Pistons and bores

milgo

milgo

milgo

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Joined
21 Aug 2003
Posts
651
Location
Essex
Hey there
Over the past week i have been gradually taking apart the engine to take the head off. I have only ever changed the oil etc before so this is quite a big thing for me to do. I bought the car a few weeks back now and am just giving it an overhaul for piece of mind really. Got round to actually getting it off today and i just wanted your opinions on the internals. G40's like to melt pistons and luckily it doesn't look like there is any of that going on, but there is a lot of flakey gritty stuff sitting on the cylinders, is this just carbon build up after 15 odd years? It is all loose but i just left it on for the picture.

DSCF0007.jpg


Also wondered what you think of the bores? The pistons have no play in them and the bores look ok to me. I can quite clearly see the hone marks.

DSCF0009.jpg
 
The black crap is carbon and completely normal, you can scrape it off but it comes back in no time. Just fish out the worst of the bits.

Bores look fine. As long as it's not got a noticeable step at the top and the bore isn't too oval it'll run fine.
 
a guy on the golf site had this idea of introducing water into your intake system while the engine is running to steam clean the carbon off
 
I put it up on clubpolo matt82 but it takes a while for anyone to respond :(

Jonny69 there is a step at the top of the bore which seems pretty even all the way round. Feels quite small, 0.02mm or less i'd say.
 
milgo said:
I put it up on clubpolo matt82 but it takes a while for anyone to respond :(

Jonny69 there is a step at the top of the bore which seems pretty even all the way round. Feels quite small, 0.02mm or less i'd say.
Click to expand...

Sounds like an excuse for an overbore to me...

...And some forged rods, good pistons, T34...

*n
 
lol don't tempt me :p
I have just forked out a load of money on:
fully ported and rebuilt charger
Mocal thermo oil cooler kit
Silicone boost pipes
Chip and pulley
2 new fuel pumps
and will be getting a new manifold and exhaust when they are in stock

Will be fine for a while with that lip won't it? Maybe look at getting the bottom end done when i have some more money.
 
I don't think he meant flood it by sticking the unduction into a bucket :) a Little water is good, helps to condense the air.
Think i will hire a steamcleaner and use that on it. Spilt coolant all over the place anyway when i pulled the head off so it could do with a tidy up.
 
SgtTupac said:
Water doesnt compress very good. Too much water will "hydraulic" the engine causing it to bend a rod and/or take a piston out.
Click to expand...

That would happen if you shoved loads of water in, i presume hes talking about only putting a little bit in, the extreme heat inside the cylinders would cause the water to become superheated steam and get rid of the carbon deposits.
 
Get out a dial indicator and tell us how deep the ridge is right below the maximum travel of the piston. That will indicate the amount of wear the cylinder wall has endured. You estimate it as being 0.2 mm but I'm guessing that that's not a scientific measurement.
 
Yeah thats just a guess running my finger on it. I'm a toolmaker (apprentice) so my fingers are pretty much as good as a DTI to be honest....heh
How would you run the dti up there? plonk it on the top of the piston and turn the crank? Don't have any better ways of doing it at home really.

Also wondering how clean does it need to be? After using emery cloth on the block surface should i make sure it is spotless inside the bores? As in blast it all out with compressed air or something? Is there anything else i can use to clean it?

Some of you might be interested to check out my photobucket album as well. Lots of pics of stuff i have cleaned up, had a go at porting parts of the throttle body and charger outlet. Here: http://s79.photobucket.com/albums/j136/milgo1/
 
whos had the head off an engine thats lost a head gasket?

cleanest pistons youll ever see.

i took a small vacume pipe from my thottle, held the revs at 3k or so and let it drink a litre or so.


funnily enough it did not hydro lock haha youd need to put a hose pipe in there i imagine.

i had the plugs off after and they tops of the pistons were no longer black. helps reduce pre ignition too
 
Water injection was used in aero engines during WW2 to boost power levels in emergencies or at high altitudes, also plenty of turbo engines introduce water into the engines to reduce knocking and increase power levels.

However, what's vital is to control the quantity of water injected :D Saab offered water injection in some of their turbo engines too...
 
well mine still works. ive also tried the "auto gearbox fluid mixed added to the engine oil" one too. cleaner engine, thats for sure

picture_023.thumb.jpg
 
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