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Flywheel Bolt size for Aluminum Flywheel**Contains a Reply to Hap**

Posted by danc 
danc Avatar
Dan Cramp
Menifee, Ca., USA   usa
1971 MG MGB

Bought some chevy V-8 flywheel bolts. They are 1 inch long. Looking at my Fidenza Flyweel it is about 5/8 thick at the mounting point. That's much thicker than the stock flywheel. David Anton at APT also recommended using flat washers. With the extra thickness of the flywheel and the washer, I would be getting under a 1/2 inch of grab. Has anyone run into this situation. I thought I read here that shallow headed bolts were not even necessary. Anyone??



1971 MGB
1967 MGB GT



Edited 1 time(s). Last edit at 10/11/2012 10:13PM by danc.
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Michel Tousignant
St-Lambert, Canada   can
1967 MG Midget MkII "BitsnPieces"
1970 MG Midget MkIII
1971 MG Midget MkIII

Rule of thumb:

In Steel: minimum thread depth = 1 x thread diameter
In Aluminum: minimum thread depth = 1.5 x thread diameter
danc Avatar
Dan Cramp
Menifee, Ca., USA   usa
1971 MG MGB

Saw this post from Dave Headley. If you read this Dave would you elaborate. Did the bolts you used have a shoulder?
"I have used good quality 7/16"-20 grade 8 bolts and grade 8 washers for this, torqued to 65#ft and blue Loctite for years. No problems. No clutch interference issues. None,zip,nada!devil smiley Regular 5/8" socket. Obviously clean the sh*t out of the bolt holes to assure good clamping. The catastrophic failure pictured above clearly shows that the car ran for awhile with loose bolts before shearing them.
This is a very robust joint if the bolts are tight."



1971 MGB
1967 MGB GT
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Speedracer Avatar
Hap Waldrop
Greenville, SC, USA   usa
1967 MG MGB "The Biscuit"

I can help here, sometimes experience is a wonderful thing smiling smiley I use ARP #200-2802 bolts, red loctite on threads, normal MGB manual torque specs (ignore the higher torque values given with the ARP instruction, remember these instructions are for a Chevy V8, use MGB manual torque specs). I double check the aluminum flywheel to make sure the chamfer at the bolt holes are adequate enough for the ARP bolts, by sitting a ARP bolt on the face of aluminum flywheel, the ARP bolts have a very generous radius under the bolt head, which makes them stronger, if I need a bit more chamfer, because I see the bolt is sitting proud of the base of the flywheel, I use a well oversize drill bit, or countersink bit to increase the chamfer if needed, often times it is not needed, but should be checked. The ARP bolts are like a 1/4" shorter than the stock flywheel bolts, but you are getting plenty of thread engagement. I've did it this way now with racing MGBs for almost 30 years running them at rpms above 7000 rpms, never had a failure, and I'm not alone, this has been used many, many times by MGB street performance owners, and MGB racers. Every MGB engine I rebuild here gets the ARP #200-2802 flywheel bolts.

Oh and absolutely do NOT use flat washers, ARP specifically tells you this in their instructions.



Hap Waldrop
Acme Speed Shop
864-370-3000
Performance/Race engines-heads, and DIY engine rebuilt kits
New alloy wheels options for MGBs, see vendors forum for details.



Edited 2 time(s). Last edit at 10/11/2012 06:33PM by Speedracer.

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Grant Hill
Cypress, CA, USA   usa
1972 MG MGB "Vroom"

The timing of this topic is perfect, I have my Fidenza FW coming in the mail.
When using the ARP #200-2802 bolts, do you still use the round lockplate, Moss (460-715)?? Or not required per ARP.

Thanks
Speedracer Avatar
Hap Waldrop
Greenville, SC, USA   usa
1967 MG MGB "The Biscuit"

In reply to # 2192439 by greysailor The timing of this topic is perfect, I have my Fidenza FW coming in the mail.
When using the ARP #200-2802 bolts, do you still use the round lockplate, Moss (460-715)?? Or not required per ARP.

Thanks

No, nothing under the bolt heads. Also a good tip is use somelike an thin walled 3/8 socket with a 3/8" to 1/2" on your 1/2 torque wrench because normally rh 3/8 washer should be more thiined walled, and it needs to be a 12 point socket, the edge of the socket will just kiff the flywheel maing a little crestmn, not to worry, perfectly normal with over sized 12 point heads.



Hap Waldrop
Acme Speed Shop
864-370-3000
Performance/Race engines-heads, and DIY engine rebuilt kits
New alloy wheels options for MGBs, see vendors forum for details.

Member Services:
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danc Avatar
Dan Cramp
Menifee, Ca., USA   usa
1971 MG MGB

Hap, It looks like you are saying 3/8 inch of the tread grabbing is OK (the mounting thickness is 5/8). Does this only apply to the 1" APT bolt or does it also apply to the 1" Chevy/Ford V-8 bolt. Thanks



1971 MGB
1967 MGB GT
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Basil Adams Avatar
About 12 miles from Sears Point, CA, USA   usa

Dan, How thick is the flangeon your crank? It's about 3/8" so why would it matter if you have longer threads? The engaged grip length will only be the thickness of the flange smiling smiley Basil



Basil C. Adams
1956 MGA Coupe (Show Car)
1957 MGA Roadster (Driver)
1958 MGA Coupe (Racecar)
1959 MGA Coupe (unrestored)
1960 MGA Coupe (unrestored)
1960 MGA Roadster (Driver)
MKIII Elva Courier (E1056)
1967 427 Cobra
1972 Alfa Romeo Montreal
A coupla late MGBs
1960 Austin Healy BN7
More Cars than Brains
danc Avatar
Dan Cramp
Menifee, Ca., USA   usa
1971 MG MGB

Basil, The depth of the crank flange is 3/4 of an inch. which is almost the same size of the treads on a stock B flywheel bolt . The stock bolt uses all the treads on the bolt. If you screw it in without the flywheel it goes in till the shoulder stops it. When I put it threw the flywheel 3/4" protrudes. The shoulder is the same size as the thickness of the flywheel, a little under a 1/2 ". 3/4 of the bolt threads in and the rest is used for the shoulder. That way I thought a 1 inch bolt would be too short for my 5/8" flywheel. 3/8 vs. 3/4 of thread. Have I confused you enough.



1971 MGB
1967 MGB GT
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Speedracer Avatar
Hap Waldrop
Greenville, SC, USA   usa
1967 MG MGB "The Biscuit"

In reply to # 2192596 by danc Hap, It looks like you are saying 3/8 inch of the tread grabbing is OK (the mounting thickness is 5/8). Does this only apply to the 1" APT bolt or does it also apply to the 1" Chevy/Ford V-8 bolt. Thanks


Dan, I the above ARP part number with aluminum flywheel, both Tilton, and Fidanza aluminum flywheels over the years as have many others with zero issues.



Hap Waldrop
Acme Speed Shop
864-370-3000
Performance/Race engines-heads, and DIY engine rebuilt kits
New alloy wheels options for MGBs, see vendors forum for details.

Member Services:
MG/ Triumph Performance Street/Race Engines - Cylinder Head Porting - Modified SU HS Carbs - DIY Engine Rebuild Kits With Tech Advice - Alloy wheels for MGB/TR6
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Dave Headley
Cortez, 4 corners, Colorado, USA   usa

7/16-20 Gr8 bolts, Gr8 flat washer, length A/R to give 1/2"+ thread engagement will work just fine. I use an impact wrench but the factory torque spec is good too.smileys with beer

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danc Avatar
Dan Cramp
Menifee, Ca., USA   usa
1971 MG MGB

Thanks for all the info everyone.



1971 MGB
1967 MGB GT
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