lbs of force
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NOTE: For comparison purposes, from what I've found, the ZZ3 cam recommends ~105 psi spring pressure at installed height.
Instead of trying to muddy up the intermittent misfiring waters, I'm trying to explain how compression can vary
while idling/driving in a cylinder with not bad, not good, but marginal valve seating.
And how can I state this confidently in a public forum? Because after fixing a handful of
engines in daily drivers just by replacing bent or burnt valves & hand lapping them into the seats, I
decided to take it to the next level by giving myself an old school valve grinder & matching
seat grinder.
And since then, IF I really desire a perfect idle from a high mileage motor that is in otherwise good
shape, then a methodical, detail-oriented valve job is the ultimate answer. Just need these:
* Proper clearances between valve stems & valve guides.
* Concentric valve seats in new condition.
* Refaced valves that pass Schurkey's runout check above.
* Fresh valve springs. (New stock, or beehive, or even originals that pass the valve spring pressure check.)
* No bent pushrods.
* All lifters & associated cam lobes pass a careful visual inspection.
* Timing chain isn't worn/loose/sloppy.
* EDIT: Clean valves, no carbon buildup on the backside. (From leaky valve stem seals, DI, etc)
****
By the way, I can work the Treasure Yard into all this. To minimize downtime, instead of tearing the
DD apart & then having to thrash in order to get it back together by the end of the weekend no matter
what, my preferred method is to find a set of heads out of a promising engine bay in the treasure yard,
refresh them with intent (without the time stress) ...and then swap them out over a weekend.
The bottom line is that by doing it this way, I can actually enjoy the cylinder head renewal process. And
driving an older vehicle that runs dead smooth is pure pleasure. You don't have to live with misfires -- just
got to locate the root cause and fix at that level.
Having said all that -- of course I'd recommend trying a fresh set of plugs first.
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