Re:why are blockguards bad?
 

you really need the same compound of the cylenders and block or one metal will expand and contract at diffrent rates than the other metal thus causing lots of damage.

Re:why are blockguards bad?
 

Thats what i was thinking ;D

Re:why are blockguards bad?
 

these are not my words but I do agree with them:

"Find a shitcanned Honda block sometime, bust out a liner and look at it... only the very top of the liner is as thick as it looks... below the upper lip the liner is
ribbed on the outside, and at the thinnest points is 60 thou thick. The Honda block is literally poured around the liners.

Since OEM sleeves split where they are thinnest AND seeing their greatest stress - midway up the bore - then a blockguard isn't protecting anything I can see. Can you see what it is protecting? They were originally designed to positively locate the sleeves so that they didn't shift and blow head gaskets... OK... but why are the sleeves shifting? Detonation.

I don't know how familiar you are with engine development programs, but once you solidify something up then the weak point moves elsewhere - in this case ring lands or sleeves, which run a LOT more money to replace than a headgasket. And all of this is a moot point as you wouldn't blow a headgasket if you weren't detonating in the first place. I kind of like having the headgasket as my weak point, or not
so weak point depending on tuning"

Re:why are blockguards bad?
 

^^^my new favorite noobie. :-*
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Re:why are blockguards bad?
 

I thought id throw in this ---- d-h racing they do shottie work >:(

Re:why are blockguards bad?
 

Holy ----, Fowee is going to replace me one day. Stick around man, you have some good info.

You guys have no idea about welding aluminum blocks, most machines shops I've been in aren't capable of doing it right, it's a real ------- bitch for a permenant fix. That's why you scrap an aluminum head, don't repair it.

Cast iron welding is easier then aluminum welding, I'be done cast before.

Re:why are blockguards bad?
 

I will be using a welded in str block guard in my b18 turbo, we will see how it stands up.

Re:why are blockguards bad?
 

id tend to disagree with the above statments your making. while the blocks are poured around the sleeves the mid wall thickness is actually around 160 thousandths. i know ive cut up numerous blown up b and d blocks to find this out.

As for why the cylinders break mid cylinder is has to do with deflection. the greatest point of deflection is at the middle of the cylinder in terms of material deformation but in terms of actuall cylinder movement it occus at the tallest point in the bore. alot like a sky scrapper. the top moves around the most but the point of deformation is halfway down the building.

Block guards when properly designed actually do a very good job. sure theres been lots of bad press mostly due to shoddy design. We are working on actually welding the blocks up. looks to be far more suitable for heat conduction and fit along with strength.

the other problem with sleeves like the MID kits from say darton is that they reduce the overall rigidity of the block. ive seen lots of broken cranks comming out of every block darton makes sleeve for lately. broken cranks in large quantitys means only one thing. Main journal bore deflection.

So before people go touting about how great sleeves are think twice. the best thing to do is unify the block intoa solid structure with each peice locating evey other piece in tensile and compressive loading. you want to aviod shear conditions in a cylinder block. breakage is almost immdeate. that the problem with sleeves they wekane the lower main bearing saddle structure.

theres alot more to it then meets the eye and as we make progress ill keep you posted.