[GoreMaker]

I'm planning to build up my 1977's W72 400 for some extra power, without going to any extremes. The 557 block used in that year has a lot of missing material from the casting, but this is an original matching numbers block and I really want to retain it. My power goals are around the 400hp mark without any stroking, which seems to be near the upper limit of what these blocks can handle reliably for years and years. So keeping this in mind, I was wondering if it's possible to stiffen up the webbing a bit to reduce the chances of cracking.

Would 4 bolt mains help to stiffen up that area? Are the bosses present in the casting to accommodate 4 bolt mains without removing too much material?

What about short-filling the block, is that something that might help?

Are there any main girdles available for this application? Would that help to stiffen up the bottom end?

[Gary H]

If you're going with the stock 3.750 stroke crank you won't have any issues at 400 hp. I've built several engines at that level with the 557 block and haven't had any issues at all. One, we actually used KRE D port heads on and a fairly healthy cam. No issues years later in the customers car. Nothing was done special in the main cap area. Stock bolts and caps. I would, however, be hesitant to use a stroker crank in one due to additional side loading of the block.

[TAKerry]

I am not a mechanic and all of the aforementioned lingo may as well be chinese. But I have a 557 block in my 77 T/A. The builder warmed it over slightly with a bit of a cam (whatever that means). He had no hesitation doing what he did. Car runs great! Never dyno'd but he estimated close to 400 hp with his knowledge of building motors and past experience. As far as I know he did nothing extra special as far as strengthening the block. I dont run it hard, never raced it and probably never will. Heck, I barely hit 60 going down the road. I do drive like an old man But the car will get out of its way when it wants to.

[ponyakr]

I'm on the opposite side of the fence.

Have pics of several 557 blocks with chunks missing out of main webs.

I'd do as many here have suggested in the past. Store your numbers matching engine, & save it for future sale with car.

Build what you want, using a stronger block. That way you want have to be worried whether it's gonna hold up or break.

Opinions differ.

I've read where some brag about how much power they made with a racing 557 block. That's fine IF you wanna take a chance. How lucky are you ?

[tom s]

I built one not knowing anything about the bottom end of those blocks.The build was on this site.Got real lucky.4.21 stroke 3in main crank,everything inside was high quality and light weight.The engine made just under 600 HP,is in a 70 GTO running fine now for many years.Others have not been so lucky.Tom

[GoreMaker]

Originally Posted by ponyakr

I'm on the opposite side of the fence.

Have pics of several 557 blocks with chunks missing out of main webs.

That's really interesting and I very much appreciate the photos, I've been wanting more details about these failures for years now.

Looking at the photos, it seems all the failures you've come across were at the dowel pin. And in one of the photos, I see a solid dowel pin instead of a rolled one. My understanding is that Pontiac went with rolled pins on '77+ W72 engines specifically because there was a higher chance of cracking there when high-revving with solid pins. The rolled pin allows the cap to walk slightly rather than overstress the block.

Also, it seems to me like a splayed 4-bolt main cap would really help to secure that webbing and spread the stress into the area between the cylinders, perhaps as much as 50/50 between the two bolts. The splayed bolt ends up beyond the dowel pin, and wouldn't be drilled solely into the thin part of the webbing. Unless I'm seeing the photos wrong.

[77 Canamman]

It's telling when Pontiac had to switch back to the XX481988 cast blocks in 1978 W72's due to warranty claims. Even the relatively stock sub 300 HP was too much for some of them. Another issue was quality control. The rod/piston assembly weights differed greatly in some of these. If the rotating assembly is quality and balanced, 400 HP would be my limit.

[GoreMaker]

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

[tom s]

Just me,I would not want to put anymore holes in the web.Tom

[GoreMaker]

Originally Posted by tom s

Just me,I would not want to put anymore holes in the web.Tom

Yeah, I'm pretty hesitant about that too. The holes to accommodate bolts would be much larger than the dowel pin holes.

How come no main girdles exist for this? Seems like that would be a no-brainer solution, and there's stud girdles for every other engine block ever made...

[Mike Davis]

A girdle won't help this. The webbing under the mains is very thin.
If you are investing in forged internals, I'd spring for an earlier block and save that one.

[77 Canamman]

Originally Posted by GoreMaker

Y

How come no main girdles exist for this? Seems like that would be a no-brainer solution, and there's stud girdles for every other engine block ever made...

One main reason: There are TONS of great pre 1975 400's out there still. There are not too many 1975-78 Trans Am owners with the 557 blocks that want to push the limits of their design.

[JSuchma]

FWIW.....I purchased a Butler built 461 530 HP stroker off of facebook market place around 4 years ago. Had there E-heads with the street port job and port matched RPM intake. All parts had the job number stamped on them, including the 557 block. I just could not believe that Butler would have used that block! I even got a stack of paperwork with it to prove it was built by Butler. I have also seen another Butler built motor based on a 557 block as well.

[694.1]

Hey now! We do not need this sort of irresponsible talk around here!

) I don't run it hard, never raced it and probably never will. Heck, I barely hit 60 going down the road. I do drive like an old man )

[GoreMaker]

Originally Posted by JSuchma

FWIW.....I purchased a Butler built 461 530 HP stroker off of facebook market place around 4 years ago. Had there E-heads with the street port job and port matched RPM intake. All parts had the job number stamped on them, including the 557 block. I just could not believe that Butler would have used that block! I even got a stack of paperwork with it to prove it was built by Butler. I have also seen another Butler built motor based on a 557 block as well.

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.

[Sirrotica]

Posts # 7, 11, and 12, pretty much sums up the risk of using the 557 blocks.

Now I'll add two my own experiences, both with a 557 block in 77 T/As.

One was a warmed over street engine, headers, true dual exhaust, 068 camshaft, re jetted Quadrajet, Holley Street dominator intake. At under 40,000 miles there was a catastrophic engine failure, that destroyed the block internally.

Another block failure in another 77 T/A was a defect in the cast iron. The block developed a crack that ran parallel to the bell housing surface roughly 2 inches long into the coolant jacket, just above the oil filter elbow. This area isn't even stressed, by engine operation. It was just a factory defect due to poor factory QC.

GM cut the amount of nickel (and some other alloys) used in the cast iron to save money in the 76-77 time frame. Nickel makes the cast iron more ductile, and less brittle. It also makes it wear better in areas such as cylinder walls. In my own experience the 301 and 400 engines, as well as the Iron Duke 151, 4 cylinders wore the cylinder walls out at 60,000 miles due to the iron not being as resistant to wear as the older, higher nickel blocks. The pre 75 blocks were just getting broken in at 60,000 miles. I've taken engines apart that at 60,000 miles that had such a bad cylinder ridge at the top of the cylinder, you had to use a ridge reamer just to get the piston out of the bore.....

One other thing Pontiac did in those 557 engines is use an inferior harmonic balancer. Engine harmonics can take a toll on crankshafts , as well as the main web area of the blocks. Since these engine had a insufficient balancer, the block and cranks have already had forces that tend to fatigue cast iron rapidly. Case in point, the 6.5 diesel engines also had poor quality balancer used in them. If they slip the balancer ring, (a common problem), the cast crank will fail in a very, very, short time thereafter. The 6.5 diesel engines were also victim of GM cost cutting that had weak blocks that failed very similarly to the 557 blocks, a section breaks out of the main webs. Those blocks are notorious for breaking, and are avoided by the 6.5 community for the same reasons as the 557 blocks.

My own opinion by direct experience, not hearsay, I would not consider those blocks for any performance usage. The quality control was either non existent, or very poor.

The alloy package was modified to suit the bottom line of GM, not make a durable piece of cast iron like the older blocks were. Given the poor quality control of the foundry, and the machining operations you're rolling the dice on whether the block is defective. Even if not defective, they are hard and brittle, subject to cracking in areas not necessarily in the main web area, even under daily driver usage.

A Dirty Harry quote comes to mind,

"Do you feel lucky punk, well do ya?????"

[Skip Fix]

Like Tom we built my 400 short block for my RAIV motor I raced in NMCA with a 577 block not knowing the difference. Crower billet rods TRWs balanced. Dynoed 384 with the first milder Ultradyne cam with the bigger solid I tried it reved to 7000. Hammered on it hard for 10 years and it is still together!

[Sirrotica]

It's obvious that it's the luck of the draw. Obviously they all weren't defective, but the alloy can't be changed after the block is cast.

[GoreMaker]

It sounds to me like the consensus is "it might work out fine, but it might not, and if it doesn't, then the original block was defective anyways".

Seems to me like if the block is defective anyways, "saving" it is worthless because I'm basically attempting to "save" garbage for the sake of originality. Whereas if it's not crap, "saving" it is a waste because I've got a perfectly usable block that ends up just sitting there, not being used.

Would a thorough sonic and liquid magnaflux inspection provide any insight before making a decision? This all-original engine has just under 78k trouble-free miles on it, and I did a fair bit of beating on it over the last 1k miles.

[Sirrotica]

Originally Posted by GoreMaker

It sounds to me like the consensus is "it might work out fine, but it might not, and if it doesn't, then the original block was defective anyways".

Seems to me like if the block is defective anyways, "saving" it is worthless because I'm basically attempting to "save" garbage for the sake of originality. Whereas if it's not crap, "saving" it is a waste because I've got a perfectly usable block that ends up just sitting there, not being used.

Would a thorough sonic and liquid magnaflux inspection provide any insight before making a decision? This all-original engine has just under 78k trouble-free miles on it, and I did a fair bit of beating on it over the last 1k miles.

An old time dirt track racer once told me that, if he ran used connecting rods that were taken from another race engine, he knew they were good because they had already taken abuse from the former build. He termed them as "PROVEN" parts. Unfortunately metal fatigue doesn't work that way, the more cycles of abuse they are subject to, the weaker they become.

You can't change the makeup of the iron no matter what you do after the fact. It's a risk to reward calculation, only the owner can make that decision.

To me starting with a better basic foundation is not cost prohibitive, compared to starring at a failed mangled bunch of parts, been there, done that. The expensive lessons, are the best learning experiences.

The only advantage to saving the original engine is resale value to the next owner if the car is resold. A classic car is worth much more with the born with parts, plan accordingly.