Josephine rebuild

[PJGD]

Keith; thanks for the endoscope link; it looks like a useful device and the price is right.

Scott; OK, point taken; throttle response has to be better with a lighter flywheel of course with a racing clutch pack being the ultimate solution, but idle quality has to suffer surely and that is what the OEM has to worry about. Hollowing out the front (as mounted in the car) would still be my preferred solution for a road/mild competition car.

I have one standard flywheel at about 24 lb and one that I lightened many years ago at approx. 18 lb but have never run yet. Nevertheless, I am pleased to hear that you are running a much lighter flywheel still and it is satisfactory.

[Keith Clements]

There are two types of inertia-
1- what most consider weight which is the mass being moved linearly and is important in a vehicle as more weight needs more power to accelerate and decelerate it
2- rotational inertia which is mass times the square of the distance that the mass is away from the centre of rotation. The flywheel's kinetic energy goes up by a power of two as the rotational speed increases. This is important in throttle response as to increase engine revs you need to rotate the mass quicker. So two flywheels with the same weight may have totally different rotational inertia or conversely two flywheels with the same rotational inertia can weigh very differently.
The flywheel is really only there to keep the engine going at tick over, not something a racing engine ever does. There is probably enough rotational kinetic energy in the clutch and crankshaft to keep an engine going without a flywheel whose only real function is to start the engine and provide a clutch plate.

https://www.engineeringtoolbox.com/flyw ... d_945.html

[Srenner]

Hey guys, true at some point that getting too light would require raising the idle speed to compensate for no flywheel effect. I think KC is right about the rest of the mass being capable of idling the motor, but none of us want to go hunting to find that balance point. We just want a more responsive motor!

I look at the weight of the stock flywheel as somewhat similar to the first gear ratio in the gearbox. The accepted good practice at the time it was produced. Lots of inventive, creative thinking has made modern cars massively superior in all areas. The only downside is the complexity.

So, to hijack this to another possible improvement, would adding a plenum under the carbs improve overall performance on the motor? Bolting the carb directly to the head makes for immediate reaction at the carb to the intake valves opening and closing. Since each side fires both cylinders in sequence, each side acts its own two cylinder motor. Cyl 4 fires, followed by 2, and some think that 2 is not getting the same charge that 4 got. The same thinking suggests the charge inside the balance tube compensates.

Having played with a few other motors and a few American V8s with some form of plenum, might this be an area to explore?

[Keith Clements]

Why not just go for injection?

Having had issues with the air intake side using DelLorto carbs I think the whole design of the intake system is suspect and probably only works with the Zeniths in the very particularly performance range of the standard car. As soon as you try to use more revs or bigger displacements you need to do a lot more design and development.

The Jowett design is most likely a poor compromise. Would one carb be better than two or four carbs better than two? There are arguments that could take you either way.

What is really needed is some good instrumentation on the engine to measure individual cylinder performance under all load conditions. I can remember 30 years ago looking at the Crypton analyser on my Jup showing all the ignition pulses. Now we could measure cylinder pressure , gas analyse each cylinder, look at all the temperatures everywhere to get a good idea of what is wrong.

[Keith Clements]

Just another thought on why the balance pipe is there...it is all to do with pressure wave tuning (similar to an organ pipe). I have a Jowett engine with an external balance pipe which would have a different tune. I also know some who have separated the Siamese twin intake tracts. The maths is not particularly difficult to do once you have some quantitative values and distances to plug in. I made some hyperbolic intakes for the carbs for racing in an attempt to idealise the tuning of the tract. The dyno did show a significant difference from the standard air filter arrangement, although some of that was due to the restriction caused by the filter. Hence the use of full flow foam filters for rallying. But there was an improvement over just leaving them off. Some people have increased the distance of the carb away from the head. I do not know why -but various factors apart from the tuned length of the tract could be relevant such as the atomisation of the fuel mixture or the availability of an already atomised charge ready for induction. The latter could also be a counter argument to the 2/4 conundrum that Scott brought up if you think that it takes a while for the carb to sort itself out after an intake valve opens. Fitting a super or turbo charger of course would reduce any issue on this front. My Skoda has both so I have no idea how the engine management system sorts out how much fuel to squirt into each cylinder.

[Keith Clements]

With the heads torqued down to 14 Lb-ft measurements were taken with feeler gauge all around the gasket area. The height was also checked with head on with no torque.


From this the desired shim was determined for each liner.
Note the protrusion had also been checked with the usual method with a flat ground bar or ruler across the liner face.
On removal of the liners it was found they had been put together with silicone with no gasket or shims. So the silicone was cleaned off and the test repeated.
One head was found now to protrude betwen 10 thou and 8 thou all around. But the other went from 10 thou to 6 thou along the bottom face so that face was tested for cracks. The test was done using a cleaner, penetrant (pink) and discloser (white chalk) three pack aerosol kit.
None were found.


The big end bearings were also tested for clearance using the Plastiguage.


One big end was not quite to the desired clearance being just under 2 thou whereas the others were more like 1 thou. I did experiment with a shim under the shell with a spare bearing pair and with another bearing pair but suspect a bit of grinding on the faces where they join is required to tighten them on the shaft. Since the clearance is within factory spec I am in a quandary as to which way to go!
You can also see the hex key used for the new con rod bolts that were cut to length and precisely weighed to get all the piston assemblies to the same weight.

My new Samsung s8 plus tells me that the wood burner has to be lit when I go down to the Gulag. It says -1 Deg brrrrr

[Keith Clements]

Interesting engine.
As I said there were no liner gaskets in the assembly or shims. So I measured the liner height and also noticed the chamfer on the block and the filet on the liner.
The standard liner has a height from the seal to the head gasket of 63mm and the ones in this engine were 64 mm all +- .03mm.



So having cleaned out all the old silicone the shims were reset , torqued down and checked.
Note the dimensions on the right are the clearance with the liners clamped by the centre bolt at a torque of 14 lbft and the clearances on the left are those with the head on torqued to the same. With copper rather than Halite as a seal I reckon you need less pinch on the head gasket. So I am reasonably happy with those clearances. The block may have stretched a bit but reducing where it is high might put more strain on the bottom web so I am leaving as is. That part of the gasket generally has difficulty sealing so a bit more pinch would not go amiss. I still reckon there will be enough pinch on the liner seal. We will see after a few 1000 miles if I am wrong.

These are the painted water ways.

The finished article with some sealant added to the shims.


Oh and a couple of pictures of standard and lightened flywheels.

[Keith Clements]

I use power hoist to fit the two halves of the block together.
Torquing the bolts up to 75 Lbs ft was a challenge although Amy's Teng set of torque wrenches make it easier.

The Plastigauge shows that all clearances are less than 1.7 thou. I was aiming for .0286mm or 1.125 thou.



End float was also 3 thou so within spec.

But I noticed some wear possibly caused by a push rod that jumped out!

I will check the bore tomorrow.

[PJGD]

Keith; surely the odd-man-out liner with the 64 mm dimension and radiused corner is one of the later ones intended for the metal-to-metal with o-ring seal?

Also, I am not clear what is going on with the internally painted crankcase: what is the paint, what for, and is it related to the crack testing?

And how have people separated the siamesed ports? If you extend the septum up to the carburetor flange, then there is not enough flow area for each cylinder. Separating the ports is the right direction to go in, but until the club gets around to making some new cylinder heads at which point we would be able to make some updates and improvements, I don't see how it can be done.

[Keith Clements]

All four liners were the same. Perhaps the o ring brought the liners up to the desired height but would have to squash to 4 thou. Also shims would still be needed to adjust individual liners. I prefer to rely on metal to metal contact.
The paint was presumably to help prevent corrosion. Looks like red oxide primer so not sure how it will stick to aly.
The dual porting was done by carefully opening up the ports. No more detail available.

[Keith Clements]

I was due to go to the rugby today to welcome our friends from Clermont but the match was called off. All roads within 10 miles are totally blocked with at least 2 hour delays. Amazing what a few flakes of snow will do.

IMG-20171210-WA0001.jpg

I did venture out to clear some of the 15cm snow and check the garage had all its roof supports in place but rather than stoking up the wood burner as I did yesterday decided to do some research. Eventually bought a vibration tester which should help give a value on any acceleration, velocity or displacement when the engine is in the test bed, installed in the car or when the crank assembly is on the lathe. It does have an output so I may be able to rig up some electronics to my strobe gun so as to show the angle at which the max vibration occurs. The strobe gun has a degree delay function so in theory I should be able to use that to position the weight.

If I can find a suitable position sensor (hall effect on the flywheel teeth) and write some software I might be able to link to a PC to have a pretty diagram to tell me where to put any weight. Until then I will employ some stick on weights or magnetic discs and use trial and error (the Jowett way).

[Alastair Gregg]

Keith,

You are straying into my tiny pigeon hole of knowledge here :

Whose manufacturer and did you get? was it an RMS meter or can you do FFT's on it. RMS are pretty insensitive, however V.A. is very sensitive. If you need help with FFT's I may be able to help. As per the Jowetteer article some months ago, my speciality is Acoustic Emission. Vibration thinks it is a competing technology. In your instance I worry about interference as Vibration uses low frequencies (typically 1-10KHz) which will mean it will be difficult to be specific when identifying the source location of a vibration (or in your case out of balance or mis alignment).

Let me know if I can help

[Keith Clements]

Measuring range：Acceleration：0.1~199.9m/s2 peak
Velocity：0.1~199.9m/s
Displacement：0.001~1.999 mm (P﹣P)
Accuracy: ±5% +2digits
Measuring frequency of acceleration: 10Hz~1KHz (LO); 1KHz~15KHz (HI)
Measuring frequency of velocity/displacement: 10Hz~1KHz (LO)
LCD display: 3 1/2 digits display

870693153_o.jpg

[Srenner]

One big end was not quite to the desired clearance being just under 2 thou whereas the others were more like 1 thou. I did experiment with a shim under the shell with a spare bearing pair and with another bearing pair but suspect a bit of grinding on the faces where they join is required to tighten them on the shaft.

There is no acceptable way to grind the joint due to the serrated joint. While most manufacturers use push-in bolts and/or locating sleeves to align the cap, the serrations are the alignment on our rods. When a con rod is resized, an equal amount of material is removed from both pieces. Then, as the bore is no longer round,it is honed back specification. There is no way to remove equal amounts on our rods.

The + number can be at the limit of bearing crush, so tighter is safer. Also, it is likely the bigger bore is due to stretch and the bore is out of round.

The JCCNZ Perkins bearing requires the rod bore to be honed an additional .001" and in my experience, this hone is enough to get round and proper crush.

[Keith Clements]

I was not proposing to grind the con rod but the bearing since with the shims behind it needed some relief at the joint. The Perkins bearing I tried was tighter but I decided to leave as is rather than have odd bearings. My measuring is really not accurate enough to determine if it is the con rod, the bearing or the journal that is a a thou different. I will try another assembled rod on the same journal.

Today checked out some camshafts and found a new one that fits. Plastiguage showed less than a thou of clearance on all three journals. I also took some time to make sure the new followers were a sliding fit as some were tight.

20171213_161136.jpg

Block was assembled with sealant under all the washers as most bolt holes have oil pressure in them. Loctited the oil gallery plugs. Sealed the balance pipe and will check with vacuum tomorrow.