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Old 07-17-2001, 08:28 PM   #1
89 Blazzer
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how do you tell the difference between a 350 and 400 engine?

What are things to look for? I bought a piece of $$$$ Blazer for the rims. It was cheap. The owner thinks it has a 400 in it. It is not the original engine. It is out of an early to mid 70's truck or van and has the large spark plugs also.

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Old 07-17-2001, 08:33 PM   #2
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Re: how do you tell the difference between a 350 and 400 engine?

if it is a 400 it will have a groove cut out in the front balancer also will have a balance weight on the flywheel. also some 400 had 3 freeze plugs per side. get them the casting#off the block behind the head on drivers side on top of block and i can tell ya fer shure. BEANS A NATURALLY LOW FAT FOOD this message brought to you by the national bean growers assn. i think

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Old 07-17-2001, 08:40 PM   #3
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Re: how do you tell the difference between a 350 and 400 engine?

the freeze plugs are a good giveaway and check the counter weights on the balacer and flywheel. These are getting very scarce and are also getting valuble. I sold one on ebay that needed work(spun bearing) for 300.00. I paid 50.00 for the truck it came in!! I have a book of casting #'s. If you can get the casting # off the back of the block, I can tell you more about it. The casting # is on the drivers side of the block back where the bellhousing bolts up. 2 bolt blocks are better than 4 bolts on these blocks.

your right. I don't understand the jeep thing!
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Old 07-17-2001, 09:13 PM   #4
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Re: how do you tell the difference between a 350 and 400 engine?

All 400 blocks have the numbers 509 cast in both sides of the block, this and casting numbers are the only sure ways as I have seen 400's with 350 flywheels and/or balacers, Also seen 350's the other way around

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Old 07-18-2001, 05:53 AM   #5
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Re: how do you tell the difference between a 350 and 400 engine?

hey dude i thinks you need to wake up and smell the gear oil. ALL 400 BLOCKS ARE NOT 509 CASTINGS!!!!!!!!!! THERE IS SOME OTHER # FOR 400 small blocks, but they best i.d is the casting # BEANS A NATURALLY LOW FAT FOOD!!!!!!!

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Old 07-18-2001, 06:43 AM   #6
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Re: how do you tell the difference between a 350 and 400 engine?

hey now seems that the old smelly dude is right the 400 s.b. has other casrting# 3951511 this is 1970-74 2bolt mains or 4 bolt u must pull the pan to confirm, here is another 400 #is 330817, the 509 block was 79-80 the last years for the 400 it did have 509 cast 0n the sides also that is the last 3 digits of the casting # also some bow tie racing blocks were produced.

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Old 07-18-2001, 06:54 AM   #7
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Re: how do you tell the difference between a 350 and 400 engine?

HEY DUDE All I know is what I read in the chevy casting book. Its says it not me, It does not say most it says all have the upside down 509 on both the left and right sides. Both of the blocks I run have this on them and it does not match the casting number. The casting book reads as if the 509 on the side of the block is not part of the casting number always. With that said all of the known 400 blocks I have seen and the 10 I haved had plus the 2 I am curently running and the 3 I have stored have the 509 cast in the sides. Of them only 2 came out of 79 Vans. So there may be some out there that don't but if they do, then they are 400's for sure. SO if you have a block that is said to be a 400 look first to see if it has the 400 balancer, its a bit hard to see the flywheel in most cases. But if you can check is to see if there is a balance plate or externaly blananced flywheel (not easy to see with it bolted on). If you get theis far the look at the sides 400 had both 2 and 3 casting plugs/frezee plugs so look for the 509 behind the mounting lugs. If you get this far or dont but still think it is a 400 you needed to check the numbers to make sure. GM has done many strange things that no one under standes.

K5

<P ID="edit"><FONT class="small">Edited by blazer72 on 07/18/01 08:45 AM.</FONT></P>
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Old 07-18-2001, 01:17 PM   #8
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Re: how do you tell the difference between a 350 and 400 engine?

forget the casting numbers look at the number of freeze plugs. three is a 400 HOWEVER the ones in the center on both sides can just be a casting pertrusion that is the same size of a freeze plug..

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Old 07-18-2001, 03:34 PM   #9
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Re: how do you tell the difference between a 350 and 400 engine?

I've always been told the freeze plugs theory is an old wive's tale. I don't know for sure. Just what I've been told.

If a balancer or flywheel from a 400 and 350 are interchanged, it'll have a vibration. ALL 400's are externally balanced and ALL others are internally balanced.

Out of 100,000 sperm, YOU were the fastest??
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Old 07-18-2001, 03:50 PM   #10
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Re: how do you tell the difference between a 350 and 400 engine?

The freeze plug ID thing is crap i have a 71 400sb 2 bolt main with 2 freeze plugs and i did conferm this with casting numbers the only dead giveaway on most 400's is the large notch in the dampner all 400's are externally balanced from the factory. But it could of been rebuilt and internally balanced or could have the wrong balancer. The only sure way to ID it is to check the casting numbers(as if you havn't allready been told ) Here is a web site that breaks down the casting numbers and location : <a target="_blank" href=http://www.mortec.com/>http://www.mortec.com/</a>

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