67 Block casting #

[Randy S.]

Gents

What would be the correct block casting number for 1967 L79 manuf 12/28/66?

My reference books say 3892657 ( late 66). Seller states 3858174.

[Rocco S.]

Re: 67 Block casting #

Randy,

My original, one owner '67 with L79 engine with a build date of 3/30/67 has block casting number of 3892657.

[Leif A.]

Re: 67 Block casting #

Gents

What would be the correct block casting number for 1967 L79 manuf 12/28/66?

My reference books say 3892657 ( late 66). Seller states 3858174.

The 3858174 block was used for '66 Corvettes both 300hp and 350hp engines...if it's a Flint block.

[Randy S.]

Re: 67 Block casting #

The 3858174 block was used for '66 Corvettes both 300hp and 350hp engines...if it's a Flint block.

Leif,
Thanks

So it is probably the wrong block. My Corvette Black book (1989) says most 66's used 3858174 and late (?) 66 used 3892657. Both 300 and 350Hp 67's used it.
I suppose 3858174 could be correct if it were dated 6 months prior to Dec 28,66.

[Darryl D.]

Re: 67 Block casting #

Leif,
Thanks

So it is probably the wrong block. My Corvette Black book (1989) says most 66's used 3858174 and late (?) 66 used 3892657. Both 300 and 350Hp 67's used it.
I suppose 3858174 could be correct if it were dated 6 months prior to Dec 28,66.

The '657 block was used mostly for small-journal 302 and 327
engines. However, this same casting was also used for Chevy's very first 350,
used in the 350 RS Camaro. Chevy simply machined the same bare casting for large
journals.

So, the 657 casting itself can be found in both small journal
and large journal versions, but the large journal version is somewhat
rare.

One way to visually recognize the difference, even without using
calipers, is to look at the bearing tangs in the main journals. The small
journal versions had BOTH the small journal tangs and the large-journal tangs
(see attached photo). A large journal version has only the large-journal tangs,
since the small journal tangs were disappeared when the mains were bored for the
larger journals.

So, any 657
block can be simply line bored for large journal mains if desired. I did this
for a 383 that I built, just to take advantage of the stronger crank.

[Joe R.]

Re: 67 Block casting #

Leif,
Thanks

So it is probably the wrong block. My Corvette Black book (1989) says most 66's used 3858174 and late (?) 66 used 3892657. Both 300 and 350Hp 67's used it.
I suppose 3858174 could be correct if it were dated 6 months prior to Dec 28,66.

Generally speaking, the '174 block was used only for 1966 production, and the '657 block was used only for 1967 production.

However, in certain years, there have been documented cases where early production cars had blocks from the previous model year. I don't have my 1967 JG available to check whether such cases have been documented for the 1967 production year.

Note that for manufacturing of a given model year, production generally started in late August of the previous year (August 1966 for the 1967 model year). I have seen '657 blocks that were cast in September 1966, so I know that at least some '657 blocks were being produced well before December 1966.

While it seems unlikely that a '174 block would be used in a 1967 Corvette that was assembled in December 1966, the Corvette world is full of examples of production anomalies. I would guess that a '174 block is unlikely, but not impossible. What this means is that some additional work would be necessary to validate this as the original block. Careful attention to the pad and the casting date might provide some clues.

[Steven B.]

Re: 67 Block casting #

The '657 block was used mostly for small-journal 302 and 327
engines. However, this same casting was also used for Chevy's very first 350,
used in the 350 RS Camaro.

I think you mean the 1967 SS Camaro. It was the vehicle that debuted the 350. The SS could also be had with the RS (Z22) option which was an appearance option, including most notably, hidden headlamps, parking lights in the valance, side trim, as well as taillights without the backups, as the backup lights were located in the rear valance (and I may be missing an option or two), referred to IIRC, as an RS/SS.

Steve

[Ara G.]

Re: 67 Block casting #

Gents

What would be the correct block casting number for 1967 L79 manuf 12/28/66?

My reference books say 3892657 ( late 66). Seller states 3858174.

My original motor L79 with a build date of 12/22/66 has a 657 block FYI

[Pancho T.]

Re: 67 Block casting #

My original motor L79 with a build date of 9/20/66 has a 657 block FYI