My buddy has a spare 13brew eccentric shaft and I was curious if putting that into my next 13bt build would be beneficial. I was reading about the thrust washer being bigger, but my concern is that I will be using counterweights off a s4 since I have s4 rotors. It's been a long time since I took apart an engine.

1) So the thrust washer has to do with the front counterweight and front stationary gear? I'm running s4 rotors , so I would not be able to do the bigger thrust washer modification unless I use s5 or s6 rotors, correct?

2)What advantages would I have by using a rew eccentric shaft? I read that it is harder and has bigger oil passages. lighter as well?

3)I was reading racing beats webpage and they talk about removing the factory oil jets and replacing them in carburetor jets. eccentric shaft balance should still be ok after, right? I'm thinking about doing this to my eccentric shaft

 

1. correct, the thrust washer is on the counterweight and stat gear, nothing to do with the e shaft at all. since the larger bearings are only larger in OD, you can machine the counterweight and stat gear to put them in, its been done, not really needed though.

2. the REW shaft has a bit more clearance for the rear half of the rear main bearing.

3. the carb jet mod is for running an engine at high load and high rpm for extended periods of time, like the 24 hours of daytona, its not needed (or wanted) in a street car.

 

It turns out the REW shaft has more bearing clearance on both ends for both stationary bearings, not just the rear. Something I discovered with a digital caliper.

And I agree don't swap in full-flow oil squirters in the shaft. I had some factory R5 shafts with those. Totally low oil pressure at low RPM on the street. I swapped all of them out for the checkball assemblies and oil pressure is where it's supposed to be now.

 

From building cylinder engines. I was wondering why you would want more clearance for the bearing

 

just as a critical thinking exercise. if Mazda added a little more bearing clearance at the ends of the main bearings (front of the front and rear of the rear) at the same time adding 50hp, and 1000rpm to the redline, why do you think they did it?

if it helps, the FD engine adopted the specs that the competition engines had been using since the late 70's. so the oil pressure, bearing clearances, the multi window bearing design, baffled oil pan, etc, were all adopted from the race engine to the street engine