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Old 08-28-2011, 04:45 PM   #1
1LowToy
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350 blocks

I have a 73 350 motor, how can i tell if it's a 4 bolt or disired block? Right now it's too greasy to touch, so where and what do I look for? Fondling around dirty things is not my favorite.
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Old 08-28-2011, 05:28 PM   #2
bigwheel15
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Re: 350 blocks

There should be a casting number on the back of the block, I believe there is one on the front by where the alternator mounts as well.
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Old 08-28-2011, 05:37 PM   #3
LONGHAIR
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Re: 350 blocks

As long as you are not intending to rev it's guts out, it doesn't really matter.
A 2 bolt block will stand up to the average performance build just fine.
As long as the block is solid and not execssively worn, it's good to go.
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Old 08-28-2011, 07:50 PM   #4
PaRedneckRiders
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Re: 350 blocks

I would say just pull the oil pan and check the mains.
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Old 08-30-2011, 07:47 PM   #5
85gmcguy
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Re: 350 blocks

Check the casting number (passenger side back of the block). If it ends in 010 it's either a 4 bolt main or heavy duty 2 bolt main. Either is a good starting point if it's not been overbored by .060 yet.
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Old 08-30-2011, 07:52 PM   #6
kris's66lwb
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Re: 350 blocks

010 i beleive is the code for a 350 it wouldnt telly you main bolts or any thing there should be other castin marks and or stampings showing nickle content and main bolts and all that good stuff
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Old 08-30-2011, 10:02 PM   #7
BigBlocksRule
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Re: 350 blocks

Look for 010 and/or 020 under the timing chain cover, they're the better blocks, either 2 or 4 bolt. As long as it's a daily driver and not beat hard, a 2-bolt is fine. If you like driving it like you bought it at Harbor Freight, you best start with a good 4-bolt block. Gotta pull the pan, there are no single 350 castings from this time that tell if it's 2 or 4 bolt other than 400's.
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Old 08-30-2011, 10:13 PM   #8
motornut
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Re: 350 blocks

my 78 jimmy isn't (stock 305) but it's supposed to be "period correct" 350 with 4 bolt mains
this is what the back looks like and the front numbers
you can usally blast back there with a pressure washer to see them
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