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Good old fashioned blind diagnosis ...


reAnimate

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Hi all.

 

1.8K Elise with recent DVA spec.

 

Symptoms:

 

1. Smokey exhaust

2. No.4 spark plug very very oily

3. Gets through quite a lot of oil

4. Git to start when cold

5. Poor economy

6. Down on predicted power by 10bhp or so

7. Sounds like a bag of nails when cold

 

To me, sounds like a piston ring gone?

 

Cheers,

 

 

Simon.

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Having seen the head in question before re-fitting I think it's guides, they were quite worn on the inlet side, a by-product of the porting in the inlet side is the shortening of the guide which worsens the situation WRT to the valves lateral location. When the valve starts to open the sideways thrust can cause the valve to move beyond the authority of the stem oil seal and allow oil down the guide.

 

By all means do a compression test but that may not be conclusive, it is entirely possible for the compression rings to be holding up well when the oil ring is shot.

 

Oily

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Simon,

All the clues are there!

Just carry out a compression check and forget all this about valve guides. Don't forget to do the check with the engine hot (if it will run an four), remove ALL of the plugs, disable the fuel pump, hold the throttle wide open then crank. Record your figures (including cranking speed) and then apply about 15cc of engine oil into each bore (as you re-fit the compression fitting) and recheck. If there is a marked diference in the two readings, ie a higher pressure at the second check, then the betting is a piston related failure; if no difference (excepting a holed piston of course) then look towards the top of the engine. I would imagine a normal figure around 180 psi (12 bar) depending on battery and engine condition. Your problem will, I am sure, manifest itself with this simple check.

Best of luck.

 

Steve B

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Na I'll go with Oileys diagnosis worn guide i'll bet. Is it still on Hydraulic or did you fit DVA shims it will rattle a bit when cold but strip it anyway and go for forged pistons if you can't afford that I will have within the next week of so a complete 1.6 Bottom end liners /pistons/rods/crank for disposal if any of it is any use it will be at DVA's in Jan.

 

jj

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