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SO glad i pulled the engine apart.

8K views 179 replies 42 participants last post by  MWF 
#1 ·
I recently bought a very nice spec bottom end off another migweb user, me being me, if im doing anything fairly hardcore i like to make sure its done right cause i cant afford to spend the money twice so i thought id strip the thing down over at a mates place where he has an excellent selection of dial guages etc i can borrow to check everything.

My god, it would have been a total disaster if anyone had tried to run it.
The actual components its made from are superb, the pistons for example i couldnt even find a fraction of a ten of a thousandth of an inch inconsitancy across all four and the biggest difference between the widest part of the largest journal and narrowest bit of the smallest journal on the crank was less than 2/10 of a thou, so i was completely chuffed to bits with the quality of the components,

Havent fully finished measuring every single thing yet as time got the better of me but as an example of the sort of extreme problems present, here are the stats for cylinder 3:
Top ring gap measured 20mm or so down the bore = 7 thou
Piston to bore clearance at top end of bore = 4 thou
Piston to bore clearance near bottom of bore = 2 thou
Those measurements taken at 7 degrees C

So that means that the ring gap at the bottom of the bore would be 7 - ( (4-2) * pi) thou, ie ZERO

ZERO ring gap and thats at seven bloody degrees, imagine what would have happened if this engine had ever been allowed to run, bearing in mind that the rings expand more than the bore does as temperature rises.

Just goes to show that no matter how much money you spend on an engine, if the person bolting it together for you is a cowboy you are only going to end up with scrap metal at the end of the day.

Thankfully the block should hopefully be salvageable as im planning on running around the 4-5 thou mark in terms of piston to bore clearance to make alloweances for the amount of heat that will be present due to the level of tune it will be ending up at, but obviously if it isnt going to come good then ill just start again with another block and can still use all the superb quality components still, so all in all im still thoroughly happy with the bits i bought, its just such a good job it was someone paranoid like myself that bought it all and not someone else blowing a couple of grand on it and then assuming it was built properly just cause it had been recently rebuilt.


Got to be a lesson in there about how important it is to check and double check everything when building a high spec engine. :beer:


Chip
 
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#152 ·
Yeah i always turn the piston upside down and use that to push the ring down the bore as that way you know its almost perfectly flat in the bore as the piston is such a tight fit you cant put it at an angle by mistake.
 
#159 ·
I fail to see any major importance in this thread (for archiving purposes)

I'll explain:

Even though it appears to raise an important issue, anyone going back and forth to an engineering shop and re-assembling cranks and rods, is *bound* to have a decent level of competency in the subject.
As such, he/she would never trust any critical clearance without double-checking. Especially if it has been disturbed/altered by third parties.
So I cannot see what all the fuss is about. It's like reminding to a train driver that he should remain on the tracks at all times. Well, duh...
 
#166 ·
If people really think an idiots guide is needed then I can sum up this thread.

Archive this:

"Take nothing for granted - even when done buy professional engineering shops.
Check everything for yourself (or buy someone whose expertise you trust implicitly), and make sure you are satisfied everything is correct.
If you do not then on your head be it"
 
#169 ·
jonix said:
It's unfortunate that the increasing trend these days seems to be to trust no one, because if you do, you end up with poor service or worse.
I wouldn't say that's completly true. But from my own experiance (spending thousands on 'tuning') you do have to decide who to trust, who to definatly not trust, and those whose information you would always get verified.

Cars is just like any business sectors where you get the good and the bad.
 
#170 ·
i would say if you are gony be doin this kind of thing yourself, its better to get someone who has done it before to run through the exact procedure for checking things and also ask them to recommend you a shop that they might have used themselves and were happy with their work. that way, there is more chance that when you get it back and DO check it things wont need reworked

rodgerq
 
#172 ·
rodgerq said:
i would say if you are gony be doin this kind of thing yourself, its better to get someone who has done it before to run through the exact procedure for checking things and also ask them to recommend you a shop that they might have used themselves and were happy with their work. that way, there is more chance that when you get it back and DO check it things wont need reworked

rodgerq

i agree with that mate
but i really dont know anyone who would know this kinda stuff

not hard now ive done it,and nothing compared to a full rebuild but i managed to sort a 'snapped cambelt, bent valve' engine purely through mig, and of course the haynes manual :)
 
#173 ·
theres a wealth on here mate. just need to ask and you can usually tell who knows there stuff and who doesnt ;)

im just glad i have a garage local to me who specialise in the tuning business so i have always got them to turn to aswell. handy

rodgerq
 
#174 ·
There's various vested interests lurking in this thread.
The useful info boils downs to:
-don't assume that someone else has done the work to your expectations
-if any of the previous work is of an unknown quantity then measure it
 
#175 ·
JohnA said:
I fail to see any major importance in this thread (for archiving purposes)

I'll explain:

Even though it appears to raise an important issue, anyone going back and forth to an engineering shop and re-assembling cranks and rods, is *bound* to have a decent level of competency in the subject.
As such, he/she would never trust any critical clearance without double-checking. Especially if it has been disturbed/altered by third parties.
So I cannot see what all the fuss is about. It's like reminding to a train driver that he should remain on the tracks at all times. Well, duh...
So what you and Giles are saying is you dont see the point archiving this post as you both know exactly how to build a engine properly so ***k anyone else. This post IMHO is valuable for someone who decides to undertake a engine rebuild for the first time (we all have to start somewhere). And you 2 cnuts are basically saying they shud learn from experience and not be able to check the mig archive for info on ring gaps and bore measurments. Hell i hope your rings break lmao

Hell i bet this info ends up on someones site. Any someone wants to know how to measure ring gaps and someone pipes up check my site www.maxboost.co.uk lmao lmao Rick
 
#176 ·
gooo rick. woo woo woo lmao :D

well it deffo has opened my eyes to the fact that we shouldn take even a pros work as a definate as they can make mistakes aswell.

rodgerq
 
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