What diameter(s) are the enging mounting bolts on the DT1/2/3 models? 

I've checked the on-line parts fiches, but they don't show diameter, pitch, length, etc.

I have a set of  empty engine cases and the holes measure a little over 8mm, but that seems kind of small.

Asking because I have a Trackmaster frame configured for a DT1/2/3 engine and the lower rear engine mounts are missing.  I'm going to use the empty engine cases as a fixture to repair the frame, but need to order bolts to secure the cases to the remaining mounts.


 

Lower rear is 10mm. Top rear is too. But the rest are 8mm. I'll double check the top rear shortly on my DT1 just to be sure to be sure!!.
Yep top rear is 10mm.
I've oversised my 8mm to 9mm or maybe 3/8 cant remember now.
I do remember now there's a dowel between the crabkases on one--think it's front one & might've been trying for 10mm forgetting the dowel & ended up with drill stuck in it & spinning.
It's hell at my place lol so don't follow me. That's be why i went slightly smaller.

 
Thanks!  You are correct - - - the rear mounts use 10mm diameter bolts and the front mounts use 8mm diameter bolts.  At least on the empty set of RT1 engine cases I'm using to mock up the engine/frame fitment..

Strangely, the Trackmaster frame does not utilize the upper rear engine mount.  Which might explain why the lower rear engine mounts have a tendency to break.

I'll keep the front mounts at 8mm and have the lower rear mount fixed to accomodate a 10mm bolt.

 

What about the underneath one along the bottom. Will you be using that one. It's 8mm as well. Not talking bottom back if i'm confusing it all.
Later DT250A "74 i think only had two at the front & two at the rear but nothing along the bottom.

No, the middle bottom bolt isn't used on the Trackmaster frame.  It relies on only 3 mounting points: front upper, front lower, and rear lower.

Ok,--has me wondering if you're using a "74 motor which has two front mounts & no bottom one allong the lower rail?.
Or the frame is specificaly for a "74 on motor. Motor shape changed bigtime in "74 with DT250A & 360--& SC500 for that matter. May as well go for gold & fit the 500, that'd be more fun than i could handle haha.
DT1-2-3 only had a single front mount.