pre war long 4 white metal big end bearings

[AmilcarJohn]

Could the engine have previously (originally?) been assembled with the crank journals not quite centred on the bores? Perhaps over time this could have led to a twisted conrod, but with the big and little ends remaining parallel due to location in the bore?

[Dhbangham]

Not an obvious explaination since they are both offset towards the center of the crank. BIG BUT. I had friends round puzzling over the engine this Sunday and some were not convinced about the offset, we are now devising a way to measure it accurately and report back to you.

Another Sunday and been and gone and I still haven't measured the position of the journals relative to the cylinder. I have however stripped my spare engine only to find the the front main bearing has a chunk missing, excessive end float on the crank and that the con rods are so wide that it won't accept white metal on the ends. (the fit of the bearings are way off spec.) I have improved the jig for casting the white metal, so hope to re-cast all four con rods very soon.

On measuring the second con-rods they are very mismatched, the big end are about 3mm different in width and one of the covers (caps) has been machined down by about 2 mm, and then the bore of the conrod opened up. A complete mess, it has worked for 10k or so, but I won't be happy putting them back in and will try and find another pair of good rods.

However, after four attempts. I have now successfully cast and bored a pair of conrods and it is getting much easier each time I refine the set up and get more familiar with the process.

.

[Dhbangham]

See main bearing thread to see how I prepared the crank for re-assembly.

After assembling crank and con-rods into engine I turned attention to cylinders, it there was a rather mismatched assembly of piston rings, so I bought new rings that I hoped would be correct, but the closest I found, still did not fit. To make them fit I had to increase the internal diameter of the rings by 1.5mm and widen the compression ring grooves in the piston by 0.2mm . Increasing the internal diameter, required making a recess in a rod of PVC that was a tight fit for the rings, see photo. I could then bore out all four the rings at the same time. I also chose to make the groove for the oil control ring wider, so could install modern oil control rings. Using assembly oil I installed the pistons onto the con-rods, and installed cylinders with Hylomar blue on cylinder to body aluminium gasket. Installed cam shaft and gears using the original marks, the camshaft was so worn, we could not get the inlet valve to start opening at TDC, (as per spec.) and decided not to make new keyway peg to improve the valve timing, but used the best orientation we could find with the original peg. Set valve settings and ignition timing. Once all the ancillaries were installed we primed the oil pump and pipes and started the engine. We were very worried by very low oil pressure to start with, but after time, it rose to around 20psi. Test drive revealed that the clutch travel needed adjusting and I may have to take the whole front end off again to solve small water leak between inlet manifold and cylinder head. Before doing that I will loosen off the cylinder head bolts and try twisting the cylinders and tight the manifold and cylinder bolts again. The engine sound good though.

[Dhbangham]

If anyone reading this post would like to join me when I re-metal my second engine sometime in the first half of 2026, please let me know and I will set up a workshop visit for any club member who is interested. Cheers Danieil (Cambridge)

[AmilcarJohn]

Yes please! Would love to see this in action. I'm in Cambridge too.

John

[Dhbangham]

I have two interested people so far, I may put it into the magazine and see what happens. The date is booked at Sunday 1st march 2026 10am till end of day, hopefully 4pm

[Dhbangham]

White metal update: The engine is assembled with the help of Jowett owners Rob, Tony and Barry, also Wolsey Hornet owner Giles. Oil primed, ignition timing and valves set and it started. I then drove it 40 miles. It ticks over very sweetly, but lacked power. We then took the front of the car off and timing cover and re-set the valve timing to specification (ie starts opening at TDC) not to the original timing marks. The difference was two whole teeth of the geared timing mechanism (about 12 degrees?) this can be put down to the very worn cam and followers. (Resetting the tappets also revealed my mistake of not getting the right sequence in adjusting the tappets, it seem that the safe way to do it,is to tightening the adjuster so that there is no valve just start to open, then back off, the backi off to the correct gap). The ignition timing needed resetting. Again it started well and had much more "grunt", but for some reason, it was very intermittent under load. More investigation needed. The new con-rod bearings and Main bearing adjustments seems to have been successful, with no unwanted noises and oil pressure perfect.

[Dhbangham]

Reset tappets and found that one inlet tappet had not be locked and had moved to such an extent that is was open all the time. AHHHHH. Re set the tappet and it runs better than ever. It is now accelerating in 3rd gear up an incline. Happy days.

[Dhbangham]

We had a prewar technical day in Cambridge last weekend, where I demonstrated white metalling my spare engine. This was not as successful as hoped and the problem was eventually tracked down to very uneven crank shaft journals. I am awaiting delivery of a vintage crank truing device and I will report how successul that works.

[Nick Webster]

Daniel,

All in all it was a very good day and perhaps you should look at it from the point of view that any problem is an education and it won't happen again.

I was very smitten by the Wolesley Hornet Special parked outside, partly because I had been tempted by one in the past. As a Jowett owner, should I feel guilty?

Nick

[Dhbangham]

Yes, it was an education. No guilt in coverting someone elses car, its other peoples partners where it get complicated. I have enjoyed owning an Armstong 20hp 1935 and a Lancia Belna 1935.

[Dhbangham]

More on the white metaling; At the demonstration day, Nick Webster introduced me to a volume "The modern motor engineer" which has some excellent insights into early engine maintenance. I lead me to have confidence in the possibility of making my crankshaft round in the home workshop, without having it sent away, which would involve taking off and re-attaching the counter weights and re-balancing. The book offered various methods of re-gringing by hand, including using grinding paste on a sacrificial white metal bearing. I used this method together with judicious "strapping" with fine grit ALoxide workshop roll. The result was not perfect, but I felt good enough. I was then able to - complete the bearing, that were started at the demonstration day and the two new bearing seem great.

[Dhbangham]

In the last post I said the new bearing were fine or good enough, well, when I re-visited them the other day, I decided they were not good enough. There were sill some sticking point when I rotated the crank shafts. That had to mean that there was a defect in both the white metal and the crank journal. There was also an inconsistency between one assembly and another, so that meant that there was a problem with the clamp bolts and or mating surfaces of the crank and cap. This is the list of possibilities I worked through;
a) Bent bolts. Indeed the original bolts were not straight, new ones sourced.
b) the mating surface of the cap and cranks not level. They were not level, so would clamp at slightly different position each time. Draw field the mating surfaces
The about process improved the repeatability of the assembly.

c) The crank journal was not round. By putting engineers blue on the crank journal and running the cranks bearings, it was obvious where the high spots on the crank journal were, so I used a diamond lap to knock down the high spots, ie the opposite of scraping the white metal. This was repeated about 6 times, until I got about 80% contact on the bearing. I finally polished the bearing with fine 3m abrasive.
d) crank journals were not axial, ie they had warn "round" but at an angle to the axis of the crank, this turned out not to be true, it was OK
e) crank journal was not a cylinder, ie there was a taper. Yes there was a taper, but this was sorted in process C.