283 & 327 w/4 bolt mains

[Gary L.]

Re: 283 & 327 w/4 bolt mains

Oh but their is a lesson to be learned about engines,especially the ill fated 327 small journal,Casting number 3955618 327 4-bolt main block was first introduced in 1968 as one of the first 4-bolt small journal engines for the Corvette, '' BUT'' , it did not last long. Very few of these engines were put in production before engineering changed to large journal. This engine is so rare and so few were made in production in 1968 that they are worth a fortune. Good luck finding one.

[Joe L.]

Re: 283 & 327 w/4 bolt mains

Oh but their is a lesson to be learned about engines,especially the ill fated 327 small journal,Casting number 3955618 327 4-bolt main block was first introduced in 1968 as one of the first 4-bolt small journal engines for the Corvette, '' BUT'' , it did not last long. Very few of these engines were put in production before engineering changed to large journal. This engine is so rare and so few were made in production in 1968 that they are worth a fortune. Good luck finding one.

Gary-----


The GM #3955618 is so rare that I can find no record of it, whatsoever, as an engine block. However, I can find a record of it as a seat belt applicable to 1968-69 Chevrolet light trucks.

There was a block once known as GM casting #3956618, though. However, this was a 1969 block (although released in late 1968 calendar year). While it was used for some 1969 327 applications, for these applications it was a large journal, 2 bolt main block. It was NEVER used in a 1969 Corvette as a 327 cid engine, either 2 bolt or 4 bolt main configuration.

For the most part, the 3956618 was used as a 350 block (although also used for 302) and across all the various Chevrolet car lines. It was finished into both 2 and 4 bolt main configuration. Most 1969 Corvettes with 350 use the 3956618 block although it was replaced in later 1969 by the GM #3970010.

If the 3956618 was ever manufactured into a small journal block, I have no record of it. If it was, it would have been for pre-1968 SERVICE-only since all 1968 and later blocks used for PRODUCTION were large journal.

I have no record of any 4 bolt main caps ever having been manufactured or offered by GM for small journal blocks, the 3956618 or otherwise.

[Gary L.]

Re: 283 & 327 w/4 bolt mains

Your getting close,they did change the number from 5 to 6 when they discontinued the first design. This number is even listed in motorbooks chevrolet small block v-8 ID guide. I have seen one of these blocks in my old machine shop days and I remember well arguing with the parts counter about bearings for it.For the record,GM built 3955618, 327 4-bolt 68-69, they also built 3956618, 302 4-bolt 1969, they also built 3956618, 350 4-bolt 69-76' , and last but not least, 3958618, 350 bolt 69-76'. The Corvette was the only car in 68' to get this design engine.

[Joe L.]

Re: 283 & 327 w/4 bolt mains

Your getting close,they did change the number from 5 to 6 when they discontinued the first design. This number is even listed in motorbooks chevrolet small block v-8 ID guide. I have seen one of these blocks in my old machine shop days and I remember well arguing with the parts counter about bearings for it.For the record,GM built 3955618, 327 4-bolt 68-69, they also built 3956618, 302 4-bolt 1969, they also built 3956618, 350 4-bolt 69-76' , and last but not least, 3958618, 350 bolt 69-76'. The Corvette was the only car in 68' to get this design engine.

Gary------

As I mentioned, GM #3955618 was a seat belt assembly for a 1968-69 Chevrolet light truck. So, it was not and could never have been an engine block.

GM #3958618 was a transmission side-cover assembly. So, it could not also have been a block casting.

No 1968 or later small blocks used in PRODUCTION were of the small main journal design.

[Michael H.]

Re: 283 & 327 w/4 bolt mains

327 small journal,Casting number 3955618 327 4-bolt main block .

I don't know about that casting number but you may be right on the fact that a few service only small journal 4 bolt main blocks were assembled for service in the late 60's.
I know that the 62-67 327's that were available for service in the late 60's and early 70's had a casting number somewhere around that numerical range but all that I've seen were 2 bolt main blocks.
I suppose it's possible that a few were actually made from 4 bolt main blocks. If so, they would probably be quite rare.

Casting and part numbers in the 3955xxx numerical range were definitely from the 1969 era.

[Gary L.]

Re: 283 & 327 w/4 bolt mains

Well for your info Joe Lucia, 327 casting #3955618, built in very early 68' used a crankshaft casting #3782680 that was small journal and forged, this block also used Head casting # 3973414, which used 2.02 intake and 1.60 valves and the heads were drilled with the bolt holes.This block also would have the HP stamp stamp on the VIN pad. You need to get out of your seatbelt book and invest in some books that deal with real Casting #s. Keep an open chambered mind,not a closed chambered mind. General Motors Corporation made a lot of Engineering changes during this time in the horsepower Wars.

[Joe L.]

Re: 283 & 327 w/4 bolt mains

Well for your info Joe Lucia, 327 casting #3955618, built in very early 68' used a crankshaft casting #3782680 that was small journal and forged, this block also used Head casting # 3973414, which used 2.02 intake and 1.60 valves and the heads were drilled with the bolt holes.This block also would have the HP stamp stamp on the VIN pad. You need to get out of your seatbelt book and invest in some books that deal with real Casting #s. Keep an open chambered mind,not a closed chambered mind. General Motors Corporation made a lot of Engineering changes during this time in the horsepower Wars.

Gary------


No block of GM casting number 3955618 ever existed. PERIOD. As I mentioned (now for the third time), GM #3955618 was a seat belt assembly applicable to 1968-69 Chevrolet light trucks. It could not also have been an engine block. Period.

Assuming that you are actually talking about block GM #3956618, that block was a large journal block. No block of that casting number used in a PRODUCTION vehicle EVER used a crankshaft of forging GM #3782680. Period. Is it possible that block was used as a SERVICE block for pre-1968 small journal applications? Yes, it's possible but I doubt it. For one thing, there was another SERVICE-only, 1969-released block which was used for pre-1968 applications. As I recall, the casting number was 3959512 or some number close to that.

I have no information that any PRODUCTION 327, small or large journal, ever used a 4 bolt main cap configuration. 1968 Corvettes with L-79 did not and I would think that if any 327 had used it, it would have been the 1968 L-79. The 1968 L-79 was a large journal 327. I have never seen or heard of an original 1968 L-79 that was originally equipped with 4 bolt mains.

If you have information that a 3955618 block existed ( I mean a REAL 3955618 and NOT a 3956618 that is being MISREAD as a 3955618), then please post some photos of it.

Also, if you have information that a 3956618 used in a PRODUCTION vehicle (i.e. one with a VIN derivative stamped on the engine stamp pad) with small main journal size was manufactured, please post pictures of such.

If you have information that GM ever manufactured small journal, 4 bolt main caps, please post pictures of them.

By the way, some 1968 Chevrolets may have used small journal small blocks, but those blocks were 1967 blocks and had 1967 casting numbers. As far as I know, no 1968 Corvette has ever been documented as originally built with such an engine. It may have happened for other Chevrolet models, though.

And one more thing: cylinder head GM #3973414 did not even exist until the 1970 model year. So, it's impossible that such a head could ever have been originally installed on an early 1968 engine.