Anyone seen my head??????

Paul Smith

Paul Smith

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Had the Head off today, and its still off.

Its been firing on 3 for about 2 weeks, I was hoping it was an injector but tested the compression this morning
Cyl 1 - 11
Cyl 2 - 10
Cyl 3 - 4
Cyl 4 - 6

So quite an obvious problem, So ripped the head off piston rings are fine (or appear to be) Took the valves out of the head both inlet and exhaust but no signs of any obvious damage or burns? The only thing that was odd was, the valves sit on rotators (sure thats what there called) and out of 16 I only had 4 in the head?

The other odd thing was the strongist Cylinder (No 1) had wet oil all the way up the inlet manifold and lots of it and the other three cylinders were lovely and tidy.

Gonna get the valves lapped back in again should be ok to clean up and lap back in instead of buying new ones (will check them more thoroughly but seem fine).

So after all that I am still not sure what the issue is, or cause of the low compression.
 

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You remove the collets, spring with cap and valve but under the spring is where these washer things are which are called rotators or vauxhalls, maybe different nissans.
 
Paul Smith said:
You remove the collets, spring with cap and valve but under the spring is where these washer things are which are called rotators or vauxhalls, maybe different nissans.
Click to expand...

ahh, :grinning: they,re only washers that stop the springs from cutting into the head paul (tho it would probably take a million miles for them to chafe any metal away imo)
mine always fall out when i jetwash the head, and cba to refit them :wasntme:
you can get more valvelift (before the springs get coilbound) without them in :p
 
Well at least there nothing to worry about. lol

Still unsure what the problem is with the engine as everything seemed okish.
 
Its a massive drop which is why I was concerned enough to take it apart today, there is no evidence to suggest the gasket was leaking anywhere, the gasket was actually in good nick. no evidence of water in oil either?

confusing hey?
 
I'm confident its not piston rings as they seem fine and when they went on my last engine your right there was smoke or like a dust behind.

Head gasket is in good condition and no signs of leakage

Valves seem ok unless I caught them maybe at an early age of damage so they are not so obvious? could be a build up of carbon maybe blocking a valve??????? just guessing though
 
i always fill the combustion chambers with water and blow up the ports with an airline, to check for leaking valves paul (you,ll get a ring of bubbles with a pitted/coked up valve eh)
more pics may help paul :)
 
Agree my bet is its the head, over revved or bent valves or something.
 
i was going to suggest bent valves, check ones from cyl 3+4, clear the carbon off them and stand them up. its quite easy to notice them when bent. if you cant see anything noticeable then put them back into the head you should be able to notice that they dont quite close right. if they still seem ok then it has to be headgasket or piston rings, does your oil smell a bit like petrol??
 
Hi,

I'll get a pic of the head gasket up for you, the car did occassionally smell of petrol but the oil didn't if that make sense. The Piston was dry with no visible damage, in the pic there is a mark on cyl 3 but thats where I touched it with wet gloves.

Possibly a bent valve i'll have another look, but the bend must be minimal.
 
Sorry I've not had chance to post the pics up yet.

I spoke to the place lapping in my valves and checking the head, he said I have one exhaust valve quite badly bent. He also said that it is very strange to bend just 1 valve, hopefully get the head back tomorrow.

Any thoughts, oh and its odd it was on cylinder 2?
 
Looks like I was right then ;) Valve bounce. Miss shift on gearbox or too high rev limiter/weak springs/backfire etc... so many things can do it.

BTW lapping the valves is a crude way to do it. If you can afford to get it done professionally on a SERDI head machine then do so. It will do a better job than you can of getting a seal with you USING springs to help hold the valves shut than it would with the weight of gravity alone...
 
Valve Bounce???? is that likely to just damage 1 valve?

The guy lapping the valves is using a machine to do so, its a clever bit of kit.
 
Ok it may be a serdi one, in which case its good. Yes valve bounce can be unpredictable, especially if your just board line the spring limits.
 
Cool I'll give them a shout in the morning,

Oh good to have you back on the site, not read anything from you for a while.
 
i was also right and to think of it now, i bent 2 valves when i done it a while ago. its wierd that it was cylinder 2 though...makes you think why the compression was so low on cyl 3+4 then
 
Its confusing your right, but the whole situation has been. Cylinder 1 had oil up the inlet, Cylinder 2 has a bent valve, Cylinder 3&4 low compression.

Its very odd?
 
This is going to be a stupid question perhaps and dont in any way be offended but you have referanced cylinder 1 from the timing chain havent you?
 
yes that is correct, id make sure the guy lapping the valves is doing this also, cos if he has it the wrong way around the bent valve could be number 3 and would explain a couple of things.
 
Right had the joys of rebuilding the head as he didn't he only lapped the valves so finished that at 10:30 saturday night, took a couple of hours put the throttle bodies back on and all the sensors.

On sunday started fitting the head at 11:45 finished and all tidied away by 16:30 as it was getting dark, and surprise surprise she started first turn of the key and she is the smoothest I think she has ever been, only cruised to work and back today not going above 65 mph just taking it easy. She is going really well so I am well chuffed.

I didn't get chance to test the compression as it got to dark and the fact she is going so nicely (touch wood) I don't wanna tinker to much. lol
 

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