Motor mount issues...HELP!!!
Thread Starter
7th Gear
Joined: Jun 2019
Posts: 7
Likes: 0
Motor mount issues...HELP!!!
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!!
Any tricks to help me align the bolt holes? Thanks so much for your help!!
Race Director
Joined: Mar 2017
Posts: 11,907
Likes: 4,480
From: Virginia
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.
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.
Last edited by Bikespace; Jun 18, 2019 at 06:05 PM.
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Thread Starter
7th Gear
Joined: Jun 2019
Posts: 7
Likes: 0
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.
Burning Brakes
Joined: Feb 2016
Posts: 872
Likes: 114
From: Round Hill Virginia
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.
Race Director
Joined: Jul 2004
Posts: 12,686
Likes: 329
From: Scottsdale Arizona
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.
Thread Starter
7th Gear
Joined: Jun 2019
Posts: 7
Likes: 0
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! 
Thread Starter
7th Gear
Joined: Jun 2019
Posts: 7
Likes: 0
@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? 
Last edited by mholder1977; Jun 19, 2019 at 09:50 AM.