Aaron's Dax De Dion build thread

[aaronjb]

Is it possible to go up a size in UNF or even Metric?

If the flywheel were drilled out there's probably enough meat on the crank, just about..

It happens. Exactly what happened to me with the 302 build for the GT40 only with a head bolt. Just a thought, did you have the flywheel lined up properly?
Anyway I don’t think there is need for tears! Worst case you can drill out and tap to a 1/2 inch bolt on that hole, drill the flywheel and away you go. It will be fine.

I'm as sure as I can be that the flywheel was lined up - the other five bolts had all gone in with no more than a finger on the ratchet, and most of them were done up by that point.. there's almost zero clearance on the plain shank of the bolts to the flywheel holes so it more or less had to be lined up by that point.

I'm now torn between "I want to go back in there and get at least the other five in so I can try dialling in the bell housing" and "I really don't want to touch it again and make things even worse".. the confidence has taken something of a knock today! Good job there was nobody in earshot to hear the language coming out of the garage..

[jon1d]

These things are to test our patients I am sure. Sounds like your bolts were made of cheese and not high grade steel. They take some to snap off and make the thread mess. I would look at replacing all the threads as they might be APR bolts? I would get some high tensile bolts and replace them all as you don't want the others to sheer off when you come to torque them up.

Do the bolts have the correct markings for high tensile steel bolts? No markings would make me suspicious. I have seen the same thing with bolts for prop shafts and U/J where you need a high sheer strength bolt.

[aaronjb]

The bolts were ARP bolts that came with the gearbox package - they were in original packaging from a repuso no reason to think they were counterfeit or anything like that.. very odd

[jon1d]

Sorry fat fingers should of read ARP bolts. I see the bolt is no fully threaded, is there are shank interference. Just a thought.

[aaronjb]

Yeah they are shouldered - there's (by measurement) about 0.3mm clearance between the shoulder and the hole (so 0.15mm radial or, given these are really inches, about five thou radial clearance) but on looking closely there is some galling inside the flywheel holes.. not enough lube, maybe? Maybe the flywheel was a gnats co.. whisker off line. Just weird that the other five went in A-OK and that one died in the hole.

I've got a set of 11.4 & 11.5mm drills on order (granted I already had 11.5 chineseum drills) as well as an 11.5mm hand reamer, I'll make up some drill guides on the lathe and then clear the holes of galling as well as add a bigger chamfer on the bolt head side (it looks to me like the ARP bolts have a larger fillet than the flywheel has a chamfer) and then have another go - if the threads pull out on torquing up then .. I'll drink some rum and go a size up or helicoil it.

[aaronjb]

I haven't really done anything since Sunday, but I did take delivery of (so far!):

11.5mm hand reamer
7/16-20 helicoil set, which included a new 11.5mm drill (which seems dimensionally accurate)
New tube of ARP Super Lube for bolt installation
7/16-20 die

I thought to myself .. I wonder if that 11.5mm drill shank will fit in the holes in the flywheel and lo, it did! In one of them, anyway.. the others have enough galling inside that it doesn't easily slip in. Still, that seems to prove that the holes are ~11.5mm (to within a thou or three anyway) which is good.

Going to make up a quick drill guide for the 11.5mm drill/reamer on the lathe so I can get the holes dead square..

[Daryn Smith]

Not quite the same but I tripped all the threads in my block when I was mounting the gearbox to it. I just drilled them out to the necessary size for the helicoil kit.

[aaronjb]

I can still imagine there was a lot of blue air in your garage that day! At least I'm not alone in ham fisting something.. I'm always very meticulous about cross threading things (I've spent too long fixing things other people have cross threaded!) but didn't think about the bolts getting (essentially) welded to the flywheel by their shanks.. every day is a school day, as they say!

Once all this is done I still need to dial in the bellhousing - according to the internets, doing a T56 Magnum you're meant to take the front end of the gearbox (the bearing housing) off and use the bearing races as your register face .. but I don't know if I'm up for splitting the gearbox, so I may see how I get on using the bellhousing circle (the same way you'd do a T5).

[aaronjb]

Work has been .. enough to drive a man to drink, so I haven't had much time in the garage. I did spend an hour down there yesterday making up a drill/reamer guide so I can make sure any holes I make in the crank and/or flywheel are dead straight. I could put the flywheel on my mill ... if only the mill were in service right now, but I'd need a guide for the crank anyway.

Took far longer than it should have because the only lump of something I had which was large enough was some 2" round bar, bigger than my 3-jaw chuck can hold and it takes me forever to indicate in the 4-jaw as I don't do it very often

I can't remember if I mentioned that my (Smiths electronic) oil pressure gauge is faulty in this thread or elsewhere, but .. I've tried Caerbont, who don't do repairs anymore, Speedograph Richfield who say my part number is a mechanical gauge, and Digital Speedos who I bought it off, who just never responded. I'm resigned to spending another £75 to buy a new one at this point, but that doesn't bode well for the longevity or serviceability of Caerbont/Smiths stuff.

[KevinW]

£75 is a teeny weeny fraction of what your already invested in...like that engine. So, just cough up and move on. It took me a very long time to learn that lesson and stop wasting my time pissing about worrying about a tenner or twenty here and there, life's too short.

I know what you mean about work - home working produces a lot of pressure to deliver. I am grateful for having a job, but rather envious of my step daughter mooning around with nothing to do, and being paid for it.