Main girdles

[Steve.k]

Whats your theory on main girdles guys? They work or not? Some say they even dampen harmonic frequency from internal components. Whats your thoughts?

[Frankshaft]

I don't know, I don't think they do a lot. I think they are better than not having them, sorta like stud girdles. I still see heads with pulled off stud bosses on aluminum heads. If they did anything, in theory, that wouldn't happen. I used to make BBC and big block mopar girdles. On one of my own engines, an 820 hp 496 bbc, the 3rd and 4th main cap looked terrible, it definitely was bouncing around. 2 bolt block, main studs, aluminum girdle, and a steel strap across the top of the girdle on the 1st 4 caps. It didn't appear to help. Installed Pro Gram 4 bolt billet caps, and there was zero evidence of cap walk. The bottom of the cap where it touches the block, gets all beat to crap, you can see it in the finish from the cap grinder. One the billet caps, it looked like it just came off the cap grinder after another 200 runs.

On Fords, they do keep the block from falling apart in 2 pieces when they break the block.

[Steve.k]

Our own 2bolt cleveland exhibited a fair bit of walk with stock bolts. Switch to studs for now see what that does. Some say bevel bolt hole on cap on block side as the bolt/stud pulls block material up enough to make high point. Never tried that.

[Walter R. Malik]

Some main girdles work but, most don't when simply tying the fasteners together just hovering over the main caps.
Though, they do hold everything together when the block breaks so, you don't drive over the pieces.

Valve train "STUD" girdles actually do what they are intended to do, keeping the studs from flexing.

[Steve.k]

Lol Walter. Sometimes that maybe a good thing.

[GOSFAST]

Most work fairly well depending on the overall design?

Some years back did a couple 455" Buicks, real headache getting it all setup but well worth it (in my opinion) on this particular platform.

Thanks, Gary in N.Y.

P.S I recall one of these builds above being in the 800+ HP area, not a single brg issue or lower end failure. Remember, these 455's are all 2 bolts with some really big mains!!

[Frankshaft]

Some main girdles work but, most don't when simply tying the fasteners together just hovering over the main caps.
Though, they do hold everything together when the block breaks so, you don't drive over the pieces.

Valve train "STUD" girdles actually do what they are intended to do, keeping the studs from flexing.

How do you know? Do you have video footage from inside the valve covers? Not being a smartass, just wondering, otherwise, how would you know?

[Kevin Johnson]

Some main girdles work but, most don't when simply tying the fasteners together just hovering over the main caps.
Though, they do hold everything together when the block breaks so, you don't drive over the pieces.

Valve train "STUD" girdles actually do what they are intended to do, keeping the studs from flexing.

How do you know? Do you have video footage from inside the valve covers? Not being a smartass, just wondering, otherwise, how would you know?

https://www.youtube.com/watch?v=SzD_LZ3fM-s

[Frankshaft]

Some main girdles work but, most don't when simply tying the fasteners together just hovering over the main caps.
Though, they do hold everything together when the block breaks so, you don't drive over the pieces.

Valve train "STUD" girdles actually do what they are intended to do, keeping the studs from flexing.

How do you know? Do you have video footage from inside the valve covers? Not being a smartass, just wondering, otherwise, how would you know?

https://www.youtube.com/watch?v=SzD_LZ3fM-s

What does that show? That they move. How come he didn't do the same text after the girdle installation? Because they still move.

[Kevin Johnson]

Whats your theory on main girdles guys? They work or not? Some say they even dampen harmonic frequency from internal components. Whats your thoughts?

You can look up various patents and see they were often justified for NVH reduction.

United States Patent 4,497,292
Hayashi , et al. February 5, 1985
Bearing beam structure

Abstract
A bearing beam structure is secured to a cylinder block of an internal combustion engine and includes a plurality of main bearing cap sections each of which associates with each bearing section of the cylinder block so as to rotatably support a crankshaft. At least a beam section is rigidly connected to the lower end portion of each bearing cap section to securely connect all the bearing cap sections with each other. Additionally, first and second side wall sections are rigidly connected to the opposite side portions of each bearing cap section to securely connect all the bearing cap sections with each other. Accordingly, the bearing beam structure is improved in rigidity to suppress various vibrations of the cylinder block, thereby effectively achieving total engine noise reduction.

Inventors: Hayashi; Yoshimasa (Kamakura, JP), Ogawa; Naoki (Yokohama, JP)
Assignee: Nissan Motor Company, Limited (Yokohama, JP)
Family ID: 15784620
Appl. No.: 06/433,886
Filed: October 13, 1982

[Kevin Johnson]

https://www.youtube.com/watch?v=SzD_LZ3fM-s

What does that show? That they move. How come he didn't do the same text after the girdle installation? Because they still move.

Yes, it is straight forward physics that they will still move (perfectly rigid structures are theoretical constructs) but the amount that they will move will be less because the force is distributed to more reactive forces (the other studs) via the girdle. Conversely, the forces from other studs will be transmitted to erstwhile essentially "isolated" studs. Well designed systems should display a benefit; poorly designed systems less so.

[cardo0]

A co-worker bought a girdle for his V6 GN that replaced the main caps as a one piece frame work with intergral main caps. Man talk 'bout strong looking. Wish they sold something like that for the sbc. But it does have to be alignhoned/alignbored to use.
Moves the weak block area to the lifter valley and cylinder bores.

[Walter R. Malik]

Some main girdles work but, most don't when simply tying the fasteners together just hovering over the main caps.
Though, they do hold everything together when the block breaks so, you don't drive over the pieces.

Valve train "STUD" girdles actually do what they are intended to do, keeping the studs from flexing.

How do you know? Do you have video footage from inside the valve covers? Not being a smartass, just wondering, otherwise, how would you know?

Not being a smart ass ... YES ... I have video and many Optron and Spintron results of a stud valve train, (from under the valve cover), with and without a girdle.

Some of us actually know something what we're saying.

[Kevin Johnson]

Two cases I can think of immediately. The KA24e gains about 7-8 hp if the girdle arms are sliced off. That was from a Nismo engineer and confirmed by racers. (Decreased windage turbulence.) The second engine will go unnamed but is American and modern. The aftermarket addition of a girdle negated careful factory attention to bay to bay flow.

The modern expression of a girdle is typically a bedplate block design.

[peejay]

A co-worker bought a girdle for his V6 GN that replaced the main caps as a one piece frame work with intergral main caps. Man talk 'bout strong looking. Wish they sold something like that for the sbc. But it does have to be alignhoned/alignbored to use.
Moves the weak block area to the lifter valley and cylinder bores.

A lot of the problem with that engine is the way the engine mounts are attached to the block. They hang on with two bolts at the bottom near the oil pan. This makes things flex all over the damn place. A girdle helps because of this, although good luck getting it to not drool oil, because it's still going to be pulling the block back and forth on the girdle. The real fix is to plate mount the engine, as much of a pain in the ass as that is.