396 or 402 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70 longbed · 02-17-2004, 12:45 AM

I picked up a block casting # 3969854 and most of the parts, i.e. pistons (2 sets), 2 cast cranks, heads, casting # 3935401, valve covers, oil pan , the pulleys and some other stuff.

The block # says 69 396 2 or 4 bolt main, or 70-72 402, 2 or 4 bolt main. I can see that it is 2 bolt, but haow can I check if it is 396 or 402, mic the cylinders? And if that is it, what numbers am I looking for?

dinnut · 02-17-2004, 01:06 AM

A 396 is a 402 from what ive heard in the past. 402 is the actual size but was called a 396 pre 1969.

anybody feel free to correct me if im wrong.

rangernsk · 02-17-2004, 01:07 AM

A 402 is a 396 bored .30 over by the factory. Hope this helps and good luck with your project.

smonty · 02-17-2004, 01:30 AM

The block you have is used for 396 and 402's and the heads are 68-76...oval...OPEN...427T from Mortec web site. Which means the heads are from a 427 truck motor. Hope this helps you.

Ernie

JimKshortstep4x4 · 02-17-2004, 08:52 AM

If the numbers that are stamped into the pad are readable, you can look up the suffix code and find out a lot more information on the engine.

Jim

Number98 · 02-17-2004, 10:18 AM

I was told that the 396's used in our trucks were accidently punched .030 by GM and this makes them 402's. Which would make them kinda like one in the same. Just what I was told.

Jason

68c10owner · 02-17-2004, 12:34 PM

g.m. started boring them .030 in late 1969 but still called them the 396 in cars and called them 400 in cetain year trucks, can`t remember the year. the early blocks were a 396 and if i remember right, the bore was 4.095 or something around that. from my understanding, g.m. bored them .030 to reduce emissions.

super72bb · 02-17-2004, 12:58 PM

The reason Gm changed the 396 to a 402 by boring it out was...

As you know Gm also had a small block 400 in that era. General Motors was not fond of the idea of one of their small blocks out cubing one of their big blocks. So they punched the 396 to a 402 cubic inch making it out cube the small block 400.

I don't even recall where I got this info exactly. I think it was on a show about Chevelle's I saw one weekend on my classic car or something similar.

70 longbed · 02-17-2004, 01:07 PM

Where do I find suffixcode information. The numbers are readable, if I understand correctly, that they are stamped on the pad at the pass, front side of the motor.

What should the head numbers be for correct 396/402 heads for this block?

02-17-2004, 12:45 AM	#1
70 longbed Senior Member Join Date: Oct 2002 Location: Sierra Vista, AZ Posts: 490	396 or 402 I picked up a block casting # 3969854 and most of the parts, i.e. pistons (2 sets), 2 cast cranks, heads, casting # 3935401, valve covers, oil pan , the pulleys and some other stuff. The block # says 69 396 2 or 4 bolt main, or 70-72 402, 2 or 4 bolt main. I can see that it is 2 bolt, but haow can I check if it is 396 or 402, mic the cylinders? And if that is it, what numbers am I looking for? __________________ Keith 70 CST longbed in progress. Hoping to get it back on the road soon.

02-17-2004, 01:06 AM	#2
dinnut Registered User Join Date: Apr 2003 Location: missouri city, tx Posts: 4,486	A 396 is a 402 from what ive heard in the past. 402 is the actual size but was called a 396 pre 1969. anybody feel free to correct me if im wrong. __________________ 70 longbed 496/th400/Ford 9"

02-17-2004, 01:30 AM	#4
smonty Smonty Join Date: Mar 2001 Location: Mesquite, TX, USA Posts: 769	Reply The block you have is used for 396 and 402's and the heads are 68-76...oval...OPEN...427T from Mortec web site. Which means the heads are from a 427 truck motor. Hope this helps you. Ernie __________________ 72 2WD Blazer 68 SWB Fleetside 67 SWB Stepside 2005 Chevy 1500HD Crewcab 56 Chris Craft Mahogany Runabout Looking for 36 Chevy 1/2 Ton P/U Project

02-17-2004, 12:34 PM	#7
68c10owner Registered User Join Date: Oct 2003 Location: Carmichael, California Posts: 3,006	g.m. started boring them .030 in late 1969 but still called them the 396 in cars and called them 400 in cetain year trucks, can`t remember the year. the early blocks were a 396 and if i remember right, the bore was 4.095 or something around that. from my understanding, g.m. bored them .030 to reduce emissions. __________________ Anthony

02-17-2004, 12:58 PM	#8
super72bb Senior Member Join Date: Jan 2002 Location: calgary,Alberta,Canada Posts: 387	396 to 402 The reason Gm changed the 396 to a 402 by boring it out was... As you know Gm also had a small block 400 in that era. General Motors was not fond of the idea of one of their small blocks out cubing one of their big blocks. So they punched the 396 to a 402 cubic inch making it out cube the small block 400. I don't even recall where I got this info exactly. I think it was on a show about Chevelle's I saw one weekend on my classic car or something similar. __________________ 1972 CHEYENNE SUPER SWB BLACK. 402 BB, TH400, AIR, TILT, TACH, BUCKETS, CRUISE, AM/FM, 8 TRACK. My build thread: http://67-72chevytrucks.com/vboard/s...=1#post7120181

02-17-2004, 01:07 AM	#3
rangernsk Registered User Join Date: Dec 2002 Location: Warrensburg MO Posts: 143	A 402 is a 396 bored .30 over by the factory. Hope this helps and good luck with your project.

02-17-2004, 08:52 AM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	If the numbers that are stamped into the pad are readable, you can look up the suffix code and find out a lot more information on the engine. Jim

02-17-2004, 10:18 AM	#6
Number98 Prestige Worldwide Join Date: Feb 2001 Location: Worldwide Posts: 2,553	I was told that the 396's used in our trucks were accidently punched .030 by GM and this makes them 402's. Which would make them kinda like one in the same. Just what I was told. Jason

02-17-2004, 01:07 PM	#9
70 longbed Senior Member Join Date: Oct 2002 Location: Sierra Vista, AZ Posts: 490	Where do I find suffixcode information. The numbers are readable, if I understand correctly, that they are stamped on the pad at the pass, front side of the motor. What should the head numbers be for correct 396/402 heads for this block? __________________ Keith 70 CST longbed in progress. Hoping to get it back on the road soon.



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