Motor Mount thickness

[cst350]

Tried this in the "Drivetrain" section without luck...

I have a '69 Fleetside Shortbed with a Gen 1 SBC and I'm using Prothane Motor Mounts (the kind with the single bolt coming from the bottom of the tower). They are 1 1/4" thick from the top of the tower to the engine block.

Can someone tell me if that is the same as a stock motor mount?

I'm trying to dial in my driveline angles and everything points to my motor being too high. It's driving my crazy because I am 99% sure the towers between the motor mounts and the crossmember have never been removed or damaged. Truck has been in the family since new and I'm owner #2. Cant imagine Grandpa did any "surgery". It even had the original spark plug wires on it when I got it!

[geezer#99]

Can you make your carb level?
You need it level to set the height of your trans on the mount.
Then match your pinion angle to the output shaft angle on the tans.

[cst350]

Right now the Carb is at 2deg and the tail shaft of the trans is 4. Frame is zero.

I know I can match the pinion with shims. The part that has me spinning is that my trans crossmember (from a TKO 600 conversion kit) from Company A is .8" below the frame at the mount. One from Company B is .6" above. One from Company C is same as the frame. All say my motor must be too high if i'm having trouble. Leads me to believe there is something on "my" end thats just not right.

I'm trying to fill in all of the "blanks" in my calculations.

The next would be the hight difference between the bottom of the frame and the tail shaft of my old TH400. I wish I would have taken measurements before I took it out and sold it...

[Steeveedee]

OK, some frame conversion stuff has gone on? Did I get that right, or is it just stuff you were looking up for comparison (not trying to be a wise guy)? Transmission mount shims got used on a lot of trucks; some of them were 1/4" thick, and there might have even be two of them. Just a question to help me understand where the truck is at.

[cst350]

Basically the frame is stock except for the new crossmember for the TKO kit.

The suspension is a 4/6 ECE drop.

I bought the trans as a kit. I put the motor and trans in and saw it sat low. This is with the -.8" crossmember


As luck would have it, a few years back I bought a crossmember from another company that has since stopped making them. That one I measured as "flat" with the bottom of the frame. I called a 3rd company that sells conversions and they told me theirs is .6 above the frame.

For the numbers I have now I am using the -8" with a 1.4" block, matching the highest of the 3 cross members.

[Ironangel]

I have a new 71-72 small block motor mount in my hand that measures 1" inch thick from the block mating surface to the stand contact surface. It's the plain jane 3-bolt plate with a black rubber surface. Has one 7/16" NC threaded hole in the center...Like these, the stands should look like these... https://www.classicmuscle.com/849743...SABEgLNuvD_BwE These trucks had a factory 2" rake when they were new meaning the frame sat a little higher in the rear. The motor and transmission sit practically level in both of my 72's, but they still have the two piece drive shafts and carrier bearings. One's lowered the other has 275/70-16's all 4 corners. That transmission tail shaft has to match the angle of the crank in the motor. Never mind where the frames at, the motor needs to be almost level, maybe a couple of degrees down in the rear.

[cst350]

Ironangle, Thanks for this info. I'm thinking that .25" is going to help. Plus the original rubber may compress a bit as well. Before I took it apart, I had a one piece driveshaft made. No problems with the TH400, thats why I'm curios where I started as far as yolk position compared to the frame.