london

I am in the process of building a 3rd gen race motor and would like to know what modifications i can do to the shaft if any at all.

cewrx7r1

iTrader: (2)

I have replaced my two spring loaded oil cooling jets with the constant feed racing jets. A friend keep his stock jets but removed the sping and ball from them so they are now constant feed. The racing ones have a slightly smaller hole.

Neither one of us have experienece any low oil pressure at idle.

For those who do not know what the stock ones do: after the oil pressure reaches a certain point, the valves open up and sprays oil on the inner faces of the rotors to cool them off. So you are going ***** to the wall and they are cooling the rotors. Then as soon as you go to idle the cooling oil floor stops and the rotors heat up. The constant flow ones continue to cool the rotors even if at a lower rate.

For all out racing, they increase the size of the oil passages in the shaft, but this is not needed for street racing.

If you work on the oil passages in the front side housing for the oil pump inlet and outlet, you can improve oil flow to the engine. You can also modify the outlet where it goes from the housing through the two seals into the front cover for better flow. Also the oil inlets to the stat gear bearings. Round off any flat protruding edges that cause turbulance to oil flow. I have a modifed stock component oil system that even in Houston summer heat with 10-30 Royal Purple, my pressure is 60PSI by about 2700rpm and over 4000rpm is about 110psi.

spyfish007

polishing the oil holes might keep the shaft from snapping too .... but I don't know anything about that .....

Rotortuner

ya right since when has any one snapped a shaft?

CJG

spyfish007

want to see the pics?

Rotortuner

What dod you run it without oil and sieze a bearing? I work with an old man who has built race engine from the mid 70's, thousands of engines, never a broken shaft. So lets see it. Mabe when it was made their was an air pocket in the metal or it was majorly weak.

CJG

Node

iTrader: (1)

im all bout breakage pics.
post em spyfish :-D

spyfish007

That's funny, I know someone how has seen several of them break before ... usually all at the same spot too.

13BAce

There was a guy on the RX-7 list, Sandy something, who cracked an eccentric shaft on a dealer motor.

Rotortuner

wow that is something. I wonder if it is more of a problem with the newer later engines. Most of our experience is with older 13B 4 ports. Any ways thanks for the pic.

CJG

95R2-89TII Ground Zero

Ouch....that one really hurts. I looked into doing some modifications to the eccentric shaft, and I couldn't find ****. I haven't been able to find any large mods to that specific area.

HWO

if you snap shafts you generally need a centre plate mod so you can put a bearing in the centre plate, this is used on high load high HP, high RPM engines.

Jeff20B

iTrader: (13)

Have somebody build you a new e shaft out of chromoly (sp?) like what the old Cosmo Sports had. There has got to be a stronger material these days than what the stock engines came with.

The Ace

Yep, Titanium , but it'll cost about......0,5mil bucks

cewrx7r1

iTrader: (2)

There are two easy things you can do to help prevent this:
(1) a lighter flywheel than stock puts less downward force on the
shaft end than a stock one. This reduces bending. 8lbs is a lot less than 20lbs.
(2) Balance all rotational parts of your engine when rebuilding.

95R2-89TII Ground Zero

And upgrade the oil holes in the housing to prevent any grooves from forming in the eccentric shaft, which would accelerate wear and result in breakage.