Hi peeps....was just wondering what de-stressing blocks is all about? how does it help the engine and what 'stresses' are you eliminating or have i taken the term toooo literally lol

also when building high powered engines, what are the methods of strengthening bottom ends...not talking about the crank, rods, pistons etc but the bottom end itself....IIRC on chips engine thread he has ground away structural parts of the block internally and removed all sharp edges etc etc...whats the advantages?

cheers for any input

bassboy

 

removes excessive heat build up IIRC

 

Basically, you need to take the whole engine out, strip it down, and take the block indoors.

There, after having spent a while lighting some scented candles and preparing the bedroom, you take out the massage (engine) oil and subject the block to a sensual rub down, taking care to cover every inch of its mass with your caress.

Hope that helps

 

you forgot to mention whilst doing this you should be playing some of that relaxing pan pipe music

 

ahh ok... are the edges of an engine (internally) not sharp for a reason?

dogsmoke....tried that but it still feels tense PMSL

bassboy

 

I'll be the first with a sensible reply as it was in the context of my thread.


Destressing the block as ive done it is simply a case of removing any sharp edges.

Stress is passed along the block during use, and can build up anywhere there is a sharp edge and increase the risk of a failure occuring.

By removing sharp edges you stop stress building up at a point.



I did a demonstration of this once but sadly have since lost the media to go with it.


Basically i got some fairly brittle metal rods and decided to test the theory.



I bent two and measured the force to cause them to break, was more or less the same for both, this was a control for the experiment and i did two to rule out them being all greatly different.


I put a sharp shallow cut into one rod.

I put the same sharp shallow cut into the last rod, i then dressed it out with a file, this meant it was a deeper cut now (ie the rod was thinner at its thinnest point) but it had no sharp edge to it.


I then measured the force on them.

The one with the destressed cut failed a little sooner than the 2 control rods, the one with the sharp cut fail at about half the pressure!

 

what he said lol

 

NOTHING to do with heat in the context of how ive done it.


when you perform operation on a block such as line boring it, this introduces sharp esdges, same for facing the block or facing the sump sealing edge at the bottom, so when each of those operations were done on my block i followed round and removed all the sharp edges and replaced them with a radius using a handfile.

click the link in my sig for the images of this.

 

chip at what level of tune do you think its good to do this at? is it something that SHOULD be done or something that can be done just to help things?

bassboy

 

Depends on the engine in question.

In the case of my engine, i have NO idea if its needed or not, as ive never built an XE engine with a GT35R turbo and 500-600bhp before.

So as it cost me nothing but my own time, it seems like a good insurance policy.


Im sure that many of the "205 block engines failures" could have been put off to a higher BHP level if these changes had been done though, so maybe thats relevant to the forum?
But i dont have actual numbers to back that up, its only my opinion.

It WILL improve the strength of a block, but how much by is very hard to determine without a LOT of expensive experimentation! ( and i mean millions of pounds for that, its something only a mafufacturer could fund really as it would involve building and testing hundreds of engines really to be sure of the results. )

 

Really interesting stuff Chip mate cheeRS

 

Piss off Chip, my way is better!

 

No worries


There are lots of other things you can do to manage how stress moves through the block, like dowling the mains or four bolting them etc, or a girdle, TBH if i was starting over now i would probably go for a girdle, but to do so now would mean scrapping the block after 500 quid of machining, and you have to draw the line somewhere in terms of spending i guess.

 

thanx chip some really helpful information there!

what edges would you recommend to attack with a file LOL? also is there anything that you should take into consideration...i.e does it have to be done within certain angles etc?

oh and its a Zetec block im enquiring about here

also how would you go about four bolting the mains? i have heard of this done a few times now but dont see how its possible?...mind u i have never seen a pic of this done either...

thanx chip DEFINATLY one of the most knowledgable people i know who doesnt mind giving advice without spending money with the.

bassboy

 

I agree - very interesting and in words of one syllable or less so the simpletons amongst us (of which I'm one) can understand.

Cheers Chip !!

 

One addition to what Chip has written is on aircraft engine fan blades, when we blend out nicks in the blades (which are subject to massive centripetal forces), the "blend" should be 4x the depth of the nick. So if your blending a blemish on a rod etc as Chip was, measure the depth, say 2mm, the blend would be 8mm with the deepest section being where the original blemish was.

I'd start with a weathered block (as BMW used to with their F1 blocks), then destress it as Chip has, wirelock all the fastners etc, perhaps it won't make any noticable difference for your average fast road engine, but its attention to detail.

 

Chip and Steve are two blokes who are handy to know when it comes to engines