427 or 454??? - Chevelle Tech
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post #1 of 28 (permalink) Old Aug 28th, 19, 11:59 AM Thread Starter
 
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427 or 454???

Hello, I'm new here and just bought a 71' Chevelle SS. It's not numbers matching but I did find the original build sheet and it had the LS5 option on it. I'm still trying to figure out exactly what engine is currently in it though. The casting number is: 3963512 which I am seeing it is either a 454 or 427. The date on the casting is: J 11 9, which I understand was made in October 11, 1969. So does that make it a 427? Thanks for any help.
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post #2 of 28 (permalink) Old Aug 28th, 19, 2:19 PM
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Re: 427 or 454???

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Originally Posted by flatbedlovetruck View Post
Hello, I'm new here and just bought a 71' Chevelle SS. It's not numbers matching but I did find the original build sheet and it had the LS5 option on it. I'm still trying to figure out exactly what engine is currently in it though. The casting number is: 3963512 which I am seeing it is either a 454 or 427. The date on the casting is: J 11 9, which I understand was made in October 11, 1969. So does that make it a 427? Thanks for any help.
I believe this casting number is for either a 1969 427 or 1970 454; both blocks are the same. Judging by the build date I would guess a 427; just my .02...

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post #3 of 28 (permalink) Old Aug 28th, 19, 3:30 PM Thread Starter
 
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Re: 427 or 454???

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Originally Posted by Flipper View Post
I believe this casting number is for either a 1969 427 or 1970 454; both blocks are the same. Judging by the build date I would guess a 427; just my .02...
Thanks for your quick response! Is there any other way to tell for sure if it is a 1970 454 or the 427? On the valves the casting is 3964290. Date: J 8 a bump that looks like a 0 9 and then also GM 7 T

Thanks for any help
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post #4 of 28 (permalink) Old Aug 28th, 19, 3:33 PM
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Re: 427 or 454???

Look for a counterweight on the backside of your harmonic balancer. If it has one,its a 454. if it doesn't, its a 427
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post #5 of 28 (permalink) Old Aug 28th, 19, 3:52 PM
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Re: 427 or 454???

By October of 1969 Chevrolet well into the 1970 models production run and was done installing 427 in cars.

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post #6 of 28 (permalink) Old Aug 28th, 19, 3:56 PM
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Re: 427 or 454???

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Originally Posted by flatbedlovetruck View Post
Thanks for your quick response! Is there any other way to tell for sure if it is a 1970 454 or the 427? On the valves the casting is 3964290. Date: J 8 a bump that looks like a 0 9 and then also GM 7 T

Thanks for any help
3964290 heads(closed chamber oval port) were commonly used on 396 thru 454 CI engines, so they don't pinpoint either way if your engine is a 427 or 454.

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post #7 of 28 (permalink) Old Aug 28th, 19, 4:05 PM Thread Starter
 
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Re: 427 or 454???

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Originally Posted by mr 4 speed View Post
Look for a counterweight on the backside of your harmonic balancer. If it has one,its a 454. if it doesn't, its a 427
to
Thanks for your response. it does look like there is a counterweight on the inside (backside) of the harmonic balancer. Not familiar with that but it looks like it goes a 1/3 of the way around roughly? So with the date code do you think it is a 1970 454? Would this be a LS5 or LS6? How to tell the difference? Thanks for your help!
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post #8 of 28 (permalink) Old Aug 28th, 19, 4:06 PM Thread Starter
 
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Re: 427 or 454???

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By October of 1969 Chevrolet well into the 1970 models production run and was done installing 427 in cars.

Steve R
Thanks Steve. So does that make it an LS5 or 6?

Ben
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post #9 of 28 (permalink) Old Aug 28th, 19, 4:18 PM
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Re: 427 or 454???

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Thanks Steve. So does that make it an LS5 or 6?

Ben
It could be neither. Full sized cars came with 454s too.

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post #10 of 28 (permalink) Old Aug 28th, 19, 4:35 PM
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Re: 427 or 454???

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Originally Posted by flatbedlovetruck View Post
to
Thanks for your response. it does look like there is a counterweight on the inside (backside) of the harmonic balancer. Not familiar with that but it looks like it goes a 1/3 of the way around roughly? So with the date code do you think it is a 1970 454? Would this be a LS5 or LS6? How to tell the difference? Thanks for your help!
It is likely neither. Full-size cars, as well as trucks also came with the 454, not to mention crate motors and marine engines.

I presume no suffix stamp? That would be the only way to tell what it originally was...

Really, if its NOT the original motor (untouched), then it could be anything... Most engines will have been out and refreshed/rebuilt over the past 49+ years...

IF its a factory 4-bolt main (usually verified by looking at the block plugs above the oil filter), then its either an LS6 or a truck.

IIRC, the LS5 all used 2-bolt main blocks...


But in the past 49+ years, also pretty common to add the 4-bolt caps and bolts...

I think 454 Chevelles (at least LS6) started around December 1969, and typically, blocs were a week or two prior... But October casting date probably wouldn't be out of the question in most places...

Unless it was a crate motor, then it would be a 454. No Chevrolets (full-size, Corvettes, COPO cars) used a "factory installed" 427 for the 1970 model year, and the model year production generally started in August/September (1969)

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post #11 of 28 (permalink) Old Aug 28th, 19, 4:51 PM
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Re: 427 or 454???

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Originally Posted by 1966_L78 View Post
It is likely neither. Full-size cars, as well as trucks also came with the 454, not to mention crate motors and marine engines.

I presume no suffix stamp? That would be the only way to tell what it originally was...

Really, if its NOT the original motor (untouched), then it could be anything... Most engines will have been out and refreshed/rebuilt over the past 49+ years...

IF its a factory 4-bolt main (usually verified by looking at the block plugs above the oil filter), then its either an LS6 or a truck.

IIRC, the LS5 all used 2-bolt main blocks...


But in the past 49+ years, also pretty common to add the 4-bolt caps and bolts...

I think 454 Chevelles (at least LS6) started around December 1969, and typically, blocs were a week or two prior... But October casting date probably wouldn't be out of the question in most places...

Unless it was a crate motor, then it would be a 454. No Chevrolets (full-size, Corvettes, COPO cars) used a "factory installed" 427 for the 1970 model year, and the model year production generally started in August/September (1969)
I did trucks came with 454s in 1970?

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post #12 of 28 (permalink) Old Aug 28th, 19, 5:36 PM
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Re: 427 or 454???

First year for 454 in trucks was 1973 and was the only big block option.

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post #13 of 28 (permalink) Old Aug 29th, 19, 1:25 AM Thread Starter
 
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Re: 427 or 454???

Thanks everybody for the help! At least I now know it's a 454. There aren't any VIN numbers I can find on the engine. The M22 Muncie seems to be original but a different engine was put in at some point but at least similar to what was on the build sheet (LS5 454). Thanks

Ben
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post #14 of 28 (permalink) Old Aug 29th, 19, 5:46 AM
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Question Re: 427 or 454???

Are there any numbers stamped on the ledge behind the alternator ? You might need some spray cleaner and a rag to see if there are any numbers hidden under the crud.

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post #15 of 28 (permalink) Old Aug 30th, 19, 1:46 AM Thread Starter
 
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Re: 427 or 454???

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Originally Posted by 71350SS View Post
Are there any numbers stamped on the ledge behind the alternator ? You might need some spray cleaner and a rag to see if there are any numbers hidden under the crud.
I will check again but I don't think so....
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