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?

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

Ahhh yes so it is certain frequency we are capturing as part of the girdle. Makes sense. It would make sense the same harmonics are in the valvle train or more so. The rocker girdle will still move but to a lesser degree. So thats a big help with valve gear. All interesting for sure.

[pdq67]

How do you reinforce a SBC's valley to keep it from splitting like an egg right through the cam tunnel and down through the mains??

The main's area seems to be fairly well covered.

I have always proposed making a main girdle/support that would overhang the oil pan rails and then cross-plate the tops of both banks over the top of the valley and then overhang the plate on both sides and then tie the bottom overhang together with the top overhang on both sides with long, STRONG, tie-bolts.

Probably would need to deck the block the thickness of the cross-plate and then sleeve all cylinders unless you want to make the block decks taller for increased stroke/longer rods?

Sucker should be able to contain a grenade, imho...

Comments please..

pdq67

[peejay]

Through-bolt the head bolts down into the main caps?

[pdq67]

I was thinking about tying the two cylinder banks together across the top of the valley with plate and then tie this plate to the main girdle plate using long tie bolts on the outside of each side of the block.

pdq67

[Newold1]

Maybe it's just me but I think you guys are overthinking this issue and underspending the right way to do a Ford Cleveland block.

Purchase a nice set of ProGram 4 bolt billet main caps and appropriate ARP stud kit. The 2 bolt Cleveland blocks have the bosses in them for drilling and tapping for the 4 bolt caps

A good machine shop will fit the caps, drill and tap the block and align bore the mainline and now you have a Cleveland 4 bolt block where main cap and bolt or walking caps will not ever be an issue. JMHO

[machinedave]

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.

Somebody made one for a SBC. It was years ago that I saw it. I don't remember who it was that made it.

[Steve.k]

IMG_2997.PNG

Heres one of a 2000+ hp cleveland.

[Steve.k]

IMG_2998.PNG

heres what happened after. Lol

[strokersix]

Seems to me that differential thermal expansion between added aluminum girdle and iron block should be considered. Differential expansion could create very high stresses depending on the geometry details. Looks stout but could be creating unintended consequence.

[Warp Speed]

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.

[Steve.k]

Seems to me that differential thermal expansion between added aluminum girdle and iron block should be considered. Differential expansion could create very high stresses depending on the geometry details. Looks stout but could be creating unintended consequence.

Beleive this was a blower motor so alot of stress on crank. Mid 2000 hp if memory is correct

[PackardV8]

Since many OEMs spend the money to design, test and supply halo girdles, there must be some benefit. However, some of the engines on which we see them have narrow mains with very deep main caps. Seems they might be there for front-to-back rigidity, but how does a main cap move that way?

Anyway, thoughts on halo girdles? Here's an aftermarket Ford.

[Steve.k]

It seems to me while adding strength they curb some harmonics. I know guys that swear by them and if u have good luck with certain combos you do not switch. Im betting there is damaging harmonics we cannot detect with only high strength testing equipment.

[peejay]

It seems to me while adding strength they curb some harmonics. I know guys that swear by them and if u have good luck with certain combos you do not switch. Im betting there is damaging harmonics we cannot detect with only high strength testing equipment.

DV detailed testing this by extending the main studs through an oil pan, so they could measure how much everything was deflecting while under load on a dyno.

[Steve.k]

And?