mholder1977

hello C3 experts! I am in the middle of replacing my motor mounts on my 1977 C3. I am using jack stands to raise the front of the car and using a floor jack with a block of wood to raise the engine under the oil pan. All was going well until I tried installing the new mounts (Prothane red mounts). No matter what I try, i can NOT get the darn bolt holes to line up. If I start the frame bracket long bolt first, lower the engine, the bolts in the block are off by about a half inch. If I install the block bolts first, lower the engine, the frame bracket long bolt holes don't line up. I'm running out of patience and cuss words!

Any tricks to help me align the bolt holes? Thanks so much for your help!!

Tampa Jerry

I had then same problem with my Chevelle and the red mounts. I replaced them with stock GM mounts and the problem ceased. Jerry

Peterbuilt

Here are the stock motor mount measurements.

mholder1977

thanks guys. I was afraid that it might be the red mounts. I've already purchased some OEM replacements. Hopefully these will go in easier. I appreciate the feedback!

mholder1977

BTW - this is the BEST vette forum on the net! I've been saved SO many times by the amazing knowledge and helpful members here! Kuddos to all of you!

Bikespace

Did you check the measurements? It may not be the motor mounts themselves.

I had a bear of a time putting in my driver-side engine mount (Moroso, solid steel). I know the measurements are correct. As soon as I took out the old mount, the engine shifted backwards, making alignment impossible. I ended up having to attach a ratchet strap to the joists in the ceiling to yank the engine forward to get the bolts to align. Even then, it wasn't easy, and I had to goose it with a prybar at the same time.

L-46man

Be careful how you raise the engine...lifting from the oil pan is fraught with fail.... dislodged and crushed gaskets, bent pan, etc.

Unkahal

derekderek

Part of your problem is gravity. Front is on Jack stands. Unbolt mounts, engine goes downhill towards the back wheels. Might have to unbolt trans mount so it will go back north.

mholder1977

Update: after receiving my OEM replacements last night, I was able to get the drivers side mount attached (block bolts first but loose). Lowered the engine and the bracket bolt holes lined up perfectly! So I know the drivers side fits now. I will hopefully get the passenger side done tonight. So far, I think the red mounts I was trying to install did not give enough space between the bracket bolt mounting ears for a 40+ year old frame bracket that may have shifted slightly or changed shape over time. Factory specs may not work on some of these older cars.

derekderek

Or maybe the red mounts are pretty, but otherwise useless...

mholder1977

nix1981

FWIW...I ordered a set of motor mounts that were "replacements" vs "correct" because they were a few dollars cheaper and ended up sending them back and paying a bit more for the "correct" mounts. Although the replacements looked very similar, they did NOT fit. They were not quite right and I could not get the engine to settle and get the bolts in.. Ordered the "correct" version (which was exactly like the original) and they worked perfectly. This was for a 69 car.

CA-Legal-Vette

I’m a little late to the game, but one suggestion that I can make is to loosen the transmission mount. You might find that it gives you the slack that you need to align the bolt holes. You might also find that the transmission mount is shot and that misalignment is causing you the issues.

mholder1977

Hopefully this helps others who venture into the seemingly simple task of replacing their C3 motor mounts. I had a hard time finding any other threads about motor mount bolt holes not lining up. So, now there is one!

mholder1977

@CA-Legal-Vette - You're right...I should have tried that. I know the tranny mount is good because i just replaced it a couple of weeks ago. if I have trouble with the passenger side mount, I'll try to loosen the tranny mount. I really wish I had a lift! GoFundMe?