Aluminum Flywheel Install
Apr 5, 2015 | 12:15 PM
#1
Aluminum Flywheel Install
Or, why I haven't got the tranny back in the car yet.
Bought a second hand Aasco aluminum flywheel off of kijiji last year. Now it will find a new home as my tranny is out for LSD install. Left is aluminum flywheel, new OEM disc and pressure plate. Right is stocker: excellent stuff, almost zero wear after 50,000 km and lots of track work. Can't believe it.
It's in good shape except for the flywheel bolt holes. It appears the original owner either torqued the bolts so much he dug rings about 0.015" deep around the holes, or the manufacturer used a fancy cutting tool to exactly counterbore for the stock bolts. I'm thinking the former. So instead of paying $100 locally for a 7/8" end mill to nicely spot face a correct diameter for the new bolts, I ordered a $20 one from Amazon. Of course, it hasn't arrived yet - they're saying 4 weeks for delivery(!). That's what I'm waiting for.
In the meantime, I've addressed the flywheel bolts. The original owner sent along the bolts he used. Of course, they are the stockers. Our iron flywheel is 0.152" thick there, and the aluminum one is 0.360" thick. He stripped a few of the originals, since they were too short - potential disaster ya' think?
The threaded holes in the end of the crank accept 0.400" of threaded-in bolt. This is not even one M12 bolt-diameter. This is critical to know. Typically for this application, 0.8 to 1 diameter is the minimum safe depth of bolt engagement. So, had to figure the optimum length.
Turns out, after spot-facing, the best length is 0.750". This will provide maximum thread engagement with a bit of space (about 0.080") at the end of the bolt to allow it to stretch during torquing and not bottom out.
Here is the ridiculous selection of bolts I've bought as I fussed about. Left to right:
OEM stocker 0.600" length; ARP's best 0.700"; Cut down from another Mitsubishi model 0.750"; long ones from doncarbone's collection. FYI, Ziggy at RTM Racing is the man when you need Mitsu advice and parts.
I cut the "other" Mitsu ones to 0.750" long (the white mark) using a carbide tool in a lathe. Trying to cut to length with a thin diamond saw, or a regular cut-off blade, or grinding - terrible inaccurate results. Lathe turning was fast, very accurate, and the metal stayed cool. Just gotta use a fine belt or sanding disc to gently chamfer the first thread and good to go.
More later after I get the milling cutter in my mitts...
Bought a second hand Aasco aluminum flywheel off of kijiji last year. Now it will find a new home as my tranny is out for LSD install. Left is aluminum flywheel, new OEM disc and pressure plate. Right is stocker: excellent stuff, almost zero wear after 50,000 km and lots of track work. Can't believe it.
It's in good shape except for the flywheel bolt holes. It appears the original owner either torqued the bolts so much he dug rings about 0.015" deep around the holes, or the manufacturer used a fancy cutting tool to exactly counterbore for the stock bolts. I'm thinking the former. So instead of paying $100 locally for a 7/8" end mill to nicely spot face a correct diameter for the new bolts, I ordered a $20 one from Amazon. Of course, it hasn't arrived yet - they're saying 4 weeks for delivery(!). That's what I'm waiting for.
In the meantime, I've addressed the flywheel bolts. The original owner sent along the bolts he used. Of course, they are the stockers. Our iron flywheel is 0.152" thick there, and the aluminum one is 0.360" thick. He stripped a few of the originals, since they were too short - potential disaster ya' think?
The threaded holes in the end of the crank accept 0.400" of threaded-in bolt. This is not even one M12 bolt-diameter. This is critical to know. Typically for this application, 0.8 to 1 diameter is the minimum safe depth of bolt engagement. So, had to figure the optimum length.
Turns out, after spot-facing, the best length is 0.750". This will provide maximum thread engagement with a bit of space (about 0.080") at the end of the bolt to allow it to stretch during torquing and not bottom out.
Here is the ridiculous selection of bolts I've bought as I fussed about. Left to right:
OEM stocker 0.600" length; ARP's best 0.700"; Cut down from another Mitsubishi model 0.750"; long ones from doncarbone's collection. FYI, Ziggy at RTM Racing is the man when you need Mitsu advice and parts.
I cut the "other" Mitsu ones to 0.750" long (the white mark) using a carbide tool in a lathe. Trying to cut to length with a thin diamond saw, or a regular cut-off blade, or grinding - terrible inaccurate results. Lathe turning was fast, very accurate, and the metal stayed cool. Just gotta use a fine belt or sanding disc to gently chamfer the first thread and good to go.
More later after I get the milling cutter in my mitts...
Last edited by RalliartN; Apr 5, 2015 at 12:28 PM.
Apr 5, 2015 | 12:52 PM
#2
Matching Socket
One more thing. Notice how the flywheel bolt heads are quite thin. On top of this, most sockets have a chamfer at their entrance so it finds and slips more easily over a nut (I guess). But this means less socket engagement on the bolt head, as the chamfered area grips nothing. Bad news when you have to apply so much torque, 98 lb-ft or so - rather easy to slip and eff up the bolt and your hands.
So, while on the lathe I simply cut off the chamfer. Bam. Lots more head engagement.
I'm going to do all the smaller sockets I have, say 12mm and under, since those chamfers are stupidly large for the small fasteners. It literally takes under a minute per socket going slowly (so it doesn't heat up) with a carbide tool.
I'll tell you if they break or not. Never heard of that happening, though.
Maybe your sockets don't need this. Some of my real cheapos have almost no chamfer. Weird.
So, while on the lathe I simply cut off the chamfer. Bam. Lots more head engagement.
I'm going to do all the smaller sockets I have, say 12mm and under, since those chamfers are stupidly large for the small fasteners. It literally takes under a minute per socket going slowly (so it doesn't heat up) with a carbide tool.
I'll tell you if they break or not. Never heard of that happening, though.
Maybe your sockets don't need this. Some of my real cheapos have almost no chamfer. Weird.
Last edited by RalliartN; Apr 5, 2015 at 12:57 PM.
Apr 5, 2015 | 03:58 PM
#3
Fine sanding seems to give the best result for chamfering bolts. Just angled 1 thread or so at about 45 degrees. I had a nut threaded on in case the bolt threads needed to be run over. Not needed, actually, as the threads were good to go. Now the bolt winds into the crank end almost an extra turn.
May 2, 2015 | 07:44 AM
#6
Spot-faced the bolt holes diameter 7/8". Bolt heads fit correctly. Flywheel and clutch installed now. I'm so lucky to have access to this machinery.
Based on technical info from the Aasco and ARP websites, I came up with the following flywheel installation procedure:
1. Install flywheel, install all bolts dry, torquing to about 20 lb-ft. Do not use washers.
2. Take out one bolt, use blue Loctite 242 on bolt threads. Put moly grease under the head as torque lube.
3. Reinstall bolt and torque to 95-100 lb-ft.
4. Repeat for the other six bolts, taking out the bolt across from the one you just did.
Based on technical info from the Aasco and ARP websites, I came up with the following flywheel installation procedure:
1. Install flywheel, install all bolts dry, torquing to about 20 lb-ft. Do not use washers.
2. Take out one bolt, use blue Loctite 242 on bolt threads. Put moly grease under the head as torque lube.
3. Reinstall bolt and torque to 95-100 lb-ft.
4. Repeat for the other six bolts, taking out the bolt across from the one you just did.
Last edited by RalliartN; May 2, 2015 at 08:10 AM.
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May 10, 2015 | 07:12 PM
#8
Epilogue
Everything buttoned up and car out for first spin: drivetrain behaves properly. Aluminum flywheel offers noticably faster spin-up, yet clutch take-up and ease of engagement seems same as with oem flywheel. Don't have to re-learn my clutch - unexpected and very welcome. Recommendation: get one if you can.
Will need track days to assess LSD and make long-term evaluations.
Evom forums are a godsend when taking on this kind of project.
And thank you Garrett.
Will need track days to assess LSD and make long-term evaluations.
Evom forums are a godsend when taking on this kind of project.
And thank you Garrett.
Last edited by RalliartN; May 10, 2015 at 07:18 PM.
Jul 6, 2015 | 12:55 PM
#10
Hi RalliartN,
length aside is the fastener in the link below suitable for use on a flywheel in your opinion please ?
http://www.rockauto.com/catalog/more...&jnid=2&jpid=0
length aside is the fastener in the link below suitable for use on a flywheel in your opinion please ?
http://www.rockauto.com/catalog/more...&jnid=2&jpid=0
Jul 7, 2015 | 07:49 PM
#11
No, not suitable. Here is why.
Metric grade (or class) 8.8 size M12x1.25 zinc-plated bolt recommended installation torque value is 72 lb-ft (96 N-m) - this is the one in your picture.
(reference http://www.imperialsupplies.com/pdf/...rqueCharts.pdf)
Metric grade 10.9 M12x1.25 recommended installation torque is 104 lb-ft (138 N-m).
(reference http://www.rpmmech.com/pdf/tightening_torque.pdf)
Installation torque values are supposed to give you a clamp load that is 75% of the proof load. Proof is about 90% of the yield strength of the fastener's material. The clamp load needed is based on an analysis of the environment the fastener will see in worst case service.
Typically, operating load (the force pulling/bending/shearing the bolt) is calculated and combined with considerations for fatigue life, shock, thermal stress, and a factor of safety that accounts for other rare but possible things that might affect the fastener or it's operating conditions, then required clamping load and bolt size/class/material is determined so proof load is never exceeded in operation.
Our stock flywheel bolts are grade 10.9. ARP sells even stronger ones.
Grade 8.8 like in the picture are not recommended to be installed with the roughly 98 lb-ft of torque the shop manual says to apply. That torque would take the grade 8.8 bolts too close to their yield point to get the necessary bolt clamping load.
Grade 10.9 bolts are stronger, which means they can be torqued - stretched - to apply a clamping load that does not come too close to the fastener material's yield strength.
I'd say don't be tempted by the inexpensiveness and easy availability of the 8.8's.
Use class 10.9.
I went through so much study and wasted so much time when I was looking at this earlier, like you are now. To save sanity: call Ziggy at RTM Racing for solid advice and he sells them too. That said, doncarbone found some perfectly adequate ones at a fastener store.
Metric grade (or class) 8.8 size M12x1.25 zinc-plated bolt recommended installation torque value is 72 lb-ft (96 N-m) - this is the one in your picture.
(reference http://www.imperialsupplies.com/pdf/...rqueCharts.pdf)
Metric grade 10.9 M12x1.25 recommended installation torque is 104 lb-ft (138 N-m).
(reference http://www.rpmmech.com/pdf/tightening_torque.pdf)
Installation torque values are supposed to give you a clamp load that is 75% of the proof load. Proof is about 90% of the yield strength of the fastener's material. The clamp load needed is based on an analysis of the environment the fastener will see in worst case service.
Typically, operating load (the force pulling/bending/shearing the bolt) is calculated and combined with considerations for fatigue life, shock, thermal stress, and a factor of safety that accounts for other rare but possible things that might affect the fastener or it's operating conditions, then required clamping load and bolt size/class/material is determined so proof load is never exceeded in operation.
Our stock flywheel bolts are grade 10.9. ARP sells even stronger ones.
Grade 8.8 like in the picture are not recommended to be installed with the roughly 98 lb-ft of torque the shop manual says to apply. That torque would take the grade 8.8 bolts too close to their yield point to get the necessary bolt clamping load.
Grade 10.9 bolts are stronger, which means they can be torqued - stretched - to apply a clamping load that does not come too close to the fastener material's yield strength.
I'd say don't be tempted by the inexpensiveness and easy availability of the 8.8's.
Use class 10.9.
I went through so much study and wasted so much time when I was looking at this earlier, like you are now. To save sanity: call Ziggy at RTM Racing for solid advice and he sells them too. That said, doncarbone found some perfectly adequate ones at a fastener store.
Last edited by RalliartN; Jul 7, 2015 at 07:59 PM.
Jul 8, 2015 | 07:14 AM
#13
No, not suitable. Here is why.
Metric grade (or class) 8.8 size M12x1.25 zinc-plated bolt recommended installation torque value is 72 lb-ft (96 N-m) - this is the one in your picture.
(reference http://www.imperialsupplies.com/pdf/...rqueCharts.pdf)
Metric grade 10.9 M12x1.25 recommended installation torque is 104 lb-ft (138 N-m).
(reference http://www.rpmmech.com/pdf/tightening_torque.pdf)
Installation torque values are supposed to give you a clamp load that is 75% of the proof load. Proof is about 90% of the yield strength of the fastener's material. The clamp load needed is based on an analysis of the environment the fastener will see in worst case service.
Typically, operating load (the force pulling/bending/shearing the bolt) is calculated and combined with considerations for fatigue life, shock, thermal stress, and a factor of safety that accounts for other rare but possible things that might affect the fastener or it's operating conditions, then required clamping load and bolt size/class/material is determined so proof load is never exceeded in operation.
Our stock flywheel bolts are grade 10.9. ARP sells even stronger ones.
Grade 8.8 like in the picture are not recommended to be installed with the roughly 98 lb-ft of torque the shop manual says to apply. That torque would take the grade 8.8 bolts too close to their yield point to get the necessary bolt clamping load.
Grade 10.9 bolts are stronger, which means they can be torqued - stretched - to apply a clamping load that does not come too close to the fastener material's yield strength.
I'd say don't be tempted by the inexpensiveness and easy availability of the 8.8's.
Use class 10.9.
I went through so much study and wasted so much time when I was looking at this earlier, like you are now. To save sanity: call Ziggy at RTM Racing for solid advice and he sells them too. That said, doncarbone found some perfectly adequate ones at a fastener store.
Metric grade (or class) 8.8 size M12x1.25 zinc-plated bolt recommended installation torque value is 72 lb-ft (96 N-m) - this is the one in your picture.
(reference http://www.imperialsupplies.com/pdf/...rqueCharts.pdf)
Metric grade 10.9 M12x1.25 recommended installation torque is 104 lb-ft (138 N-m).
(reference http://www.rpmmech.com/pdf/tightening_torque.pdf)
Installation torque values are supposed to give you a clamp load that is 75% of the proof load. Proof is about 90% of the yield strength of the fastener's material. The clamp load needed is based on an analysis of the environment the fastener will see in worst case service.
Typically, operating load (the force pulling/bending/shearing the bolt) is calculated and combined with considerations for fatigue life, shock, thermal stress, and a factor of safety that accounts for other rare but possible things that might affect the fastener or it's operating conditions, then required clamping load and bolt size/class/material is determined so proof load is never exceeded in operation.
Our stock flywheel bolts are grade 10.9. ARP sells even stronger ones.
Grade 8.8 like in the picture are not recommended to be installed with the roughly 98 lb-ft of torque the shop manual says to apply. That torque would take the grade 8.8 bolts too close to their yield point to get the necessary bolt clamping load.
Grade 10.9 bolts are stronger, which means they can be torqued - stretched - to apply a clamping load that does not come too close to the fastener material's yield strength.
I'd say don't be tempted by the inexpensiveness and easy availability of the 8.8's.
Use class 10.9.
I went through so much study and wasted so much time when I was looking at this earlier, like you are now. To save sanity: call Ziggy at RTM Racing for solid advice and he sells them too. That said, doncarbone found some perfectly adequate ones at a fastener store.
The bolts Doncarbone got are in my garage now, I bought his lightweight flywheel and clutch. I have no idea where he found them though. LOL