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Anyone have optimal dimensions for where to drill for shock mounts in rear floor of my 57? I have new floor section there without holes.

Someone had welded a makeshift shock crossmember but it was too low and the shocks did not have any travel so I chopped that off.

Here is a picture with the crossmember still in. So where to drill is the question. Also exhaust is routed through there now but he said he left me room to mount the shocks, will find out tomorrow what it looks like. But for now dimensions where to drill would be appreciated.

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Is there the angled top piece in the trunk? I believe if it has the hole, or even if it doesn't, I'd drill at a right angle to that triangle part in the middle of it and keep going through the rest.
 

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I was going to copy your image and then edit it to show where the hole was from the factory, but for some reason your post would not allow me to copy the image; is that one of the NEW FEATURES of this software? or something the OP did ?

Regardless, it should be in the center of the RH side of the 'triangular notch' in the trunk floor (ie extend your shock longitudinal line and you will be close. In fact the shock bar could have been located a couple of inches higher on the frame to line your shock up with that flat on the floor and would probably have been perfect. NOTE: The floor sheet metal is REINFORCED with a THICK metal in that whole area of the 'notch' to spread the shock load over a larger area. If your new floor doesn't have that reinforcement, then your shock will punch thru the floor in pretty short order...
 

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... your post would not allow me to copy the image; is that one of the NEW FEATURES of this software? or something the OP did ?
FYI: Click on the pic in the post and it opens the pic in a separate window. Then right click on the pic to open the menu that has a selection to copy the pic.
 

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If that works for you, then you have different software or platform than I... doesn't work here on my workstation (running windows 10).
 

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Hmmm, I'm running windows 10 also.
 

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Trifive Automotive Electrical Wiring Expert
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Anyone have optimal dimensions for where to drill for shock mounts in rear floor of my 57? I have new floor section there without holes.

Someone had welded a makeshift shock crossmember but it was too low and the shocks did not have any travel so I chopped that off.

Here is a picture with the crossmember still in. So where to drill is the question. Also exhaust is routed through there now but he said he left me room to mount the shocks, will find out tomorrow what it looks like. But for now dimensions where to drill would be appreciated.
Does it have the heavy sheet metal support under the floor for the shocks? They have the holes drilled. The sheet metal floor won't support the shocks. The heavy support doesn't do very well. I would put a shock bar in where it belongs anyway.

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Apparently the new software only allows SAVING of the HTML... and not the image itself... :(

OK... I went to a different thread and I was able to save images from some postings, so the posts made by folks in this thread inserted their images in some way that only allows the html to be saved... (No option to save image).
 

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The next option is to use the Windows 10 Snipping Tool which will allow saving to a .png file.
For Windows 10Select the Start button, type snipping tool in the search box on the taskbar, and then select Snipping Tool from the list of results.
 

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Does it have the heavy sheet metal support under the floor for the shocks? They have the holes drilled. The sheet metal floor won't support the shocks. The heavy support doesn't do very well. I would put a shock bar in where it belongs anyway.

View attachment 321109
I agree with Don. install a shock bar and call it good. Most are using that method any way.
Terry
 

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Anyone have optimal dimensions for where to drill for shock mounts in rear floor of my 57? I have new floor section there without holes.

Someone had welded a makeshift shock crossmember but it was too low and the shocks did not have any travel so I chopped that off.

Here is a picture with the crossmember still in. So where to drill is the question. Also exhaust is routed through there now but he said he left me room to mount the shocks, will find out tomorrow what it looks like. But for now dimensions where to drill would be appreciated.

View attachment 321104
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This is a blow up of your photo just above the shock The hole would be through the triangular bump down
on the same side as the shock in your photo

As said by Acardon - a shock support bar is the best solution.





It would be welded at the end to the frame with the shock mounting brackets near the
triangular bump down in your floor.
 

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After looking at your photo again it appears that you had an after market shock mounting asm. It could be that your shocks were too long for that asm. or the rear axle had been lowered by the PO moving the frame farther away from the axle.

Also I noticed that the shock mtg brkt photos I attached previously were bolted to the frame not welded.
 

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Discussion Starter #13 (Edited)
Okay now with that junk crossmember out of the way and exhaust in you guys can see what I’m trying to do with shocks loosely mocked in (see pic) I just want to mount it in the stock location. Did they have reinforced floor mounts from the factory? I need this car on the road in 2 days so no time to order any new parts from the US. I know proper shock bars are better but I’m out of time for now. I'm thinking we can reinforce it with some steel plates top and bottom too, just need the actual dimensions where to drill. Thanks guys.

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Discussion Starter #14
Thanks guys for all your input. In the commotion I forgot my 55 Pontiac (Canadian same as a Chevy) has original shock mounts so I was able to get a measurement off of that.
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Yes, that area (the indented area plus some around it) was reinforced with a shaped THICK piece of metal tack welded to the floor and tieing into the body support (at least on wagons)... I Had to remove mine for the custom chassis and I think I still have the reinforcement pieces if you need a measurement of how thick the metal was...?
 

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Trifive Automotive Electrical Wiring Expert
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If that's a single thickness of sheet metal, the shocks will rip the floor at the first bump. At least put some heavy plates on the bottom.
The reinforcements are about .100" thick.
 

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For my custom chassis with C4 suspension, I had to remove the shock mnts in the body to clear the rear suspension. First by cutting out the sheet metal and the reinforcements, then grinding/priming the cuts, applying flat plates to cover the hole, and repainting underneath to match the underfloor paint.

For installation of a shock bar it might be a good idea to do a similar task of removing the body shock mounts to make more space for the bar and shock mounting?
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Trifive Automotive Electrical Wiring Expert
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I did the same on my 56. I was able to raise the shock bar and the welded bar with gussets actually stiffened the frame considerably.
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I'm NOT trying to tell 55Laurenthian what to do, but he really needs to understand how the original body was reinforced in the shock mount area before he mounts shocks in 'sheet metal'. As ACardon has posted, "it will rip out the sheet metal at the first bump" if he does so.

I went to the garage to check the pieces I cut from my Nomad and do some measurements. I am including photos here also, but the 'sheet metal' in the original floor was a bit over 0.060"; your replacement floor metal is likely similar thickness, but might not be the same strength since the replacement floor metal came from China! In addition, the factory welded in to the bottom of the floor a THICKER (~0.075") stamped reinforcement, and between the floor metal, and the reinforcement panel was an additional piece of metal (~0.150") which was sandwiched between the two pieces of stamped sheet metal. This additional rectangular reinforcement was sized at ~ 2" x 2.5" . The total thickness including both panels and the reinforcement is ~ 0.280". and this seemed sufficient with the factory shocks on a typically driven trifive when they were new. BUT even with this reinforcement it could tear out of cars when air shocks or stabilizer shocks were employed!
Measurements were made with a Starrett micrometer.

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Anyone have optimal dimensions for where to drill for shock mounts in rear floor of my 57? I have new floor section there without holes.

Someone had welded a makeshift shock cross member, but it was too low and the shocks did not have any travel so I chopped that off.

So where to drill is the question......for now dimensions where to drill would be appreciated.
Michael....Agree with most of the others...Grind down the welds and install another shock bar...Mounting them to the trunk floor was one of GM's lesser than brilliant design ideas...The only thing you might need the holes for is to make it easier to access the top shock nut....That what I used mine for...I which case you would not have to beef up the metal...Once you get the new shock bar in place, you can readily determine where the hole needs to be.

 
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