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spitfire6

Con Rod Piston Squirt Hole?

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Hi,

 Only a question as I have no desire to modify.

 

On the OEM 1500 spit and GT6 conrods the orifice at the big end that squirts oil into the piston, is it worth modifying?

Never ever heard about modifying it for increased cooling or increased pressure to big-ends.

I had thought only performance engines squirted oil in to the pistons?

 

Cheers,

Iain.

 

 

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conrods with squirt holes?

Never seen one in a Triumph!  Don't think Triumph did either.

 

If you think the combustion chamber is too hot (high compression or lean mixture, that you don't want to correct) think of a water spray in the charge.

 

How does losing oil from the big end increase the pressure to them?

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Hi John,

 I thought the hole and "dimple?" at the base of the conrod was a squirt hole? 

I seem to remember a dimple with a hole in my conrods. It was a very long time ago!

 

Do you have access to a con rod to see if it was my imagination?  Maybe I am thinking of the one at the top of the conrod? is this pressure fed?

 

Feeling a wee bit stupid now. LOL.

 

Thanks,

Iain.

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"Hole and dimple"?    Some ?late? conrods have a hole through the base of the stem, that opens the bottom of the big-end bolt.  I've presumed that this was to ventilate that hole and prevent pressure build up on assembly.  That it's as wide as the bolt hole and almost as wide as the connecting beam shows the importance of the I-beam section.  The picture below is of a conrod with such a hole; It's bent (!) but not at the hole!

 

The "hole and dimple" on the top of the small end IS to do with lubrication!   It was put there in the pious hope that it would catch oil spray and take it to the gudgeon pin.   Yes, really.   I grind off the 'dimple' as part of lightening and equalising my con  rods.  I risk instant universal conrod breakup by saying so, but small end fauilure has never been a problem!

 

There is no oil-way communication between the big and small ends.  The small end is splash-lubricated.

 

John

post-690-0-54872600-1504775913_thumb.jpg

Edited by JohnD

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conrods with squirt holes?

Never seen one in a Triumph!  Don't think Triumph did either.

 

If you think the combustion chamber is too hot (high compression or lean mixture, that you don't want to correct) think of a water spray in the charge.

 

How does losing oil from the big end increase the pressure to them?

Hello All

             I think Iain may be thinking of TR 2/3/4 con rods? I seem to remember them having a oil drilling up to the little end with a cross drilling halfway up!

 

Can not check as gave spare ones away and others inside the engine.

 

But it may be my memory of another engine!

 

Roger

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This may be a question for the experts - I'll ask on the TRR Msb.   Unless anyone here knows for sure?

John

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If this photo shows what I think it does then TR4 conrods DO have an oilway up from the big to the smal end!

It's from the Rimmers catalogue, and a hole in the big end in line with the beam of the rod can't really be anything else.

My thanks to Richard71 on the TRR board!

John

post-690-0-98815800-1504801916_thumb.jpg

Edited by JohnD

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Whilst at a vintage machine shop early last year (on my recurrent big end failure investigation) I was shown some gorgeous pre war Riley conrods that not only had that centre drilling but halfway up (well just below piston skirt line) they had a tiny drilling through the side of the conrod into it, to squirt oil on to the the compression face of the cylinder wall.

 

Was also shown some new v v expensive forged rods that they had just received for something special they were building for someone, and they had a hole drilled through the rim of the conrod into the journal so that it emerged just on the edge of the shell, this hole was also angled so that oil being ejected from the journal would squirt on the cyclinder wall.

 

A bit of research showed that (I think Carillo) have an option on their rods, where instead of drilling a hole in the journal they cut a slot on the edge to do the same thing. As there appeared to be no downside to this I machined a similar grove in my new forged rod set. Did it do any good? don't know, but it doesn't seem to have done any harm and when stripped last winter there appeared to be no ill effects.

 

Alan

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My understanding of oil lubrication is that it is the viscosity of the oil in the bearing that keeps it from metal to metal contact. The pressure is just to promote flow into the bearing, as oil is lost from the sides.

That's why our camshafts include a pumping flat on the rear bearing to push oil upwards into the rocker shaft.

 

So where does the push come from to impel oil upwards from big end to small, along another tiny diameter oilway? That hole may coincide with the oil way in the crank journal once per revolution when some residual pressure may give it a push, but enough to "squirt" a jet from the big end or even halfway up the beam, to reach the piston? Seems like wishful thinking to me!

John

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Further investigation finds this picture, from a biker site, it's a Honda, I believe:

 

post-690-0-88426200-1504955346_thumb.jpg

 

And jets, fixed to the crankcase, directed up the bores and connected to the main oil ways, are apparently popular in turbo diesels, because of the greater heat those generate in their combustion chambers.

 

The second is also seen here in a  simulation:  https://www.youtube.com/watch?v=uMnFbsy0Hgg, and given enough oil flow and pump capacity will work fine, but the first can hardly be described as showing a 'jet', more a vertical dribble!

 

JOhn

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Wow, who knew, well of course all of you but me, but did you know that Rover V8's utilise a technique to squirt oil from the main Big End bearing cap on one cylinder onto the bore wall of the opposing cylinder, not that I have spent huge amounts of time reading about Rover V8's, but I would have said enough over the years and especially about lubrication in general whilst on my #5 BE failure quest that I though I'd have stumbled across this before, so of course it could be untrue but does come from a Rover SD1 site.

You will note that one side of the jointing face of each big end contains a groove. This enables a spray feed of oil to lubricate the wall of the opposite cylinder. Therefore it is important to fit the pistons the correct way round.
Each connecting rod is marked with a boss and each connecting rod cap with a rib. Locate the piston in its bore with a piston ring compressor. Make sure that the boss on the connecting rod faces the right way, that is towards the front of the engine on the right hand bank of cylinders, as shown in red, and towards the rear of the engine for the left hand bank of cylinders, as shown in blue. When correctly fitted, the bosses and ribs for each pair of connecting rods on one journal should face each other.

There should be a picture here, but I can't find out how to upload attach a new picture with the new software, so I'll leave you hanging whilst I find out how!

Alan

Thanks to someone fiddling behind the curtains I now have pics again! Thanks your efforts are appreciated! so here is the shot of how the rover V8 oils the bores.

 

oilspray.jpg.c0dd76a8be7d5593bbbcef1c43338bb1.jpg

Edited by oldtuckunder
add piccy

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