high hump low hump differences - The 1947 - Present Chevrolet & GMC Truck Message Board Network

timberjim36 · 01-01-2012, 12:19 AM

ok so prob a goofy a#* question but is there a difference between a low hump tranny tunnel firewall and a high hump tunnel firewall

clinebarger · 01-01-2012, 12:30 AM

The high hump was used to clear 4 speed manual transmissions, Yes they are different/larger than a low hump.

timberjim36 · 01-01-2012, 12:33 AM

I understand the humps heights are different I think I worded it wrong I'm wondering if there is a difference in the firewall

prostreetC-10 · 01-01-2012, 02:22 AM

There may be a point where there is less clearance on the low hump as it starts to come up to the fire wall. The bolts are all the same though. You can take out a low hump and install a high one. I prefer the high hump because it kind of divides the driver's and pass area so it's not just one big flat looking floor board.

timberjim36 · 01-01-2012, 02:41 AM

ok the reason i was wondering is i plan on installing a bbc in my 67 and it has a high hump for the sm465 and i've read a few posts about firewall clearance and high hump low hump preference so i was wondering if high humps had more firewall clearance than low hump apps.

prostreetC-10 · 01-01-2012, 02:44 AM

The truck above was a 250 6 cyl and sm 465. Is now a 460 BBC and M-22. Everything fit perfect....with a few mods but firewall wasn't even close to an issue.

timberjim36 · 01-01-2012, 02:46 AM

did you use the stock style motor stands or after market ?

clinebarger · 01-01-2012, 02:46 AM

Quote:

Originally Posted by prostreetC-10

There may be a point where there is less clearance on the low hump as it starts to come up to the fire wall. The bolts are all the same though. You can take out a low hump and install a high one. I prefer the high hump because it kind of divides the driver's and pass area so it's not just one big flat looking floor board.

SBC/L6/column shifted 2wd trucks dont have bolt-in trans tunnels.

Longhorn Man · 01-01-2012, 09:03 AM

the firewall is the same

prostreetC-10 · 01-01-2012, 11:12 AM

Quote:

Originally Posted by timberjim36

did you use the stock style motor stands or after market ?

No....I had the right BBC stands from a 68 custom camper with a 396.

Quote:

Originally Posted by clinebarger

SBC/L6/column shifted 2wd trucks dont have bolt-in trans tunnels.

Mine was an L6. Not sure what you mean.

Longhorn Man · 01-01-2012, 03:08 PM

A two wheel drive inline six with an automatic or 3 speed should have had a low hump that is part of the floor pan and not bolted in place.
Posted via Mobile Device

prostreetC-10 · 01-01-2012, 03:46 PM

Ah....that's good to know. So what the heck do you do when you want to convert?

**68bowtie** · 05-05-2012, 12:35 AM

Quote:

Originally Posted by prostreetC-10

Ah....that's good to know. So what the heck do you do when you want to convert?

bump... same question, what's involved with converting a low to a high? Just drilling the holes???

Willys47 · 05-05-2012, 03:01 AM

I got the big block stands and put a bbc in a low hump with a t400 with no problems

old Chevy guy · 05-05-2012, 02:57 PM

Theres a depresion in the floor where you need to cut it out. then drill holes and use the clips like on a front fender for the bolts. Wait till you have the high hump and then you can better see where you will want to cut and how much.

bobs409 · 05-06-2012, 06:55 AM

Installing a high hump is just a matter of cutting the hump out and drilling some holes. You'll also want to lightly roll the edge a bit. I just used a dolly and hammer, real easy.

I installed a new repro low hump floor pan into my wrecker and did as I mentioned. Firewalls are all the same.

One other thing depending on how correct you want it. I welded square nuts on the bottom of the holes as the factory did. Real easy to do, just a few tack welds on each. New square nuts are available just about anywhere.

projectx · 10-09-2012, 08:15 PM

Can the high hump only be purchased used? I can't seem to find one anywhere.

**leddzepp** · 10-09-2012, 08:20 PM

Quote:

Originally Posted by projectx

Can the high hump only be purchased used? I can't seem to find one anywhere.

Yes. They come up for sale here on the parts board all the time. You can look there for one, or if you become a subscribing member you can post a want-to-buy ad and I am sure someone will have one for sale.

projectx · 10-09-2012, 08:27 PM

Cool. Thanks.

novice · 09-06-2017, 04:23 PM

I know this is an old thread but, I'm putting together a 68 with 454 and muncie 4 speed. Will I have to convert to a high hump or will the low one work with the manual shift??

*randy500* · 09-06-2017, 06:27 PM

Quote:

Originally Posted by novice

I know this is an old thread but, I'm putting together a 68 with 454 and muncie 4 speed. Will I have to convert to a high hump or will the low one work with the manual shift??

Muncie sm 465, truck trans with granny low should have the high hump so the boot etc fits right, car 4 spd m20, m21, m22 etc can use the low hump.

novice · 09-06-2017, 07:43 PM

Thanks Randy. That's what I needed to know. You saved me some work. I have the m20

01-01-2012, 12:19 AM	#1
timberjim36 Registered User Join Date: Jun 2011 Location: cape cod ma Posts: 160	high hump low hump differences ok so prob a goofy a#* question but is there a difference between a low hump tranny tunnel firewall and a high hump tunnel firewall __________________ 1980 crewcab dually soon to have a gen VI 454 rectangular port heads holley strip dominator crusader marine stand alone tbi setup with a TCI tcu controlled 4L80 (daily driver) 92 harley electra glide ultra classic

01-01-2012, 12:30 AM	#2
clinebarger Senior Member Join Date: May 2009 Location: Fort Worth, TX Posts: 6,370	Re: high hump low hump differences The high hump was used to clear 4 speed manual transmissions, Yes they are different/larger than a low hump.

01-01-2012, 12:33 AM	#3
timberjim36 Registered User Join Date: Jun 2011 Location: cape cod ma Posts: 160	Re: high hump low hump differences I understand the humps heights are different I think I worded it wrong I'm wondering if there is a difference in the firewall __________________ 1980 crewcab dually soon to have a gen VI 454 rectangular port heads holley strip dominator crusader marine stand alone tbi setup with a TCI tcu controlled 4L80 (daily driver) 92 harley electra glide ultra classic

01-01-2012, 02:22 AM	#4
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: high hump low hump differences There may be a point where there is less clearance on the low hump as it starts to come up to the fire wall. The bolts are all the same though. You can take out a low hump and install a high one. I prefer the high hump because it kind of divides the driver's and pass area so it's not just one big flat looking floor board. Attached Images __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video!

01-01-2012, 02:41 AM	#5
timberjim36 Registered User Join Date: Jun 2011 Location: cape cod ma Posts: 160	Re: high hump low hump differences ok the reason i was wondering is i plan on installing a bbc in my 67 and it has a high hump for the sm465 and i've read a few posts about firewall clearance and high hump low hump preference so i was wondering if high humps had more firewall clearance than low hump apps. __________________ 1980 crewcab dually soon to have a gen VI 454 rectangular port heads holley strip dominator crusader marine stand alone tbi setup with a TCI tcu controlled 4L80 (daily driver) 92 harley electra glide ultra classic

01-01-2012, 02:44 AM	#6
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: high hump low hump differences The truck above was a 250 6 cyl and sm 465. Is now a 460 BBC and M-22. Everything fit perfect....with a few mods but firewall wasn't even close to an issue. __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video!

01-01-2012, 02:46 AM	#7
timberjim36 Registered User Join Date: Jun 2011 Location: cape cod ma Posts: 160	Re: high hump low hump differences did you use the stock style motor stands or after market ? __________________ 1980 crewcab dually soon to have a gen VI 454 rectangular port heads holley strip dominator crusader marine stand alone tbi setup with a TCI tcu controlled 4L80 (daily driver) 92 harley electra glide ultra classic

01-01-2012, 09:03 AM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: high hump low hump differences the firewall is the same

01-01-2012, 03:08 PM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: high hump low hump differences A two wheel drive inline six with an automatic or 3 speed should have had a low hump that is part of the floor pan and not bolted in place. Posted via Mobile Device

01-01-2012, 03:46 PM	#12
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: high hump low hump differences Ah....that's good to know. So what the heck do you do when you want to convert? __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video!

05-05-2012, 03:01 AM	#14
Willys47 Registered User Join Date: Dec 2007 Location: Nanaimo B.C. Posts: 604	Re: high hump low hump differences I got the big block stands and put a bbc in a low hump with a t400 with no problems Attached Images __________________ I was hooked on these trucks since 1982 when I drove my budys fathers 1968 Custum GMC 396 automatic dana 60 rear with a power lock diff what a ride more fun then we will we can ever tell!!

05-05-2012, 02:57 PM	#15
old Chevy guy Registered User Join Date: Apr 2007 Location: Foster Rhode Island Posts: 1,176	Re: high hump low hump differences Theres a depresion in the floor where you need to cut it out. then drill holes and use the clips like on a front fender for the bolts. Wait till you have the high hump and then you can better see where you will want to cut and how much. Attached Images

05-06-2012, 06:55 AM	#16
bobs409 1969 Custom 30 wrecker Join Date: Sep 2001 Location: Pottsville, Pa Posts: 2,611	Re: high hump low hump differences Installing a high hump is just a matter of cutting the hump out and drilling some holes. You'll also want to lightly roll the edge a bit. I just used a dolly and hammer, real easy. I installed a new repro low hump floor pan into my wrecker and did as I mentioned. Firewalls are all the same. One other thing depending on how correct you want it. I welded square nuts on the bottom of the holes as the factory did. Real easy to do, just a few tack welds on each. New square nuts are available just about anywhere. __________________ Bob 63 Impala 283/PG/3.36 (under restoration) 66 Impala 327/PG/3.36 66 Chevelle SS 409/M22/3.55 69 Chevelle 307/PG/3.08 (future restoration) 69 C10 short stepside 454/TH350/3.73 69 Custom 30 tow truck 350/4 spd/4.10 (resto done, CRUISIN TIME!) 71 Cheyenne 20 fleetside 350/4 spd/4.10 71 Chevelle 6/PG/3.08 72 Chevelle 454/M21/4.10

10-09-2012, 08:15 PM	#17
projectx Registered User Join Date: Jun 2012 Location: Washington, NC Posts: 35	Re: high hump low hump differences Can the high hump only be purchased used? I can't seem to find one anywhere.

10-09-2012, 08:27 PM	#19
projectx Registered User Join Date: Jun 2012 Location: Washington, NC Posts: 35	Re: high hump low hump differences Cool. Thanks.



Register or Log In To remove these advertisements.

09-06-2017, 04:23 PM	#20
novice Registered User Join Date: Dec 2013 Location: washington north carolina Posts: 123	Re: high hump low hump differences I know this is an old thread but, I'm putting together a 68 with 454 and muncie 4 speed. Will I have to convert to a high hump or will the low one work with the manual shift??

09-06-2017, 07:43 PM	#22
novice Registered User Join Date: Dec 2013 Location: washington north carolina Posts: 123	Re: high hump low hump differences Thanks Randy. That's what I needed to know. You saved me some work. I have the m20

Register or Log In To remove these advertisements.