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Concerns on i-beam/tri-beam connecting rods

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Would you please comment on the following:

What are the reasons for not implementing oil grooves on i-beam and tri-beam rods’ big end?

And meanwhile this groove does present on h-tuff rods.

Both rods are intended for the same engine (ej20/sti/ej25) and made by same manufacturer.

What is the true purpose of these grooves, what effect do these grooves make on engine and why does the same manufacturer make rods for one and the same engine with these grooves and without them?

What could be the possible reasons for doing so?

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Hello, the notch was designed to squirt oil to cool the piston without affecting the oil pressure or flow to the bearings, With all the engines I have built and pulled down season after season I have never noticed any extra wear or overheating without them. so i going with the "i dont care" either way when building a race or street engine,


I'd suggest splash rather than squirt lubrication, but thats more sematics than anything.

Some connecting rods will have a drilling that is supposed to direct a squirt at the gudgeon area, and others are actually rifle drilled along their length to pressure feed oil to the small end bushing. As Ross said you're unlikely to need the additional oil supply, unless maybe using a dry sump/vacuum system, as there is a lot of oil splashing around and many oil control rings also feed oil to that area of the piston. If you're using oil squirters to cool the underside of the piston, that's another source of oil splash in the gudgeon area.

I was somewhat surprised at the big end being left in a shot-peened state and not machined flat and parallel, as I would have thought it would potentially cause galling?

As I noticed Manley doesn't make final processing on i-beam rods ever. Reasons why they do not do this, I belever, are known only by themselves.

Ah, it may be because they're selling to engine builders that are expected to set their own side clearances for the specific crankshaft the builder is using?

In that case, it could be a good thing.

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