[Tom Vaught]

I posted a long time ago about the merits of the 67 block.
Maybe this post will clarify some of my thoughts in that area.

Tom V.

[kookykrispy]

So is a 67 considered to be among the strongest 400's? I ask because I want to build a (relatively) bullet-proof shortblock (and I'd like to stay with a factory block) in the near future to support cranking up the boost on my 6-71 and possibly adding a bit of squeeze too.

[screamingchief]

I went out and looked at all my blocks,all had thicker bulkheads than Skips block,most are early '70's (1-350,3-400's,1-455) blocks,one of them,a '70 YS 400 block was obviously thicker and cast differently from the later blocks,it looked more like the '67 block pictured by SergeF,but it still had some slight differences from that one too.

I tried to take pics but most turned out terrible,I'll take more tomorrow and post 'em,I'll try and get the year,and block casting #'s as well.

I'll dig thru my stored pics too,might have a pic of the bottom end of the 455 I dropped into my firebird not too long ago.

Gotta go,need sleep...

[GRX]

Two blocks here, an early '67 "WT" - #9786133 ... and an early '75 "YJ" - #481988.

Comparring them side by side I noticed some VERY interesting differences, particularly in the parting lines. The two blocks look the same but the molds were structured quite differently. I'll post some images later today after another project is finished.

[Jeff Walker]

Here's a couple pics of the block from my race car. It's a 1969 block.

[Skip Fix]

Looks like the material out to the dowels vs the bolts is the biggest thing showing up.

[70 lucerne lemans]

You guys have me nervous now! I just finished building my early 1975 400 block,I thought it had the thicker webbing,now Im not sure.Ill post the date code later if anyone could help.The motor is already done so I guess it would only be for peace of mind at this point.I did fill the block and stud the mains,looking for around 550-600 hp keeping it under 6000rpm.

[screamingchief]

My '70 YS block looks to be virtually identical to the pics of Jeff Walker's race block.

The bottom end on the '70 YS is still assembled,but that's the spittin' image of the casting it uses,his pic is better than what I'd get,really did'nt wanna break it down just for this deal,so that pic saves me some effort.

Only visible difference is the '70 block has the extra motor-mount bosses.

I'll be back with those pics a bit later.

[Skip Fix]

My block(actually a brand new one) is a 76 casting made in 77, and the same casting my original 78 TA 180 hp had. I wanted opinions before I said what year it is. I'm glad we have some pictures to compare what areas are different.

[70 lucerne lemans]

I just looked at my date code again- I165 and casting # 500557.It looks like it was made in sept. 1975,I misread the code before.Dude could you chime in on this,I was planning on racing this one.

[69birdboy]

500557 is not the thick one. I have one with the same casting number, and it's got good thick cylinders, but not thick under the caps!! I was planning on using mine to race too, but discovered I have to look for an earlier one.

[PONTIAC DUDE]

I really don't know about the date and run of the blocks.
I just go by looking at the webbing area. You will also notice that some blocks have the same meat under the cylinder and have a wider casting to meet the cap. In other words I have seen some blocks that are narrower then the cap and some that are the same width. Some that are wide then cut narrower right after the cap area on the block to the pan rail.

As far as how much abuse a certain thicker casting block will take over another. Your guess is as good as mine.
But bottom filling, deburring and studs to offset loads can't hurt.

Most I have encountered split right up the middle to the camshaft or from the dowels to the cam.

[HWYSTR455]

I selected a block that a machine shop had and held for me for 3 years. I was ready to start on that engine, dropped the pistons & caps off, and when I went to pick it up it was a different block then I had originally picked. Mine's a 77 block, and the cap area is narrower then the thickness of the caps. I filled it to the bottom of the freeze plugs, studs & 4 bolt aftermarket caps, and I'm going ot throw it in my driver with a 3" stroker kit & e-heads. I'm going to spray it with a 150 shot and cross my fingers! Oh well, it's what I ended up with, and don't feel like throwing it in a corner. Think it will last if I don't put slicks on it?

[flamedabone]

You guys act like the thin block is a BAD thing...

Here is my '75 block from this spring. The motor was two years old...

The car is my daily driver mid/high 12 second 3000lb car. Fairly mild really..

-Abone.

[PONTIAC DUDE]

Originally Posted by HWYSTR455

I selected a block that a machine shop had and held for me for 3 years. I was ready to start on that engine, dropped the pistons & caps off, and when I went to pick it up it was a different block then I had originally picked. Mine's a 77 block, and the cap area is narrower then the thickness of the caps. I filled it to the bottom of the freeze plugs, studs & 4 bolt aftermarket caps, and I'm going ot throw it in my driver with a 3" stroker kit & e-heads. I'm going to spray it with a 150 shot and cross my fingers! Oh well, it's what I ended up with, and don't feel like throwing it in a corner. Think it will last if I don't put slicks on it?

Good luck. I have split 2 of those kind of blocks. Not trying to be a smart a$$ but, Personally I don't know why the shop 4 bolted that block? Makes it even weaker in that area.

[79bluebird]

when did they stop makin the the thick version block? i have a late 72 400 that i makin a 416 stroker

[Colin]

Originally Posted by 79bluebird

when did they stop makin the the thick version block? i have a late 72 400 that i makin a 416 stroker

I have heard 1974...but I dont know. I do know that a '74 block (may be a '73) that I have appears to have more meat than the one Skip posted pics of.

[screamingchief]

Well,,,after some frustration with my digicam I'll post my pics.

First set is my race cars 400:
casting= 481988
date code= D093
Code= XN
application= '73 230 HP,A/T,4bbl.

[screamingchief]

Next,spare 400 bare block w/caps:Valley is the same as race 400.

casting number= 481988
date code= l053
code= YH
application= '74 190 hp,A/T,2bbl.

[screamingchief]

And for now my spare 455 block,bare w/caps:

casting number= 485428
date code= ?183
code= YU
application= '74 250 hp,A/T,4bbl.