Flywheel Redrilling

[Dirk37]

Does anyone have experience with having a flywheel welded and redrilled? I'm looking into getting a Mitsubishi F5M51 trans in my 89 and I think using the mitsubishi flywheel would make the clutch setup the easiest. Shomethe$$$ had this trans in his sho swapped prelude and used a sho flywheel and pressure plate with a mitsubishi clutch disk, but that seems like kind of a ***********, especially with parts becoming less available for the sho.

 

[shomethe$$$]

Hello, not sure I'm getting which flywheel you want to use? The Mitsubishi will not fit easily, the bore is different and so is bolt pattern and possibly the offset. The starter will have to be changed. It's also a pull clutch vs. the Sho's push clutch. Stick with the sho flywheel, it's not that hard to find. I bought one off this forum. I suggest use what I had, get the car running and if you can't find Sho parts then you can convert it back to pull w/ all Mitsubishi parts.

As for re drilling shouldn't be too hard even with Mig, you would have to get it rebalanced unless your welds have no voids. Still not sure what can done about the bore, it will require a lathe.

Hope this helps.

 

[rubydist]

depending on the number and location of current holes, you may be able to get new ones drilled without having to weld the existing holes closed.

 

[LOUDSHO92]

I work as a manufacturing engineer as an aerospace company and one of the big issues is if you have complete welds with no voids especially in a system with a lot of vibrations. Your flywheel would face this. I would only do the welding if you could get it x-rayed and ensure that there are no voids. This would help with the balancing and to make sure that you do not develop any cracks or failures.

 

[Dirk37]

Hello, not sure I'm getting which flywheel you want to use?

Oops don't know how I missed that. I'm thinking of using the Mitsubishi flywheel. Then I could use all Mitsubishi parts which are more readily available and way cheaper. Boring it out shouldn't be a big issue as I have access to a lathe. I'm trying to find a donor 3g I can scavenge all the parts off of and start mocking stuff up, I was just thinking of how I want to do this.

As for making sure the welds are good, I've got a friend that can do tig which in my experience has very few to no voids. Maybe one of you guys can weigh in?

Once I get it welded up, I was thinking of using the sho flywheel I have as a template to redrill the holes in the new one.

 

[sperold]

This is just my opinion, but I would go with the "clusterfuch" arrangement. The SHO parts you need are far from obsolete, but that is not the main issue.
The ultra high rpm of these engines means things are subjected to forces that exceed the norm, and welding the center of the flywheel would make me nervous.
There is a metallurgical issue and a "how well it is done physically" issue.
I have noticed you have done a lot of unusual things very successfully in the past, so you may have a lot of proof / advice on this being not very daring.
It is worth remembering that the flywheel is directly in front of you when you are in the drivers seat.

In the old days, when everyone had a stock car and a local circle track to perform on, we had a 6 cylinder 232 inch engine that was revved far beyond its design. Not being satisfied, we moved to a 300 inch engine which did not reach the revs of the small one, but came close. Only problem was, after every race we had to drop the tranny and housing and retighten the flywheel bolts. Every time, no matter what locktite or additives or swapped parts were employed.
May have nothing to do with your quest, but it illustrates what can happen that is a least partially unexplainable.

Just my opinion.

 

[LOUDSHO92]

Oops don't know how I missed that. I'm thinking of using the Mitsubishi flywheel. Then I could use all Mitsubishi parts which are more readily available and way cheaper. Boring it out shouldn't be a big issue as I have access to a lathe. I'm trying to find a donor 3g I can scavenge all the parts off of and start mocking stuff up, I was just thinking of how I want to do this.

As for making sure the welds are good, I've got a friend that can do tig which in my experience has very few to no voids. Maybe one of you guys can weigh in?

Once I get it welded up, I was thinking of using the sho flywheel I have as a template to redrill the holes in the new one.

We also Tig every day at my job and we still get voids. The thicker the material the more chance you have with issues like pores. In fact on a repair we are doing on titanium honeycomb we had about 20+ findings in x-ray. Welding thin stuff.

You would need to make sure and match the alloy for the flywheel. Then the other question is if the flywheel has any heat treatment and if so the welds will be weaker then surrounding material. Stress relief or heat treatment would then help to ensure full strength.

It sucks when you have to deal with this stuff.