Readying cylinder head and block mating surfaces.

[Steve Webb]

Hi guys,

Very sadly the timing belt let go on my 2.5 V6 Vauxhall (Opel) Omega. I’ve stripped it down to the block. The valves in the head are all bent but the pistons appear to be ok.

Firstly I’ve heard putting oil in the cylinders is a way to check it’s sealing ok; if the oil sits on top it’s sealing, if it leaks past then its new engine time. is this correct?

Secondly i’m going to use feeler blades and a straight edge to check for hidden dents and blemishes. should I use very fine emery paper to clean the surfaces of the block and heads?

Any other tips?

heres a photo of one of the ‘v’s’

[URL=http://s1226.photobucket.com/user/webbybear1/media/hg_zps1dd1c1b2.jpg.html][IMG]http://i1226.photobucket.com/albums/ee402/webbybear1/hg_zps1dd1c1b2.jpg[/IMG][/URL]

cheers guys

Topic

[college man]

Oil is used in a wet compression test with the head on.
You would do a normal dry compression test.then add a small
amount of oil and due the compression test again.If the compression
jumps up the rings are at fault. You could use very fine emery to
clean the surface.

[Bill]

By the look of the pistons they smacked the valves real good. :ohmy: . Fine emery should be just fine.
How did the engine run before the belt broke? Did it consume any oil? How many KL’s/Miles on the engine?

The reason I ask is that the color of one piston (Center) makes me suspect a problem.

[Steve Webb]

Thanks for the replies guys 🙂

The engine consumed virtually no oil and has 101000 miles on it 🙂

picked up new heads today. cant wait to put it back together. College man, are you saying that I should put it all back togerther and THEN do compression test to see if they’re ok? there’s definitely no way to check it while i’m at this point woth the heads off?

cheers

[college man]

I have never seen the oil method you spoke of.
I only know of the traditional compression test.
so yes everything goes back together.

[Steve Webb]

Great stuff thanks for that 🙂

[EricTheCarGuy]

I think you’l be fine with the emory cloth to clean the heads but I like to use these when cleaning heads and blocks.

http://www.jbtoolsales.com/3m-007528-1-roloc-2-bristle-disc-120-grit/

If you don’t have compressed air however, they won’t do you any good.

Another consideration is the type of gasket used. If there is a graphite gasket or thick paper gasket marks on the surfaces aren’t too much of a concern. If however you have a steel head gasket, the surface needs to be almost like a mirror. I would not use any abrasives when this type of gasket is used. I’d wipe it down with a solvent soaked cloth and be done with it.

Good luck and keep us posted.

[Steve Webb]

Thanks for all the replies.

Well I had a go at cleaning them up. Emery has done well but i’m a little concerned about this pitting on the LH head…

[URL=http://s1226.photobucket.com/user/webbybear1/media/chg1_zps623deb52.jpg.html][IMG]http://i1226.photobucket.com/albums/ee402/webbybear1/chg1_zps623deb52.jpg[/IMG][/URL]

Note this photo was taken prior to any use of emery so I’ve still to clean it up. But technically i’d definitely get a feeler gauge in there so is this head no good? I have heard it mentioned I can put a sealant in there. Any info would be great 🙂

cheers

[Bret]

I believe it is possible to machine mating surfaces like blocks and cylinder heads back flat but that also changes all sorts of stuff out of spec making your compression ratios smaller and god knows what else, im not a mechanic 🙁 but you could machine it or go with it but a new head is probably cheaper then getting it machined

Those valves dont look to happy or are those the bent ones like you mentioned

[Author]

Replies