Nice. I like the idea of a caulking gun. Eesh 1 minute....oh I see...assemble and torque in 5 minutes... .. 1minute to put in use...impressive
So, after doing the valve adjustments, what makes it seem like the lifters or rockers are clattering for a second at startup? It happened once last night.... sounded like driver's side maybe 1 and today it sounded like the passenger side front when I went to pull it back in garage after rinsing the bay off a bit...
But it didn't do it the few times I started it earlier....
It's like 3 or 4 clacks then goes away.......
I picked up some rislone engine treatment to run a bit (500 miles?) (1000?)and am going to change the oil...Only have maybe 500 on this change but it's already pretty dark and smelly..
Hello scott2093,
Welcome to the rabbit hole that threatens to swallow you up when you start to pay closer than
average attention to the sounds of a SBC valvetrain.
Especially if it was previously enjoyed,
has had parts replaced, motivated either by a broke/fix scenario...or a perfectly good stock cam
was taken out so that it could be replaced by a bigger/badder/mo' better one.
Seriously,
That '3 or 4 clacks' comment tells me that your ear is getting pretty sharp on this stuff. Good.
My short answer is that you should replace the oil & filter asap, and see if you can eliminate/mitigate
what you are hearing. Any loss of an oil's viscosity and/or microscopic debris inside can lead to a
hydraulic lifter bleeding down sooner than it normally would. (Lifters that have bled down while the
engine was off and now take a handful of cycles to pump back up to a fully quiet configuration.)
****
My longer answer, based on chasing this same phenomenon many moons ago and wondering why
the issue was so intermittent & random?
Welcome to the 'Which Lifter stopped on top of the cam lobe?' Lottery. :0)
OK. Most normal, well-adjusted people leading the good life have never, ever given a single thought
to the 720° distribution curve of exactly where a V8 engine comes to rest after the human switches
the key off. But since we're in the hunt for why you have one or more hydraulic lifters intermittently
clacking a few times immediately after startup...we have to go there. :0)
Now there are a handful of flexplate/flywheel/ring gear devos in the audience that, after years of 'reading'
the wear on high mileage ring gears, will tell you that the majority of the time the crankshaft stops
in 1 of 4 positions in the 360° of rotation. And those positions coincide with one of the cylinders
coming up on the compression stroke. Makes perfect sense. As the speed lessens from idle towards
zero rpm, there comes a point where the increasing resistance of a compression stroke is more than
the remaining inertia of the rotating assembly brings to the situation.
And way back when, when times were tight and the old truck in the driveway had a bad spot in the
ring gear causing the starter to zinnnnnnnggggggg when it once in awhile hit the bad spot? Well, the
extra frugal guys would drop the flywheel, remove the ring gear, change the phasing 45°, reinstall the
gear, and get some more reasonably reliable good use out of the wounded part.
At least that's the stories that The Elders liked to share with yours truly. Never did it myself, but I
appreciated the underlying thought process. NOTE: The more affluent dudes would buy a new ring gear,
replace the bad one on their flywheel, and be done with the nonsense. But it was a different time, especially
growing up in the midwest where The Elders had more time than money to invest in their vehicles. (!)
People didn't think of replacing a perfectly good flywheel with a bad ring gear on it for $$$, when a $$
ring gear would get the job done. (See attached.)
...but I digress. Hopefully the above sold you on the concept that the crankshaft tends to stop in
one of 4 distinct positions. But now let's layer on the fact that the camshaft spins at exactly 1/2
the speed of the crankshaft. This means that the
camshaft is going to essentially stop in 1 of
8 specific spots.
Here comes the lottery aspect. Let's say that 15 out of 16 lifters all meet the OEM factory specifications
for all the internal bits. And the oil is clean, proper viscosity, and there's no tiny foreign objects/debris
that could hold a check ball off of the seat? But lifter #16 was put together with a too-loose
tolerance? Or possibly a small defect in the circular seat where the check ball has to seat in order
to keep the 'oil pressure at shutdown' inside the lifter plunger?
Big picture time. 15 lifters good, 1 just a little looser than the others but otherwise functional?
Well, IF the engine stops where the marginal lifter is sitting on the base circle of the cam, then
when the engine is restarted all is quiet under the bonnet. On the other hand, IF this one little
bit looser lifter is sitting on top of it's cam lobe when the engine stops, then this lifter is now
subjected not to the 'closed valve' spring pressure, but instead it's seeing the 'full open'
valve spring pressure. And all this extra pressure is going to eventually force the engine oil out
of the inside of this lifter. Voila! When you restart the engine, that extra valve train clearance
in this one assembly = clack clack clack clack...quiet that you hear.
In a perfect world, all 16 lifters are of factory quality & meet assembly line tolerances. There's no
cam lobe or lifter base wear. The oil is clean, and the check valve in the oil filter is top quality. This
engine will start and run clack free.
With just 1 iffy lifter, thanks to the engine stopping position lottery will be pretty intermittent.
With 2 iffy lifters, it will be more often. And if all 16 lifters came from a bad batch, then obviously
it will clack on every single start up, because no matter where the engine comes to rest, there will
be at least one intake and exhaust cam lobe up high. Pretty cool, huh?
****
Getting back to the short answer. Change the oil and filter asap, and see if we're just dealing with
16 good lifters with just a bit of microscopic debris not allowing the check ball / check disk / whatever
from doing it's job inside one or more of your 16 hydraulic lifters.
EDIT: Brought forward a couple of hydraulic lifter diagrams from the beginning of this thread. Due to the
super tight clearances, Clean oil is key. (!)
Hope this helps. By the way, if you are still reading all this, I don't think that this startup clattering is due
to your valve adjustment. But if you haven't changed the oil since disturbing that intake manifold
you need to rectify that as soon as practical.
For what it's worth. Remember, Nothing Good is Easy. :0)
Cheers --
