[Dauntless1971]

I looking at a 77 400 XA code thin casting block and would like to know if there was a basic worry free level of horsepower that it was capable of. I had picked up a set of 1968 number 16 heads but one was cracked, more on that in another post. I have heard that the crankshaft is also not very desirable.

[Formulas]

Every 557 engine i tore down was clapped out in stock form, at first i never paid attention to block numbers after 1970 until i keept finding only 557 blocks then it clicked, i keept seeing a pattern, ALOT of crank and bearing wear if all the rods were still attached at all

[Dragncar]

Well, I seen one bracket raced at the track.
RAIV cam, forged rods and pistons, ported 62s. Ran 11.10
It ended up cracking main bulkheads, all of them.

[steve25]

I would have no concern with longevity running such a block provided these guidelines are met.

Lighter aftermarket rods and pistons are used.

The stroke stays at 3.750”

A good balance job is done.

HP does not top 400.

All sharp edges are rolled over in the main web .

The motor is set up with a compression and tune so that it does not ever detonate .

A full size balancer is employed.

Rpm is held to no more then 5800.

[b-man]

Find a better block.

Yeah I know some people have used them for mild to high performance builds but with the money invested in machine work and parts it doesn’t make any sense to me anyway to build off of a 557 block.

The block core is one of the cheapest parts, starting with a good one is just common sense.

[Jay S]

FWIW…Bulter sells kits that include 557 blocks with 4” cranks and rates them for 500HP. I think about the only mod they do is line honing for ARP main studs.
https://butlerperformance.com/i-3164...html%3Fq%3D557

[77 TRASHCAN]

I'm not an expert....Is the XA block, automatically a thin 557 block???

I wonder how many Pontiac blocks, Butler has left???

A 4" stroke 400 block engine, is a pretty cool combo, to me. 6X-4 heads gets the comp ratio over 9:1, easily. Mill a pair of 6X-8's down to 95 cc's and you are right at 9:1

I am NOT advocating using the thin block, though!!!

[Jay S]

Jeff I think the better question is how many old 400 blocks does Butler’s have left since they are selling 557s instead. Lol

All the 1977 400s where 557s. In 78 I think the XA code was a 301

[steve25]

How many here had a 78 TA with the W72 package, let me jump the gun here.

I had two, one with 40k miles on it and another with 80k on it when I got it .
Both auto trans models.
This 80k one when I got the first thing I did was replace the timing chain and gears and I stuff a Isky 270 Mega cam in it and took off the cat and installed a duel exh., removed the EGR and rejetted the carb.

I drove that car to work until it had 120k on it and beat the snot out of it at least 3 times a week.
Now this was the all with the thin main web block that it seems everyone here is talking down even though I bet not many of you drove one of these when they where new
For a every day car back then they where quite satisfying as looking back on the sales numbers show.

I can’t see why the OP of this string would not be pleased with one of these 400 motors if it was making a real 300 hp and not the 220 hp that all the buyers of the W72 package back in 78 and 79 seemed to be ok with.

['ol Pinion head]

78 180 horse 400 blocks were 557's.
78 & 79 W72 blocks were 481988 XX blocks.

Personally would not have an issue with .030 milled 6X-4's, & a build with a cam like a Summit 2801 on a 557 casting 400 block. Block squared & decked minimally. Have gone that route multiple times. Going in a max 400 hp build for a '75 up 2nd Gen or a '78 up A-G body, the late block fits, & in the core world, should be easier to find. In an earlier F-body or '64-74 A-body, I'd keep looking for an earlier nice clean 400 block core.

[Dauntless1971]

One of the reasons I am consider using the 557 block is the seller also has a set of 62 heads to go along. I suppose for the price I might buy the whole package and take the block to the scrap yard should be worth at least ten dollars.

[Skip Fix]

The RAIV 400 I ran the crap out of in NCMA after I could not run the heads on a 455 was a 557. Even heavy TRWs and Crower billets(before there were less expensive forged rods)Low 12 through exhaust @ 111mph weighing almost 4000 lbs. Pulled for and E head 455.

Tom S here had a mulle motor 557 block that has seen way more HP than mine!

[b-man]

I can see using the 557 if you lived in a country outside the USA where Pontiac blocks are scarce.

Otherwise why when you can use a different 400 block that’s not known for an inherent design flaw.

Just because you already have it doesn’t mean you have to use it.

[77 TRASHCAN]

I read the description of Butlers, "stroker" 557 build.
The one thing that stood out, AND that I've thought about a lot, IF, IF a person builds on one of those blocks is to de-burr the entire main web area. Pictures I've seen here of blowed up 557's all seemed to have a common problem. The broken piece started at either an oil hole in the main web, OR from a dowel pin hole. Some started at one of these spots and ended at the other. The edges of those holes ARE very sharp.

My 77 TA engine was pulled at 102,000 only because the #7 cam lobe had left the building. It had the hub balancer, no problems. Of course I highly maintained that engine, I intended for it to last forever. The AT shifted at 4000 and thats about all it ever got, I made less power, evern a few RPM's above that.

[Jay S]

The 557’s I have seen that broke had the crack start at the dowels, then work it’s way over to whatever area was next weakest. Some blocks have small cracks at the dowels that just barely started, so before you rebuild one they need to be checked in that area. The crack often will find it’s way to the oil hole in the mains, it is not where the crack started though, they have quite a bit of material in the center of the block and a reinforcement rib there.

I don’t think there is much for casting flashing in the main webbing that you can clean up that will help.

Bulter’s charge a grand more for the earlier blocks for the same kit as the 557. They sell a lot of 557s, I have even seen some Butler 557s with 4.25” cranks.

[b-man]

Checking the Butler website I see engine kits ranging from 11 to 22k and complete engines from 14 to 24k.

If I were in the market paying an extra grand to not be stuck with an inferior 557 block would be a no-brainer.

You could also source your own 400 block core and ship it to them and save in the neighborhood of half a grand.

[Jay S]

Originally Posted by b-man

Checking the Butler website I see engine kits ranging from 11 to 22k and complete engines from 14 to 24k.

If I were in the market paying an extra grand to not be stuck with an inferior 557 block would be a no-brainer.

You could also source your own 400 block core and ship it to them and save in the neighborhood of half a grand.

Kind of makes you wonder what kind of sales pitch Butler’s do when selling 557.

[77 TRASHCAN]

Originally Posted by Jay S

Kind of makes you wonder what kind of sales pitch Butler’s do when selling 557.

If you don't have current knowledge of the Pontiac brand, like reading, here, you may not know......

[i82much]

This thread is like reading about someone deciding whether or not to use a condom the next time they go to Thailand. I mean it's your choice but if you decide not to play it safe, you already have a pretty good idea of what the consequences are gonna be for your junk!!!

[Jay S]

Originally Posted by i82much

This thread is like reading about someone deciding whether or not to use a condom the next time they go to Thailand. I mean it's your choice but if you decide not to play it safe, you already have a pretty good idea of what the consequences are gonna be for your junk!!!

That is a hilarious.

A 557 block and stock d ports is more like picking up a chick at a church potluck. It could still go wrong, but you have decent odds, some of us drive 50 year old 10 second street cars. We like to gamble some.