Hitchcocks Forum

Hello,
I was reading the forum discussion about big end bearings and a writer was converting to a roller big end because the only plain big ends are Indian made and fail after 10,000 miles.

Does anyone know if the white metal lined bearings are any good and if there are alternative manufacturers please?

I am planning to fit a steel connecting rod to my Redditch made 500 Bullet, and was going to opt for the plain bearing, but now i'm not so sure.

Any advice or comments would be appreciated,

Thank you.

It's a controvertial issue. The floating bush big ends were originally brought in (in the 1950's or even earlier) because the roller bearings of the time couldn't cope and were failing.



Now the "performance" upgrades use a high flow oil pump and roller big end.



I think the answer, if there is an answer, is that the floating bushes are absolutely fine PROVIDING they have a sufficient supply of oil (pressure and volume). I suspect most big end failures are actually an oil supply failure. An horrifically off-kilter crank (balance or alignment) wouldn't help matters either.



My Indian 350 bullet will have done over 70k miles on its original floating bush big end.

Enfield designed and introduced the floating bush big end in the 1930s with the intention of making the crankshaft/crankpin bearing easier to assemble and therefore more reliable in production. They were also looking at increasing engine speeds as performance increased. It's the fit between the components in a floating bush design that is crucial to long life and health as the oil film strength is crucial, exactly as in a shell fitted spilt big end. Oil needs to be clean and fresh obviously but that's true for all engines really. The bush design is much cheaper to repair than a roller, I've rebuilt several where only the bush needs replacement as it functions as the sacrificial component. I can't comment on the quality of the current bushes though.

REgards, Mark

When the big end went on mine it was as a result of oil starvation (a leaking oil filter housing).

I had a good chat with Andy Berry who is an authority on Royal Enfields and a well respected engine builder. I recall that he had some reservations about the way the threads were cut into the current Indian crank-pins, rather than any issue with the actual bushes. I don't think that he suggested that the Indian big ends were avoided, it was more a case that the roller big ends were better.

The problem with these jobs is that you start off with a simple re-build, I was going to go with a floating bush, then you get mission creep, you think let's have a roller big end, then you think why not the top of the range roller big end, it's only a few pounds more.

My engine was 60 years old and despite the floating bush being totally knackered, the crank pin only showed signs of normal high mileage wear and the bottom end would probably have lasted a few more decades had I not run it low on oil.

Given mine hell and it has survived well. The Bullet Whisperer tweaks the engines up to 40 plus bhp and sticks with white metal bearings. Like all components they will fail if abused but personally I'd save my money.

Thank you all for your kind advice. A plain bearing is what i hope to use.

The main bearings on my '86 350 bullet failed at about 66,000 mikes and i changed the big end bearing while I was at it, but the original seemed OK.

I think all the steam engines on br had plain bearings and a lot more hp. Only one was the peppercorn class that had timkin rollers fitted made a very heavy loco. A new built one Tornado was build by public subscription as the silly buggers scrapped the whole lot. Remember when tiger cubs came out, did roller bottom ends before warrenty expired. Rotary aircraft I believe used plain bearings, not the bearing fault in in crap manufacture. Noticed some in india that appeared to be made of phosper bronze.

Round about the time Rhodesia became Zimbabwe (1979/80-ish) they overhauled a lot of their old Beyer-Garratt locomotives and converted them to roller bearing axles. I wonder if any have survived?



Sorry, not much use in a RE Bullet context! ISTRC that Tom Lyons who produced the tuned Fireball Bullets in the USA was offering steel conrods AND the option of a bronze floating bush for the big end, presumably leaded phosphor bronze?



A.