M20B25 no compression

[Ninja_Penguin]

ive got an m20 that was ripped out the other day. it wouldnt start in the car, there was spark, and fuel getting to it, dizzy was ok leads were good, plugs were good etc.

when turning the crank with a bar and socket it was like there was no compression in any of it. didnt get the pop noises out the manifold. we took the head off and i cant work out why there is no compression. the head isnt cracked, the block isnt cracked there was no sign of HG failure (although one lot of waterways were rusted solid on the HG) we put oil on the pistons and it didnt seem to leak past the rings. other than taking them out to look at them. the water had all the antifreeze in it since it had been sat for a few years. (ran fine beforehand)

is there anything else that would cause there to be no compression.

[Simon13]

did you turn it over with no spark plugs fitted? With out actually using a guage to compression test it you won't know.

[Ninja_Penguin]

no it had all the plugs in it still lol im not that silly :p we had an M50 sat beside it and turned that over the same way and you could feel the compression and hear it.

[chh137]

Sticking valves ,valve seats rusty/poor condition ? how long was engine stood?

[Ninja_Penguin]

6 year i think. a fair while. valves all open fine i did check the seats and from what i could see they looked ok ill have another look tomorrow properly. never thought about rusty valve seats.

[chh137]

Ones that were open when engine standing could be rusty . close vavles and run some petrol or diesel on them to check for a good seal.

[Ninja_Penguin]

ill try that tomorrow and let you know of the results.

we put oil in the bores and didnt see any air bubbles coming up through the rings so im assuming they're good

[chh137]

Oil maybe a bit to thick , try diesel.

[Ninja_Penguin]

ive got petrol. ill try that.

[chh137]

Petrol is fine, best of luck .

[chh137]

Any news?

[Ninja_Penguin]

rings have gone, valve seats leak lol just been up and poured petrol in the bores. cylinders 1,2,4,5,6 drained pretty quick. did the same with the valves, got to the 3rd valve and admitted defeat. they need cleaning up too.

[chh137]

Ah well thats life. Sounds like a low cost rebuild job. lol.
Nothing a few hours graft wont sort out.

[Ninja_Penguin]

this is true. the bores look good so thats good. the head is FULL of oil staining so will need a good clean. had a look at a thread about stripping the head down. its looks insanely complicated compared to my C20XE head which was literally unbolt cams, lift out lifter, use spring compressor to drop valves.

[chh137]

Good learning curve for you. NOT insanely difficult. Just take your time and be methodical.will give you some satisfaction when its up and running.
Six pot smoothness ,nothing like it.

[Simon13]

about the easiest engine to work on. Very simple things M20 hence why they're so good!

[Ninja_Penguin]

bit closer inspection...not good.

this is on all 6 of the pistons



big conrod bearings had shiny patches and a few light scores. so would need new bearings i think. crank looks perfect, no marks on it. so this is what its like now lol



what parts are worth selling? obviously ill be keeping a few bits like the sump, cam cover. head ill strip down to learn how to do it.


and i know of easier engines to work on lol.

[kam-325i]

do i spy Tays torque wrench there !!!!

[Ninja_Penguin]

no just a rubber mallet, impact gun, and various ratchets lol. my mates garage so no idea what tools are what