327 Question
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From: Fountain Hills AZ
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Sorry, I thought you meant 2bolt main blocks.
YES, there were lots of 2bl carb 327s, MAINLY in Camaros.
No, the 307 was NEVER in a small journal version. The 307 was introduced in 68 (to replace the 283), and in 68 ALL small blocks were the big journal block. Also, for it's production run (68-73) the 307 was ONLY available as a 2bl carb engine.
Tom Parsons
YES, there were lots of 2bl carb 327s, MAINLY in Camaros.
No, the 307 was NEVER in a small journal version. The 307 was introduced in 68 (to replace the 283), and in 68 ALL small blocks were the big journal block. Also, for it's production run (68-73) the 307 was ONLY available as a 2bl carb engine.
Tom Parsons
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From: Folsom CA
The 327 main/rod journal size was increased in 1968 for several good reasons. It commonized the block main bore machining, commonized main/rod bearing shells, commonized big end rod bore macinining, not to mention crankshaft machining, all between the 327/350 engines.
It was made possible when the 327 went to the cast crank in '68 and had larger size raw journals cast in.
That was probably a very big cost savings to GM at the time due to a reduction in complexity.
It was made possible when the 327 went to the cast crank in '68 and had larger size raw journals cast in.
That was probably a very big cost savings to GM at the time due to a reduction in complexity.
Pro
Joined: Jan 2007
Posts: 524
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From: Auckland New Zealand
ALLLLLLLLLLLL 327 engines were 2bolt only.
ALLLLLLLLLLLLLLLLL small journal engines were 2 bolt only.
The very first year model for a 4bolt small block was 1969 (NO, none of the 67 or 68 big journal small blocks were 4bolt)
ALL 69 302 engines (they were Z28, hi-rpm engines) were 4bolt.
Beginning with the 69 models, various 350 engines (including many truck 350 engines) got 4bolt blocks.
NOT ALL truck 4bolt 350 engines got forged cranks (it is commonly believed that if an engine had 4bolt mains, it also had a forged crank. WRONG).
For a rebuild, a crank MAY NOT always get ground. I have torn down a few engines, and discovered a crank would be good to go with only polishing. Low perf engines, that have been well maintained, and had regular oil changes will oftern have a near perfect crank.
A lot of people will swear all day long on Sunday that SB400 engines had 2bolts in 70-72 and 4bolts in 73-80. NOT SO! ALLLLL 70-71-72 SB400s were ONLY 4bolt engines. ALLLLLL 73-80 SB400s had 2bolt mains. NOW, there MAY be an exception to this. This is NOT solidly documented. SOME, maybe SOME, VERY EARLY 73 models got the very tail end of 4bolt SB400s from the 72 models. But we're talking about an EXTREMELY SMALL quantity of very early 73 cars that MAY have received a 4bolt SB400. So, for the record, 70-72 400s were all 4bolt and 73-80 400s were 2bolt only. That is NOT from me, that is from official GM documentation. And I'm in agreement with that, because all the 70-72 400s I've torn down/rebuilt were 4bolt blocks and all the 73-80 400s were 2bolt.
That would be similar (thinking) to a very early 63 FI Corvette receiving a left over 62 FI unit-------------------DIDN'T HAPPEN!
I emphasize this 2-4bolt SB400 issue because there have been MANY people swear that 4bolt 400s were installed AFTER the 72 model run---------------------------but none of 'um have provided any proof/documentation (I suspect those people can't tell a 72 from a 73 Chevy).
Tom Parsons
ALLLLLLLLLLLLLLLLL small journal engines were 2 bolt only.
The very first year model for a 4bolt small block was 1969 (NO, none of the 67 or 68 big journal small blocks were 4bolt)
ALL 69 302 engines (they were Z28, hi-rpm engines) were 4bolt.
Beginning with the 69 models, various 350 engines (including many truck 350 engines) got 4bolt blocks.
NOT ALL truck 4bolt 350 engines got forged cranks (it is commonly believed that if an engine had 4bolt mains, it also had a forged crank. WRONG).
For a rebuild, a crank MAY NOT always get ground. I have torn down a few engines, and discovered a crank would be good to go with only polishing. Low perf engines, that have been well maintained, and had regular oil changes will oftern have a near perfect crank.
A lot of people will swear all day long on Sunday that SB400 engines had 2bolts in 70-72 and 4bolts in 73-80. NOT SO! ALLLLL 70-71-72 SB400s were ONLY 4bolt engines. ALLLLLL 73-80 SB400s had 2bolt mains. NOW, there MAY be an exception to this. This is NOT solidly documented. SOME, maybe SOME, VERY EARLY 73 models got the very tail end of 4bolt SB400s from the 72 models. But we're talking about an EXTREMELY SMALL quantity of very early 73 cars that MAY have received a 4bolt SB400. So, for the record, 70-72 400s were all 4bolt and 73-80 400s were 2bolt only. That is NOT from me, that is from official GM documentation. And I'm in agreement with that, because all the 70-72 400s I've torn down/rebuilt were 4bolt blocks and all the 73-80 400s were 2bolt.
That would be similar (thinking) to a very early 63 FI Corvette receiving a left over 62 FI unit-------------------DIDN'T HAPPEN!
I emphasize this 2-4bolt SB400 issue because there have been MANY people swear that 4bolt 400s were installed AFTER the 72 model run---------------------------but none of 'um have provided any proof/documentation (I suspect those people can't tell a 72 from a 73 Chevy).
Tom Parsons
I'm on the lookout down this part of the world for some old 327/350/400 short block and this info is invaluable.
This is a definite copy and paste into my 327 info file.
Thanks
Neville
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Neville,
If you EVER run across a good, rebuildable SB400, latch on to it!
The last year for the 400, stateside, was 1980 and they are becoming rather scarce. I have NO CLUE what the sources for a 400 are in your part of the world.
When properly built, they make an excellent big torque engine that will drop right in where any small block was originally installed.
If you find one, and should desire to build one, there is plenty of knowledgeable people that can provide any and all information that you may need.
Also, what do you have in the way of quality engine machine shops in your area?
Tom Parsons
If you EVER run across a good, rebuildable SB400, latch on to it!
The last year for the 400, stateside, was 1980 and they are becoming rather scarce. I have NO CLUE what the sources for a 400 are in your part of the world.
When properly built, they make an excellent big torque engine that will drop right in where any small block was originally installed.
If you find one, and should desire to build one, there is plenty of knowledgeable people that can provide any and all information that you may need.
Also, what do you have in the way of quality engine machine shops in your area?
Tom Parsons
Pro
Joined: Jan 2007
Posts: 524
Likes: 12
From: Auckland New Zealand
Neville,
If you EVER run across a good, rebuildable SB400, latch on to it!
The last year for the 400, stateside, was 1980 and they are becoming rather scarce. I have NO CLUE what the sources for a 400 are in your part of the world.
When properly built, they make an excellent big torque engine that will drop right in where any small block was originally installed.
If you find one, and should desire to build one, there is plenty of knowledgeable people that can provide any and all information that you may need.
Also, what do you have in the way of quality engine machine shops in your area?
Tom Parsons
If you EVER run across a good, rebuildable SB400, latch on to it!
The last year for the 400, stateside, was 1980 and they are becoming rather scarce. I have NO CLUE what the sources for a 400 are in your part of the world.
When properly built, they make an excellent big torque engine that will drop right in where any small block was originally installed.
If you find one, and should desire to build one, there is plenty of knowledgeable people that can provide any and all information that you may need.
Also, what do you have in the way of quality engine machine shops in your area?
Tom Parsons
I think I have found a motherload source for some good sb 327 & 400 used short blocks from where I buy some of my parts from down here. The guy took me around out back of store where he showed me some containers. One was full of shelves of cyl heads (mostly chev and ford) another cranks (including std size 265, 283, 327) and bare blocks (chev ford and chrysler) and yet another used short blocks (chev ford and chrysler) and there were some 400s in there that he pointed out. He is looking to clear alot of this, so I'm going to go down and have a better look.
New Zealand is full of places like this. Amazing amount of old US 50s 60 70s stuff has been brought into this country by the container load, over the years and hoarded by these squirrels all over the country.
What would be the casting numbers to look out for ie 4 bolt blocks?
Neville
Last edited by Nev Williams; Dec 17, 2011 at 08:34 PM.
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Casting number for a 4bolt SB400 block is NOT what you want to look for. What you want to look for is a CASTING DATE before July 72. As I mentioned, the SB400 went to 2bolt blocks for the 73 model and PROBABLY, engines cast in Aug, or at least LATE Aug of 72, went into 73 model cars. The casting numbers for SB400 blocks are 330817, 3951509, 3951511. Any of those casting numbers could have had 2 or 4bolt mains. As I said, the 2 or 4bolt configuration is dependant on when it was cast, NOT casting number.
Tom Parsons
Tom Parsons
