1968 427? or 454?
Thread Starter
Cruising
Joined: Feb 2015
Posts: 11
Likes: 0
1968 427? or 454?
I recently purchased a 1968 corvette. The person I purchased it from was about 950mi from me. I got some pictures from him and his rep was flawless. Well i am not so sure about that now.
He advertised the car as a1968 corvette cov. BB car NOM 427 4sp. moter and powertrain new.
Well not getting into all the when the car arrived ti was a 427 car witha new bb engine. 427 so i thought.
Well the other day i got some numbers off the engine block which indicates the block is a 454 1976 Truck block. But the engine runs but pops thru the carb and backfires when i try to kick in the secondaries. Iknow nothing about the build. Neither does the person I bought it from.
It bothers me to run around with 427 emblems with a 454 engine?
I did read that the 454 can be built with 427 guts. is there any way for me to know for sure?
Also what does anyone think it causing the backfireing thru the carb and exhaust? Timing? Carb settings Quadrajet.
Thanks for any info.
He advertised the car as a1968 corvette cov. BB car NOM 427 4sp. moter and powertrain new.
Well not getting into all the when the car arrived ti was a 427 car witha new bb engine. 427 so i thought.
Well the other day i got some numbers off the engine block which indicates the block is a 454 1976 Truck block. But the engine runs but pops thru the carb and backfires when i try to kick in the secondaries. Iknow nothing about the build. Neither does the person I bought it from.
It bothers me to run around with 427 emblems with a 454 engine?
I did read that the 454 can be built with 427 guts. is there any way for me to know for sure?
Also what does anyone think it causing the backfireing thru the carb and exhaust? Timing? Carb settings Quadrajet.
Thanks for any info.
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 493
From: Salmon Arm, BC
Backfiring through the secondaries could be caused by the air valve (flap) not having enough tension on the spring and it's opening too quickly causing a lean condition. It's too bad that the seller wasn't on the up and up with you....that the kind of thing you want to confirm with good digital pics before dropping your cash...too late now, enjoy the extra cubes is all I can say 
Tech Contributor
Joined: Jun 2004
Posts: 20,910
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I recently purchased a 1968 corvette. The person I purchased it from was about 950mi from me. I got some pictures from him and his rep was flawless. Well i am not so sure about that now.
He advertised the car as a1968 corvette cov. BB car NOM 427 4sp. moter and powertrain new.
Well not getting into all the when the car arrived ti was a 427 car witha new bb engine. 427 so i thought.
Well the other day i got some numbers off the engine block which indicates the block is a 454 1976 Truck block. But the engine runs but pops thru the carb and backfires when i try to kick in the secondaries. Iknow nothing about the build. Neither does the person I bought it from.
It bothers me to run around with 427 emblems with a 454 engine? Unless you're running in some sanctioned race class I wouldn't lose any sleep over the engine size emblems.
I did read that the 454 can be built with 427 guts. is there any way for me to know for sure? My first track engine (I stored the original engine away so I wouldn't accidentally blow it up) was a 1974 454 pickup engine that I put a 427 crank and pistons in.
Also what does anyone think it causing the backfireing thru the carb and exhaust? Timing? Carb settings Quadrajet.
Thanks for any info.
He advertised the car as a1968 corvette cov. BB car NOM 427 4sp. moter and powertrain new.
Well not getting into all the when the car arrived ti was a 427 car witha new bb engine. 427 so i thought.
Well the other day i got some numbers off the engine block which indicates the block is a 454 1976 Truck block. But the engine runs but pops thru the carb and backfires when i try to kick in the secondaries. Iknow nothing about the build. Neither does the person I bought it from.
It bothers me to run around with 427 emblems with a 454 engine? Unless you're running in some sanctioned race class I wouldn't lose any sleep over the engine size emblems.
I did read that the 454 can be built with 427 guts. is there any way for me to know for sure? My first track engine (I stored the original engine away so I wouldn't accidentally blow it up) was a 1974 454 pickup engine that I put a 427 crank and pistons in.
Also what does anyone think it causing the backfireing thru the carb and exhaust? Timing? Carb settings Quadrajet.
Thanks for any info.
Safety Car
Joined: May 2008
Posts: 3,753
Likes: 721
From: Lafayette Louisiana
Nice 68 Corvette!!!
Nice beautiful 68 Corvette, LeMans Blue I think and med blue interior!!!
Couple of thoughts for you.
Too bad advertised as 427 but was said to be NOM engine. If it turns out the only way to tell is from the engine block and not obvious otherwise, I would get the bugs out and run it and enjoy it!! If you paid 68 NOM engine prices, then, maybe this is ok after all. There are lots of BB's out there with all manner of engines. And I would leave the 427 emblems on too, so what, it is a BB 68. But I understand how these things can bug a person too.
Second, Crescent City Corvette Club is having a Legends Corvette Show in Boomtown Casino in Harvey this Sat, April 11. You might consider bringing it and entering it in the show. Lots of very knowledgeable Corvette folks that like to look at beautiful Corvettes. And a fun time for all!
My 2 cents anyway.
Couple of thoughts for you.
Too bad advertised as 427 but was said to be NOM engine. If it turns out the only way to tell is from the engine block and not obvious otherwise, I would get the bugs out and run it and enjoy it!! If you paid 68 NOM engine prices, then, maybe this is ok after all. There are lots of BB's out there with all manner of engines. And I would leave the 427 emblems on too, so what, it is a BB 68. But I understand how these things can bug a person too.
Second, Crescent City Corvette Club is having a Legends Corvette Show in Boomtown Casino in Harvey this Sat, April 11. You might consider bringing it and entering it in the show. Lots of very knowledgeable Corvette folks that like to look at beautiful Corvettes. And a fun time for all!
My 2 cents anyway.
Last edited by 20mercury; Apr 6, 2015 at 12:32 PM.
Thread Starter
Cruising
Joined: Feb 2015
Posts: 11
Likes: 0
Nice beautiful 68 Corvette, LeMans Blue I think and med blue interior!!!
Couple of thoughts for you.
Too bad advertised as 427 but was said to be NOM engine. If it turns out the only way to tell is from the engine block and not obvious otherwise, I would get the bugs out and run it and enjoy it!! If you paid 68 NOM engine prices, then, maybe this is ok after all. There are lots of BB's out there with all manner of engines. And I would leave the 427 emblems on too, so what, it is a BB 68. But I understand how these things can bug a person too.
Second, Crescent City Corvette Club is having a Legends Corvette Show in Boomtown Casino in Harvey this Sat, April 11. You might consider bringing it and entering it in the show. Lots of very knowledgeable Corvette folks that like to look at beautiful Corvettes. And a fun time for all!
My 2 cents anyway.
Couple of thoughts for you.
Too bad advertised as 427 but was said to be NOM engine. If it turns out the only way to tell is from the engine block and not obvious otherwise, I would get the bugs out and run it and enjoy it!! If you paid 68 NOM engine prices, then, maybe this is ok after all. There are lots of BB's out there with all manner of engines. And I would leave the 427 emblems on too, so what, it is a BB 68. But I understand how these things can bug a person too.
Second, Crescent City Corvette Club is having a Legends Corvette Show in Boomtown Casino in Harvey this Sat, April 11. You might consider bringing it and entering it in the show. Lots of very knowledgeable Corvette folks that like to look at beautiful Corvettes. And a fun time for all!
My 2 cents anyway.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Hopefully youre not losing cam lobes, the advice on full tuneup first is sound.
There are some unsavory characters that will try and convince you its NOM-I think most have no idea what it really is. (too much hassle for me BTDT and as sale time it meant nothing other than everything was old).
If its a 454 its not NOM anyway take advantage of it if you pull the motor stroke it to a 496 kits arent much, dress it as a 427. You will laugh at the amount of part throttle torque you can make with one its rediculous and noone will know the difference externally
427 is just a large 383 think of it that way.
There are some unsavory characters that will try and convince you its NOM-I think most have no idea what it really is. (too much hassle for me BTDT and as sale time it meant nothing other than everything was old).
If its a 454 its not NOM anyway take advantage of it if you pull the motor stroke it to a 496 kits arent much, dress it as a 427. You will laugh at the amount of part throttle torque you can make with one its rediculous and noone will know the difference externally
427 is just a large 383 think of it that way.
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Burning Brakes
Joined: Aug 2008
Posts: 878
Likes: 55
From: Deep South Denmark
It could be a 454 block with a 427 crank making it a ... 427.
If it is a manual transmission car you can remove the flywheel inspection cover and look at the flywheel. If it has 427 internals it has an internal balance flywheel and 454 an external flywheel.
Search the forum for pictures of the two flywheel types.
It is only an indication as various aftermarket combinations may have a different combination.
If it is a manual transmission car you can remove the flywheel inspection cover and look at the flywheel. If it has 427 internals it has an internal balance flywheel and 454 an external flywheel.
Search the forum for pictures of the two flywheel types.
It is only an indication as various aftermarket combinations may have a different combination.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If the engine is tuned up and runs well, it just has more 'cubes' than the engine you thought you bought. The '76 'truck' 454 will not rev like the '68 427 would...and likely will not make as much power. But, it will have more low-end torque than the '68 L36. You should also be able to run it on unleaded regular fuel, if the engine still has its original internals.
That 454 block can be rebuilt with internals similar to the original 427 engine, if you wish. Or it can be rebuilt with modern internals to make it significantly better than the L36 engine. It all depends on what you want and how much you want to spend. If you can get it running well, I would just leave it alone.
Other than having 'different' ID stamp numbers/letters on the block, there is very little difference between the 427 and 454 blocks.
That 454 block can be rebuilt with internals similar to the original 427 engine, if you wish. Or it can be rebuilt with modern internals to make it significantly better than the L36 engine. It all depends on what you want and how much you want to spend. If you can get it running well, I would just leave it alone.
Other than having 'different' ID stamp numbers/letters on the block, there is very little difference between the 427 and 454 blocks.
Last edited by 7T1vette; Apr 7, 2015 at 01:16 PM.
Team Owner
Joined: Jul 2004
Posts: 40,412
Likes: 792
From: Redondo Beach, California
I'd wonder about those 76 BB truck heads. The back firing issue is most likely a carb/timing issue.
As posters have said, the 454 and 427 blocks were pretty much identical, except the 454 had more stroke on the crank. I've got what I've been told is a 454 70 Coupe, although the block number corresponds to a 69 427 SS Chevrolet Impala. I assume the engine has a 454 crank. It doesn't matter since I'm installing an all new 496/502 BB engine.
BTW...a 454 crank can be adapted to be internally balanced with tungsten/depleted uranium weights added to the crank throws. With this crank, the front damper and rear flywheel will have 427 part numbers!!! Good way for a NCRS guys to cheat on extra HP!
As posters have said, the 454 and 427 blocks were pretty much identical, except the 454 had more stroke on the crank. I've got what I've been told is a 454 70 Coupe, although the block number corresponds to a 69 427 SS Chevrolet Impala. I assume the engine has a 454 crank. It doesn't matter since I'm installing an all new 496/502 BB engine.
BTW...a 454 crank can be adapted to be internally balanced with tungsten/depleted uranium weights added to the crank throws. With this crank, the front damper and rear flywheel will have 427 part numbers!!! Good way for a NCRS guys to cheat on extra HP!
Safety Car
Joined: Apr 2006
Posts: 4,057
Likes: 421
From: BC
In 69 and 70 the 427 and 454 actually used the same block. Casting number was 3968512 for both. No diff. 427 was internally balanced and 454 externally and you can tell by crawling underneath and looking for the counter weight behind the harmonic balancer which the 427 doesn't have. Sounds like that isn't your major problem though...
