Big block 400 in 70 GMC Sierra Grande? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rzrback · 12-08-2009, 11:23 PM

Happy tuesday pm, Im new to the site and had a question on my truck. Everything ive seen shows factory engines were 396 or 402. My GMC has a factory big block... SPID shows it as a 400 cu in? Could this be a mistake? or a special order of some kind? included some pics. thx in advance for any input

Longhorn Man · 12-08-2009, 11:30 PM

very nice lookin truck there
That would be the 402 big block
GM was stupid the way they did this back then. They built a 402, and called it a 396, a 400, or a 402... depending on what body it was in.
GM did a lot of cool stuff, but they did some retarded crap too.

rzrback · 12-08-2009, 11:36 PM

Hey thanks for the quick response! That makes sense. Well sorta makes sense ha. I didnt think they made a true 400. Thx again for clarifying

*2tons of fun* · 12-09-2009, 12:18 AM

they didnt make a true 400 big block, there is a 400 sbc.

its kind of like the 52 or 56" rear springs. any 73-87/91 could have one or the other, no rhyme or reason and no differentiating between the 2.

**too much stuff** · 12-09-2009, 01:06 AM

Nicely optioned truck you have there!!! It is indeed a 396/402 big block. Just to clarify, the 400 small block wasn't available in the 67-72s...

airdale94 · 12-11-2009, 02:16 AM

Quote:

Originally Posted by Longhorn Man

GM was stupid the way they did this back then. GM did a lot of cool stuff, but they did some retarded crap too.

They're all stupid now! But trust me Ford is the worst. Heated PCV, and a 5.4L V-8 motorcycle engine. Overhead cams are great but when you you build them to motorcycle specs. (weight), they just ain't stong enough, for me. Maybe they should have put a 427 FE in it. Or let International build it for them.

Sorry for the rant.

jackyl9999 · 12-11-2009, 04:02 AM

Welcome from paragould. Nice truck there. Always love to see a nice GMC. Looks like mine.

Longhorn Man · 12-11-2009, 04:58 PM

Quote:

Originally Posted by airdale94

They're all stupid now! But trust me Ford is the worst. Heated PCV, and a 5.4L V-8 motorcycle engine. Overhead cams are great but when you you build them to motorcycle specs. (weight), they just ain't stong enough, for me. Maybe they should have put a 427 FE in it. Or let International build it for them.

Sorry for the rant.

no argument here.
GM pretty much sucks these days. I've been saying that for years on here.

rzrback · 12-19-2009, 01:04 AM

Scared me there for a min Dr Evil....confirmed a 70 by the vin. Heres a few more pics.

**special-K** · 12-09-2009, 08:59 AM

That is one fine Sierra Grande you have there.

Since your`s is a`70,that`s definitely a 402 you have there.last 396 was`69.The called it a 400 to round it off.A 350 id actually a 347.?,I believe.What`s odd to me is I`ve had a few 70/71 402 trucks and they all still said 396 on the SPID.They were all Chevys.Maybe only GMC got it right.

71tahoe · 12-09-2009, 11:29 AM

Welcome from Jonesboro.

Except for the 400 designation for the big block, the cubic inch displacement number is pretty accurate. 350, 4 inch bore, 3.48 stroke: 2 x 2 x 3.141592 x 3.48 x 8 = 349.8477579

dan42 · 12-09-2009, 11:41 AM

Quote:

Originally Posted by special-K

That is one fine Sierra Grande you have there.

Since your`s is a`70,that`s definitely a 402 you have there.last 396 was`69.The called it a 400 to round it off.A 350 id actually a 347.?,I believe.What`s odd to me is I`ve had a few 70/71 402 trucks and they all still said 396 on the SPID.They were all Chevys.Maybe only GMC got it right.

To re-inforce his point, here's the SPID on my '70 Longhorn, which has the original 402 in it:

Dr. Evil · 12-10-2009, 09:12 PM

Are you sure it is a 70 ?
My Spid uses 3 digit codes. Yours has 6 like some of the Chevys.
Just a question, GM has done strange things in the past.

Zoomin · 12-10-2009, 11:14 PM

Quote:

Originally Posted by Dr. Evil

Are you sure it is a 70 ?
My Spid uses 3 digit codes. Yours has 6 like some of the Chevys.
Just a question, GM has done strange things in the past.

Different assembly plants - each with their own version of the database.

big mike71 · 12-10-2009, 09:38 PM

Nice truck, Let's see some more pics

hayhauler71 · 12-10-2009, 11:15 PM

Quote:

Originally Posted by big mike71

Nice truck, Let's see some more pics

Please let us see more pics.

**clay68c10** · 12-19-2009, 01:16 AM

Man, that thing is clean. Love that blue.

Dr. Evil · 12-19-2009, 09:51 AM

I apologize for the scare, I am by no way an expert , As a matter of fact , The more I think I know , the less I actually do. I will chalk this one up to another learning experience...

Sweet Truck , I have her sister Josephine in Gold.

OhOneWS6 · 12-19-2009, 11:09 AM

Nice truck. If you compare the motor option codes on dan42 & rzrback's SPID you will notice both contain "L47" Not sure why I pointed that out but I did. LOL

Longhorn Man · 12-19-2009, 12:52 PM

your 70 has a 71/72 grill.

rzrback · 12-20-2009, 10:43 PM

Good eye Longhorn Man! yep, still have the factory grill without the black centerline....At some point might have it redone...but not a priority.

**425HP409** · 12-21-2009, 01:59 PM

In 1970 due to tightened emission laws, Chevrolet bored the 396 out .030 inches to make it a 402. There was no actual 396 in 1970 and later. They also changed to a low riser intake manifold. The same engine in a Chevelle was still called a 396 for sales. The SS396 had made a name for itself and they didn't want to mess with it by calling it a SS402.
The same cubic inch displacement engine was put in the trucks but named a 400 for some reason....

*2tons of fun* · 12-25-2009, 04:33 AM

Quote:

Originally Posted by 425HP409

In 1970 due to tightened emission laws, Chevrolet bored the 396 out .030 inches to make it a 402. There was no actual 396 in 1970 and later. They also changed to a low riser intake manifold. The same engine in a Chevelle was still called a 396 for sales. The SS396 had made a name for itself and they didn't want to mess with it by calling it a SS402.
The same cubic inch displacement engine was put in the trucks but named a 400 for some reason....

thats funny, because i just pulled a virgin 396 out of my 70.

ripdog28 · 12-25-2009, 10:45 AM

2Tons, did you measure the bore? Is it possible that it was a replacement engine which someone else put in it?

**425HP409** · 12-29-2009, 01:09 PM

Quote:

Originally Posted by 2tons of fun

thats funny, because i just pulled a virgin 396 out of my 70.

I did some further research and found out through Motors Repair Manual that the 396 was still used in the trucks in 1970, whereas the cars used the 402. The 402 was used in the trucks in 1971 and 1972. The trucks used a 454 starting in 1973.
The 396 had a bore of 4.094" and stroke of 3.76". The 402 had a bore of 4.126" and stroke of 3.76" I hope this helps to eliminate the confusion.

12-08-2009, 11:23 PM	#1
rzrback Registered User Join Date: Nov 2009 Location: Rogers AR Posts: 12	Big block 400 in 70 GMC Sierra Grande? Happy tuesday pm, Im new to the site and had a question on my truck. Everything ive seen shows factory engines were 396 or 402. My GMC has a factory big block... SPID shows it as a 400 cu in? Could this be a mistake? or a special order of some kind? included some pics. thx in advance for any input Attached Images __________________ RZRBACK 1970 GMC Sierra Grande

12-08-2009, 11:30 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Big block 400 in 70 GMC Sierra Grande? very nice lookin truck there That would be the 402 big block GM was stupid the way they did this back then. They built a 402, and called it a 396, a 400, or a 402... depending on what body it was in. GM did a lot of cool stuff, but they did some retarded crap too.

12-08-2009, 11:36 PM	#3
rzrback Registered User Join Date: Nov 2009 Location: Rogers AR Posts: 12	Re: Big block 400 in 70 GMC Sierra Grande? Hey thanks for the quick response! That makes sense. Well sorta makes sense ha. I didnt think they made a true 400. Thx again for clarifying __________________ RZRBACK 1970 GMC Sierra Grande

12-09-2009, 12:18 AM	#4
2tons of fun Account Suspended Join Date: Jan 2009 Location: galt ca, Posts: 749	Re: Big block 400 in 70 GMC Sierra Grande? they didnt make a true 400 big block, there is a 400 sbc. its kind of like the 52 or 56" rear springs. any 73-87/91 could have one or the other, no rhyme or reason and no differentiating between the 2.

12-09-2009, 01:06 AM	#5
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,713	Re: Big block 400 in 70 GMC Sierra Grande? Nicely optioned truck you have there!!! It is indeed a 396/402 big block. Just to clarify, the 400 small block wasn't available in the 67-72s... __________________ 67 gmc custom lwb dakota truck. Sold...And bought back 69 swb 4x4 project (in progress) 70 c-10 lwb texas truck 70 4x4/BB/bkts/posi/tach(retired) 70 swb (wifes) 70 jimmy camper 71 K-5 factory 2wd 71 cheyenne 4x4/tach/posi/ plow rig 71 Cheyenne20 BB, buckets, tach, tilt, 4 speed 72 jimmy CST wyoming rig 72 jimmy Colorado rig 72 lifted texas 4x4 3/4 ton burb 65 fury conv. 383/auto 65 chrysler 300 "L" 413 auto

12-11-2009, 04:02 AM	#7
jackyl9999 Registered User Join Date: Feb 2003 Location: Paragould, Ar Posts: 571	Re: Big block 400 in 70 GMC Sierra Grande? Welcome from paragould. Nice truck there. Always love to see a nice GMC. Looks like mine. __________________ 1970 Gmc Grande Sierra Swb 2wd LSX (LQ4/4L80e) 1990 K1500 Daily

12-19-2009, 01:04 AM	#9
rzrback Registered User Join Date: Nov 2009 Location: Rogers AR Posts: 12	Re: Big block 400 in 70 GMC Sierra Grande? Scared me there for a min Dr Evil....confirmed a 70 by the vin. Heres a few more pics. Attached Images __________________ RZRBACK 1970 GMC Sierra Grande

12-09-2009, 08:59 AM	#10
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,861	Re: Big block 400 in 70 GMC Sierra Grande? That is one fine Sierra Grande you have there. Since your`s is a`70,that`s definitely a 402 you have there.last 396 was`69.The called it a 400 to round it off.A 350 id actually a 347.?,I believe.What`s odd to me is I`ve had a few 70/71 402 trucks and they all still said 396 on the SPID.They were all Chevys.Maybe only GMC got it right. __________________ "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 ~

12-09-2009, 11:29 AM	#11
71tahoe Registered User Join Date: May 2006 Location: Jonesboro, AR Posts: 916	Re: Big block 400 in 70 GMC Sierra Grande? Welcome from Jonesboro. Except for the 400 designation for the big block, the cubic inch displacement number is pretty accurate. 350, 4 inch bore, 3.48 stroke: 2 x 2 x 3.141592 x 3.48 x 8 = 349.8477579

12-10-2009, 09:12 PM	#13
Dr. Evil Registered User Join Date: Nov 2008 Location: Bernardsville, NJ Posts: 164	Re: Big block 400 in 70 GMC Sierra Grande? Are you sure it is a 70 ? My Spid uses 3 digit codes. Yours has 6 like some of the Chevys. Just a question, GM has done strange things in the past.

12-10-2009, 09:38 PM	#15
big mike71 Registered User Join Date: Mar 2009 Location: independence mo Posts: 2,111	Re: Big block 400 in 70 GMC Sierra Grande? Nice truck, Let's see some more pics __________________ I'm not as good as I once was, But I'm as good once as I ever was.

12-19-2009, 01:16 AM	#17
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,934	Re: Big block 400 in 70 GMC Sierra Grande? Man, that thing is clean. Love that blue. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

12-19-2009, 09:51 AM	#18
Dr. Evil Registered User Join Date: Nov 2008 Location: Bernardsville, NJ Posts: 164	Re: Big block 400 in 70 GMC Sierra Grande? I apologize for the scare, I am by no way an expert , As a matter of fact , The more I think I know , the less I actually do. I will chalk this one up to another learning experience... Sweet Truck , I have her sister Josephine in Gold.

12-19-2009, 11:09 AM	#19
OhOneWS6 Registered User Join Date: Dec 2009 Location: DFW, TX Posts: 764	Re: Big block 400 in 70 GMC Sierra Grande? Nice truck. If you compare the motor option codes on dan42 & rzrback's SPID you will notice both contain "L47" Not sure why I pointed that out but I did. LOL __________________ 72 Cheyenne Super 1/2 LWB White/Dark Yellow 07 Avalanche 2LT 74 Sleek Craft Rebel Jet Boat W/Pontiac 400 Last edited by OhOneWS6; 12-19-2009 at 11:10 AM.

12-19-2009, 12:52 PM	#20
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Big block 400 in 70 GMC Sierra Grande? your 70 has a 71/72 grill.



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12-20-2009, 10:43 PM	#21
rzrback Registered User Join Date: Nov 2009 Location: Rogers AR Posts: 12	Re: Big block 400 in 70 GMC Sierra Grande? Good eye Longhorn Man! yep, still have the factory grill without the black centerline....At some point might have it redone...but not a priority. __________________ RZRBACK 1970 GMC Sierra Grande

12-21-2009, 01:59 PM	#22
425HP409 425hp409 Join Date: Oct 2008 Location: Prosper Texas Posts: 841	Re: Big block 400 in 70 GMC Sierra Grande? In 1970 due to tightened emission laws, Chevrolet bored the 396 out .030 inches to make it a 402. There was no actual 396 in 1970 and later. They also changed to a low riser intake manifold. The same engine in a Chevelle was still called a 396 for sales. The SS396 had made a name for itself and they didn't want to mess with it by calling it a SS402. The same cubic inch displacement engine was put in the trucks but named a 400 for some reason.... __________________ Charles 68 SWB, Dad bought new, now 396 & factory ac 64 Impala SS, 409 425HP, 4 speed AC 64 Bel Air Wagon, 400 Small Block 57 Bel Air all original 283 w/Factory Air 77 GMC Sprint, 454/425HP 67 Olds 442, all original 90 ZR1 Corvette

12-25-2009, 10:45 AM	#24
ripdog28 Registered User Join Date: Apr 2008 Location: Imperial Beach, CA Posts: 1,040	Re: Big block 400 in 70 GMC Sierra Grande? 2Tons, did you measure the bore? Is it possible that it was a replacement engine which someone else put in it? __________________ 69 c-10 BBC 462ci, forged crank, H-beam rods, 10.5-1 KB forged pistons, Dart Iron Eagle 308cc, Straub Cam, Comp Cams chrome moly full rollers, Weiand Team G, Prosystems 950, TH400/3500 Dalenzie stall, Currie 9+ Detroit Locker w/31spline axles.3.5/6in drop. My Build. Last edited by ripdog28; 12-25-2009 at 10:47 AM.

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