400 motor AKA 402 BB - The 1947 - Present Chevrolet & GMC Truck Message Board Network

gmcbigbl · 09-06-2005, 06:11 PM

The GMC build sheet reads "400 cu. in. V-8 engine"
Truck has a turbo hydra-matic tranny.
Is this a 400 sb or 402 bb

panhandler62 · 09-06-2005, 06:16 PM

If you post a pic twenty people will rush to answer you. lol

The fast way to tell is to look at the exhaust. Small blocks have the center ports siameezed together where the big block exhaust ports are evenly spaced.

Blazer1970 · 09-06-2005, 10:39 PM

If you are talking about a '67 - '72 truck it is a 402 big block. The 400 small block was never used in these trucks.

**special-K** · 09-06-2005, 11:24 PM

Quote:

Originally Posted by Blazer1970

If you are talking about a '67 - '72 truck it is a 402 big block. The 400 small block was never used in these trucks.

Correctamundo!!Does it have a big block in it now?

Longhorn Man · 09-06-2005, 11:34 PM

Welcome to the board from Central Ohio.
I am pretty sure you are first member from China....I'll bet parts are a real pain huh?

As stated, the 400 that was listed on these trucks would be a 402 big block, the 400 was never installed factory. In many of the '70 trucks it was still listed as a 396 on the option sheet, badged as a 400, yet was actually a 402.

gmcbigbl · 09-07-2005, 04:02 AM

It is a 1970 GMC Sierra Grande with the original engine. The entire truck is original with only 68000. It has the CST interior with bucket seats and console The color is yellow(ocre)? I'm gonna e-bay it soon and wanted to make sure of engine cubes.
If someone tells me how, I will post a few pics.
BTW It's not really China, just joshing

**special-K** · 09-07-2005, 07:37 AM

I wundered if it was a town in Kansas or something.

69Goody · 09-07-2005, 12:27 PM

My 69 GMC camper unit has a Small Block 400 in it...but it had a 350 originally and says so on the build sheet.
The 400 small blocks did not start production until 1970. As far as whether they were used in production or not...I'm not sure. I would not put it past as an option or custom request.
I believe my 400 small block came as an upgrade early in its life. Possibly to get a little more power under warranty without any other mods needed.

One way to tell would be to look at the exhaust ports on the heads. If they are evenly spaced, then you are looking at a big block motor. 0_0_0_0
If the two center exhuast ports are right next to each other 0_00_0 then you have a small block.
The sure fire way to tell is look for the block ID code imprinted on it.

I would tend to believe that if it were a big block 402, it would have said 402 on the build sheet and not 400. No one would under state the Cubic Inches.

Tx Firefighter · 09-07-2005, 12:43 PM

4 bolts for each valve cover = small block
7 bolts for each valve cover = big block

panhandler62 · 09-07-2005, 12:53 PM

It's funny but, other than the simple tricks of counting bolts and looking at the exhaust ports that 69Goody, TX Firefighter and I put forth, I am having a hard time thinking of how to tell someone how to spot a rat, even though I know for a fact that I would know instantly if I was looking at one when the hood came up!

It's no wonder we have so many unsolved crimes -- people are lousey witneses! LOL

COBRO · 09-07-2005, 02:42 PM

My 72 c-20 came with the 402 BB and its listed as a 400 on the glove box door and fender emblem so seems you have a BB - just more of the GM confusion. HTH::::CB

mplex2000 · 09-07-2005, 02:50 PM

Hehe...simple panhandler...big blocks are...big :P

It is kind of funny that you (me) can look at one and see that it's a BB or SB, but how would you tell a newcomer to tell?

edmonton72 · 09-07-2005, 03:04 PM

Are you guys sure that these trucks never came with the 400 sb? It says 400 cu. in v-8 engine on the potion list on my 72 and it has 350 in it now. My dad and i always argue about if it came with a 400 or a 402. Is there any other way to figure out if it came with a 402?

cableguy0 · 09-07-2005, 03:11 PM

They absolutely did not put 400 small blocks in these trucks. my bet is someone blew up the 402 that was originally in your truck was blown up or swapped to a car and replaced with a much cheaper and easier to find 350

Blazer1970 · 09-07-2005, 03:16 PM

Quote:

Originally Posted by cableguy0

They absolutely did not put 400 small blocks in these trucks. my bet is someone blew up the 402 that was originally in your truck was blown up or swapped to a car and replaced with a much cheaper and easier to find 350

Correct. 400 small blocks were used in full size cars in these years, but ABSOLUTELY NOT IN TRUCKS.

GasHog396 · 09-07-2005, 03:23 PM

Big blocks are going to have a water pump by-pass hose that goes from the intake to the pump, right on the front of the engine. It looks like a piece of heater hose that is L-shaped. A small block does not have this by-pass hose (at least none of the 1000s I've seen have had one.). A factory (short water pump) BB will also have a remote mounted power steering reservoir on the left fender. A SB pump has the reservoir incorporated on the pump.

Longhorn Man · 09-07-2005, 05:33 PM

no 400 small blcoks onless it says C.O.P.O. on the option sheet, then it MIGHT have a 400 small block. There was never a 400 small block option.
Like I said, in 70, the option sheet said 396, the fender said 400 and the engine was a 402. They DID low ball the C.I.D. ...for insurance reasons is the common stated reason.

09-06-2005, 06:11 PM	#1
gmcbigbl Registered User Join Date: Sep 2005 Location: Wisconsin Posts: 67	400 motor AKA 402 BB The GMC build sheet reads "400 cu. in. V-8 engine" Truck has a turbo hydra-matic tranny. Is this a 400 sb or 402 bb

09-06-2005, 06:16 PM	#2
panhandler62 Java Mechanic Join Date: Jun 2005 Location: Martinsburg, WV Posts: 6,763	If you post a pic twenty people will rush to answer you. lol The fast way to tell is to look at the exhaust. Small blocks have the center ports siameezed together where the big block exhaust ports are evenly spaced. __________________ 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 ....

09-06-2005, 10:39 PM	#3
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	If you are talking about a '67 - '72 truck it is a 402 big block. The 400 small block was never used in these trucks. __________________ Tim

09-07-2005, 07:37 AM	#7
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	I wundered if it was a town in Kansas or something. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

09-07-2005, 12:27 PM	#8
69Goody Registered User Join Date: Jul 2004 Location: Southern Tip of OHIO 45680 Posts: 49	My 69 GMC camper unit has a Small Block 400 in it...but it had a 350 originally and says so on the build sheet. The 400 small blocks did not start production until 1970. As far as whether they were used in production or not...I'm not sure. I would not put it past as an option or custom request. I believe my 400 small block came as an upgrade early in its life. Possibly to get a little more power under warranty without any other mods needed. One way to tell would be to look at the exhaust ports on the heads. If they are evenly spaced, then you are looking at a big block motor. 0_0_0_0 If the two center exhuast ports are right next to each other 0_00_0 then you have a small block. The sure fire way to tell is look for the block ID code imprinted on it. I would tend to believe that if it were a big block 402, it would have said 402 on the build sheet and not 400. No one would under state the Cubic Inches. __________________ Only the Mediocre are always at their best... '69 GMC LWB 406, TH400, 3.73 Posi' Things I've learned from my truck...If I was an automaker, my vehicles would be overpriced, run rough, and get 5MPG.

09-06-2005, 11:34 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Welcome to the board from Central Ohio. I am pretty sure you are first member from China....I'll bet parts are a real pain huh? As stated, the 400 that was listed on these trucks would be a 402 big block, the 400 was never installed factory. In many of the '70 trucks it was still listed as a 396 on the option sheet, badged as a 400, yet was actually a 402.

09-07-2005, 04:02 AM	#6
gmcbigbl Registered User Join Date: Sep 2005 Location: Wisconsin Posts: 67	It is a 1970 GMC Sierra Grande with the original engine. The entire truck is original with only 68000. It has the CST interior with bucket seats and console The color is yellow(ocre)? I'm gonna e-bay it soon and wanted to make sure of engine cubes. If someone tells me how, I will post a few pics. BTW It's not really China, just joshing

09-07-2005, 12:43 PM	#9
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	4 bolts for each valve cover = small block 7 bolts for each valve cover = big block __________________ I'm on the Instagram- @Gearhead_Kevin

09-07-2005, 12:53 PM	#10
panhandler62 Java Mechanic Join Date: Jun 2005 Location: Martinsburg, WV Posts: 6,763	It's funny but, other than the simple tricks of counting bolts and looking at the exhaust ports that 69Goody, TX Firefighter and I put forth, I am having a hard time thinking of how to tell someone how to spot a rat, even though I know for a fact that I would know instantly if I was looking at one when the hood came up! It's no wonder we have so many unsolved crimes -- people are lousey witneses! LOL __________________ 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 ....

09-07-2005, 02:42 PM	#11
COBRO Active Member Join Date: Jan 2005 Location: RDM,Oregon Posts: 285	My 72 c-20 came with the 402 BB and its listed as a 400 on the glove box door and fender emblem so seems you have a BB - just more of the GM confusion. HTH::::CB

09-07-2005, 02:50 PM	#12
mplex2000 Registered User Join Date: Jul 2005 Location: DFW Posts: 463	Hehe...simple panhandler...big blocks are...big :P It is kind of funny that you (me) can look at one and see that it's a BB or SB, but how would you tell a newcomer to tell?

09-07-2005, 03:04 PM	#13
edmonton72 Nothings as cool as my 72 Join Date: May 2005 Location: Edmonton, AB, Kanuckastan Posts: 181	Are you guys sure that these trucks never came with the 400 sb? It says 400 cu. in v-8 engine on the potion list on my 72 and it has 350 in it now. My dad and i always argue about if it came with a 400 or a 402. Is there any other way to figure out if it came with a 402? __________________ 1972 C10 Longbox In the middle of body off restoration Rebuilt 355, turbo 400, 3.42 12-bolt Rolling chassis finally done and cab mounted. Now onto sanding, bondo and more sanding.

09-07-2005, 03:11 PM	#14
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	They absolutely did not put 400 small blocks in these trucks. my bet is someone blew up the 402 that was originally in your truck was blown up or swapped to a car and replaced with a much cheaper and easier to find 350 __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

09-07-2005, 03:23 PM	#16
GasHog396 Registered User Join Date: Jun 2003 Location: Ponder, TX Posts: 33	Big blocks are going to have a water pump by-pass hose that goes from the intake to the pump, right on the front of the engine. It looks like a piece of heater hose that is L-shaped. A small block does not have this by-pass hose (at least none of the 1000s I've seen have had one.). A factory (short water pump) BB will also have a remote mounted power steering reservoir on the left fender. A SB pump has the reservoir incorporated on the pump. __________________ '67 1/2 Ton Short Bed / 396 cid / AC w-R134a / 5 Lug Leaf spring rear axel / 5 Lug Frt Disk Brake Conversion '97 Trans Am - Black / LT-1 / K&N FIPK Cold Air Kit / Hooker Cat-Back Exhaust / 160 Thermostat '02 Buick Regal GS / Bone Stock

09-07-2005, 05:33 PM	#17
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	no 400 small blcoks onless it says C.O.P.O. on the option sheet, then it MIGHT have a 400 small block. There was never a 400 small block option. Like I said, in 70, the option sheet said 396, the fender said 400 and the engine was a 402. They DID low ball the C.I.D. ...for insurance reasons is the common stated reason.



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