Bell housing bolts
 

66 GTO 4 speed is the car. Did the bell housing to block bolts use flat washers, lock washers, both?

For reference only, the AMK Fastener Catalog shows 6 bolts and split washers for the manual bell housing. Our host sells a kit which appears to be six hex washer head bolts (RP).

Bell housing bolts
 

Digging around on line some more on this produced an exploded view of bellhousing, clutch linkage, manual transmission, etc. This appears to be from an assembly manual or MPC. It appears to be for 1968, showing 3 speed trans. Not exactly the combo I’m working on, but as close as I could find. Anyway, this illustration shows flange head bolts used to attach bell housing to block with no flat washers and no lock washers. It also shows the trans bolting to bell housing with lock washers only. I was trying to figure out how to include a link to this diagram, but I’m not that tech savvy. This diagram appeared at the end of a long discussion regarding what was “correct” regarding this issue. As usual, there were at least two different versions being argued with some of the usual “expert opinions” expressed. I’m going with what the diagram showed.

Parts book shows/list no washers;

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I dont ever recall seeing washers on those bolts but if washers were used they would not be listed in the parts book unless they were something special. Standard fasteners were in Group 8.900 and had there own parts catalog which listed them by dimension only, not by application.

no washers, originally on these bolts on the factory assembly floor.

IF lock washers had been used, can one imagine how many would have hit the floor?

No washers on the bolts from PMD

The '66 Parts Book I use has the fastener section with listing for washers and other common hardware used in different applications as well as shows size.

My recent search for bell housing bolts for a '67 is this, the four speed bell housings use the flange bolts, and automatics use a standard bolt and no washer. I don't recall ever pulling an automatic transmissions off with washers on the bolts.

AMK sells nice looking bolt kits, here is the automatic mounting bolts ( https://www.amkproducts.com/i-kits/p...y=Transmission ) Not sure about the washers, they seem to think they used them.

These are the most common Bolts I come across, I'm sure there were other marks/makers.

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Bell housing bolts
 

Reused my original flange head bolts. I had bought the AMK master engine bolt kit, but the flange on the bell housing bolts included(see attached photo) seemed too thin to me.

Interesting! Evidently the standard parts were published in the parts books at one time. My oldest MPC is 1973 and does not include the standard parts section. The standard parts catalog has been published for a long time, not sure when it became a separate publication evidently some time between your MPC and my 1973 MPC. Always learning something new!