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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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#102 ·
The Simps said:
I must admit, as many have, its just a case of bolt together. then again the couple of engines of witnessed rebuilt have both come back with the bottom ends fully assembled so, assumingly they are correct.
Just reminded me of something a boss once said "Never assume, it makes an a s s out of u and me". Something that applies to engine building as we can see!
 
#106 ·
Well I must say this has been one of the best threads to read on MIG in a very long time.

Very good information for anyone starting an engine rebuild,

Well done chaps.
 
#109 ·
No problem mate, is it still holding together ok on its 80% increase in power at the moment?
We'll step that up to 100% increase this week once we have the controller installed.

PMSL @ when you said earlier about trying the gas from 0-120, after i told you to use it in short bursts only.

Give your mum my regards.


Chip
 
#117 ·
RDS said:
They sorted that poor chap on the high power forum with Nitrous fitted to his MR2 Turbo yet? ;)
The poor chap who has only gained about 50lbft, not double that like he was expecting you mean?

Not sure yet mate, think he is still having some sort of ignition or ECU related problem, but i havent seen the car since it was running perfectly on 50bhp jets so i dont know how its getting on currently on the 100bhp jets.


Chip
 
#118 ·
0ddball said:
so modest with it too
point me at a more useful one if you disagree you argumentative ****er :beer:

you seem to have learnt a lot from it, and so does everyone else, so i stand by my comment, its neither accurate nor modest, just my honest opinion.
 
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