Need help id'ing a bbc - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ofnaman · 12-17-2007, 07:59 PM

I am in the process of rebuilding my big block and I cannot seem to find a definate answer on if it is a 396 or 402. I do not have my measuring equiptment with me and I was planning on picking up the re ring kit tommorro. The casting # on the block is 3969854. All of the info I can find on it say's it's either a 396 or a 402. It is a '70 and the tag in the glove box say's it's a 400. I was under the assumption its a 402, but now I'm unsure. Also if it helps the head casting # is 3975950. Also the rod bearings are from '69. Thanks in advance.

72armyswbtruck · 12-17-2007, 10:27 PM

Should be a 396, if I remember correctly the 396, 400 and 402 were all a 396 just listed as different ones because of insurance and corporate politics
Trucks vs passenger cars.

JimKshortstep4x4 · 12-18-2007, 01:03 AM

The block casting number does not give you the size of the engine as it was used for different applications.

The suffix code on the right hand front of the block will give you more information as to the application of the engine.

There is a possibility that the engine has been bored in the past, so I would suggest measuring the bore to make sure.

Jim

mnunn454 · 12-18-2007, 02:57 AM

Buy both sets of rings and return the set you don't need?

Yullose · 12-18-2007, 03:04 AM

Go buy a set of digital calipers at a local auto parts store and measure the bore. There is NO cheaper way to know for sure.

I think you can even buy them at Sears in the tools section.

If it was a motor that came out of a brand new car, you could have a pretty good chance of "guessing" the bore was still stock.

With a 30yr old block, anything goes. It could be std, .010, .020, .030, etc...

Get the correct rings the first time and save the hassle of returning parts.

Digital calipers are real handy to have in the toolbox.
You'd be amazed how often you find a need for them once you own a set.

**70cst** · 12-18-2007, 03:09 AM

Quote:

Originally Posted by 72armyswbtruck

Should be a 396, if I remember correctly the 396, 400 and 402 were all a 396 just listed as different ones because of insurance and corporate politics
Trucks vs passenger cars.

I think the 402 was actually bored out differrently than the 396? I think? So the outside of the engines were the same but the guts were differrent.

Yullose · 12-18-2007, 03:52 AM

FWIW...

The stock bore on a 396 was 4.094"
The bore size on a 402 was 4.125"

427's & 454's shared the same 4.250" bore.

The 396 and 402 are both big blocks. The 400 emblems were used for both the 400 small block AND the 402 big block. There never was an emblem with a 402 on it. If you see an old Caprice with 400 emblems on the fender, it could have either motor in it.

RustyParts · 12-18-2007, 03:58 AM

Engine ID from MorTec website.
3969854....396.......1969......2 or 4 bolt.

70cstjr · 12-18-2007, 04:33 AM

its a 402 they stopped making the 396 in 69 and in 70 they started making the 402 calling it the 400. at least your glovebox calls it a 400 ours calls it a 396 but has the same option code for the 400. so if that engine is original its the 400 (402)

bglad420 · 12-18-2007, 05:46 AM

GMC was 402
Chevy was 396

Yullose · 12-18-2007, 06:00 AM

Quote:

Originally Posted by bglad420

GMC was 402
Chevy was 396

I'll remember that, next time I see a GMC Camaro, GMC Chevelle or a GMC Caprice...

Edit to add... I don't think there was a firm line ever drawn as to when/where the 396 to 402 changeover happened. It was sometime in 1970.

I've seen 1970 Camaros and Chevelles with 396's in them...with the correct 396 emblems and all. I've also seen 402's in other passenger cars/trucks of the same year. One thing IS for sure... in 1971, it was only the 402 (or 454) going between the fenders. The 454 started in 1970.
I think the reason for confusion was... GM started running out of production 396's in 1970 and substituted them with the 402 near the end of the 1970 production year. That's why all the 71's then had the 402.

It's funny that this debate still continues today... and now online. It use to be something we bickered about at the dragstrip or in the garage before the internet came along.

It still doesn't change the fact that the original poster needs to accurately measure the cylinder bores so he can get the correct set of rings.

Yullose · 12-18-2007, 06:21 AM

bglad420

I see you are in Bellingham.

Ever hear of Meridian Performance up there ? I think the guys name was "Tye" or something ?

ofnaman · 12-18-2007, 07:41 AM

I was aware of the changeover in '69 and '70, and that's were my problem lies. The block is original to the truck, and has not been bored (factory marks on the pistons and block are still there). The biggest problem I have calling it a 402 is the fact that it has '69 rod bearings in it. I am aware that they made 402's in '69 for these trucks, but they also made some '69 396's. I have all of the measuring tools, but they are at work and I cannot get to them until tommorro. I was hoping to do a quick ring/bearing replace, so I could get my only driver running quickly. I am not going to bore it at this time (that will come after I get a house and garage, and another daily driver). There is virtually no wear on the bearings at all. The cam lifters failed and the truck of course started running very bad. I originally was going to just replace the cam and gaskets, but after thinking about it I decided to do the whole thing since it only takes about 30 minutes to pull the engine.

mnunn454 · 12-18-2007, 09:25 AM

Quote:

Originally Posted by Yullose

FWIW...

The stock bore on a 396 was 4.094"
The bore size on a 402 was 4.125"

The .029" difference is just under 1/32nd of an inch, and 4.125 = 4-1/8" exactly.

So, if the heads are off and if you have a machinist's 6" ruler with 1/64" graduations, you should be able to use it to determine the diameter. Granted, the caliper idea is better, but in a pinch, at least with the machinist's rule you could tell which bore it "isn't".

Olden Days · 12-18-2007, 10:56 AM

copied and pasted from Mortec
3969854....396.......69......2 or 4 bolt
3969854....402.......70-72...2 or 4 bolt

head 3975950....68-70...oval...OPEN...396, 402 Truck, 366T, 427T

It shows those casting as being either 396 or 402 .If you are possitive the motor has not been changed you could guess 402 but It would be wise to measure.
Here is the link, go look it up. http://www.mortec.com/bbc.htm

Walts_restoration · 12-18-2007, 11:02 AM

werent the 402's the factory rebored 396's that were bored incorrectly, and when they bored 30 it straightened them out? am i right cause thats what i heard

Olden Days · 12-18-2007, 11:08 AM

Quote:

Originally Posted by Walts_restoration

werent the 402's the factory rebored 396's that were bored incorrectly, and when they bored 30 it straightened them out? am i right cause thats what i heard

No, starting in 70 they went to 402 and discontinued the 396 bore. Nothing to do with straighting out bad 396's

**70cst** · 12-18-2007, 11:22 AM

Quote:

Originally Posted by bglad420

GMC was 402
Chevy was 396

Geeeeeeeeeeeeeeeeeeee...my factory 402 BB in my Chevy 70cst is a GMC motor?

ofnaman · 12-18-2007, 06:51 PM

The front tag # is to323tbg. Does this help? Thanks

ofnaman · 12-19-2007, 06:44 AM

Anyone know how to decipher the front engine tag code?

Quote:

Originally Posted by ofnaman

The front tag # is to323tbg. Does this help? Thanks

webfoot · 12-19-2007, 07:07 AM

SS396 was a branding/marketing deal, no point in changing it to an SS402 for 6 cubes when you already had years of getting the "SS396" nameplate going.

You did have the "Malibu 400" in 1970, which was a non-SS Chevelle with a 402 BB in it.

jhow66 · 12-19-2007, 08:43 AM

TBG=1970, 402, 310hp, truck, L-47, 10, 20, 30 series

70rs/ss · 12-19-2007, 08:47 AM

TBG 1970 Truck 402 310 400 L-47 10, 20, 30 The 402 is just a 30 over 396, whatever you wanna call it or say where it came from they are 30 over 396. I heard they were 396's that didn't clean up from the final hone and they were set aside, then when all the good ones were done (396) they ran a 30 over bore and made the 402's, ultimately it doesn't matter it is still a 396 block with a standard or 30 or 40 or 60 over bore.

12-17-2007, 07:59 PM	#1
ofnaman Registered User Join Date: Aug 2007 Location: reno Posts: 397	Need help id'ing a bbc I am in the process of rebuilding my big block and I cannot seem to find a definate answer on if it is a 396 or 402. I do not have my measuring equiptment with me and I was planning on picking up the re ring kit tommorro. The casting # on the block is 3969854. All of the info I can find on it say's it's either a 396 or a 402. It is a '70 and the tag in the glove box say's it's a 400. I was under the assumption its a 402, but now I'm unsure. Also if it helps the head casting # is 3975950. Also the rod bearings are from '69. Thanks in advance. __________________ A sweet 2000 Deville.....

12-17-2007, 10:27 PM	#2
72armyswbtruck Registered User Join Date: Feb 2004 Location: Idaho Posts: 4,034	Re: Need help id'ing a bbc Should be a 396, if I remember correctly the 396, 400 and 402 were all a 396 just listed as different ones because of insurance and corporate politics Trucks vs passenger cars. __________________ "Remember, They can Kill You, but they can't eat You, That's against the law!!!!!!!!!"

12-18-2007, 01:03 AM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Need help id'ing a bbc The block casting number does not give you the size of the engine as it was used for different applications. The suffix code on the right hand front of the block will give you more information as to the application of the engine. There is a possibility that the engine has been bored in the past, so I would suggest measuring the bore to make sure. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

12-18-2007, 02:57 AM	#4
mnunn454 Registered User Join Date: Dec 2006 Location: Rhode Island Posts: 602	Re: Need help id'ing a bbc Buy both sets of rings and return the set you don't need? __________________ 69 C-10 SWB Fleetside 454/TH400 (For Sale) http://67-72chevytrucks.com/vboard/c...ct=1299&cat=12 70 El Camino 454 TH700 29 Model A 4-DR Sedan Deluxe

12-18-2007, 03:04 AM	#5
Yullose Registered User Join Date: Dec 2007 Location: Mooresville, NC Posts: 76	Re: Need help id'ing a bbc Go buy a set of digital calipers at a local auto parts store and measure the bore. There is NO cheaper way to know for sure. I think you can even buy them at Sears in the tools section. If it was a motor that came out of a brand new car, you could have a pretty good chance of "guessing" the bore was still stock. With a 30yr old block, anything goes. It could be std, .010, .020, .030, etc... Get the correct rings the first time and save the hassle of returning parts. Digital calipers are real handy to have in the toolbox. You'd be amazed how often you find a need for them once you own a set. Last edited by Yullose; 12-18-2007 at 03:05 AM.

12-18-2007, 03:52 AM	#7
Yullose Registered User Join Date: Dec 2007 Location: Mooresville, NC Posts: 76	Re: Need help id'ing a bbc FWIW... The stock bore on a 396 was 4.094" The bore size on a 402 was 4.125" 427's & 454's shared the same 4.250" bore. The 396 and 402 are both big blocks. The 400 emblems were used for both the 400 small block AND the 402 big block. There never was an emblem with a 402 on it. If you see an old Caprice with 400 emblems on the fender, it could have either motor in it. Last edited by Yullose; 12-18-2007 at 03:56 AM.

12-18-2007, 03:58 AM	#8
RustyParts Registered User Join Date: May 2006 Location: Wyman, Kentucky Posts: 403	Re: Need help id'ing a bbc Engine ID from MorTec website. 3969854....396.......1969......2 or 4 bolt. __________________ 1972 GMC Jimmy, 4WD, 454 CI, 350 Turbo, 4" lift, 35" tires The math teacher said my son "Bubba" could be a mathmatical genius. cause he's got 13 fingers!

12-18-2007, 04:33 AM	#9
70cstjr Registered User Join Date: Sep 2007 Location: laura, ohio Posts: 935	Re: Need help id'ing a bbc its a 402 they stopped making the 396 in 69 and in 70 they started making the 402 calling it the 400. at least your glovebox calls it a 400 ours calls it a 396 but has the same option code for the 400. so if that engine is original its the 400 (402) __________________ PROJECT CIRCUIT RIDER

12-18-2007, 05:46 AM	#10
bglad420 Registered User Join Date: Dec 2005 Location: Bellingham, WA Posts: 167	Re: Need help id'ing a bbc GMC was 402 Chevy was 396 __________________ 70 GMC LWB Fleetside, 402BB, TH400 90K original only cost $50.

12-18-2007, 06:21 AM	#12
Yullose Registered User Join Date: Dec 2007 Location: Mooresville, NC Posts: 76	Re: Need help id'ing a bbc bglad420 I see you are in Bellingham. Ever hear of Meridian Performance up there ? I think the guys name was "Tye" or something ? Last edited by Yullose; 12-18-2007 at 06:22 AM.

12-18-2007, 07:41 AM	#13
ofnaman Registered User Join Date: Aug 2007 Location: reno Posts: 397	Re: Need help id'ing a bbc I was aware of the changeover in '69 and '70, and that's were my problem lies. The block is original to the truck, and has not been bored (factory marks on the pistons and block are still there). The biggest problem I have calling it a 402 is the fact that it has '69 rod bearings in it. I am aware that they made 402's in '69 for these trucks, but they also made some '69 396's. I have all of the measuring tools, but they are at work and I cannot get to them until tommorro. I was hoping to do a quick ring/bearing replace, so I could get my only driver running quickly. I am not going to bore it at this time (that will come after I get a house and garage, and another daily driver). There is virtually no wear on the bearings at all. The cam lifters failed and the truck of course started running very bad. I originally was going to just replace the cam and gaskets, but after thinking about it I decided to do the whole thing since it only takes about 30 minutes to pull the engine. __________________ A sweet 2000 Deville..... Last edited by ofnaman; 12-18-2007 at 07:41 AM. Reason: screwed up

12-18-2007, 10:56 AM	#15
Olden Days Living In The Past Join Date: Nov 2003 Location: Rockies Posts: 709	Re: Need help id'ing a bbc copied and pasted from Mortec 3969854....396.......69......2 or 4 bolt 3969854....402.......70-72...2 or 4 bolt head 3975950....68-70...oval...OPEN...396, 402 Truck, 366T, 427T It shows those casting as being either 396 or 402 .If you are possitive the motor has not been changed you could guess 402 but It would be wise to measure. Here is the link, go look it up. http://www.mortec.com/bbc.htm Last edited by Olden Days; 12-18-2007 at 11:06 AM.

12-18-2007, 11:02 AM	#16
Walts_restoration Real Projects never die Join Date: Jan 2007 Location: Lawrence, kansas Posts: 1,508	Re: Need help id'ing a bbc werent the 402's the factory rebored 396's that were bored incorrectly, and when they bored 30 it straightened them out? am i right cause thats what i heard __________________ Ill put it this way, ive got a few lawn ornaments My name tag says Ryan KansasTwister On other forums

12-18-2007, 06:51 PM	#19
ofnaman Registered User Join Date: Aug 2007 Location: reno Posts: 397	Re: Need help id'ing a bbc The front tag # is to323tbg. Does this help? Thanks __________________ A sweet 2000 Deville.....

12-19-2007, 07:07 AM	#21
webfoot Registered User Join Date: Nov 2007 Location: Hermiston, OR Posts: 947	Re: Need help id'ing a bbc SS396 was a branding/marketing deal, no point in changing it to an SS402 for 6 cubes when you already had years of getting the "SS396" nameplate going. You did have the "Malibu 400" in 1970, which was a non-SS Chevelle with a 402 BB in it. __________________ *Running in place gets you nowhere fast.* -me 1968 GTO 4-spd covnvertible 1970 K-20 4-speed, factory AC.



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12-19-2007, 08:43 AM	#22
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: Need help id'ing a bbc TBG=1970, 402, 310hp, truck, L-47, 10, 20, 30 series __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

12-19-2007, 08:47 AM	#23
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: Need help id'ing a bbc TBG 1970 Truck 402 310 400 L-47 10, 20, 30 The 402 is just a 30 over 396, whatever you wanna call it or say where it came from they are 30 over 396. I heard they were 396's that didn't clean up from the final hone and they were set aside, then when all the good ones were done (396) they ran a 30 over bore and made the 402's, ultimately it doesn't matter it is still a 396 block with a standard or 30 or 40 or 60 over bore.

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