Correct bolts/screws to attach trans adapter plate to GM Engine

[Ken Roberts]

M10 x 1.5 bolts look very close to the size of 3/8 x 16 bolts as shown in the picture. Metric ARP bolt to the left to fasten the Graziano to the adapter and a typical 3/8" bolt to the right.

The transaxle to adapter plate is the same size......M10 x 1.5. Not M8 x1.25. The M8 x 1.25 bolts are for the rear side supports and top shifter cable bracket on the Graziano. The side mounted CV heat shields are also the same size and will be needed. (6), The two starter bolts are M12 x 1.5 x45

 

[Joel K]

M10 x 1.5 bolts look very close to the size of 3/8 x 16 bolts as shown in the picture. Metric ARP bolt to the left to fasten the Graziano to the adapter and a typical 3/8" bolt to the right.

The transaxle to adapter plate is the same size......M10 x 1.5. Not M8 x1.25. The M8 x 1.25 bolts are for the rear side supports and top shifter bracket on the Graziano.
View attachment 97194

The 3/8” did thread into the block a couple turns, I only finger tightened and thought they should go in a bit more then figure I’d ask the forum. Those ARP bolts are nice with the torque design and integrated washer. I also ordered some Milspec cadmium plated washers that will clear the counter bored holes so I think I am all set on this item. As always, I appreciate the help.

 

[Joel K]

Just to close this thread out, for the LT4 it turned out I needed the following bolt and washer to mount the transaxle plate.

90128A289 Zinc-Plated Alloy Steel Socket Head Screw, M10 x 1.5 mm Thread, 40 mm Long, packs of 10

98032A341Cadmium-Plated Steel Mil. Spec. Washer for 3/8" Screw Size, 0.625" OD, MS-27183-58, Packs of 50

Thanks again for all your input.