Bearing shells

griff851

Todays mission was to measure bits, primarily the Mystery rods and crank. I now know why they are different. They have a 44.99mm hole in the big end (standard for a "B" rod is 45.013-45.019, Almost the same as corrillo (44.983mm). It had a set of SP5 shells in it. Nice as they have 3 little holes to trap oil in the shell. Bad as they are no long available. It was suggested 996/998 shells as a replacement but they would give a 0.408mm interference fit, which would make the eng just a bit too tight. The starter would never budge it.😄
Interestingly The rod says "A" yet I have a "B" crank (41.998mm)
Does anybody know what shells are run with 851/888 Corrillo rods? Ideally I need a shell 1.489-1.475mm. Obviously closer to 1.489mm the better.

Griff

Mr.R

griff851 wroteTodays mission was to measure bits, primarily the Mystery rods and crank. I now know why they are different. They have a 44.99mm hole in the big end (standard for a "B" rod is 45.013-45.019, Almost the same as corrillo (44.983mm). It had a set of SP5 shells in it. Nice as they have 3 little holes to trap oil in the shell. Bad as they are no long available. It was suggested 996/998 shells as a replacement but they would give a 0.408mm interference fit, which would make the eng just a bit too tight. The starter would never budge it.😄 Interestingly The rod says "A" yet I have a "B" crank (41.998mm) Does anybody know what shells are run with 851/888 Corrillo rods? Ideally I need a shell 1.489-1.475mm. Obviously closer to 1.489mm the better. Griff

Hi Griff,
This ones a new one on me, I'd assumed that the Carrillo's would accept standard Ducati shells, when I rebuilt my 916 crank using 851 rods I used standard Ducati Blues and Reds then Plastigauged the bigends to see which combination came out spot on.
However back to your problem, I do know that you can use slimmed down VW Shells from a Golf/Rabbit or Polo, so maybe a trip to your local VeeDub dealers is on the cards?
When I used to build plain bearing cranks for Endurance Racing, I'd often fit tighter shells than recommended to the cranks, the colour codes on Honda shells are only microns different and a carefully set up crank as long as it wasn't hammered before it had all settled in would outlast a crank set to Honda's specs.
Keeping the revs down for the 1st practice session would do the job.
I found this out when I couldn't get the 'correct' sized Honda shells and had to fit the next size (Tighter on the crank) available, that bike went onto finish as the 1st non works bike home at the IOM TT, it was a P&M RSC Aircooled 16 valve 4, back in the early 80's.
A recent conversation with one of the top V Four Honda Race engine builders (Here in the UK) confirmed this, he said that he always used tighter clearances than Honda recommended and his motors were more reliable and put out more power than the HRC speced bikes!
He's one of the guys that I mentioned in my thread on PCIII's, who now runs a Dyno room only 16 miles from my home.

Steve R

griff851

Thanks Steve. I'll look into the VW bits. I'm with your Honda mate on the tighter the better as long as there is some room for oil.😄 The little end bushes were worn so they are being replaced, while the rods are at the machine shop I might get the BE bored to save mucking around. With the cap torqued down I have .02mm elongation so that might be the best thing to do anyway. Or just use my original rods. Ah the fun of it all.

Griff

griff851

Today, after being plagued with agony last night over not knowing what size bearing shells came in, I measured a set up (not easy as they have a curve) and got an approx of Red 1.45mm and Blue at 1.60. The interesting thing is the box says .25 m, so does the book. I can't quite work out how crush would grow 0.1. Something odd there.
The shell itself was for a standard rod 851/900M and a host of others. So we measured up my original rod Steel H section thing which looks remarkable similar to to the funny colored one. 45.005mm. The book/s say 45.013-45.019mm for a "B" rod. The temp today was 22°C.
So 45.005-41.998(Crank journal) = 3.015/2 (2 shells) = 1.507
That leaves 0.057 with a red shell and -0.093 with a blue.
Tolerance is 0.024- 0.056mm
Therefore using the measuring method, its off to the machine shop for either rod, and fit blue shells with instructions to bring the tolerance down to minimum + what ever the U-beaut coating the ceramic guy has for bearing shells.
The exchange rate has dampened the Corello idea.(Thats global meltdown in action for you)
As my rods don't have stretched end caps, as the odd colored ones have (Hard life for the ex SP4), they will make the journey I feel.
Next we use Plastiguage and see what results come up, before we actually go to the machine shop.

Griff