Interesting Issue With 7 Bolt Mains

[Raptor]

We talked to the machine shop today concerning the only 7bolt motor we have sent them "4g64". They wanted me to know it would cost about twice as much to do the line-bore/hone due to the process they had to go with on the fully girdled cap. They also said the motor in question wasn't worth building if it wasn't done. On that cap, there are flat spots on the opposite side from the bearing journals used to fixture the entire cap for machining. When they clamped it down to the flat F65 table, they measured all the machined surfaces by the journals and found them to be all different heights, not by a little bit either. This is the way it came from the factory. Makes me wonder if that couldn't also be one of the contributors to the 7-bolts propensity to crankwalk.

It does use the same style cap as the 4g63 7-bolt for any that didn't know.

[Goat Blower]

The 2G motors used three different bearings if I remember right. There are marking stating such on the block or caps.

I didn't know they switched to a girdle on the 2.4 7-bolt version caps. The 6-bolts seem a little weak without the standard 6-bolt girdle main caps.

[Raptor]

Wasn't an issue with the difference in bearing size, the girdle was different from side to side all the way down. In effect it was twisted. They have all the specs to blueprint the motor to exactly how mitsu designed it, everything from the correct cylinder placement to any other critical dimension. This one was just that far off.

[Jacek]

In which direction did the mains enlarge? Just curious nature. Im trying to think why mitsu would make different sized mains.

[Raptor]

They are all the same diameter, there is a cutoff year where the bearings are narrower on the newer blocks but the diameter is the same across the same block.