Con rod technical question

[RobD]

Does anybody have an explanation for the strange rectangular shape and the slot at the top of the Fulvia conrod?

[frankxhv773t]

I can't see it in this cutaway. It would be interesting if you could post a picture.

[RobD]

Frank, Here is a stock picture taken from the Cavallitto site, you can see the square-ended profile at the  top of the rod and if you look up into the small end you can see the underside of the slot. It seems to be providing a channel for lubrication but I must say I've never seen anything quite like it.
Having helped Pip, my engine builder, strip down the spare engine yesterday prior to having it bored etc. I'm in awe of Lancia's engineering prowess. The V4 really is an amazing piece of design and so beautifully made. The crank looks as if it's fully-machined , ie, even the surfaces of the crank webs appear to have been faced up. If so, it must have cost a fortune to produce.

[Parisien]

Have to agree Rob, wouldn't look out of place in a modern art gallery!!!!


P

[frankxhv773t]

I am sure there is someone out there with an engineering bent who knows Fulvia engines thoroughly and can give a definitive answer. I don't think the block on the end of the rod is particularly unusual. I have seen similar on other rods. Whether the groove inside the small end has anything to do with lubrication will depend on whether the small end gudgeon pin is fully floating or semi floating but either way I can't see where it would get an oil supply from. What does strike me is that the groove inside the small end seems to be beneath the block on the outside. Perhaps it is something to do with thermal expansion of that end of the rod?

[ben]

I suspect that the lumpy bits on either end of the rod are there to provide stock for machining away when the rods are balanced and matched into sets.
The slot across the top of the rod allows oil in to lubricate the little-end.The gudgeon pin is the fully floating type The crankcase will be full of oil mist and the area inside the piston is probably particularly oil rich as the oil scraped from the cylinder walls by the bottom piston ring is pumped into it through a series of radial holes in the piston wall.

I should say that these comments are based on some old components from an engine scrapped many years ago that have been adding to the clutter on my bench ever since so they may not be universally true for all Fulvias.

[ColinMarr]

I had the pleasure yesterday of the opportunity to ask this question of Peter Gerrish. Peter’s immediate answer confirms Ben’s suggestion that the works originally used these ‘lands’ (my term) for material to be removed for rough balancing, with fine balancing done by removing metal more selectively elsewhere. Peter also said that Series 1 rods were different – they didn’t have these lands and balancing was achieved by removal and polishing wherever needed.

Colin

[frankxhv773t]

Thank you. All is revealed. I was sure someone would have the real gen and I feel I know rather more of the intimate life of con-rods than I did before.

[RobD]

Thanks Colin,
I don't know Peter but his reputation goes before him and his and Ben's explanation makes perfect sense. My next question to the forum is about balancing and I wondered if anybody has any tips on any aspect of prepping a Fulvia engine. I intend to have the crank / flywheel /clutch assembly and front pulley balanced by a reputable firm but I'd be interested to hear if there is anything to bear in mind given the Fulvia's unusual crank configuration.
Bob

[fay66]

I had the pleasure yesterday of the opportunity to ask this question of Peter Gerrish. Peter’s immediate answer confirms Ben’s suggestion that the works originally used these ‘lands’ (my term) for material to be removed for rough balancing, with fine balancing done by removing metal more selectively elsewhere. Peter also said that Series 1 rods were different – they didn’t have these lands and balancing was achieved by removal and polishing wherever needed.

Colin

Peter made a Betty Rees trophy specially for Fulvia 50 in 2013 that was presented to myself, part of the trophy is a con rod mounted to a block of wood, this must be a series 1 con rod as although it has the slot, there is no excess of material and the top is rounded.

Brian
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