On 12/1/22 12:51 am, Noddy wrote:
> On 11/01/2022 7:51 pm, Grumpy Tech wrote:
>> On 11/01/2022 6:35 pm, Xeno wrote:
>
>>> Yeah. Didn't understand the concept of valve *float* and valve
>>> *overshoot*, both circumstances that can lead to valve impact if
>>> insufficient clearance is allowed - and a thinner shim head gasket
>>> will take that clearance down by a *lot*. I didn't expect Darren to
>>> be able to do it but I did expect Daryl to know how it's done. He is
>>> *supposedly* qualified after all. Too much time pushing a broom I
>>> guess. Checking piston to valve clearance isn't rocket science by any
>>> means and there's plenty of info on the net for the uninitiated. But
>>> to fit a thinner head gasket and *not* check the clearance, that's
>>> nothing short of *criminal*.
>>> The funny thing is, I was expecting it to be a more esoteric cause,
>>> lean combustion, injectors at 100% duty cycle or MAF sensor pinning.
>>> I was overthinking it and not making sufficient allowance for the two
>>> clowns who were working on the 4AGE(20). I trust Les has learnt his
>>> lesson.
>>>
>> So it's his fault the engine failed even though he advised Les that
>> there were serious issues with the engine and failure was likely.
>
> Actually, it was *not* my fault that the engine died, and I'll go into
> some detail as to why that is to put this ridiculous bullshit claim of
> Clasener's to bed :)
>
>> I'm  guessing Les wanted to compete and went with the motor anyway as
>> availability of a replacement motor in a limited timeframe may have
>> been an issue.
>
> The issue with this engine was that Les was trying to build it on a
> budget, using parts from an engine that had already failed before I ever
> laid my hands on it.
>
>> Wouldn't be the first time someone has failed to take advice and it's
>> cost them dearly.
>
> No, but in fairness to Les and myself, the cause of this engine's demise
> had nothing to do with either of us. Well, at least certainly not me :)
>
> For those who don't know and who may be half interested in discovering
> the truth of this matter, the engine in question was a Toyota 4AGE 20
> valve, known as a "Gold Top" of I remember correctly, and this is the
> engine here:

Toyota never made a Gold Top, they only made a Black Top and a Silver
Top in the 4A-GE20
>
>> https://www.imagebam.com/view/ME69PME
>
> It's a 1600cc 4 cylinder "high performance" engine that has a fairly
> high output for it's capacity and a healthy appetite for rpm, which

You want horsepower from a small capacity, you have to have revs. That's
the way it works Darren.

> Daryl's mate Les used to use in his Lotus 7 Replica for competition work:
>
>> https://www.imagebam.com/view/ME69Q3J
>
> Now, it's been Clasener's claim for a while that this engine died as a
> result of insufficient piston to valve clearance, and this is claim is
> absolutely fraudulent. It is a complete fabrication invented by Clasener
> for the sole purpose of having something to argue about. In reality, and

Not a fabrication Darren, *a diagnostic assessment* based on the
evidence presented. Oh, and an understanding of what goes on *inside* an
engine Darren. It's what you learn *during an apprenticeship* and then
you continue to build on that during your life. No need to fake it till
you make it - your MO. And you never made it either, faking it even now.

> as usual, he is *completely* wrong and has achieved nothing other than
> making a complete moron out of himself.

In fact, the engine made a complete moron out of you.
>
> Allow me to show how :)
>

You're joking, right?

<bullshit snipped>

>
> Now, to the keen eye there's a few things to observe in these pics.

A keen eye needs a keen brain behind it. Uh oh, there's your problem.
>
> In the first instance, you can see the three used pistons which were in
> excellent shape, and the one new one. Secondly, you can see the
> competition head gasket that was used, which is a compressible gasket
> and not a "shim" as Clasener incorrectly refers to it, and lastly you

But it is *used* as a shim gasket Darren, thinner, reduces the head
height/combustion chamber size and increases the CR. And reduces piston
to valve *clearance*.

> can see the remains of the pink plasticine that was used to check the
> pison to valve clearances on the exhaust valve releifs of the number one
> piston :)

Doesn't look like plasticine to me.

Anyway, Daryl dobbed you into it when he said he couldn't do the check.
Why am I not surprised?
>
> Inlet and exhaust clearances where checked on all four pistons which is
> standard procedure, and especially in an engine using non standard

No, standard procedure is to check *one piston*. All other factors being
equal, all other cylinders should be *identical* or well within
*tolerances*.

> connecting rods, but residue of the plasticine only remained on the
> exhaust cut outs on the number one piston as they were a rough "as cast"
> finish where all the other surfaces were machined smooth. I wasn't all
> that fussed about cleaning it off as it would burn off the moment the
> engine was first fired :)

What a load of codswallop.
>
> Setting the valve clearances was the last major task:

You bloody fool! Setting the valve clearances is done *before* you check
piston to valve clearance. You seem to have matters arse about here.
What's the point of checking the piston to valve clearance and then
*changing* the valve clearances which will, in turn, change the piston
to valve clearances? Don't you understand the concepts here. Oh, that's
right, you think a *static check* will do the job - if the engine
rotates by hand, all is well. No concept of dynamic operation at all. I
propose that you never checked piston to valve clearances at all and
you've had plenty of opportunity (3+ years) to dummy up a couple of
photos with something that, quite frankly, doesn't look like remnants of
plasticine. Either that, or you didn't have a clue *how* to check the
clearances on an engine with VVT.
>
>> https://www.imagebam.com/view/ME69PM9
>
<snipped bullshit>

> Finally, the clearances were set and the camshafts installed for good,
> and it was ready for it's timing belt and to be put back into the car.
>
>> https://www.imagebam.com/view/ME69S4W
>
> So, after all this long winded chest beating, what have we learned?

That you are a bullshit artist. But we knew that long ago, you just
confirmed it yet again.
>
> What we've learned is that apart from a little bit of piston to bore
> clearance variation which Les was advised could lead to a bit of ring
> flutter and oil control problem, this engine went together well and had

Excessive ring groove clearances will cause ring flutter, oil
consumption (through pumping) and a small degree of compression loss.
You should know that, and you would have done had you ever completed an
auto machining or motor mechanic apprenticeship. FWIW, ring flutter is a
natural phenomenon related to ring pack *mass* that the engine designers
try to engineer so it occurs *above* the normal working range of the
engine. Ring groove or ring side wear will aggravate the situation and
bring the flutter down to the normal *upper* working range of the engine.

> no clearance issues whatsoever. The engine was installed back into the

Umm, clearance issues, yes it did have them. Bathurst, remember? That
clearance issue was a *biggie* and turned the engine into a *disposable*
unit in very short order. Well done you.

> car and test fired by me and it fired straight up with excellent oil
> pressure and had no temperature issues.

It won't have temperature issues *under no load* you clown.
>
> At this point the car was handed back to Les were it was booked into a
> dyno session. It ran the dyno session successfully where it bed in
> nicely, and as Les was still playing with tune settings a second dyno
> session was booked not long after. Subsequently to this it did a full
> test and tune day at Winton raceway before it was packed onto it's

Winton raceway is flat, no great RPM stresses because there's no long
downhill run. Been there, and on the track too.

> trailer and taken to Bathurst for a class race meeting which was the
> ultimate purpose of having done all this work in the first place.
>
> And it was at Bathurst where things turned to shit.

It was actually in your workshop where things turned to shit. It just
wasn't *evident* until Bathurst.
>
> On the seventh Lap of Les's race, as he was coming through the Chase at
> the end of Conrod Straight, the engine had a change of exhaust note and

So, as I noted, Les had the very fast run down conrod straight. That is
classic territory for stretched con rods and valves hitting pistons.
Let's dissect that. If the con rods stretch, that will *reduce* the
clearance at the piston/valve interface. Alloy rods will stretch the
most so you need to allow at least 0.030" more clearance if they are
fitted. Piston to valve clearances are usually 0.080" for inlets and
0.100" for exhausts. Typically, if the engine is being used for
*competition* and used at high RPM levels, you can add at least 5% to
those numbers. The engine has 8 new exhaust valves. If those new valves
were *heavier* than the originals, then you would need an even greater
clearance allowance since they will *loft* further due to their
increased mass. Either that or put heavier springs on the valves to
better control the loft. The new *thinner* gasket would definitely have
reduced the clearance by up to whatever the difference is. For instance,
if the old gasket was 1mm compressed and the new one 0.8mm compressed,
you now have *reduced* the piston to valve clearance by 0.008". If the
OEM gasket is 1.2mm, then you have reduced the clearance by 0.016". How
about we assume the new gasket was .6 compressed. We're now losing
0.024" clearance. Can we afford to lose that much clearance when, for
racing purposes it is recommended to add that much and more if the
engine is used for racing.

> blew a heavy plume of white smoke out of the exhaust. It was
> instantaneous, and it was abundantly clear that something in the engine
> had broken, and it's race meeting was over.

Your story has drift, lots of it.

On 04/02/17 10:21 AM, D Walford wrote:
> Not 100% sure, 2 possibilities, one is it was faulty manufacturing,
> the other is the valve hit the piston, even in a stock engine there
> isn't a lot of clearance and this one had aftermarket conrods and a
> different thinner head gasket.

Aftermarket conrods? Was the rod ratio different? That will affect the
piston to valve clearance. Different *thinner* head gasket? I knew you
had used a *thinner* head gasket. ;-)

>> The clearance was measured and found to be enough, all was good

WTF is *enough*? Engines have *specifications* and mechanics work to
specifications. You vary the specifications if you modify things.

>> during run in on a dyno and a number of laps of Winton plus the
>> warm up and first lap at Bathhurst so I doubt it was a clearance
>> issue, if it was I think that we would have known about it well
>> before it failed so that leaves a manufacturing fault.

So Daryl says it was good for the *first* lap at Bathurst. Obviously it
then went belly up on the second lap. I'll make an assumption here that
Les took it easy on the first lap, then gave it stick on the second lap
and that's when shit happened.

Do you realise what you have is a *classic failure case* of an exhaust
valve hitting a piston when overspeeding the engine during a long
downhill run. It just doesn't get more classic than that. Con rods
stretch during these events, and reduce piston to valve clearance in
doing so, and valve float and *loft* mean that the valve and the piston
will be in much, much closer proximity than is the case under normal
running. Conrod Straight isn't named thus for no good reason.

What's more, the *piston to valve hit* does not need to be sufficient to
*knock the head off the valve*. For a start, the valves are angled in
relation to the piston so a hit will always be on one side of the valve
head. All that needs to happen is the valve stem immediately under the
valve head is bent very slightly, just a few thousandths of an inch
sufficient to do two things; create a compression leak past the valve
face, and interfere with the cooling of the valve head. If the valve
head is not fully contacting the valve seat, you have seriously
compromised valve cooling, no doubt about it. After all, the valve seat
is responsible for 80% of the cooling of a valve, the stem a mere 20%.
Valves operate on a cycle average temperature, they are being heated
during the exhaust stroke when they are open, have hot exhaust gas
blasting through, and are not contacting their seat. For the other three
strokes, intake compression and power and ignoring valve lead and lag
for a moment, the exhaust valve is seated and heat is being conducted,
through its contact with the valve seat, to the head and thence into the
coolant. Typical exhaust valve temperatures are ~700C but the cycle
*average* temperatures are in the neighbourhood of ~425C. That maximum
tem is achieved only during the exhaust stroke, during the remainder of
the cycles the valve is cooling hence the comfortable cycle average
temperature.

Ok, picture this, you're on a downhill run at *higher* than normal
maximum RPM, clearances are insufficient and valve float and lofting
occurs. The piston contacts one side of the valve head and bends the
stem ever so slightly, just enough to prevent the valve head from making
full contact with the seat. You are now going to lose a small amount of
compression on the compression stroke but, because of the very high RPM
levels, this won't be so noticeable to the driver. But, on the power
stroke, you will have a *hot blast* of combusting gases under high
pressure blasting across the seat and heating the valve head. This at a
point in time when that valve head should be *losing heat* through the
valves seat to the coolant, the valve is supposed to be closed and
sealed after all. So you now have 2 cycles of valve head heating and
only 2 cycles of cooling. Even the two cycles of cooling will be reliant
on the *relatively* cool air to do the job on the intake and compression
strokes because the valve seat contact has been compromised. The valve
head temperature will rise rapidly and the hottest point, the normal
point of failure, will be under the valve head on the taper at the valve
neck.

https://www.researchgate.net/figure/Temperature-fields-inside-a-exhaust-valve-5_fig2_307615254

It's very easy to see why the valve head would break off at the neck. As
the valve head temperature rose due to compromised cooling, the metal at
the neck would become *plastic*. Of course, it must be remembered that
the valve is also being hammered into the seat @ ~4,000 times a minute
due to the action of the spring. A recipe for failure right there, and
it took but a very slight tap on the valve to initiate the process. BTW,
the overheating process can occur in *seconds*,

But why conrod straight, you might well ask. Well, the RPM of the
typical engine is limited by the load placed on it. On a dyno, the
engine RPM is restrained by the load placed on it. At Winton, all is
level so wind resistance vehicle mass, etc, all limit the top speed. At
Bathurst, conrod straight is a long downhill run, the mass of the car in
question is very low and wind resistance much less than a standard car.
That means it is quite easily possible to exceed the engine's *safe* RPM
limit *in top gear* on that downhill run. It is quite easy to see the
valves lofting quite a bit under those circumstances and being in a
location where collision with the piston is almost guaranteed. It's why
engines used in racing are given *extra* piston to valve clearance
compared to road going cars.

Actually, engines used in racing are likely to get stronger lightweight
valves - like titanium ones. They are 40% lighter for the same strength.
By reducing the mass by such a significant amount, you move the point of
valve bounce, float and loft way up higher in the RPM range. It's also
much better to use lighter valves rather than heavier springs as it
reduces loads and wear on cam lobes, tappet faces, rockers, etc.

>
> Les returned to Melbourne and brought the car around for me to look at
> where he showed me the video of the failure taking place, and after
> pulling a plug and looking into the cylinder with a Borescope it was
> obvious that the engine had dropped a valve and suffered a terminal
> failure.

Yep, a dropped valve *head*, as expected under the circumstances and
highly predictable.

Lofting - valve tap - leaking - overheating - head drops off

Logical scenario, step by step.
>
> I didn't do anything else to it, and Les went home with his tail between
> his legs and pulled the engine apart to see for himself. Once he did, he
> sent me these photos.
>
>> https://www.imagebam.com/view/ME69PMI
>> https://www.imagebam.com/view/ME69PMH

Look at that valve head Darren, broke right at the hottest point of the
whole valve and, I might add, the hardest point to cool because it is
the furthest point from either the guide or the valve seat. Pretty
logical really. When a valve breaks there Darren, you first think
*heat*. Then you think *why the heat*. A tap from the piston won't
normally knock a valve head clean off like that. It will *bend* the
valve first, at the stem, the weakest point. But it won't break it. That
will come later when the little bastard gets hotter'n hell.
>
> What these pictures show is that an exhaust valve on number one cylinder
> has hit a piston, but moreover it did so while the valve was fully open

That bit you got right *but* it was likely *lofting* so open more than
full, ie. more than the height of the cam lobe. Could even have been up
to coil bind territory.

> at the limit of it's travel. That much is obvious from the fact that the

The limit of travel is when the coil spring gets into coil bind. You
really don't want to go there, things get nasty when that happens. Valve
heads even drop off. Oh, that's right, that's exactly what happened.

> valve was snapped off around half way up it's stem, and as the piston
> turned it sideways and tried to bury it into the seat pocket it caused
> the piston to rock in it's bore pushing it hard up against the cylinder
> wall and splitting it open.

Yep, *exactly* par for the course.
>
> Anyone who has even the most "basic" of engine experience will tell you

Well, that would be you!

> that this is most decidedly *not* the result of inadequate piston to
> valve clearance :)
>
> In the case of piston to valve clearance issues, you mostly see it on
> inlet valves as with big overlap cams like this engine ran the inlet

I showed you proof that it was the exhaust valve that would hit, not so
much the inlet. You have this arse about as well - and you had the proof
in front of you.

> valve begins opening very early while the piston is still moving up the
> bore towards top dead centre. As the two are moving towards each other
> interference can occur if clearances are not where they're supposed to
> be. In the case of exhaust valves it's a different story as the exhaust
> valve is moving *away* from the piston as the piston nears top dead
> centre, and as a result piston to valve contact with exhaust valves is
> quite rare. Not impossible, but certainly far less likely than it can be
> with inlet valves.

You're talking shit here.
>
> However in either case the net result is usually the same in that unless
> you have things stupidly wrong about the most you'll ever see happen in
> the case of piston to valve contact near the very end (exhaust) or very
> beginning (inlet) of the valve's period is for the valve to bend
> slightly just behind the head, which will result in the valve no longer
> sealing against it's seat resulting in a loss of compression in that
> cylinder.

And that is *exactly* the start of the process of engine destruction -
as Les' engine will attest. The exhaust valve will cook up.
>
> And that is *not* what happened in the case of Les's engine.

The *evidence* shows that it is *exactly* what happened.
>
>
<snipped ever more bullshit>

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)