Stringing up the frame - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Lord_glum · 03-19-2019, 07:35 PM

Before I send the frame out I want to string it up to check squareness. At 1 time I found a post for what dimensions to check but it’s lost to me.

On another note,
Anyone happen to have a measurement for the rear frame rail height? I am Installing the rear frame crossmember and ran into the issue below. The crossmember is sitting on the bottom rail. Doesn’t appear that way because of the perspective.

Thanks for the help.

**71CHEVYSHORTBED402** · 03-19-2019, 07:52 PM

Rear frame rail height is 4.1/10" OD.

Lord_glum · 03-19-2019, 08:12 PM

I should clarify it’s a 68 shortbed.

My frame measures:
3 7/8 id inside rail
4 3/16 od top to bottom of the outside.

**Grumpy old man** · 03-19-2019, 11:05 PM

this should help

JustToxic · 03-20-2019, 10:44 AM

Just a word of advise, when trying to find square. GM's measurements are very, lets say "loose". Don't be surprised if the frame is 1/2-3/4" out of square. Also, check with a body shop that has a frame machine to see what the collision safe measurements are. Last frame I cut down a frame, the frame to start with was 9/16" out of square but that was okay according to specs from a body shop.

Lord_glum · 03-20-2019, 10:23 PM

Thank you all for the help and information. I will use this later this week when I hope to have this completed.
I also found I was shipped the wrong crossmember and the new 1 is in the mail.
Thanks for the help.

03-19-2019, 07:35 PM	#1
Lord_glum Registered User Join Date: May 2018 Location: Illinois Posts: 40	Stringing up the frame Before I send the frame out I want to string it up to check squareness. At 1 time I found a post for what dimensions to check but it’s lost to me. On another note, Anyone happen to have a measurement for the rear frame rail height? I am Installing the rear frame crossmember and ran into the issue below. The crossmember is sitting on the bottom rail. Doesn’t appear that way because of the perspective. Thanks for the help. Last edited by Lord_glum; 03-19-2019 at 08:29 PM.

03-19-2019, 07:52 PM	#2
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,118	Re: Stringing up the frame Rear frame rail height is 4.1/10" OD. __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assm. guide "kit" for restoring it from ground up. With assys, the guide accts for 1000s of OEM identifications and part numbers, all written in short order. 700+ images include assm, illust., charts, and points of interest. Much of the info. applies to all 67-72 GM trucks, and to a lessor degree all 67-72 GM vehicles. My build thread, and more on the guide https://67-72chevytrucks.com/vboard/...d.php?t=730025

03-19-2019, 08:12 PM	#3
Lord_glum Registered User Join Date: May 2018 Location: Illinois Posts: 40	Re: Stringing up the frame I should clarify it’s a 68 shortbed. My frame measures: 3 7/8 id inside rail 4 3/16 od top to bottom of the outside.

03-19-2019, 11:05 PM	#4
Grumpy old man Senior Member Join Date: Dec 2013 Location: Gods country East,Tn Posts: 8,545	Re: Stringing up the frame this should help Attached Images __________________ 1967 Factory short bed - Old school '71 - 350 / 4bolt / 487 heads / Edelbrock C3BX Muncie M-22 4 speed / Hurst Comp plus Factory 12 bolt posi 3.73 / 255-70-15 Smoothed firewall / Factory cowl induction Power disc brakes / power steering / 3.5-5" drop

03-20-2019, 10:44 AM	#5
JustToxic Registered User Join Date: Jul 2016 Location: Elkhart, Indiana Posts: 292	Re: Stringing up the frame Just a word of advise, when trying to find square. GM's measurements are very, lets say "loose". Don't be surprised if the frame is 1/2-3/4" out of square. Also, check with a body shop that has a frame machine to see what the collision safe measurements are. Last frame I cut down a frame, the frame to start with was 9/16" out of square but that was okay according to specs from a body shop. __________________ 1967 Chevy C20 to K20 Conversion "Simply Toxic" http://67-72chevytrucks.com/vboard/s...d.php?t=749409 1971 Chevy C20 Custom Camper LS Swap http://67-72chevytrucks.com/vboard/s...d.php?t=763775

03-20-2019, 10:23 PM	#6
Lord_glum Registered User Join Date: May 2018 Location: Illinois Posts: 40	Re: Stringing up the frame Thank you all for the help and information. I will use this later this week when I hope to have this completed. I also found I was shipped the wrong crossmember and the new 1 is in the mail. Thanks for the help.



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