piston chambers, what to look out for

[LUV2XLR8]

im rebuilding a 1.4 bottom end from an 8v corsa sri.

I was looking at the piston chambers and there seems to be an area at the top of the chambers (tdc) that are dirty.

is this normal?

what else should i look out for when rebuilding a bottom end?
:D

[Adam]

Build up of carbon?

[LUV2XLR8]

yea probably carbon, i supose this is normal?

anything i should look out for as in wear and tear?

[Adam]

See if you can still see the hone pattern on the bores(cross pattern)

[LUV2XLR8]

yep i can see that :D the pistons them selves are a little dirty.

how can i tell if the pistons rings need changing? (obviously if they snaped id know lol )

also the shell bearings, how do i tell if they need changing?

[Adam]

Have you heard/seen the engine running.

[Jon_nova1]

youd need to get the engine running to be able to tell about the piston rings and bearings unless your taking the block apart?

you should be able to clean the piston tops, maybe with abit of oil and a rag? you can get rid of the lip by sanding it, although you need to be careful, it sounds like the engines done a few miles, look at the cylinder head, where the oil flows, is it stained a browny colour? this would show its not had oiol changes regularly, otherwise if it looks all good then i dont think you'd need to worry too much about the stuff your looking for

[SRI crazy]

if you clean the carbon of the piston the car will be realli smokey until it gets the carbon built up again lol, you would only need to change the rings if they are not sealing the cylinder and you can check the shell bearings for wear but if you do make sure and clearly mark the caps because you can very easily put them on the wrong way again

[Sirnixalot]

if you clean the carbon of the piston the car will be realli smokey until it gets the carbon built up again lol,

how you figure that? carbon on the piston tops wouldnt seal anything even on an old engine, i could understand if you meant the valve seats or where the valve itself seals to the seats, but all that takes is some time and lapping paste.

[Stuart]

the carbon will be back within about 10 miles anyway...

[LUV2XLR8]

i havnt heard the engine running as i just bought the bottom end from a breakers.
ive taken the block apart and i have all the pistons out.
the rings look ok, they dont seem to be snaped or cracked either.
i think the shell bearings might need changing as ive sen a mark on one of them.
i think the engine has only done about 75k but thats what it said on the clocks in the car, could be another engine :S

[SUP4NOV4]

You will need a feeler gauge to measure the rings to see if the are worn or need replaceing you will have to check your RING END GAPS also you will need to check the bore size useing an internal DTI olso for ovality.
The bearings SHELLS both big end and mains can easy inspected is there any cooper showing this is a sign of wear also are there any pits in the surface of the shell the shell need to be 110% clean and free from any contamination front and back you should also check the crowns PISTON for measurement if you need any help just ask i will anser i am an engine reconditioner.

[LUV2XLR8]

thanks mate, il be going over the engine today, if i am confused again i will get in touch with you
thanks

[Adam]

Check the shells for wear, if its worn you'll see as the surface of the shell will be marked/worn.

[LUV2XLR8]

looking at my piston chambers earlia, i noticed on chamber 1 there is a slight lip on the top :( would this effect the compresion?
i'll be putt new rings, bearings etc in so that would hopefully bring compresion up

[Adam]

You might have trouble getting the pistons out, as the rings catch on the "lip" at the top of the bores.

[LUV2XLR8]

i have taken the pistons out already before i noticed the lip :S so does this mean that it should be ok?

[Jon_nova1]

yes, but you could do with carefully sanding it, the lip is where piston ring ends

[garyc]

If your putting new rings in you would be best off honing the block or getting it done properly. I'd also get it decked while its apart too.

[SUP4NOV4]

Yes i would second that you can hone the block with a honeing tool its easy available for around ?20 to ?25 dont use sand paper. if you have a workshop near you should get the block checked for taper and ovality if you get it checked they will probably hone it for you. Be carefull when fitting your rods and crank are your mains and big end caps keept with there original rod? Also when fitting your big end caps make sure the bearing and cap tags are all faceing the right way what ever you do dont mix them up.

[LUV2XLR8]

i have all the pistons, big ends and main ends in order.
I also have a honeing tool, so i'll try that see if that helps the bore.


I'd also get it decked while its apart


whats decked? is it expensive?

[Sirnixalot]

the block face is machined to maintain true flatness, if you machine enough off you can raise the compression but im sure SUP4NOV4 will explain more :thumb:

[Adam]

As above.
Its like a head skim, but on a block.

[Jon_nova1]

wouldn't you have issues with the pistons hitting the cylinder head? or do you skim the pistons too?

[Adam]

The amount removed is tiny.

[Jon_nova1]

oh right lol

[Adam]

Still should measure the combustion chamber etc tho, to get the final comp ratio.

[garyc]

No the pistons should be a couple of thou shy of the top of the block. I dont think its that dear to do. A decent machine shop should be able to advise more.