3959512 large journal 4 bolt block
 

Hi guys, I stumbled across a block and was wondering what it was. Im an engine machinist and didnt have a clue as to what this was. I did a google search, and seams like its kind of a rare bird, I founda lot of info on this site. I think I have one thats even more rare. I have a standard 4 inch bore, large journal,with a vent hole and 4 bolt main 3959512 block, it does hace CE on the front pad, I dont know what kind of starting asking price would be reasonable for this block. I also have several other283 and 327 blocks,427 heads and dont know where the best place is to sell this stuff.I prefer to stay away from ebay(just because its a pain) any tips or suggestions would be great, thanks

Just "happened to stumble across this stuff" so you thought you'd sign up here, eh?

:D:lurk:

Ebay is still the best location to sell your items. Large viewing base. Costs a fortune for large items to the buyer for shipping.

Google it and you'll find a lot of info. Appearantly it was a `62-`67 327 block sold for racers. Thicker walls than standard and 2 bolt but some may have been converted to 4

Where are you, I'm interested... But only if I can inspect the block

Harry

west michigan, Ill get the date code and stamp off the front pad tomorrow and let you know tomorrow.

The original 512 casting is/was a 62-67 small journal 327 block.
LATER replacement bare blocks/short blocks were somewhat of a hybrid. That is, they had features of BOTH 67-earlier and 68-later blocks. This permitted using the block in a 67-earlier replacement application for engines that used a road draft tube and/or a fitting in the rear hole to permit plumbing a PCV valve.
For 68-later applications, the rear hole could be plugged and valve covers with holes and a twist-on oil cap could be used and the PCV valve plumbed into the valve cover.
I am somewhat familiar with this 512 block you have because I have one in one of my cars with a 77 casting date. NO PRODUCTION BLOCKS received the rear hole for crankcase ventilation beginning with 1968 vehicles-----------------they all used valve covers with holes.
Also, you mentioned the block was stamped with with a CE-------------------------that is a service replacement block, which means it was PROBABLY cast AFTER 1967 production engines. Therefore, IF, big IF, it was cast after 67, but had features to allow it to be compatable with 67-earlier cars (such as the rear hole for crankcase ventilation), then it would have the large journal crank bores and the different pad for a spin-on oil filter.
Now, regarding the 4-bolt mains. As I pointed out above, this would be a REPLACEMENT block, cast AFTER 1967. NO, I repeat, NO 4-bolt main blocks were used in production UNTIL the 69 models. I DO NOT KNOW of any authoritative documentation that confirms the manufacture of a 1968 4-bolt main production block. Thus, if no 4-bolt main production blocks were made in 68, then it is HIGHLY UNLIKELY that any replacement 4-bolt blocks were made in 68.
One thing that has NOT been provided by topls69 is a casting date. If the casting date indicates the block was cast AFTER Sept 1968, then it is possible it could be a factory 4-bolt block. Otherwise, as already pointed out, it could have easily been converted by a machine shop to 4-bolt.

Tom Parsons

In addition to being a production block from 62-67, I believe the 3959512s were also service replacement blocks for a number of years. I have one with a 1970 casting date, large journals, and 4-bolt caps. Mine's been decked, so the pad is blank, but a CE on the pad probably indicates it was a warranty replacement. My guess is the 4-bolt configuration was from the factory--based on postings by JohnZ, the warranty replacement engines were machined and built to whatever configuration the original (failed) engine had. So, they could be 2-bolt or 4. If you find one, you don't know what you have until you take it apart.

EDIT: posted at the same time as DZAUTO.

One significant side note about one of these 512 style replacement blocks.
For ANYONE who owns a 67-earlier car, and wants BIG displacement in a small block, and wants to retain the ORIGINAL appearance, this is the perfect "cake and eat it too"!
With the hole in the rear, it will permit using the 67-earlier style crankcase ventilation system, RETAIN ORIGINAL VALVE COVERS (such as early finned alum covers) WITHOUT HOLES, but yet stroke it with a SB400 style crankshaft. Thus, replacing a tired 327 with a 383 torque monster (make your 57 Chevy look like it has a stock 283). :thumbs:
I wish I had 10 of these blocks! :D

Tom Parsons

The 3959512 and that whole series of 39595xx blocks were replacement castings for the out of production 283 and 327 blocks beginning in late 68 early 69 when the CE program started. Any replacement engines/blocks before 68 would have used current production engines/blocks. After 69, those small journal blocks were no longer used in production. GM recast the blocks with new casting numbers to service the small journal requirements as follows.
3959532 283 PASS/TRUCK CE
3959534 283 Chevy II/Nova CE
3959512 327 PASS/TRUCK 327 CE
3959538 327 Chevy II/Nova CE

I have a 3959532 283 and a 3959538 327 Chevy II and both were cast in 69. Don't know if they are large or small journal since the pans are on them.
The 3959538 was a warranty replacement shortblock in my 67 Nova and was an L-79 configuration.

I have a later one (I think from 73) which is still a small journal and two bolt main. It is 3959512

The small journals are a little bit surprising if it was cast in 1973. I understand that all production SBCs (including 327s) were switched to large journals starting in 1968, and I always assumed that was for commonality and efficiency. I wonder if they kept the small journal machining operation?

If the casting date ends in "3", maybe yours is actually a 1963 production block?

well the font was really small on the casting so I thought it was a later block. Did the font and size change for the 512?

The 9512 block never had a production application; it was produced exclusively for 4"-bore Service and "CE" 5/50 warranty replacement usage, in both small-journal and large-journal versions. Most of them were cast at the Saginaw Service Foundry and machined at the Saginaw Service Engine Plant. :thumbs:

The 512 block in my 64 built Sept.1, 1963 has a casting date of H-18-3 or Aug. 18, 1963. A recent rebuild showed it to be a small journal. It has a blank pad and no CE marking. Since the bore and pistons were original I don't think it had ever been decked. It is date correct for the car so it must have been a service replacement quite soon in the car's use. :thumbs: Dave

John, thanks for the info. Just curious, could one made in the 70s have small journals?

Interesting. I have a 327 (365) engine that I purchased from GM across the counter in about '72. When i can I'll take a look. I believe it to be small journal. I know it to have the forged crank and domed forged pistons and 30/30 cam solid lifters. The stampings are very faint, but as I remember is was CE. Parts manager told me I got the last one as he had lots of difficulty obtaining it and it was removed from the parts book next edition. Actually as I recall, it was removed from the new parts books before he received it. Didn't think he'd get it at all.

I have a 512 in my 54. It was made in 1971 and has large journals.

Yes - they were machined for both SJ and LJ applications. :thumbs:

The 512 CE block I bought new from Chev in 1976 as a 327/350 short block, was cast in March 1970, and assembled in 1974 according to the CE number on the stamp pad.

It has small journals (guaranteed, I did a ring and bearing and rod replacement about 3 years ago), and now powers my '37 Ford pickup, after performing well in the '651 Corvette for 30 some years.

Doug