I have new Grade 8 bolts for the clamshell motor mounts that were originally on my 305 TPI that i am now using on my 383 LT1 swap. See pic. The bolts are just a hair long and I need to use washers to make up the space. Anyone think this will be a problem? I am using solid motor mounts - not sure if that matters or not.

Do NOT put washers between the clamshell & the block - I can pretty much GUARANTEE that you'll have a HELL of a time trying to get the horizontal bolts through to mount the engine to the K-member (ask me how I know).

You should be able to place the washers under the bolt heads ("inside" the clamshells) without any problems though.

I wonder why it would be a problem though? Because all it really does is cause the motor to be mounted 1/16" or 3/32" higher... the bolt holes should still aline perfectly fine. I am not saying you are wrong but that is just my thought, I think with the size of these washers I will not be able to get them inside the clamshell.

I guess its not worth to find out anyways but I am curious now...

Now I also ran into another problem, one of the bolts will not thread into the hole in the block. Looks like some of the threads are messed up and the bolt wont even catch the first threads. I can just run a tap through this to get it fixed up right? Anyone know which tap? I bought a bunch of bolts and now forget which exactly it is... i want to say 3/8-16 but I am not sure. Maybe 5/16-__?

Retap it. Most SBC holes are 3/8-16

If you cant fit a washer in the clamshell, grind some length off the bolt and clean the tip up with a file or a die

You will pay hell getting the two mount bolts back through using washers under the mounts

sounds good. Thanks for the help, I'll see if I can first find a shorter bolt tomorrow and if not then I will mess with the washers/bolts to make it fit in the clamshell.

If you're running solid moroso mounts, you should just buy the uppers and lowers and it'll bolt right up with no fab work.

I bought the lowers from UMI but I dont think they sell the uppers, I actually could not find new ones anywhere but no need really. Got my old ones blasted and powder coated and they look great. I just bought shorter bolts and now everything is good to go. Just a pain to go back and forth to ACE all day...

Thanks for the help everyone

It actually moves the clamshells "outward", farther from the centerline of the mounting axis. I had a little bit of correct alignment, just enough to see that the holes overlapped by about 33-40% - enough so that I could fit a tapered punch in to align the holes when I'd apply some force, but nowhere near enough to have even a chance of getting the actual bolt started.

Man, there's been several days that that's pretty much defined my swap...

Ahh makes sense now...