Difference between V8 manual and auto flywheel bolts 3.5/4.5

[Tony H]

I don't want to rob the flywheel bolts from my man trans 3.5 for my project so wondering what is the difference between man trans and auto trans flywheel bolts. The man trans bolts are impossible to source. The auto bolts look identical from pictures. The mounting surface on my new custom flywheel is thinner than the original 3.5 flywheel.

[Frank Reiner]

What is the thickness of the flywheel flange?
Add 11.5mm to that dimension to arrive at the required underhead length.

[Tony H]

How long are the auto trans bolts?? 3.5 flywheel is 11.2mm thick and new flywheel 9.6mm. 4.5 Auto flywheel bolts are plentiful, but I don't want to buy them just to see if they will work.

[Frank Reiner]

The autotrans bolts are 23mm long underhead.
The required length for your flywheel is 21.1mm.

[Tony H]

So the auto trans bolts would provide sufficient thread engagement? They are practically free vs unobtainable for man trans bolts.

[Frank Reiner]

Tony,

The original PN was 116 032 02 71. Superseded by 116 032 06 71.
The original bolt was necked and was tightened by the angle-of-rotation method.
The present bolt is full threaded and is tightened to 85-90 ft/lbs (lubricated).

In your parts gathering expeditions did you acquire any bolts from the 560 crankshafts?
They are the correct ones!

[subforry]

I used these "ARP (208-2801)" to attach a flywheel (manual trans) to a m130. Worked fine. The ARP catalog is a little hard to work but they likely have something that will come close.

[Tony H]

No I do not have any 560 bolts but I am sure they are plentiful as well. I found necked down bolts from a 77 450SLC https://www.ebay.com/itm/264381810453 and full threaded bolts from a 380SL https://www.ebay.com/itm/266421433974?_skw=mercedes+380+flywheel+bolts&itmmeta=01JGSYY2H45NP028TN84MF9M62&hash=item3e07f47676:g3cAAOSwLXZlDKkf&itmprp=enc%3AAQAJAAAA4HoV3kP08IDx%2BKZ9MfhVJKkW2Z%2FJOVb0Q8qibXgx9vClWZ7a4vnb4%2BlD597QaLqNpLxmkzYZk CFPDdI0Ny%2BqjMdjPTXnRf5GGMAzGweRipIWmgW%2FlAYkU7u0uRx%2BXQlANolfpAcyzckY5bRI15FoLhyJZaJm2v4Lau0TST8 h1tem38OcNc3FK21%2Fry3z1phN%2F3CyH02OGpD0bq8R9f3eQdHGnT%2Fus5gefDYFFqVjUF%2FGVuYlyIlymFS8QtQoLmQxHhW R7zZ5%2Bs4gSm8NgE48Gz31zkpy3z8GHUVxb0LKVUAr%7Ctkp%3ABk9SR-io-L6GZQ

[Frank Reiner]

Tony,

The bolts from the 450 could be OK; make sure that the price is for all eight, not just one!
The bolts from the 380 are for torque convertor-to-ring gear; 10mm. Not for crankshaft!!

[Tony H]

Thanks Frank-just quick looking at items. I realized the 380 bolts were not crank bolts after posting. I communicated with the seller regarding the 450 bolts-the picture is the actual item and 8 are included.

[rwd4evr]

I found these. Cheap insurance. 22 or 28mm UHL(under head length). Stock bolts for the same BMW or a new supra will work too. I think they're like 45-50$. 68$ for arp is a deal though.
Arp pn 201-2801 for the 22mm ones and 201-2802 for the 28mm.

Sent from my SM-G991U using Tapatalk

[Tony H]

I considered ARP as an option if I could not find appropriate MB ones. The 450 ones were very inexpensive and if they have the proper thread engagement, they should be fine. The necked down portion has a spec for min diameter and it they meet the spec they should be good.

[Tony H]

Received the bolts. The auto bolts are identical to my stick shift bolts. Under head length=23mm. Thread engagement=13.5mm so I am good. Cost $13.73 for 8.
3.5 bolt on the right.