402 main bearing caps

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Bblock007
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402 main bearing caps

Post by Bblock007 »

Hi,

What do you guys know about main bearing caps for the BBC 402 1970 L34?? I was searching for info and ran across a post on this forum and they were talking about the SBC and the different types and the cast numbers. I think the SBC post, the guy was asking about how to tell the location of the caps. Seemed his weren't marked? In reading the post someone suggested to try fitting each cap and the correct cap will fit seamlessly. They said you can run your fingernail across the interface and it will be smooth. Soooo... I went to look at my short block and see how mine looked. Something I didn't catch was, are they talking about the bore or are they talking about the width of the cap and it lining up with the block? Because I measured with my caliper and the caps are measuring 1.085" and the block location it bolts to is 1.105". Okay, I think I am answering one of my questions here. They were probably talking about the bore aligning pefectly with the proper cap in place.

Okay so the 2nd question are there differences in the caps. The one I have look to be 362? 1-4 and the 5th is 366? or 386? 3 and some combo of 6 and or 8 but I think 366.

Thanks for any info.
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Re: 402 main bearing caps

Post by Kevin Johnson »

Not sure if this will be of any help ...

https://youtu.be/U2Yb15B1Lvs?t=877
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modok
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Re: 402 main bearing caps

Post by modok »

Bblock007 wrote: Sat Sep 25, 2021 5:03 pm In reading the post someone suggested to try fitting each cap and the correct cap will fit seamlessly. They said you can run your fingernail across the interface and it will be smooth. Soooo... I went to look at my short block and see how mine looked. Something I didn't catch was, are they talking about the bore or are they talking about the width of the cap and it lining up with the block?
Meant the bearing bore.
enginepieces
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Re: 402 main bearing caps

Post by enginepieces »

If you look real close you can see the hone marks in the metal look for the lines to match. Each one will be different just like a finger print. I use a bright light and a magnifying glass. After you find all the right places for the caps torque the caps and check the bore size to insure the cap placement. Good luck and enjoy the engine.
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Re: 402 main bearing caps

Post by Kingbee »

I hope you don’t mind me asking. I’ve been told over the years that a 402 is nothing more than a .030 over 396. Is this true? Was the L34 option advertised as a 402 or a 396? Thanks
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Re: 402 main bearing caps

Post by bigmike »

Kingbee wrote: Sun Apr 03, 2022 9:36 pm I hope you don’t mind me asking. I’ve been told over the years that a 402 is nothing more than a .030 over 396. Is this true? Was the L34 option advertised as a 402 or a 396? Thanks
Sort of a 396 had a bore of 4.094 and the 402 had a bore of 4.125 so it was .031 over bore. The block castings had some changes from the 1969 396 to the 1970 402 also. I pulled a 402 BBC out of a 1971 chevy in early 1980s and it said 400 on the front fenders. Never saw 402 on any front fenders chevys from what I know chevy always called the 402 a 400 on front fenders as far as I know. 1970 was a messed up year for GM as there was a long strike.
I had a 1968 L34 396 engine. I don't know what they did with the L34 engine in 1970 or 1971. Most likely it was a 400 those years.
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Re: 402 main bearing caps

Post by ProPower engines »

i think at the time Pontiac was 402 so it could say it had the biggest bbc at the time when the 396 came about
The 402 made its way into trucks as well as a number of different chevys as well.

But I never seen a 402 badge on any chevy did see it on a Pontiac under the hood info sticker but not the fender.
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