I've seen this touched on in a few other threads so I figured I would give the subject its own thread.

I've seen comments on both sides of the fence but is there any definitive proof that they add strength to the bottom end of a stock block?

No, you aren't going to find any proof, just a lot of opinions. The closest thing to proof is that Mopar engineering used a cross bolt design for HD applications.

All I’m going to say is ….. I’ve been 9.0’s at 3500lbs .070 jet in a plate , another plate with .073 on top of that . Stock block , stock main caps with studs …. That’s it !

Spray and pray . Don’t be scared !

IF I was using a stock block still , I’d put alum main caps , use a vacuum pump , aluminum rods and make damn sure the straps showed very little heat . Conservative timing and keeping oil out of the chambers will go a long way to keeping the engine out of detonation .
Just my opinion and what has worked for me

A flowed nitrous kit also helps a lot , the tech help
You get helps a ton . Everything that keeps the engine happy keeps it alive . Granted the block can only handle so much , but pay attention to all the things that make it more prone to break and hopefully you can make it live . My opinion no reason you can’t make 800 to even 1000 with good tuning and attention to details

We run a lot of them with girdles. We believe they help. I can say, I don't see how they can't hurt. Think about it, you stud the main caps and the tie them into a girdle that bolts to the oil pan rail. How can it not help? We have been running over 800hp with this setup for years. Bearings usually look really good when we do check ups. Only time they don't is usually with a repaired crank or where we have had other issues.

Do the caps show evidence of moving ? My stock block showed a lot of movement (no girdle stock caps with just studs )

I I don't know about a big block. But I can tell you on my small block the main bearings looked 100% better on tear down after the girdle than they used to.

I used to see the outer 1/3 of the main bearing right down to the copper, opposite of the deck.

Meaning the block was flexing all over the place on the power stroke.

Now that has been greatly minimized since the girdle

Small block 360, 1/2 fill, 800hp+. But same principal.

Yes...We still see some cap walk. We usually do an off season check, and we will generally see some light cap walk. We do race all these, and we run the timing near or at the max they will take.

consider a girdle insurance. is it going to help you make power? not really but if you cant keep your bottom end together it wont matter either. and yes we do see alot less cap walk with our girdle kits, after market cross bolted mains dont work. we've even made a girdle kit for a JP1 hemi that was a cross bolted main block. still had cap walk before the girdle. now if your only tying the studs into the girdle you wont get much benefit as the caps will still flex and walk around.

yes, i have proof... when i launched a rod in high gear at over 140mph, the girdle stopped it from swinging through my oil pan, didnt lose a drop of oil , didnt drive through any

My thoughts, I would tie it into the pan rail not just bolt it on (is there a pan gasket between?) dowels or sleeves of some type. Also some type of notch on top of all main caps so when bolted down it’s captive to the caps and pan rail. After this is done torqued down and line honed.i think that would be a tight non-flexing bottom end.

I always believed a girdle prevents flag poling of main studs, which causes blocks to crack from reverberation. I had cap walk in my 472, running too 6800, 10.60 @ 126. I swapped in a girdle and aluminum caps, never saw it again. Engine ran to 7k once it got better heads. For $400 and no machining, even if its minimal I'd think it's money well spent.

We stud the oil pan when we run a girdle...I think it helps the most.

Cross bolting the mains does basically NOTHING for cap walk. Been there seen that many times. Yet many believe it is the be all end all. There are other remedies for this and IMO a center counter weighted crank is your friend. As far as girdles go what can it hurt, especially combined with aluminum caps, lite bobweight and conservative on the timing. Do all that and I believe a stock block, provided the cylinder walls are good can last a good long happy life.

It does not hurt anything - the thicker the better - but I agree a good set of billet aluminum main caps with good studs everywhere along with a lightweight assembly like 2100 grams or below will go along way in reducing cap walk! the other factor is timing and a solid tune - too lean can be mean to the bottom end!

No, not in my opinion. I have not seen one on the market worth messing with. If you want to see girdles that work. Check out the girdles they run on diesels.

Mine did not Rod cut right though that girdle

Wow...Look at the bolt hole where it was bolted to the main cap, its all stretched out....Damn.

Late great Monte Smith had probably tried about everything before there was race blocks available. His opinion, based on experience, was that only thing that really helps stock factory big blocks, is aluminum main caps. He had had no help from girdles. I kind of trust his opinion.