Man with spanners - thinks he's a mechanic

Need help from a fellow owner, something to air - discuss away!

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ChrisL
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Re: Man with spanners - thinks he's a mechanic

Postby ChrisL » Sun Jun 21, 2020 2:03 pm

Indeed! I tried again with 10cc of oil and got:

1. 10
2. 125
3. 50
4. 190

so I thinks for 2&4 its more a case of them not bedding in, only got 50 miles on the clock. 1&3 loo like more head work required. I'm going to order dome new inlet valves (already put new exhaust valves in) and see where I stand...
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Dick
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Re: Man with spanners - thinks he's a mechanic

Postby Dick » Sun Jun 21, 2020 2:14 pm

Before you go to far you may need to do a leak back test. Dont strip engine down try another compression test but take the cams out of the head . odd sort of test but it only takes a few min to do take all the plugs out first

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DJ.
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Re: Man with spanners - thinks he's a mechanic

Postby DJ. » Sun Jun 21, 2020 3:38 pm

Is that to see if it is the valves not closing fully?

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Re: Man with spanners - thinks he's a mechanic

Postby Dick » Sun Jun 21, 2020 4:59 pm

You win
:D

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Re: Man with spanners - thinks he's a mechanic

Postby Dick » Sun Jun 21, 2020 6:58 pm

Chris you need to find out what is causing the loss of compression before you pull it apart. Do the comp test without cams first . If you can perform a leak back test do one . Can you get an end scope to look in the cylinders.

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ChrisL
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Re: Man with spanners - thinks he's a mechanic

Postby ChrisL » Mon Jun 22, 2020 8:12 am

That makes a lot of sense, as you say no point pulling it apart without knowing what's causing the issue, thanks :D
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ChrisL
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Re: Man with spanners - thinks he's a mechanic

Postby ChrisL » Sat Jun 27, 2020 11:35 am

Ok So the scores on the doors!

Full Engine
1. 10
2. 125
3. 50
4. 190

Cams off
1. 100
2. 95
3. 25
4. 95

All cam off tests were run with the cylinder starting in bottom dead centre, as the inlet valves wouldn't be opening so I needed to start with a known amount of air the pressurise. I ran no. 3 twice to make sure it wasn't an error.

I think what this is telling me is no.1 the shims are too big preventing the valves from closing properly. No.3 is the pain as I don't know if this is a valve seating issue or piston rings not sealing.

What to do next? Well I could put the same amount of oil in each cylinder with the cylinders in same position and measure how long it takes the oil to drain, that should tell me if it's cylinder or valve. The other option would be to take the head of and do the same test on the head, probably with parafin or petrol....

Suggestions welcome...

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Chris
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Re: Man with spanners - thinks he's a mechanic

Postby Dick » Sat Jun 27, 2020 7:39 pm

Chris chances are the rings have bedded in we do it very fast on our engines . So dont worrie about that to much . You should be see around the 90 with the cams out so i would say its valve problems. The Zetec heads have to shimmed up so near to perfect or they drop power and looking at you numbers you need to make sure when you re-do you spend the time on it this time. Pull the head off and take valves out checking the valve seat and the valve for seating or damage . If your not happy get valve seats recut and lap valves in once the valves are all in and fitted . No short cuts in this job then reshim the head i do this off the car one cam at a time oil it up fit cam and wind it over a good few times b4 you start to measure. Take your time dont rush remember once the head is fitted on the car you dont want to be doing it again.

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ChrisL
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Re: Man with spanners - thinks he's a mechanic

Postby ChrisL » Mon Jun 29, 2020 2:52 pm

Thanks Dick.
I've taken the head off and started to try and identify which valves are the problem by filling the caps up with acetone and looking for leaks. So far it looks like the exhaust valves, which are new!

Will re run the tests to be sure and try re-lapping them and re re running the tests, as you're right I don't want to be doing this again!!

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Re: Man with spanners - thinks he's a mechanic

Postby Dick » Tue Jun 30, 2020 3:08 pm

You need to strip the head down and check every valve and every seat for damage. You should get the angles checked and the flatness of them all. If the valves are only just touching the seats when closed due to incorrect tapper clearance then this can have a bad effect on them. Get this all done before you start lapping the valves in .


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