dhutch
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| posted on 1/3/12 at 10:29 AM |
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Big-End to Sump Clearance
Is there a minimum clearance that you should aim for between the big end and the sump?
I only ask as I have a shortened sump from another member and having put it on my 1900 cvh have found the increased stroke causes the big end to hit
the sump (i turned that off fairly fast, i can tell you) no damage done but clearly it needs more clearance than that!
Question is, do i hammer (plenish..) out a bit of a dip to get a few mill, or do i cut it out and splice in a new clearance channel down the middle to
get me 10-15mm or so?
If cutting/welding I can screw it down to a board to keep the flange flat/straight, but not if im going down the plenishing route.
Daniel
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loggyboy
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| posted on 1/3/12 at 10:43 AM |
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I always thought you need plenty of clearance as you dont want the crank to be hitting any oil in the sump?
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owelly
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| posted on 1/3/12 at 10:52 AM |
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As Loggyboy says, you need enough clearance to hold enough oil without the crank and big ends splashing through the oil unless you have a dry sump.
[Edited on 1/3/12 by owelly]
http://www.ppcmag.co.uk
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dhutch
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| posted on 1/3/12 at 11:11 AM |
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The other half of the sump (under cyl 1 and 2) is much deeper and wider with added wings, so there is a half decent oil capacity to it, just shallow
under cyl 3 and 4.
Obviously if its too close, and a non-draining dip you going to get the big end hitting that pool, but if i make it into a bit of a shallow channel
into the main sump, while not ideal, I cant see it being the end of the world.
Daniel
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loggyboy
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| posted on 1/3/12 at 11:15 AM |
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I would want about 10-15mm
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pewe
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| posted on 1/3/12 at 11:30 AM |
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Just to confirm the above comments.
Years ago British Leyland had problems with one of their models seizing on motorway runs.
Turned out that the dipstick was incorrectly calibrated hence the sump was over-filled.
On longer runs the crank thrashed the oil and whipped it into a froth drastically reducing its lubrication properties.
Dry sumping may not seem attractive at this stage but may be worth considering?
Cheers, Pewe10 
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loggyboy
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| posted on 1/3/12 at 11:50 AM |
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My brother once over filled his Nova - (he was 17 and didnt realise you had a wait a few minutes to let oil filter thru the system after topping it up
before checking the dip stick!)
Within 40 miles he had thrown a bottom end thru the side of his block!
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Dusty
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| posted on 1/3/12 at 12:33 PM |
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Get the welder out!
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dhutch
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| posted on 1/3/12 at 01:16 PM |
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quote:
Originally posted by Dusty
Get the welder out!
Balls!
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pewe
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| posted on 1/3/12 at 04:18 PM |
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Daniel, to help take the guess-work out of it try standing the sump off the engine at the same angle as when fitted.
Fill it with sufficient liquid (typically 4 or 5 litres) to represent oil level when full and measure where the top of the level reaches from the
flange. Then measure each throw of the crank at its lowest point from the sump flange surface on the block and that will tell you whether there is
sufficient or any clearance.
And if you are already on that track - great minds and all that.....
Better to sort it out now than seize the engine later.
Cheers, Pewe10
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dhutch
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| posted on 1/3/12 at 05:08 PM |
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quote:
Originally posted by pewe
Daniel, to help take the guess-work out of it ...
My plan with this was simply to retain the exisiting dipstick and fill to the
'max' line of that. The oil volume is reduced from around 4.5l afair to about 3.2l but you get half of that back with the remote oil
cooler and then the normal low miles and frequent oil changes.
With the sump off and the dipstick in the standard oil level look near enough to me, about an inch clearance to the big ends i think.
Daniel
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