Cutout for high hump questions? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**67 twins** · 10-02-2020, 06:13 AM

I've cutout my floor for the high hump & had a few questions.
First should I treat the cut edge with something or just shoot it with rustloeum?
Second what do you use to seal the panel to the floor?
Lastly what type of hardware to use for installation? The OE high hump looks like it uses specific weldnut plates. I was thinking maybe clip nuts or possibly even rivnuts.
Thoughts?

**67 twins** · 10-02-2020, 06:14 PM

Ttt

**LockDoc** · 10-02-2020, 08:11 PM

Quote:

Originally Posted by 67 twins

I've cutout my floor for the high hump & had a few questions.
First should I treat the cut edge with something or just shoot it with rustloeum?
Second what do you use to seal the panel to the floor?
Lastly what type of hardware to use for installation? The OE high hump looks like it uses specific weldnut plates. I was thinking maybe clip nuts or possibly even rivnuts.
Thoughts?

I would just clean the edge up with a flap wheel, prime and paint it with the Rustoleum. Install the hump with hex head sheet metal screws (5/16 x 3/4 or 1 inch should work. Use some Rope Caulk between the panels and undercoat the underside with some spray undercoating.

There may be some other ideas from other members on here too.

LockDoc

gmc684x4 · 10-02-2020, 08:15 PM

I did what locdoc did to my 68 years ago when i made it a 4x4
Factory there is a spot welded ring that you bolt into

LS short box · 10-02-2020, 09:47 PM

No offense to the other posts above but I hate sheet metal screws sticking thru the bottom of any floor pan. I use 1/4-20 bolts just long enough to have washer under the bolt head and then a washer with a nylock nut on the bottom side. If you want a little more profile bolt head you could use button head bolts. So much a cleaner look. In regards to sealant a nice bead of gasket maker has worked well for me.

gmc684x4 · 10-02-2020, 09:53 PM

When i rework my 68 i will add factory high hump ring to get rid of the sheet metal screws as i have one on a scrap cab

Andy4639 · 10-03-2020, 10:14 AM

Here is how I did mine after buying it. I took and put a seal around it like a campshell uses and then shot self tapping sheet metal screw in it.
Sorry for the cluter in the pictures but you get the idea.

**LockDoc** · 10-03-2020, 11:16 AM

Quote:

Originally Posted by LS short box

No offense to the other posts above but I hate sheet metal screws sticking thru the bottom of any floor pan. I use 1/4-20 bolts just long enough to have washer under the bolt head and then a washer with a nylock nut on the bottom side. If you want a little more profile bolt head you could use button head bolts. So much a cleaner look. In regards to sealant a nice bead of gasket maker has worked well for me.

All you have to do is cut the points off of the screws with a cut off wheel after they are in.

LockDoc

10-02-2020, 06:13 AM	#1
67 twins Senior Member Join Date: Mar 2019 Location: Herculaneum MO (20 minutes south of St. Louis Posts: 608	Cutout for high hump questions? I've cutout my floor for the high hump & had a few questions. First should I treat the cut edge with something or just shoot it with rustloeum? Second what do you use to seal the panel to the floor? Lastly what type of hardware to use for installation? The OE high hump looks like it uses specific weldnut plates. I was thinking maybe clip nuts or possibly even rivnuts. Thoughts? __________________ 67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris

10-02-2020, 06:14 PM	#2
67 twins Senior Member Join Date: Mar 2019 Location: Herculaneum MO (20 minutes south of St. Louis Posts: 608	Re: Cutout for high hump questions? Ttt __________________ 67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris

10-02-2020, 08:15 PM	#4
gmc684x4 Registered User Join Date: Jul 2012 Location: Whitehorse yukon Posts: 1,218	Re: Cutout for high hump questions? I did what locdoc did to my 68 years ago when i made it a 4x4 Factory there is a spot welded ring that you bolt into

10-02-2020, 09:47 PM	#5
LS short box Registered User Join Date: Jun 2015 Location: Carlos MN Posts: 2,006	Re: Cutout for high hump questions? No offense to the other posts above but I hate sheet metal screws sticking thru the bottom of any floor pan. I use 1/4-20 bolts just long enough to have washer under the bolt head and then a washer with a nylock nut on the bottom side. If you want a little more profile bolt head you could use button head bolts. So much a cleaner look. In regards to sealant a nice bead of gasket maker has worked well for me.

10-02-2020, 09:53 PM	#6
gmc684x4 Registered User Join Date: Jul 2012 Location: Whitehorse yukon Posts: 1,218	Re: Cutout for high hump questions? When i rework my 68 i will add factory high hump ring to get rid of the sheet metal screws as i have one on a scrap cab

10-03-2020, 10:14 AM	#7
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Cutout for high hump questions? Here is how I did mine after buying it. I took and put a seal around it like a campshell uses and then shot self tapping sheet metal screw in it. Sorry for the cluter in the pictures but you get the idea. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.



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