Car Porn

[6PAK72]

The TR6 lost a flywheel bolt in, fortunately, street driving. A known problem, due to torsional flex of the crankshaft - long story that I can share if anyone wants to hear a really interesting materials-physics story.

The repair includes the Fidanza aluminum flywheel and ARP bolts. The guys at ARP were fantastic to work with, they knew the car, the problem and the solution. The Fidanza was $250 off eBay, down from $350 ask.

We'll see you hopefully at the Bud Show of Dreams.

[DanB]

Dude, there's only four bolts holding yer flywheel on, no wonder it wants to come aloose! Next you'll be telling me that vintage brit inline-6 has fewer than 7 main bearings...

I keed! I keed because I love!

[DanB]

For what it's worth, I've lost flywheel bolts *twice* with the Datsun
And it has six of 'em...

Long cranks like to do the torsional spring dance...

[drgrumpus]

Loctite, my son, loctite.

[DanB]

They were loctited! I was considering going to JBWeld, but instead modded the aluminum flywheel with flanged steel bushings for the bolts. Mucho better-o!

[MiataSteve]

Is there some sort of mechanical locking mechanism like a bendable tab? how about safety wire?

[breakaway500]

Loctite has a shelf life,so be carefull. I use the paste versions nowadays as I can apply it cleaner.
Fresh red Loctite applied properly will hold most anything threaded,and require torch heat to release on a bolt as big as a flywheel uses.
Has worked wonders for me for years on many,many jobs.

[MiataSteve]

Loctite should work. The key, as you probably know, is clean threads. We always used activators prior to locker application when I worked at GE (in a galaxy far, far way). Try mechanically cleaning both thread surfaces first followed by brake clean or try this.

http://www.permatex.com/products/Automo ... robics.htm.


This should do the trick. http://www.permatex.com/products/Automo ... er_RED.htm

Data Sheet: http://www.permatex.com/documents/tds/A ... /24026.pdf

If its good enough for Mil jet engines... As Breakaway says there is a shelf life. We used expiration dates on all chemicals

[DanB]

I would still highly recommend steel bushings for the aluminum holes. AND Loctited, properly cleaned/prepped/primered threads.

[MiataSteve]

I would still highly recommend steel bushings for the aluminum holes. AND Loctited, properly cleaned/prepped/primered threads.

Dan, are you recommend steel bushing in the alum flywheel? Loss of clamping force due to differences in expansion rates of alum and steel?

[breakaway500]

This is the stuff I use,which is red Loctite in stick form.Much easier to apply than the juice version. Available in two sizes...also in blue for a less severe hold.



http://www.thetoolwarehouse.net/p-3341- ... 37700.aspx


Avoid the whole flywheel problem and drop an LS4 in that TR-6!

You could then duel it out with Wild Bill in his SBF powered Austin-Healey in PA class!

[6PAK72]

Hah! An LS-6 would fit nicely!

Actually, the problem is not with the bolts working out - Loctite makes no difference. Complex explanation follows:

The TR6 crank, with 7 bearings DAN, has a tortional (roatational) vibration that starts up around 4500rpm, and gets really bad at 6000rpm. The "flex" whip-saws the flywheel, and at it's outer edge it oscillates nearly .5 inch!!! at 5000rpm. Kas Kastner discovered this in1969 at Daytona...very dramatic story.

What happens is that the OEM 7/16" x 1" bolts (yes, only 4...) actually stretch, and the heads shear off as the flywheel angles against the heads in the ensuing increased space.

So the Group-44 and Jack Drew's (RIP) approved solution is to lighten the rotating mass as much as possible - aluminum flywheel, LUK aluminum-frame Porsche clutch, and CV throw-out bearing from Gunst. Then you have to use a Grade 8 bolt with a much higher hardness, to eliminate the stretch. With less stretch, you raise the torque from the factory 50-75ft/lbs to 100-110ft/lbs.

Dan, I was going to use the sleeve, but the tech line at ARP said most definitely do NOT do that. They suggest a 7/16"d x .073 washer under the bolt head (3/4"), and they suggest not Loctite, but ARP Assembly Lock. Probably the same thing, but hey, they seemed to know what they were talking about.

The really fun part is that the transmission has to be removed from the TOP, not from underneath. So, the entire interior comes out.

Yup, that Miata is looking better all the time....

[6PAK72]

I would still highly recommend steel bushings for the aluminum holes. AND Loctited, properly cleaned/prepped/primered threads.

Dan, are you recommend steel bushing in the alum flywheel? Loss of clamping force due to differences in expansion rates of alum and steel?

ARP shared that if I were to want to use the sleeves, they would sell me an ALUMINUM sleeve of 8086 aircraft-hardness stock, but that I would have to ream the bolt holes in the flywheel. If the reaming was not perfectly straight, the 4-point fixing would be out of tension, even is the run-out dial did not pick it up, and I would risk serious failure.

[drgrumpus]

As for thread lockers in jet engines, I think that became a no-no 20 years ago. Same for tab washers and lockwire. On the SR71 we had to go from lock wire to mid-grip helicoils most everywhere.

On cars, tab washers are useless. Safety wire can help, but must be done correctly-not easy.

Grumpus

Tab washers were to blame for the TOYLET running rough at NHMS last month. An important screw fell out of the bottom of one of those beautiful 45DCOE's.

[MiataSteve]

As for thread lockers in jet engines, I think that became a no-no 20 years ago. Same for tab washers and lockwire. On the SR71 we had to go from lock wire to mid-grip helicoils most everywhere.45DCOE's.

Yeah, now that you mention it...locking thread inserts was the preferred method. Probably not a viable solution for the crankshaft holes. Thread lockers where still used 15 years ago on some of the instruments.

SR71.....I did some work on the fuel probes.