Original Big Block Truck? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

manimal · 11-05-2006, 08:13 PM

Is there any way to tell if a truck originally came with a big block? I have a 1972 c20.It has the 8-400 emblems on the front fenders,the right frame towers,a th400,dana 60,front/rear sway bars,disc brakes,p/s,had cruise control. The cab has a low hump.

Longhorn Man · 11-05-2006, 09:08 PM

Is the option sheet still in the glove box?
Look under the hood, passenger side down low on the firewall. You're looking for a head shield. That is a big block truck only piece.
If you don't have a build sheet, nor option sticker, you can only go by what is there.
Now... on that cruise control... do you plan on getting it back together... or would you be willing to sell some of it?

**kwmech** · 11-05-2006, 09:08 PM

What about the glovebox sticker? With the emblems I would guess big block

sameyrasmea72 · 11-05-2006, 09:13 PM

With a low hump, I would say small block.

**uncle** · 11-05-2006, 09:11 PM

Low hump is probably strike 1.

**kwmech** · 11-05-2006, 09:14 PM

Not always, I have had 2 trucks now with 400s and low hump. My current one is a 69 GMC 30 series--started life as a class B motorhome ---small hump

Longhorn Man · 11-05-2006, 10:00 PM

and if it was a 3 speed manual, it woulda had a low hump, but i too have seen a few low hump 402/Th400 trucks.

**uncle** · 11-05-2006, 10:08 PM

Factory dual exhaust with hangers riveted on? Isn't the fuel line larger also? If it's a coil spring truck, alot of the big blocks had a brace running from the frame to the support that the trailing arms bolt to.

sameyrasmea72 · 11-05-2006, 10:27 PM

Long shot , but it might have the emission control sticker on the drivers inner fender.

Bob Moore · 11-05-2006, 11:01 PM

If the SPID on the glove box is gone, look at the back of the seat on the passenger side for the build sheet. Usually under the springs and almost impossible to remove whole. If it's there check the VIN to make sure the seat hasn't been changed.

HOTFUN · 11-05-2006, 11:36 PM

The C20 402 automatic only used a 3:54 gear ratio.

Longhorn Man · 11-06-2006, 12:49 AM

Quote:

Originally Posted by HOTFUN

The C20 402 automatic only used a 3:54 gear ratio.

not true, longhorn jeff has a 69 longhorn C/20 with the big block, he has 4.10 gears. (396 instead of 402... but that's splitting hairs)

**Bob B.** · 11-06-2006, 01:42 AM

Big Block TH 400 shorts had the high hump, but I think the long beds used the low hump. Something about raising the transmission to correct the driveshaft angle?

manimal · 11-06-2006, 12:12 AM

WOW! now I'm really confused. It has part of the emission sticker that says 402,as far as the heat shield will have to look tomorrow.Thanks Guys.BTW it is a custom camper.

409biscayne · 11-06-2006, 02:36 AM

My 68 bb t400 long box has the high hump , as does my 70 bb 4 speed . What about remote resevoir p/steering pump , all my bb have had these .

sameyrasmea72 · 11-06-2006, 02:43 AM

Did all bb come with a TH 400, or could some of them come with a TH 350?

junkyardjohn · 11-06-2006, 09:18 AM

Quote:

Originally Posted by sameyrasmea72

Did all bb come with a TH 400, or could some of them come with a TH 350?

THE GENERAL NEVER PUT A T-350 BEHIND A BIG BLOCK. ANY AUTO MATIC IN BIG BLOCK TRUCKS WERE A T-400 FROM THE FACTORY.

I'VE NEVER SEEN ANYTHING BUT A HIGH HUMP IN FACTORY BIG BLOCK TRUCKS. MAYBE THEY EXIST BUT I'VE NEVER SEEN ONE, & I'VE SEEN A FEW.

JOHN

Huck · 11-06-2006, 08:40 AM

The one constant of a big block cab is the exhaust heat shield on the lower part of the firewall---passenger side. Hump size was transmission dependent to my knowledge. The other key as mentioned would be the power steering --assuming it had that--you would have a couple of extra holes on the upper inner drivers fender where the windshield washer tank would normally mount. This would be for the PS resevoir. If the heat shield is there, it was a big block.

manimal · 11-06-2006, 12:58 PM

Well no heat shield but there was an "add on"a/c on the truck when I bought it. The hoses ran right where the heat shield should be. The original fender has the extra holes for the resevoir but has been changed to pump w/res. Oh Well I got a smokin deal on the truck anyway and other than eating flexplates and starters I havent been left stranded.

panhandler62 · 11-06-2006, 01:02 PM

For more confusion ... I thought the 400 emblem refered to the small block, not the rat. Isn't the 396 labled as a 402 in those years in trucks?

sameyrasmea72 · 11-06-2006, 01:09 PM

Quote:

Originally Posted by panhandler62

For more confusion ... I thought the 400 emblem refered to the small block, not the rat. Isn't the 396 labled as a 402 in those years in trucks?

The 400 emblems were for the bb. I didnot think there was a 400sb in these trucks. I have seen several original old trucks where the glovebox said 396, the fender emblem said 400, and the emission sticker under the hood said 402 all on the same truck.

manimal · 11-06-2006, 01:07 PM

Yeah the 396 became a 402 but the emblems refer to it as a 400 big block.

panhandler62 · 11-06-2006, 01:18 PM

OK.. I'll blame the confusion on how many of US like to put 400sb mills in trucks..

Longhorn Man · 11-06-2006, 04:22 PM

lol, that is true. the first 400 small block in the trucks was 73 if I'm not mistaken.
And there were no 396 engines built after 69, they were all 402 from 70 on up.

gregbr · 11-06-2006, 07:00 PM

My 70 GMC C-10 has the factory 402, T400, High hump....came with glove box sticker & build sheet. All numbers match and there is NO heatheat on the passenger side. Greg

11-05-2006, 08:13 PM	#1
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	Original Big Block Truck? Is there any way to tell if a truck originally came with a big block? I have a 1972 c20.It has the 8-400 emblems on the front fenders,the right frame towers,a th400,dana 60,front/rear sway bars,disc brakes,p/s,had cruise control. The cab has a low hump.

11-05-2006, 09:08 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Original Big Block Truck? Is the option sheet still in the glove box? Look under the hood, passenger side down low on the firewall. You're looking for a head shield. That is a big block truck only piece. If you don't have a build sheet, nor option sticker, you can only go by what is there. Now... on that cruise control... do you plan on getting it back together... or would you be willing to sell some of it?

11-05-2006, 09:08 PM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,599	Re: Original Big Block Truck? What about the glovebox sticker? With the emblems I would guess big block

11-05-2006, 09:13 PM	#4
sameyrasmea72 Senior Member Join Date: Aug 2003 Location: Lubbock, Texas Posts: 2,443	Re: Original Big Block Truck? With a low hump, I would say small block. __________________ 72 Cheyenne Super 80 Silverado Blazer 2wd

11-05-2006, 09:11 PM	#5
uncle Senior Member Join Date: Aug 2003 Location: Conyers,Ga. Posts: 7,288	Re: Original Big Block Truck? Low hump is probably strike 1.

11-05-2006, 09:14 PM	#6
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,599	Re: Original Big Block Truck? Not always, I have had 2 trucks now with 400s and low hump. My current one is a 69 GMC 30 series--started life as a class B motorhome ---small hump

11-05-2006, 10:00 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Original Big Block Truck? and if it was a 3 speed manual, it woulda had a low hump, but i too have seen a few low hump 402/Th400 trucks.

11-05-2006, 10:08 PM	#8
uncle Senior Member Join Date: Aug 2003 Location: Conyers,Ga. Posts: 7,288	Re: Original Big Block Truck? Factory dual exhaust with hangers riveted on? Isn't the fuel line larger also? If it's a coil spring truck, alot of the big blocks had a brace running from the frame to the support that the trailing arms bolt to. Last edited by uncle; 11-05-2006 at 10:16 PM.

11-05-2006, 10:27 PM	#9
sameyrasmea72 Senior Member Join Date: Aug 2003 Location: Lubbock, Texas Posts: 2,443	Re: Original Big Block Truck? Long shot , but it might have the emission control sticker on the drivers inner fender. __________________ 72 Cheyenne Super 80 Silverado Blazer 2wd

11-05-2006, 11:01 PM	#10
Bob Moore Registered User Join Date: Feb 2004 Location: Tacoma WA Posts: 1,365	Re: Original Big Block Truck? If the SPID on the glove box is gone, look at the back of the seat on the passenger side for the build sheet. Usually under the springs and almost impossible to remove whole. If it's there check the VIN to make sure the seat hasn't been changed. __________________ 67 C-20 LWB, tilt, speed alert, vac, 454, T400 67 C-10 SWB, factory air with more to follow

11-05-2006, 11:36 PM	#11
HOTFUN Registered User Join Date: Jan 2001 Location: Lincoln, Nebraska Posts: 2,145	Re: Original Big Block Truck? The C20 402 automatic only used a 3:54 gear ratio. __________________ '66 CST BBW swb fleet 327 fac ac '67 CST 4x4 swb 327 stepside project '72 Cheyenne K20 50k original '72 Cheyenne Super K20 project '73 Sierra swb 4x4 frame off in paint stage '74 Cheyenne Super swb w/16k actual '71 & 72 Cheyenne K10 4x4 swb's '70 426 HEMICUDA conv SHAKER 4 sp Dana 60 '60 Impala conv 327 PG fac ac loaded 3rd owner '72 GMC K2500 4x4 '59 Apache CST BBW fleetside swb 283 '73 ElCamino SS LS1 T56 true SS bucket tach '76 ElCamino SS 52k survivor '87 Grand National 41k True 2nd to last built in 1987. '86 K30 454 SRW fleetside CA since new '88 Trans Am GTA 39k bought new 2018 DEMON plum crazy @ 840HP! "Need for speed"

11-06-2006, 01:42 AM	#13
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,348	Re: Original Big Block Truck? Big Block TH 400 shorts had the high hump, but I think the long beds used the low hump. Something about raising the transmission to correct the driveshaft angle? __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.

11-06-2006, 12:12 AM	#14
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	Re: Original Big Block Truck? WOW! now I'm really confused. It has part of the emission sticker that says 402,as far as the heat shield will have to look tomorrow.Thanks Guys.BTW it is a custom camper. Last edited by manimal; 11-06-2006 at 12:13 AM.

11-06-2006, 02:36 AM	#15
409biscayne Senior Member Join Date: Nov 2005 Location: Spokane , Wash. Posts: 790	Re: Original Big Block Truck? My 68 bb t400 long box has the high hump , as does my 70 bb 4 speed . What about remote resevoir p/steering pump , all my bb have had these . __________________ Can-Am Motorsports 37 Chev Coupe 331 4 speed 5.13 posi . ex-gasser . 64 Biscayne 409 2x4 4 speed 4.11 posi 65 Nova Wagon Drag Car 383 t400 (Dragin-Wagon) 68 c10 cst 396 t400 a/c buckets lwb 4.11 posi (SOLD)

11-06-2006, 02:43 AM	#16
sameyrasmea72 Senior Member Join Date: Aug 2003 Location: Lubbock, Texas Posts: 2,443	Re: Original Big Block Truck? Did all bb come with a TH 400, or could some of them come with a TH 350? __________________ 72 Cheyenne Super 80 Silverado Blazer 2wd



Register or Log In To remove these advertisements.

11-06-2006, 08:40 AM	#18
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,269	Re: Original Big Block Truck? The one constant of a big block cab is the exhaust heat shield on the lower part of the firewall---passenger side. Hump size was transmission dependent to my knowledge. The other key as mentioned would be the power steering --assuming it had that--you would have a couple of extra holes on the upper inner drivers fender where the windshield washer tank would normally mount. This would be for the PS resevoir. If the heat shield is there, it was a big block.

11-06-2006, 12:58 PM	#19
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	Re: Original Big Block Truck? Well no heat shield but there was an "add on"a/c on the truck when I bought it. The hoses ran right where the heat shield should be. The original fender has the extra holes for the resevoir but has been changed to pump w/res. Oh Well I got a smokin deal on the truck anyway and other than eating flexplates and starters I havent been left stranded.

11-06-2006, 01:02 PM	#20
panhandler62 Java Mechanic Join Date: Jun 2005 Location: Martinsburg, WV Posts: 6,764	Re: Original Big Block Truck? For more confusion ... I thought the 400 emblem refered to the small block, not the rat. Isn't the 396 labled as a 402 in those years in trucks? __________________ Keith 11 Lincoln MKT -- Momma's wagon 13 G37xS -- middle age crazy car 68 C20 Fleetside -- RIP Decorating the whole town up at a cost of $27 ....

11-06-2006, 01:07 PM	#22
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	Re: Original Big Block Truck? Yeah the 396 became a 402 but the emblems refer to it as a 400 big block.

11-06-2006, 01:18 PM	#23
panhandler62 Java Mechanic Join Date: Jun 2005 Location: Martinsburg, WV Posts: 6,764	Re: Original Big Block Truck? OK.. I'll blame the confusion on how many of US like to put 400sb mills in trucks.. __________________ Keith 11 Lincoln MKT -- Momma's wagon 13 G37xS -- middle age crazy car 68 C20 Fleetside -- RIP Decorating the whole town up at a cost of $27 ....

11-06-2006, 04:22 PM	#24
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Original Big Block Truck? lol, that is true. the first 400 small block in the trucks was 73 if I'm not mistaken. And there were no 396 engines built after 69, they were all 402 from 70 on up.

11-06-2006, 07:00 PM	#25
gregbr Senoir Member Join Date: Mar 2002 Location: Rock Hill, SC USA Posts: 1,214	Re: Original Big Block Truck? My 70 GMC C-10 has the factory 402, T400, High hump....came with glove box sticker & build sheet. All numbers match and there is NO heatheat on the passenger side. Greg __________________ 67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424

Register or Log In To remove these advertisements.