The Stovebolt Site Forums The Shop Area Engine Shop Engine bolt spinning?

Anyone have a great idea how to get this nut and bolt out. Just spins and can't really get on top to put pressure on it?

That looks like the front engine mount. If so, the one that you have the nut off of and the other one toward the center don't need to be removed to pull the engine. Remove the two outer nuts and the engine should come out. The two inner bolts are carriage bolts and the square under the head may have rounded or the square hole in the front engine plate has worn allowing the bolt to turn. BTW, you need to remove the cotter pins before attempting to unscrew the nuts. Attached is a picture of what you're dealing with from the Service Manual.

Took picture after I put cotter pin back in. Not pulling motor,was replacing motor mount rubber. The passenger one just spun off with ease. Driver side is rusted or stretched and stuck.

The inner bolts are carraige bolts on this particular truck. Maybe someone put them in the wrong place? Thanks for the info.

From the factory they were 7/16 carriage bolts. They engage the square holes in the bottom of the engine plate below the crank pulley.

breezy is going to eventually get to the head on that bolt. Maybe raising the engine will give him enough room to reach underneath and maybe put some downward pressure on the head so it doesn't spin. It's definitely a tight spot.

When I restored my front engine mount, I needed to weld and reshape one of the holes. A previous owner had used a hex head bolt with the head ground off at an angle so it would fit through the hole without hitting the crank pulley.

[on edit] breezy, maybe grind a slot in the end of the bolt with a cutoff wheel so you can hold it with a screwdriver.

If the nut is rusted to the bolt threads you are not going to be able to hold a carriage head. So you either tighten the nut with a big impact driver until bolt breaks or you cut/slit/split the nut with an angle grinder and die grinder and chisel it off. Cut thru the slots in castle nut (and thru bolt) and don't take any prisoners. Time to go nuclear.
Do whatever you have to do but don't replace with carriage bolts!!!!!

Seems there is a clearance issue with using hex head. I'm not familiar with this area and how much clearance there is BUT.... for reassembly if hex head won't work, I would consider a 1/4 thick plate up top with threaded holes to receive bolt from bottom. Length of bolt will need modified to stick thru plate 2-3 threads and not hit whatever. Use flat washer and lock washer under head and mild locktite on threads. Could be one plate with two holes which won't spin or two plates that may hit crossmember and not spin....or use an anti-spin device. 7/16 head is .297 thk so not much help with a 1/4 plate. Depends on where the interference is as to reducing bolt size/nut thk/plate thkness for designing a remedy. PDlighting indicates a remedy.

I still don't understand where carriage bolt goes, Kevin says inner are carriage and shows a pic with them at outer? Carl says carriage are outer. The conversation says hex was used where they were not supposed to be used?..and it worked.

I understand the design just not the reason behind it. Totally unacceptable for a mechanic to work on. Glad I didn't have to make a living back then turning wrenches.
Not much different today though. Instead of using a cable to adjust heater controls let's hook up an electric motor hooked to a computer and buried in the dash!!
Engineers have not gotten any smarter. Just my opinion

You've got at least two engineers replying on this post of yours. We can discuss our experience with mechanics if you wish. But let's dispense with bad mouthing trades.

I'm sure they say the same thing about mechanics like myself.
Sorry

Well I'm not an engineer and only do my best at mechanics but I will engineer this style mount when I switch to the 235.

OK, but let us know how you get the nut off so we can add it to the archives. You will receive brownie points and some green stamps.

Was ready to get the heat wrench out but with 50 years of oil leaks I decided that wouldn't be a good idea. Lol
I'll post when I get it done.

Don't worry about fire down there, just keep a rag handy. Shouldn't take much to put a big slit in nut and blast it off with a hammer and punch. I assume you meant cutting torch not just heat. Heat won't help if you can't hold the head. Will the bolt withdraw or will it hit something?

From what I've read the bolt on the driver side will come out. Yes I meant the cutting torch. Going to try and get a pair of vice grips on it first. If that doesn't work cutting wheel on 4" grinder should make quick work.

The problem with the carriage bolts is that over the years the square under the head and the square hole in the front engine plate wear, and eventually won't keep the bolt from turning. The length has to be just right to get the bolt in with the crank pulley in place. I suppose a guy could pull the balancer off and get to the bolt heads or even just tack weld the head to the plate, although that's kind of a drastic measure. But then again, how many times will you need to take those bolts out. Another approach might be to weld some tabs on the plate to capture the flats on the head of a hex bolt, but that might eventually have the same issue as the carriage bolts.
In defense of the designers, they weren't necessarily worried about it working for 70 years. My daily driver truck has some bolts with "wings" attached to the bolt head which work at least once during assembly when threads are clean, but I've had to deal with a couple of them when working on the truck.

What bartamos said about fire. Go in hot and quick and cut it off. But like I said, the two inner bolts don't need to be removed to get the engine lifted. If you don't have a radiator in the way, you could probably cut the mount loose with a sawzall.

Perfect

https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/download/Number/64076/filename/IMG_8589.jpg

This shows the carriage bolts on the outside. But,

https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/download/Number/64072/filename/IMG_8583.jpg


Are on the inside🤔

I like the cutting wheel option!

PD...I know I'm missing something but on your second link pic I don't see any close interference issue. So why were carriage bolts used at all in any hole?
I think the poster was asking that also.

I put new carriage bolts in the outside holes where the dimples are on the cover plate, and used grade 5 bolts up through the round holes I drilled in the engine plate and secured them with locknuts.
Worked swell.

You could always use a nut splitter. You tighten the jaws on the nut aligned perpendicular to the bolt and it splits the nut off and in most cases, without damaging the bolt. I’ve used it several times on my truck. No flame involved.

This style allow you to get into some tough places and there are several for sale on eBay.

Why didn't GM just use welded nuts there or a threaded boss?

Sucess!!! By Getting a pry bar behind the washer. Prying down and a few zips and off it came.

👍

With either of those methods, you couldn’t use a secondary locking device (castle nut w/cotter pin).

As a clarifier, some of us didn’t understand that the two center bolts attach the motor through a sleeve in the rubber mount itself only. The outer bolts only attach the motor mount assembly to the cross member. This system isolates the motor from a direct connection to the frame.

New bolt in with nylon lock nut. It will do for the time being.

Good Job! There's always more than one way to skin a cat.

I deleted my earlier post about what bolts go where and what they do. It was full of errors.
I have since located my complete engine mount with all of its original hardware.
Even with that assembly in my hands, and the knowledge of where all of the bolts go, I am at a loss for words as to how to describe this in print or verbally in person.
If someone was right next to me, interested in how it goes together and how it goes on the truck, the best that I could do to help them understand would be to grunt and point like a caveman.
These mounts are ridiculous in their complexity. Why did they do this? My only guess is that it is all about the lack of quality rubber used back then. That oily location is a rough environment for that kind of rubber. Given that, it was necessary to make it adjustable for when the rubber became flattened.
In The Book, it explains that if there is metal-to-metal contact of parts, you need to file the metal until you have a gap. Are you kidding me?!
I guess that I know now what my Life's Mission has become.
DESIGN AND BUILD AN AD FRONT ENGINE MOUNT WHICH A PERSON DUMBER THAN A CAVEMAN CAN SIMPLY BOLT INTO PLACE AND FORGET ABOUT IT FOR 50 YEARS.
That's right! All caps.
Sue me.

When you produce you first (tested) mount , I be in line to purchase one!