20 replies to this topic

[mike.]

Ok so my MG engine is pretty much stripped down now. clutch assemblys and transfer case is off, timing cover, chain and camshaft are out, heads off etc

Only thing i've got left to do is remove the gearbox, but i'll do this at a later date because i'm only doing that to fit new cam followers, i will not be disturbing the crank assembly.

Anyway, i've done all this without cleaning much of the engine. So now i've got gaskets to scrape off, grime to wire brush from the block and pistons and deck to clean up and decoke. So obviously theres going to be alot of dust/grit from this going everywhere and i'm wondering if its a problem? Inevitably some dirt will fall though soe of the holes and into the block/gearbox. But is this really a problem? Because once the gearbox is off i can clean all the oil and water jackets out and clean any grit from the gearbox.

I found the best way to clean up and decoke the mating faces on the head ive just refurbed was to use a wire brush attachment and some fine sand paper. Using this method on the deck on the block will put dust down all th holes in the block but is this really that bad if i squirt something down all the jackets later on to clean them out?

Also what is the best way to decoke pistons? I've tried srubbing them with a rag and white spirit but it did next to nothing. I'll need to scrape them with something. If i put some oil round the bore, and some thick grease round the gap between the piston and block, will i be ok to use some fine sandpaper to gently ebrade the coke off? (this wont damage or scratch the pistons will it? Do'nt know how soft they are) Then when i retract the piston again, any swarft should be caught in the grease or on the bore right?

Thanks for the help

[GreaseMonkey]

What I find useful is turning the engine till you have two pistons right at the top. If the pistons are really coked up I use a wirebrush like a tooth brush, put some white spirit on top of the piston and scrub a little till it becomes abit broken down and then get a little more white spirit on a rag and rub in circles on the piston and you should see the coke start to break down and "melt" away leaving a nice clean piston. Once you have done as much as you can with the two pistons clean them with a dry rag wipe any dirt off and then turn the engine to bring the other two pistons up and then work on them.

[Saxo-Fiesta-Mini]

put the psitons so they all line up in the middle put redex on and leave and then tape the top of the block shut with blue masking tape then wire brush away i normally use a petrol 2 strok mix to clean engines stops rust and helps shift the *poop poop*

[mike.]

Ok so thats how i'll clean the pistons.

But what about any swaft that does go down the water jackets and things? Does it matter if i'm going to take the block off the gearbox and wash out all the openings?

Edited by minimadmike, 22 February 2009 - 01:02 PM.

[mike.]

Right i've tryed scrubbing the deck and pistons with white spirit, redex and just now petrol. The carbon is having none of it.

If i use sand paper/wire brush with a rag down the bores, then when i take the gearbox off clean the oil and water ways out as best I can and get any crud from the gearbox will this be ok?

If not what else can i use?

Cheers

[Jordie]

Blow air through all the water and oil ways.

But if your stripping it down that far, its false economy not to remove the crank and check the bearing shells. You could put it back together and it could start knocking on a big end in several weeks. If that did happen, its a engine out and rebuild job.....worth the risk?

Jordie

[mike.]

I have thought about it but i don't really trust my torque wrench to do those sort of parts. A proper one is like 60 quid.

If i did take the crank out i'd replace the bearings anyway, which ads to the expence further.

Also pistons and rings, new rings and pretty expencive and the compressor is too isn't it?

If i did take the engine that far apart, i think i'd want to change all the bearings and get everything fully sorted like new. But then its just been taken out of scope for what i had in mind for this engine.

I know the engines pretty low mileage because the cross hatch hone marks are still on the bores and the head was in mint condition...

hmmm i'll have to have a good think about this because i know if i take it apart i'll end up replacing everything i can't clean up fully. I'll have to price things up...

[mike.]

Right well heres a quick pic of what i'm trying to clean up:



Also since i'm now considering rebuilding this engine. Take a look at the cam bearings. I noticed they look a little scored/worn, does this have an relation to how worn the crank bearings may be and does this ware look significant?

[Saxo-Fiesta-Mini]

most engineerin firms would relace them bearings with the score marks uless they knew the age of them and then engines history lol

your meant to leave the pistons soakin in the redex overnight hench having all the cylinder halfway down and put enough to submerg the piston faces then tomorow would be clean and new

[mike.]

Ow i see. Well surely some of the redex would seep past the rings and dilute any oil in there, so when i come to moving the pistons they'd have a fair bit of friction and damage the bore. Maybe im just being paranoid...


Anyway basically i think i'm looking for somebody to say 'OMFG those bearings look screwed, you better rebuild that engine because all the bearings will be like that!'

Otherwise if somebody says that they look fine and in pretty good nick then may aswel just leave it altogether...

[mike.]

Any other opinions on those cam bearings?

[Ethel]

It's really hard to say from a photo. A few dinks won't matter too much, as long as there's nothing protruding above the bearing face. I would agree with Jordie that it's well worthwhile doing the job properly. New crank bearings, oil pump and big end bolts. The super cheapy "beam" torque wrenches with a pointer and scale are, if anything, more accurate and you could always borrow a wrench or chat up a local mechanic.

Or apply the torque literally - put a foot long lever on the nut and hang the right weight off it.

[mike.]

Well i was going to replace the oil pump, clutch and fit a new cam/followers/timing gears as well as a stage 3 head. I suppose it would be worth replacing the bearings.

Can pistons rings be reused?

I see a set of big end bearings are about £20, same for mains so isn't too bad. But i see piston rings are more like £50, plus the compression tool.


I i did strip it down i'd want to replace all these parts anyway. I might even check with my insurance and see about 1330 or something....

At the moment i have a clark torque wrench from machine mart, was about £20. Its been fine for head gaskets and ball joints and things but don't know if i'd trust it for an engine rebuild.

[rozzer1275]

sorry if i repeat anyone

try the following to clean top of pistons

scrap off old head gasket with stanley blade paint scraper
wipe with meths
cover the whole face of the block with masking tape
cut out one of the piston holes
rotate piston to top
clean with wire brash on drill (care not to wire brush block face)
hover (and blow out) dust from piston gap
tape up hole
move on to next piston

when finished clean tape residue with meths

[mike.]

Cheers, that sounds like a good method. I did have a quick go with the wire brush attachment before but it look liked it scratched the top of the piston so i stopped.

Anyway i'm now considering stripping the engine completly and replacing the bearings. I doubtr i'll go to the trouble of a rebore, with the expence of new pistons and rings that'll set me back about £400 altogether. I think thats getting abit out of hand so i better stop dreaming before i end up blowing all my money on it!

So can i take the pistons out, clean the up good and proper and put them back in with the old rings? Or is that bad practice?