Commpression figures

[mikey14sr]

Anyone know what pressure I should be getting? Gonna try to borrow a compression gauge tomorrow and can't find the figures in my copy of haynes. It's for a standard 1.3.

[dan23]

i borrowed one from work they said should be over 100 to be in good cond example lees than 100 on all 4 pistons = wear.
i think mine were 135 or 155 cant remember exact number
but is mine a 1.4
as long as its over 100 on all 4 it should be fine i think

[mikey14sr]

Cheers for that, I'll post up the results if I manage to get some pressure out of it.

[leebo]

how do you go about testing the commpression?

[Adam]

Fit a compression guage to the spark plug hole, and think you do the test at Wide Open Throttle.

As long as all cylinders are about the same compression, everything is fine.
Obviously not if all four are very low.

What are checking it for? Worn rings or something?

[mikey14sr]

I'm checking mine because I'm almost certain the rings are shot, It's used 10 litres of oil since I re-built the top-end, thats about 1000 miles. Even according to an origional owners manual I've got that's 9l/1000m too much.
Also it runs as rough as a v8 with four sparkplugs missing until it's warmed up, and it still has a misfire at idle then.

[mikey14sr]

Ok guy's here's your teaser for this morning.
The engine hasn't been run for three weeks, I've checked the plugs this morning and the results were a little dumbfounding, Plugs 1,3 and 4 were black and oily, Plug 2 was as it should be, dry and light brown.
I cleaned them all, and got her started, noticable misfire throughout the revs from cold, in the past this has cleared up once warm but not today, Once the temp was up to the halfway mark I left it to idle for a bit. It was still misfiring, almost stalling every 10 seconds.
So the question is, do I even bother to do a compression test, or just get hold of a new motor as soon as funds allow?

[Welsh Dan]

new head?

[mikey14sr]

new head?

Head was fully re-conned at christmas

[craig green]

do comp test anyway.

Get new bottom end........

[Adam]

Do a compression test and see what you get.

Then, iirc, put a little bit of oil in each cylinder and do a compression test again.
The compression should go up if the rings are worn and you put a bit of oil in the cylinder.
I think thats what i read ages ago anyway.

[craig green]

Mikey. Did I read you were going to put it on a 1600 bottom end?

If so Ive got the internals from a sweetly rebuilt 1600. The block split accross a head bolt hole so removed balanced/deseamed rods, ARPs, new mahle pistons & lightened & balanced crank with the journals. Done 12k.

Let me know if you are interested. Ive got another crank case in the shed but will need a bore job.

[mikey14sr]

Nah craig, was gonna put this top-end onto a 1400 bottom, the way things are going at the moment I might end up putting the good bits onto the astra and taking the grinder to whats left of the nova.

[craig green]

perhaps it was wombleSRi.

His avatar looks like yours.

[mikey14sr]

Ok guys finally got hold of a compression tester and here's the results;
http://img.photobucket.com/albums/v689/mickyd79/CRtestResults.jpg

It would seem that from these readings, that the main problem is the valves in No.2 cylinder are hardly sealing, and that the rings in No.2 and No.4 are just slightly worn?

If anyone could confirm my diagnosis it would be helpfull.

[mikey14sr]

Thinking of re-lapping the valves in the old head to save a bit of time, thats if people agree it's the valves causing the low compression?

[mowgli]

if the compression is ok, then either the valve stem seals are shot, or your breather could be blocked.

[Stuart]

id say 2 was a bit down comapred to the rest, and the wet test suggest naff all difference so the bores should be "fine"... relap the valves. and there could be a head gasket failiure between the combustion chamber and an oilway.

[mikey14sr]

That's what i thought Stuart, 5-10psi between dry and wet tests isn't really enough to be bothered about.

As for gasket failure between no.2 and an oilway, I've just remembered there wasnt a copper ring around the oil supply hole on the gasket that was fitted, if it's gone there I'll be visiting the muppet that sold it to my dad.

On the bright side the old head is cleaning up nicely so I'm going to spend some time on that one getting the valves re-lapped to minimize the time that she'll be in bits.