Main girdles

[rebelrouser]

I have only used them on big block Mopar's, since its a Y block design the girdle bolts to the pan rail, a good strong arrangement. My experience is on engines over 650 horse it helps keep the bottom end together. Of course it seems it is just a band aid, because around 700 HP its just moves around what cracks. I have had cylinders go barrel shaped, pushing against the block fill and cracking the outside of the block. And with the girdle the number 2 main does crack, but the block will across the oil feed hole to the cam bearing on number 2 main. Best money I ever spent was for an aftermarket block.

[Frankshaft]

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.

Whatever. Quit drinking the kool aid, Jesus.

[Mark O'Neal]

I thought about making one for the SB Ford, which I have for the past 20 years....but with a thicker main cap that the girdle could lay flat on. Then maybe weld some plate diagonally across the lifter valley.

Then I costed it out...and how much can you spend on a crappy block before you just go an buy a Dart?

[swampbuggy]

^^^^^^^Yep Mark O, an engine is kinda like a house/structure, if the foundation/engine block is not strong enough you are asking for problems. Mark H. BTW i build houses.

[Zmechanic]

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.

Did it test in multiple axes? As in, axial stretch, and radial deflection? The forces that tear up bottom ends tend to be axial along the main bolts/studs (which is why if you beef up the mains, it'll eventually just rip out the webbing). The forces rocker girdles help with are radial (trying to bend the studs sideways). Two different beasts. You could likely deflect the simple "halo" girdle in the stud's axial direction just by pulling on it by hand. It may help stop some deflection radially, but studs with extra clamping force would help with that too.

I mean, the halo girdle probably doesn't hurt. But imho it's a naive application of something that works (rocker stud girdle), in a misapplied attempt to fix a completely different kind of problem.

[Mark O'Neal]

^^^^^^^Yep Mark O, an engine is kinda like a house/structure, if the foundation/engine block is not strong enough you are asking for problems. Mark H. BTW i build houses.

Btw...I'd rather build houses...

[Kevin Johnson]

Note in the bearing beam patent that additional mechanical advantage is employed by not making the structure simply planar. Suzuki used so-called stiffeners (4mm thick) with the G13B that used three dimensional mechanical advantage. BMW used triangular plates of similar thickness to tie the ferrous main caps to the alloy block skirts in versions of the M54. The Chrysler update of the AMC straight six used a bar to tie together the mains. The Mazda BP used a formed main bearing support plate to tie the mains to the skirts. Just ideas to ponder.

[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.

Did it test in multiple axes? As in, axial stretch, and radial deflection? The forces that tear up bottom ends tend to be axial along the main bolts/studs (which is why if you beef up the mains, it'll eventually just rip out the webbing). The forces rocker girdles help with are radial (trying to bend the studs sideways). Two different beasts. You could likely deflect the simple "halo" girdle in the stud's axial direction just by pulling on it by hand. It may help stop some deflection radially, but studs with extra clamping force would help with that too.

I mean, the halo girdle probably doesn't hurt. But imho it's a naive application of something that works (rocker stud girdle), in a misapplied attempt to fix a completely different kind of problem.

I can't find it, but I remember that the numbers were significant and they didn't actually affect power output!

[Zmechanic]

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.

Did it test in multiple axes? As in, axial stretch, and radial deflection? The forces that tear up bottom ends tend to be axial along the main bolts/studs (which is why if you beef up the mains, it'll eventually just rip out the webbing). The forces rocker girdles help with are radial (trying to bend the studs sideways). Two different beasts. You could likely deflect the simple "halo" girdle in the stud's axial direction just by pulling on it by hand. It may help stop some deflection radially, but studs with extra clamping force would help with that too.

I mean, the halo girdle probably doesn't hurt. But imho it's a naive application of something that works (rocker stud girdle), in a misapplied attempt to fix a completely different kind of problem.

I can't find it, but I remember that the numbers were significant and they didn't actually affect power output!

Yes, many prominent figures in racing have "peeked behind the curtain" so to speak and found things that look extremely ugly on their face, but yet seem to work. Such as a pro stock engine's cam accelerating and decelerating the equivalent of nearly 1k rpm through a single revolution. Or a nitrous pro mod engine's crank snout deflecting up to 0.060".

[Newold1]

And Steve.k ?

In your more recent post you drop the BOMB you should have dropped in the first post !- 2000HP!

In my opinion there ain't no stock Ford Cleveland block that's gonna last at 2000HP with a girdle or 4 bolt billet main caps and bolts!! The block structure in the webbing over the crankshaft in that block will just break and pullout. Need to run a Cleveland at 2000HP, get a block that can take that!

Don't post and ask for discussion about an issue that's self evident. Make the post realistic with the parameters set out in the first post PLEASE!
Thank You!

[Steve.k]

Newold thats not my engine i just posted that as example of a extreme case. Obviously the cleveland block is structurally to weak. But it is interesting. Im more interested if it works on the regular two bolts which are plenty. I know some that run 750 hp on two bolt with only girdle and aftermarket fastners.

[arlancam509]

someone mentioned earlier, the bed plate. here are a few pictures i took of a honda. pretty stout stuff.

the iron main caps are cast into the aluminum.

[Steve.k]

Ahh yes. Almost like ol FE

[Leftcoaster]

Thanks for posting, stout looking piece indeed

Anyone know what aluminum and presumably cast iron alloys are used in that girdle, and their co efficients of expansion?

Surely they must be near identical for such a critical application

[Steve.k]

someone mentioned earlier, the bed plate. here are a few pictures i took of a honda. pretty stout stuff.

the iron main caps are cast into the aluminum.

What do you think that piece is worth if you have failure. Wow.