Rod to piston oil spray

Question and answer direct with GC. Competition engines and 'live' projects only. Good photos to illustrate your post are expected.
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vcg
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Rod to piston oil spray

Post by vcg » May 1st, 2008, 1:20 am

Guy, will you GC/Cunningham rods work on 131 2.0Lt without oil jets fitted to the block? Looking at the pictures of your rods I see no oil spray holes towards the pistons. Integrale and Tipo blocks had oiljets and no oil holes in the rods, if I remember right. What happens with 131 that doesn't have oil jets? Thanks,
Vassilis
124 BS1, 124 BC1, 131 Racing, E Type 4.2 SII, XJ-S 3.6

Guy Croft
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Re: Rod to piston oil spray

Post by Guy Croft » May 1st, 2008, 8:38 am

The GC rods have bleed slots in the rod cheek that provide oil for bore lubrication. This is a proven way of doing it and I copied it years ago from Abarth Gp4 037 rods. In addition GC race pistons have dual pin oiler drillings to take care of the pin/rod bush lubrication. In fact I have actually run the TC engine without any kind of bleed or spray bore lubrication, splash and vapour seemed to do the job well enough though that is a long way from saying I recommend the practice!

On engines with oil sprays one can reasonably assume that they have the additional function of controlled spray lubrication of the piston underside region for cooling and enhanced ring-wetting/bore lubrication on cold start to reduce start-up emissions of HC. Their ability to prevent 'knock' (detonation) at really dangerous levels (sufficient to hole pistons/damage heads/blow gaskets) is however, in my experience, zero, and moreover I have a reliable report from a race engine builder well-known to me that they reduce measurably reduce power output and thus I would not use them on a competition engine unless pressure-charged at boost of 15psi or higher. And I would be using them solely as a means of keeping the piston temperature down and preventing degradation of the alloy material per-se. All materials lose strength as temperature rises and so if you wanted to make a reasoned case for using them on an engine you really would have to have data-logged in-cylinder temperature records to demonstrate that need. F1 engines use them and at 300bhp per liter I figure you'd need them too.

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tmvolumex
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Cunningham rods

Post by tmvolumex » September 28th, 2014, 8:47 pm

Guy,
How much clearancing in a Fiat / Lancia block do 2 liter Cunningham rods require?
Is the rod length the same as stock or are custom pistons required to use them?
Thanks,
Tom
GC_31

Guy Croft
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Re: Rod to piston oil spray

Post by Guy Croft » September 29th, 2014, 12:36 pm

Direct interchange Tom,

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Piotrek125p
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Re: Rod to piston oil spray

Post by Piotrek125p » June 11th, 2016, 12:44 pm

GC, could you tell me how depth should be a bleed hole in rod cheek ? It should be up to bearing edge or shallow/deeper ?

In my opinion it should up to edge or slightly deeper, but it is not supported by my experience, only conjectures.

I marked on this photo this holes.
Gc vs std piston & rod (3).JPG
GC Cunnigham rod.
Gc vs std piston & rod (3).JPG (234.03 KiB) Viewed 2914 times
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Guy Croft
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Re: Rod to piston oil spray

Post by Guy Croft » June 11th, 2016, 7:32 pm

well, buy a set and you'll find out won't you Piotr?

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Piotrek125p
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Re: Rod to piston oil spray

Post by Piotrek125p » June 11th, 2016, 7:46 pm

Too much for my budget. Maybe in future.
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Guy Croft
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Re: Rod to piston oil spray

Post by Guy Croft » June 11th, 2016, 7:53 pm

yes they all say that..

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Piotrek125p
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Re: Rod to piston oil spray

Post by Piotrek125p » June 12th, 2016, 3:49 pm

This is a way that Ford make this groove on a rod cheek.
20160612_112145.jpg
20160612_112145.jpg (31.8 KiB) Viewed 2868 times
Today discover from a laboratory about engines on Lodz University of Technology :)
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Re: Rod to piston oil spray

Post by Guy Croft » June 12th, 2016, 4:00 pm

probably been reading my forum...

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Piotrek125p
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Re: Rod to piston oil spray

Post by Piotrek125p » June 12th, 2016, 4:24 pm

No doubt, we all should take a lessons from the best and we are doing it here, dear GC.
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