400 block worth saving or junk ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sleepertruck72 · 03-25-2008, 07:47 AM

I tore down the 400 block that was in my truck previously. It is a 2 bolt main casting # 3951509. The cylinder walls only have 3/16 of an inch between each other according to my tape measure. I dont have one of those mechanic gauges or whatever is used to measure all that. The motor smoked a little on the freeway before I pulled it. Is it worth rebuilding or is is not able to be bored anymore ? It all came apart pretty easy. Thanks for your help.

ed2552 · 03-25-2008, 07:53 AM

they are siamesed bores, which means there is no water between them, because they are so big

sleepertruck72 · 03-25-2008, 07:57 AM

So does that mean it is still ok to bore or just put back together with new stuff. Youre talking to a tile guy not a mechanic so I ask about a million questions about this stuff.

drivethechevy · 03-25-2008, 08:02 AM

i dont know about boring it id have a machine shop determin that but you shouldnt having a problem puting new parts it in and drivin it again

haysonj · 03-25-2008, 08:08 AM

You'll have to have someone check it with a dial bore gage. If it has never been bored before it should be alright. My book says it can be safely bored .030 over

sleepertruck72 · 03-25-2008, 08:19 AM

dial bore gage, I knew there was a name to that tool. I will have someone check it before I decide to give it away or junk it. Thanks for all the help

Down south truckin · 03-25-2008, 08:30 AM

don't junk it I've bored one .060 over before and a buddy of mine did one years ago .060 they were both racing motors my buddy poured his with hardblock to keep from giving any problems.sell it to a poor racer and he'll find a way to use it the cylinder walls don't have to be perfect like everybody thinks I know this from experience.

sleepertruck72 · 03-25-2008, 08:41 AM

80 bucks of beer money sounds good to me Am I too cheap ? I have no use for it I was going to put in in my 67 project but I think I am going to sell the truck as I have no money and time to do anything to it

chevy72blu · 03-25-2008, 08:45 AM

Dont forget to have it magnaflux'ed as well. No use rebuilding a cracked block.

I agree with what others have said, though I am leary about a .060 400 SBC. There was a recent thread that turned into a pretty lengthy discussion about the danger of those siamese ports.

The fact that it was smoking most likely means you will want to re-bore it, which gets increasingly dangerous the more you do.

Good luck with it!

**special-K** · 03-25-2008, 02:59 PM

Guys pump those up to 427 cu.in. and would love to buy a spare block.For guys that use them,what you have is gold.

03-25-2008, 07:47 AM	#1
sleepertruck72 Registered User Join Date: Nov 2007 Location: Turlock California 95380 Posts: 2,075	400 block worth saving or junk ? I tore down the 400 block that was in my truck previously. It is a 2 bolt main casting # 3951509. The cylinder walls only have 3/16 of an inch between each other according to my tape measure. I dont have one of those mechanic gauges or whatever is used to measure all that. The motor smoked a little on the freeway before I pulled it. Is it worth rebuilding or is is not able to be bored anymore ? It all came apart pretty easy. Thanks for your help. __________________ 72 C20 Longbed 05 1500 Z71

03-25-2008, 07:53 AM	#2
ed2552 Registered User Join Date: Jan 2007 Location: Charles City IA Posts: 1,626	Re: 400 block worth saving or junk ? they are siamesed bores, which means there is no water between them, because they are so big __________________ '67 C20, Under the Knife!, LWB, Eaton HO-52, Rear Coil Springs 72' GMC C2500, 350, TH400(?), Dana 60 '67 K10 4-spd., 305, SM465, Dana 44, 12 Bolt, RUST! '65 C60 292, 4 spd, 2 spd Rearend, 15' Grain Box, MINT! 09 Yukon Denali 82k Miles 6.2L/6A

03-25-2008, 07:57 AM	#3
sleepertruck72 Registered User Join Date: Nov 2007 Location: Turlock California 95380 Posts: 2,075	Re: 400 block worth saving or junk ? So does that mean it is still ok to bore or just put back together with new stuff. Youre talking to a tile guy not a mechanic so I ask about a million questions about this stuff. __________________ 72 C20 Longbed 05 1500 Z71

03-25-2008, 08:02 AM	#4
drivethechevy Registered User Join Date: May 2007 Location: Buffalo MN Posts: 606	Re: 400 block worth saving or junk ? i dont know about boring it id have a machine shop determin that but you shouldnt having a problem puting new parts it in and drivin it again __________________ Trial and Error, its expensive but its a mistake i most likely wont make again 1971 chevy k10 custom deluxe http://67-72chevytrucks.com/vboard/s...d.php?t=341257 1968 chevy k/10 fleet http://67-72chevytrucks.com/vboard/s...d.php?t=334731 1948 desoto custom coupe fluid drive(family heirloom)

03-25-2008, 08:08 AM	#5
haysonj Registered User Join Date: Dec 2007 Location: Santa Maria, Ca. Posts: 1,423	Re: 400 block worth saving or junk ? You'll have to have someone check it with a dial bore gage. If it has never been bored before it should be alright. My book says it can be safely bored .030 over __________________ 69 Chevy 4x4 383 Power

03-25-2008, 08:19 AM	#6
sleepertruck72 Registered User Join Date: Nov 2007 Location: Turlock California 95380 Posts: 2,075	Re: 400 block worth saving or junk ? dial bore gage, I knew there was a name to that tool. I will have someone check it before I decide to give it away or junk it. Thanks for all the help __________________ 72 C20 Longbed 05 1500 Z71

03-25-2008, 08:30 AM	#7
Down south truckin Senior Member Join Date: Feb 2006 Location: Lilburn Georgia Posts: 1,240	Re: 400 block worth saving or junk ? don't junk it I've bored one .060 over before and a buddy of mine did one years ago .060 they were both racing motors my buddy poured his with hardblock to keep from giving any problems.sell it to a poor racer and he'll find a way to use it the cylinder walls don't have to be perfect like everybody thinks I know this from experience.

03-25-2008, 08:41 AM	#8
sleepertruck72 Registered User Join Date: Nov 2007 Location: Turlock California 95380 Posts: 2,075	Re: 400 block worth saving or junk ? 80 bucks of beer money sounds good to me Am I too cheap ? I have no use for it I was going to put in in my 67 project but I think I am going to sell the truck as I have no money and time to do anything to it __________________ 72 C20 Longbed 05 1500 Z71

03-25-2008, 08:45 AM	#9
chevy72blu Registered User Join Date: Apr 2004 Location: Las Vegas, NV Posts: 2,188	Re: 400 block worth saving or junk ? Dont forget to have it magnaflux'ed as well. No use rebuilding a cracked block. I agree with what others have said, though I am leary about a .060 400 SBC. There was a recent thread that turned into a pretty lengthy discussion about the danger of those siamese ports. The fact that it was smoking most likely means you will want to re-bore it, which gets increasingly dangerous the more you do. Good luck with it! __________________ RIP EastSideLowLife '72 C20 SWB convert. 5 lug, LS1/4l60e

03-25-2008, 02:59 PM	#10
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,861	Re: 400 block worth saving or junk ? Guys pump those up to 427 cu.in. and would love to buy a spare block.For guys that use them,what you have is gold. __________________ "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 ~



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