396 vs 427 Why?
#21
Race Director
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How can the 3855961 casing number be the same for a 396 nd a 427 ci motor. There is no way a 396 can be bored out to a 427. Confused.
I can not find anyone who can explain why GM used the same casting number for two different cubic inch blocks.
Help me solve this puzzle.
Thanks George
I can not find anyone who can explain why GM used the same casting number for two different cubic inch blocks.
Help me solve this puzzle.
Thanks George
The 548 block could be either a 265 or a 283.
The 307 and 327 have the same stroke. A FEW 307s have been known to be bored to 327 (although it would scare me to bore one that much!).
#22
Melting Slicks
I remember some guys punching the 283 out .125 to create 301's. A lot of those blocks were really thin and caused problems. Some held together with no problem. It was just a matter of how thick the walls were in the original castings.
Steve
Steve
#23
Race Director
How About 4X4`s from 283 V8`s
How did this get to SB`s...
#25
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Let's try to stay on topic.
#27
Safety Car
The 1965-66 396 "961" block (2 bolt & 4 bolt mains) is a THIN wall casting. Regardless of core shift, boring one out to 4.250" (427) will result in either breaking through a water jacket, or dangerously thin cylinder walls that will cause the engine to run hot and be impossible to keep cool without boiling over on the street. [/QUOTE]
So how do you rebuild a 396 that needs to have the bores cleaned up?
So how do you rebuild a 396 that needs to have the bores cleaned up?
#28
Race Director
The 1965-66 396 "961" block (2 bolt & 4 bolt mains) is a THIN wall casting. Regardless of core shift, boring one out to 4.250" (427) will result in either breaking through a water jacket, or dangerously thin cylinder walls that will cause the engine to run hot and be impossible to keep cool without boiling over on the street.
Commonly refred to as .030 over.
#29
#30
Le Mans Master
Thread Starter
Boring out a 396 30 over would not make it a 427
#31
Le Mans Master
Thread Starter
One of my racing friends had one of these five 4-bolt main cap 396's out of a 65 Chevelle that we ran in a 68' Camaro. When a rod scored a cylinder wall in the block we looked to add a thin wall sleeve. Our machinist ran the block through a sonic test and came back to tell us it could be bored an 1/8th over, to a 427 bore, to clean up the cylinder. The set of 427 pistons cost a little bit, but worth the expense. One of our rivals who ran a SS legal 375hp/396 67' Camaro heard a rumor of what we did and claimed it could not be done safely, so we had our pin-striper paint "396 ? - 427 ?" on the sides of the hood scoop (just to keep him guessing). The guessing lasted about two drag race meets, before the track times improved to answer the question.
We ran this over-bored block for a year of racing with L72 pistons, with no failures. We then tore it down and swapped in L88 pistons (12.5:1 CR), and at the second or third weekend outing at the strip with the much faster configuration we blew a hole in the #5 or #7 cylinder wall. We added a sleeve and continued to run the block for the balance of the race season, and the entire next year.
This photo is from a month or so before we scored the 396 block (we suffered a drunk hitting the front end of the car the weekend before this photo, and we were forced to run with no hood).
We ran this over-bored block for a year of racing with L72 pistons, with no failures. We then tore it down and swapped in L88 pistons (12.5:1 CR), and at the second or third weekend outing at the strip with the much faster configuration we blew a hole in the #5 or #7 cylinder wall. We added a sleeve and continued to run the block for the balance of the race season, and the entire next year.
This photo is from a month or so before we scored the 396 block (we suffered a drunk hitting the front end of the car the weekend before this photo, and we were forced to run with no hood).
George
#33
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The real answer to this question with any individual block is to have the bores sonic tested to see if there is enough material to bore out the specific block you are considering. If you fail to have the blocked checked, you run the risk of breaking into a water jacket or suffering from a weak (thin) cylinder wall.
Could the 65' block you have commented on be a 427? Verify all the qualifiers (date, main caps, casting number). Have them check the bore diameter with a bore gage. If it's 4.125", or close, it's a 396. If it's 4.250", or close, it's a 427. If you are considering the block to purchase, consider the cost of a sonic test of the cylinder walls as insurance.
The other question, the girl? She was the Camaro owner's girlfriend (then wife, then ex-wife). She could have doubled for Natalie Wood with similar good looks, with ample additional qualifications (perfect for a distraction during late night heads-up racing).
#34
Racer
Someone really needs to analyze the structural integrity of the brassier she is wearing! Is it a thin wall in jeopardy of causing overheating amongst spectators? It looks bullet proof.
#35
Le Mans Master
Thread Starter
#36
Le Mans Master
Thread Starter
The answer is some early 396 blocks have been successfully bored out to the 427 bore. This is what we did, with a 396 block that had four bolt caps for all five main bearings (another indicator, in addition to the 1965 casting & 961' casting number).
The real answer to this question with any individual block is to have the bores sonic tested to see if there is enough material to bore out the specific block you are considering. If you fail to have the blocked checked, you run the risk of breaking into a water jacket or suffering from a weak (thin) cylinder wall.
Could the 65' block you have commented on be a 427? Verify all the qualifiers (date, main caps, casting number). Have them check the bore diameter with a bore gage. If it's 4.125", or close, it's a 396. If it's 4.250", or close, it's a 427. If you are considering the block to purchase, consider the cost of a sonic test of the cylinder walls as insurance.
The other question, the girl? She was the Camaro owner's girlfriend (then wife, then ex-wife). She could have doubled for Natalie Wood with similar good looks, with ample additional qualifications (perfect for a distraction during late night heads-up racing).
The real answer to this question with any individual block is to have the bores sonic tested to see if there is enough material to bore out the specific block you are considering. If you fail to have the blocked checked, you run the risk of breaking into a water jacket or suffering from a weak (thin) cylinder wall.
Could the 65' block you have commented on be a 427? Verify all the qualifiers (date, main caps, casting number). Have them check the bore diameter with a bore gage. If it's 4.125", or close, it's a 396. If it's 4.250", or close, it's a 427. If you are considering the block to purchase, consider the cost of a sonic test of the cylinder walls as insurance.
The other question, the girl? She was the Camaro owner's girlfriend (then wife, then ex-wife). She could have doubled for Natalie Wood with similar good looks, with ample additional qualifications (perfect for a distraction during late night heads-up racing).
#37
The answer is some early 396 blocks have been successfully bored out to the 427 bore. This is what we did, with a 396 block that had four bolt caps for all five main bearings (another indicator, in addition to the 1965 casting & 961' casting number).
The real answer to this question with any individual block is to have the bores sonic tested to see if there is enough material to bore out the specific block you are considering. If you fail to have the blocked checked, you run the risk of breaking into a water jacket or suffering from a weak (thin) cylinder wall.
Could the 65' block you have commented on be a 427? Verify all the qualifiers (date, main caps, casting number). Have them check the bore diameter with a bore gage. If it's 4.125", or close, it's a 396. If it's 4.250", or close, it's a 427. If you are considering the block to purchase, consider the cost of a sonic test of the cylinder walls as insurance.
The other question, the girl? She was the Camaro owner's girlfriend (then wife, then ex-wife). She could have doubled for Natalie Wood with similar good looks, with ample additional qualifications (perfect for a distraction during late night heads-up racing).
The real answer to this question with any individual block is to have the bores sonic tested to see if there is enough material to bore out the specific block you are considering. If you fail to have the blocked checked, you run the risk of breaking into a water jacket or suffering from a weak (thin) cylinder wall.
Could the 65' block you have commented on be a 427? Verify all the qualifiers (date, main caps, casting number). Have them check the bore diameter with a bore gage. If it's 4.125", or close, it's a 396. If it's 4.250", or close, it's a 427. If you are considering the block to purchase, consider the cost of a sonic test of the cylinder walls as insurance.
The other question, the girl? She was the Camaro owner's girlfriend (then wife, then ex-wife). She could have doubled for Natalie Wood with similar good looks, with ample additional qualifications (perfect for a distraction during late night heads-up racing).
with everything but the bore on the 396. The standard 396 bore was 4.096" up until 1970 then they were bored 4.126" to 402".