Head off, Pistons with dents, wierd valves. What now?

[SuluR]

Hey guys

After trying everything else, and no luck, i have the head off the misfiring-while-idle engine.

Pistons 1 3 and 4 looks fine (with a very VERY faint mark from vavles) but this is how piston 2 looked:

close up:

I managed to work them out a little bit:

Looking at the underside of the head (valves) i found that the cylinder two vavles were discoloured. Although dont look burned of damaged, more like they were replaced?

Is it possible that this engine had a snapped timing chain(causing the damage) and the person who replaced it didnt do a good job (misfiring).

Im sorry this is such a long problem, Any help will he much appreciated.

I will post pics of the cylinder head asap showing the valves.

Cheers

 

[frank]

either valvebounce (over-revved) or wrong valve timing imo, and you can bet the valves on # 2 are bent eh
i usually straighten the valves with a penny under the contact side (but i,m pretty ghetto lol) fit another head maybe ?

 

[SuluR]

Theres are the vavles from #2:

and this is how th rest look:

None of the vavle seem like they are bent though
Also you can see the rest of the vavles have a nissan logo (or something) while #2 doesnt

 

[frank]

it looks like they,ve been replaced (but not "ground in" tho maybe)
i usually test the seal by filling the chamber with soapy water and blowing up the ports with an airline

 

[Low Rider]

The engine definately had work done on it, the valves from Cyl #2 are not Nissan valves, so have been replaced by someone along the way through a random garage.

 

[SuluR]

how do i go about grounding the vavles? they do seem iffy. other then that im stuck for ideas. anyone have a spare head? lol

 

[frank]

maybe it was,nt re-shimmed to suit the new valves eh (and running with zero or negative valve clearance )

 

[SuluR]

I cant find anything in the Haynes book about shimming Is it hard? what is it

 

[frank]

I cant find anything in the Haynes book about shimming Is it hard? what is it

they,re are the steel biscuits that are fitted to the top of the buckets suluR, you have to select the correct thickness for the running clearance between the cam and valve
i would check that the valves are sealing ok first

 

[SuluR]

I just found the shimming bit in the book. Whats the best way to check the vavles are closin properly? (with ameture tools )

 

[frank]

I just found the shimming bit in the book. Whats the best way to check the vavles are closin properly? (with ameture tools )

with the chamber filled with water and a tyre inflater up the ports (and look for bubbles)

 

[SuluR]

Okay ill give it a try. Thanks frank (Y)

 

[SuluR]

I filled the chamber with water and the a vavle (from #2) leaked water without even using air. So the next obviouse question. How do i make it fit properly?

Cheers frank (Y)

 

[frank]

lol, they must be slightly bent eh, you need to see the bubbles really to see which side is high (oil wont run away so quick eh)
i usually wedge a penny under the tight side and tap down the high side with a copper drift, but it takes some practice to be able to get them dead straight tho :grinning:
you may be best to find a 1.0 head tbh

 

[SuluR]

I was planning to get another head anyway, but i thought i might aswel give a go fixing this. As you can probably tell frank, im the noobest guy on the net when it comes to engines. Last few days have been the most couragous (Y)

Back to the vavle, ill try wedging pennys and tapping. I cant seem to see any bend to the vavle, tho ill try get some bubbles going see where it really is bent/not sitting.

 

[frank]

its all good practice/experience eh suluR (Y) good luck

 

[jowley]

best thing to do is fit new valves and get them shimmed up valves are only 8 quid each

 

[SuluR]

oo, where from?

 

[jowley]

a motor factors or engine center place