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 Big End Movement 
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Firing on two.
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Joined: October 5th, 2009, 8:22 pm
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Location: Stone, Staffs
Post Big End Movement
So decided to strip down a spare engine I have, pedigree unknown as bought off fleabay a year or so ago - had in the celeste whilst rebuilding with hc pistons and did knock a bit - now I have it with cylinder heads and barrels off, what degree of lateral movement should I expect on the con rods from the big ends? One side is nearly tight but the other moves around 2mm back to front....suspect it is goosed but your wise response would be welcome!

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April 26th, 2015, 1:50 pm
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Joined: March 5th, 2009, 6:23 pm
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Post Re: Big End Movement
Had a look in the shed, one with the "death rattle", has 3 to 4mm play.
Maybe use yours with LC pistons/barrels.


April 26th, 2015, 6:04 pm
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Post Re: Big End Movement
Apologies, meant I was rebuilding original engine with HC pistons and had the noisy one in as a temp.....I was intending of rebuilding it with 652 big bore but I'm not so sure now......

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April 26th, 2015, 6:13 pm
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Post Re: Big End Movement
Bump! Anyone please got a definitive on this? Ken?

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April 30th, 2015, 9:44 pm
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Joined: March 6th, 2009, 1:40 am
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Post Re: Big End Movement
Hi Nels,
I wasn't quite sure about the description you'd given, but guess that it must be 'side to side rock at the little end' if the crankshaft is still inside the casing.
I usually test them using a method found on a French site, which involves holding the crankshaft suspended by one conrod and giving the little end of that rod a good thump downwards with a gloved hand.
If there's any radial play in the big end, a 'clack' will be audible; that's when it's time to put that one in the 'back to Roy for recycling by Burton box...

Edit. Just been out and checked the four (unkown quantity) crankshafts which are sitting on a shelf in the shed, all of them show a trace of play when the conrods are rocked.
There's also a factory recon 435 crankshaft, which shows a similar amount of movement, however that one's got no oil in the bigend/crankpin since it's never been fitted.


Nelsthebass wrote:
Bump! Anyone please got a definitive on this? Ken?

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April 30th, 2015, 10:25 pm
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Post Re: Big End Movement
Cheers Ken.....I guess from this then is that provided it doesn't move vertically on the crank due to the big end bearing being knackered a small amount of lateral movement should be OK?

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May 2nd, 2015, 11:24 am
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Post Re: Big End Movement
yes there is a bit of side to side on the journal which can make it feel like there is wear

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May 2nd, 2015, 1:25 pm
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Post Re: Big End Movement
Right then....had a look again today and one side has no lateral movement on big end and also no top to bottom movement on piston back to the big end - however, on the other side, this has both lateral movement and circular movement on big end so I guess it's fubar'd.......fuck it I'm really annoyed cos I wanted to put 652 cylinders on this without rebuilding the engine currently in the car but that's all gone tits.

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May 4th, 2015, 6:18 pm
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