[BruceWilkie]

Originally Posted by GRX

The 400 block is stronger than the 389. Generally thicker casting and webbing. I know this because I have had both side by side on my bench numerous times.

Depends on the year and casting.

Seems a trend that the 59 389, 67 400 were strongest of the lot... my old 68 350 was notably beefier than my 70 350 block. Early 455 seems a bit beefier than later 455's. Per previous post... pre-sono I had a 59 that was .150 overbore(4.21)... what I have now should go 4.25 bore. Deck is thicker than 400 plus reinforcement rib along pan rail.

If I can find time today I'll take some pics of my 59 389 my 69 400 and a 72 455 block. Wish I could easily open the wifes 406... its a 557 block.

About 8-9 years ago all 4, plus a 73 400 were all side by side. Should have taken pics back then.

If I had all 5 to chose from now the strength order would be 59 389 2 bolt drilled, 73 400 2 bolt drilled, 69 400 2 bolt caps 4 bolt drilling, 72 455 2 bolt caps 4 bolt drilled, and the 76 400 2 bolt.

A majority of the 68 and 69 400 blocks are all the same casting and most(all I've ever seen) were drilled for 4 bolt caps. Whether it had 2 or 4 bolt caps depended on application.

The rare 69 and 70 RAV non production blocks were basically the 59 389 casting with revised bell and lifter bracing. The SD 455 was also a "special" casting with similar features. The special 389 (Harvey machine) Aluminum blocks were patterned same as the 59 block. Most 1960 blocks are about the same as the 59 but the deck drillings are different to accomodate the change from reverse cool to conventional cooling that year. 61 was the bell pattern change somewher in late 61 early 62 they changed to "thinwall" casting technique,and 64 added the modern starter pad though b body still used trans mount starter.

[Steve Barcak]

Originally Posted by BruceWilkie

Depends on the year and casting.

Seems a trend that the 59 389, 67 400 were strongest of the lot... my old 68 350 was notably beefier than my 70 350 block. Early 455 seems a bit beefier than later 455's. Per previous post... pre-sono I had a 59 that was .150 overbore(4.21)... what I have now should go 4.25 bore. Deck is thicker than 400 plus reinforcement rib along pan rail.

If I can find time today I'll take some pics of my 59 389 my 69 400 and a 72 455 block. Wish I could easily open the wifes 406... its a 557 block.

About 8-9 years ago all 4, plus a 73 400 were all side by side. Should have taken pics back then.

If I had all 5 to chose from now the strength order would be 59 389 2 bolt drilled, 73 400 2 bolt drilled, 69 400 2 bolt caps 4 bolt drilling, 72 455 2 bolt caps 4 bolt drilled, and the 76 400 2 bolt.

A majority of the 68 and 69 400 blocks are all the same casting and most(all I've ever seen) were drilled for 4 bolt caps. Whether it had 2 or 4 bolt caps depended on application.

The rare 69 and 70 RAV non production blocks were basically the 59 389 casting with revised bell and lifter bracing. The SD 455 was also a "special" casting with similar features. The special 389 (Harvey machine) Aluminum blocks were patterned same as the 59 block. Most 1960 blocks are about the same as the 59 but the deck drillings are different to accomodate the change from reverse cool to conventional cooling that year. 61 was the bell pattern change somewher in late 61 early 62 they changed to "thinwall" casting technique,and 64 added the modern starter pad though b body still used trans mount starter.

From experience, I will agree with what Bruce states here.

GRX- making a statement like this- "The 400 block is stronger than the 389." is really inaccurate as there are many casting versions of each displacement. Certain 400s are indeed stronger than certain 389s but, some 389s are stronger, much stronger than any production 400 block.

I learned this on my own about 20 years back quite by accident. Sadly, no known printed book or article has yet to recognize this. Not sure why the authors leave this important info out of their publications.


The '59 and early '60 389 block is the strongest & toughest of all production blocks regardless of size or year. the only exception is the '58 370 is equal to the '59-"60. pontiac started taking weight out of the engine in 1961 and more out in 1964, It appears they put some back in for 1967.
If you are looking to build something to last a long time or for a keeper, you would be wise to seek out an early block as a foundation. You may or may not need an adaptor depending on your trans choice. If you are building a manual trans, you can use a 58-60 bellhousing. This fits later 4-5-6 speed trans and uses a stock starter. If using an automatic, you will need an adaptor.

With all the choices for blocks today, my preference for both my nitro burning AA/Fuel dragster and my 577" blown stroker is a '59 389 block. I have other engine designs using these early blocks as well.

'59 was the first year using the modern side motor mounts and there is very little to adapt to fit late model/aftermarket parts after you take care of your bellhousing needs.
Good luck to you whatever you choose.
I would discourage using a '64-6 389 block.

[GRX]

Originally Posted by BruceWilkie

Depends on the year and casting.

Originally Posted by Steve Barcak

From experience, I will agree with what Bruce states here.

GRX- making a statement like this- "The 400 block is stronger than the 389." is really inaccurate as there are many casting versions of each displacement. Certain 400s are indeed stronger than certain 389s but, some 389s are stronger, much stronger than any production 400 block.

You guys are absolutely right. My bad for making such an all inclusive statement.
I'll go sit in the corner with my Dunce hat on now.

I still say the way the mold was constructed, and the resulting parting lines in the casting, has much to do with the overall strength of the block. Nickle content and thickness too of course. For those who haven't seen it yet, there are many very good pics of blocks in this thread. Including some I posted with mold parting lines (posts 156, 157, and 158)

http://forums.maxperformanceinc.com/...g+lines&page=8