[ID67goat]

Originally Posted by GoreMaker

Ultimately, they'll build whatever the customer asks them to, even if it seems unreasonable. They'll just make sure you know what is and isn't covered if you choose to use a questionable component.

So far, I'm still leaning towards using my numbers matching 557 block for this build.

Actually, I don't think that they really care what the customer wants or what is best for the customer. I have one of these (4.25 stroke) short blocks from them....and when I was ordering the short block , I made it clear that it would be going in a 67 GTO, and that the heads/cam that I was using on my 428 (which would be put on this new engine) was making 420 rwhp.....but what I ended up with was a 557 based stroker, that was not balanced very well, with main journals out of round, and it required motor mount adapters for me to put it in my car. Last trip to the dyno was 460 rwhp......is it a ticking time bomb? Maybe?

Probably only reason I haven't had a problem is that the car is just a street car and only raced maybe once a year.

I think you will be fine building this up like you want for a street car, but there is no way I would trust a 557 block if you were going to the track every weekend.

[Skip Fix]

FWIW my RAIV heads are going on a different short block when I get to that project.

[b-man]

Safest bet?

Tuck your numbers matching block under your workbench and save it to preserve the value of your car.

Building off of a stronger 400 or 455 block might save you the headache of replacing a failed thin web block further on down the road.

If keeping the original numbers matching 400 557 block to retain the best resale value isn’t a priority then roll the dice and build your 557 block.

[GoreMaker]

I didn't buy this car as an investment to increase my estate value. The car has a very unique meaning to me that's way more valuable than any resale. So it's not so much a value thing as it is a desire to keep it original and whole, for whatever that's worth. Therefore preserving the block to keep from devaluing the car doesn't mean jack to me. I'd just like to keep the car original while still having it put out more power than stock... 200hp/325tq isn't the kind of thrust I'm accustomed to these days. I'd be much happier with 400hp/450tq with horsepower that peaks just under 5000rpm, so that's what I'm aiming for. I don't want or need more power than that, I have other cars for that stuff.

Having said that, most of the nostalgia of this car comes from my previous ownership of a '78 W72 that had a 988XX block from the factory. So maybe I should just get an old 988 (not XX) casting from somewhere and avoid the chance of having to build an engine twice...

[Sirrotica]

Originally Posted by GoreMaker

I didn't buy this car as an investment to increase my estate value. The car has a very unique meaning to me that's way more valuable than any resale. So it's not so much a value thing as it is a desire to keep it original and whole, for whatever that's worth. Therefore preserving the block to keep from devaluing the car doesn't mean jack to me. I'd just like to keep the car original while still having it put out more power than stock... 200hp/325tq isn't the kind of thrust I'm accustomed to these days. I'd be much happier with 400hp/450tq with horsepower that peaks just under 5000rpm, so that's what I'm aiming for. I don't want or need more power than that, I have other cars for that stuff.

Having said that, most of the nostalgia of this car comes from my previous ownership of a '78 W72 that had a 988XX block from the factory. So maybe I should just get an old 988 (not XX) casting from somewhere and avoid the chance of having to build an engine twice...

You've given yourself good advice........

Building a foundation on sand, or bedrock, has a lot to do with what kind of a structure you end up with down the road.

[mgarblik]

If it were my car and my plans were for 400 reliable Pontiac HP, I would store the original 557 short block for future car sale value. Then buy an older casting that can easily handle the HP you plan to make. Using the weak 557 casting, every time you floor the accelerator, make a power shift, do you want to be worried chunks of the block are going to end up in the oil pan along with other parts failures? Seems that would take allot of fun out of the project. The cost to build a 557 block vs an older casting is the same, except for the block. $ 400-500 will buy a good 400 core block from an earlier casting series. They are simply far superior in all the areas that matter for strength and durability. If you insist on using a 557 block, having a light rotating assembly, a really good harmonic balancer like an ATI, and an accurate internal balance job is about the best band aid you can put on those blocks. 4 bolt main caps won't benefit on that block. There isn't meaningful material to bolt into. The cross-section where the mains tear out in the pics provided don't look to be 3/16" thick. IMO, a halo cap strap deal might actually be worse than leaving the caps alone. Now you are tying 5 weak caps and block structure together and creating a larger lever to tear the block out. It's just like I tell my students in the engine building classes: The short block creates the durability, the cylinder heads make the power. A weak lightweight block is just like building your dream house on the beach without a foundation. There is a reason PMD felt 200 or so HP was where they wanted to be with that casting.

[Jay S]

Maybe I can help. I designed and built some girdles for Pontiacs for different levels of performance. I made 10 of this prototype, these fit in stock type oil pans with no modifications, I have plans for 3 of them. I will likely find homes for the other 7 at some point, and I can always make more. I have worked on this off and on, and haven’t pursued selling any, not sure what they would run for cost now with inflation. It was going to cost around $450 with all the fasteners before the feds decide to put us all into debt. Hoping to keep it all under $500.

Could possibly also just do the halos without the frame rail supports with studs for a little insurance, the one in the photos shims the oil pan down a .25”. It will fit any factory 3” block as long as it has stock factory 2 bolt or 4 bolt caps, may fit with some aftermarket caps too, it is designed for the milidon and canton pans. I am working on a second engine now that is more for testing.

Here is the photo of a 462 cid 500557 i did, which is the original engine in my 77 4 speed W72 trans am, likely 550 HP or so. It has the orginal 6X heads I ported and flow 292 cfm @28” intake and 224cfm on the exh. 2.125” intake valve, 1.77 exh, 192 intake port volume. Cam is a Bullet hybrid roller set up with .630” lift. It mostly a cruiser.

It has a Milidon 7 qt pan with the kick out. One picture is of it back when I installed it, it fit with no mods, the other with my enthusiastic assistant helping check the mains. Lol

I will put the stock intake back on eventually when I get a chance to port one and weld it so it seals up with the bigger RA4 size ports. Stock looking 550hp smog era engine.

[GoreMaker]

Huh, that looks really cool. Can you explain what the outside bolts screw into? I'm trying to understand what the girdle ties into beyond holding the main caps together.

I just did a cursory search for engine blocks. While older 400 blocks aren't exactly "rare", they're not cheap. And 557 blocks are EVERYWHERE and really affordable. It seems to me that a product that helps resolve the weak main webbing issue would be very welcome and popular since it would open up a whole lot of performance for those plentiful blocks.

[Jay S]

The outside bolts (7/16” dia grade 8 gold bolts) your seeing go through the bridge support which tie the right and left halo’s together. Then goes through the pan rail support to tie the entire thing to the pan rails. The halo’s are sandwiched between the bridge support and pan rail support.

For a really high hp application the main caps can be machine flat and 1” thick strap on the bridge support. Those photos have stock caps and .25” bridge supports. No machine work other than a line hone on the mains for using main studs.

[GoreMaker]

Nice! Does this preclude using a windage tray?

[Jay S]

Here are a couple others I modeled on solid works also to fit a stock oil pan. This one has billet aluminum bridges but cost was almost 3x more to make it. Looked like it offer better support on #1 main.

The other one that appears to have some type of windage tray on it is the expandable halo style with a tray designed to reinforce the 1 and 5 caps.

[Jay S]

I haven’t finished designing a windage tray to fit it., or tried modifying one to fit. One would work with it but would need to be modified and bolted to a couple of the bridge supports. The way it is now it should have some crank scraping action to it.

I am hoping to try some different stuff to see if windage is effected on this second engine I am working on. Some trials with and without it to see if there is any parasitic loss/gain from running variations of theses.

[Formulabruce]

Originally Posted by GoreMaker

I was planning on a replacement internally balanced rotating assembly with at least forged rods and pistons, and possibly a forged crank.

not boosted, I would recommend Hypereutectic pistons.
less wear and long life for your motor.
Other than that make 100% CERTAIN that you are balanced within 1/2 a gram and youll be good. Shoot for the torque you want at driving speeds. HP will almost always be way up past where youll use it or feel it.
Dyno's do NOT Measure HP...... only calculate it with a bunch of variables
that can be programed in to the machine.
The Torque is REAL, and you can feel it.

[Aus78Formula]

Just build it. If it gets pulled for something else it will never go back in.

[Jay S]

I doubt my original engine would have ever made it back in my car if I didn’t keep it in the car. It would be lost in my engine shed with the other 75 engines for the day when my kid or kin are trying to figure out what all those engine belong too.

My research has suggested a lot problems breaking out the main bulk heads on 557 blocks originated from issues that came from the factory’s machining with improper machining on the dowels pins. They had severe issues when they were first introduced in late 1975 and into 1976. A crack would start at the dowel and slowly get bigger. They solved the issue in 77 with roll pins to index the caps but then created another issue, the roll pins did not index the main caps as well. Some spun main bearings, I have a 77 W72 I bought that had than happen.

If you have a skilled machinist hone the dowel holes for the slightly bigger 5/16” size and use ARP main studs with a proper line honing the 557’s will take a good amount of abuse. Not sure what Bulter’s do on the dowels when they rework 557s. But Jim Bulter told me he liked to do 4” cranks in them on mild builds with 350 Hp. Rodney Butler has told guys that with main studs he doesn’t have issues with 550 hp for street use with 3.75” and 4” cranks. Jim was obviously a little more conservative on his opinion. Lol

[Elarson]

Originally Posted by mgarblik

If you insist on using a 557 block, having a light rotating assembly, a really good harmonic balancer like an ATI, and an accurate internal balance job is about the best band aid you can put on those blocks. 4 bolt main caps won't benefit on that block. There isn't meaningful material to bolt into.

Yup, do this. And a few more thoughts:

Avoid detonation at all costs. Good fuel and don't squeeze a lot of ignition advance in it.
Keep the rpm reasonable (maybe under 6000 and don't full-throttle lug it at low rpm)
And don't start lusting for more than the 400 hp that you're planning for the build.

Eric

[mgarblik]

Originally Posted by Jay S

I doubt my original engine would have ever made it back in my car if I didn’t keep it in the car. It would be lost in my engine shed with the other 75 engines for the day when my kid or kin are trying to figure out what all those engine belong too.

My research has suggested a lot problems breaking out the main bulk heads on 557 blocks originated from issues that came from the factory’s machining with improper machining on the dowels pins. They had severe issues when they were first introduced in late 1975 and into 1976. A crack would start at the dowel and slowly get bigger. They solved the issue in 77 with roll pins to index the caps but then created another issue, the roll pins did not index the main caps as well. Some spun main bearings, I have a 77 W72 I bought that had than happen.

If you have a skilled machinist hone the dowel holes for the slightly bigger 5/16” size and use ARP main studs with a proper line honing the 557’s will take a good amount of abuse. Not sure what Bulter’s do on the dowels when they rework 557s. But Jim Bulter told me he liked to do 4” cranks in them on mild builds with 350 Hp. Rodney Butler has told guys that with main studs he doesn’t have issues with 550 hp for street use with 3.75” and 4” cranks. Jim was obviously a little more conservative on his opinion. Lol

You bring up some good points about the roll pins, (spring pins) they used to crutch the 557 blocks. I can see where those pins might help keep the block from cracking in a stock type application. Since they are a spring pin and not solid. They would tend to install easier in assembly as a solid pin would not be inserted into a paper thin casting. The roll pin would compress and go into the hole easier. But they left very little pin sticking into the cap and the fit was loose. So cap walk would become an issue quickly as power moves up the chart. Might equalize the tendency for the cap to just break out, rather than the block at that thin intersection. Have seen dozens of the cap corners break off. I guess that's better than the block . In any event, when a block with double the HP making potential is available for $400.00-500.00, and if numbers matching stuff is not a concern, that's pretty cheap insurance. Good luck with whatever Pontiac you decide to build. As mentioned, people have made big power with 557 blocks. Since I have never even won $2.00 on a scratch off lottery ticket, I want the cheap insurance.

[tom s]

I guess I really need to buy a loto ticket!Made almost 600 with a 557 and made 435 and 478 with a couple 301T blocks!I think they were like 200HP with a turbo.Tom

[mgarblik]

Originally Posted by tom s

I guess I really need to buy a loto ticket!Made almost 600 with a 557 and made 435 and 478 with a couple 301T blocks!I think they were like 200HP with a turbo.Tom

Why not? Spending Lotto money on Pontiac stuff would be great fun! Having a great machine shop, and careful assembly, and quality parts will help stack the deck in your favor. So I certainly wouldn't say "it can't be done". You and others have proved that.

[GoreMaker]

I've spoken to a few engine shops about this, both local shops and some far-away shops that specialize in Pontiacs. The local shops have no clue. They have no understanding of casting differences from year to year. I usually stop taking them seriously when they ask me if I'm talking "Pontiac big block or small block?"

The engine shops that specialize in Pontiacs seem to all agree: 557 blocks are fine for most builds up to 500hp if prepped adequately. Butler Performance even lists their 557-based builds and kits right on the site, they don't pretend they're anything else. These shops will even build strokers with 557 blocks and still offer the same warranty. The primary concern with 557 blocks seems to be the dowel pins at the main caps. Solid dowel pins in the stock holes apparently stress the main webs, especially at higher RPM. The pins fit too tightly, and they're not quite long enough. The rolled spring pins used in W72 engines mostly resolve that issue, but they're not adequate for higher power builds because they allow the caps to walk a bit, which becomes its own issue. Every shop I spoke to (spent a total of over an hour talking to 3 different Pontiac shops on the phone) basically uses a dowel pin "fix" to help prevent failure at the main webbing: longer dowel pins that fit less tightly than the originals. There's also the usual cleaning and de-burring going on. But none of them have any reservations about building a 500hp stroker using 557 blocks while still offering their full warranty.

There's a crapton of 557 blocks out there. It would be an enormous shame to discount all of them, especially since not every build needs to be a 750hp super stroker.

So with this in mind, I think I'll move ahead with my 400hp build using my stock block and heads. I've chosen a Pontiac-centric machine shop to do the prepping and machining and I look forward to working with them.