Rocker Geometry Woes

[Captain Obvious]

Maybe the valve was sticking in the guide as well and if the rocker pushed next to the valve stem (instead of ON the valve stem), it might have released the keepers.

 

In any event, I'm thinking that trying to get a look at the piston top would be a good idea. 

[Zed Head]

New valve seals would probably hold the valve up while the retainer got pushed down by the offset rocker arm.  Still curious though, that the engine ran so poorly.  It's common for people to test an engine by disabling an injector or a spark plug.  Sometimes 5 doesn't sound a lot different than 6.  And I've seen several accounts of people driving around with an odd noise only to find out later that a rocker arm had fallen off.  His symptoms seem more severe.

 

From the work-rate shown in his prior posts I'm assuming that the head is already removed and/or the problem has been fixed and he's out driving again.  We're having good weather here in the PNW.  Not a good time for the car to be down.

[rossiz]

i didn't get a chance to work on her today - hope to get in there tomorrow and do a thorough inspection of things.

 

here's my theory of the "big bang": i think the rocker arm shot off towards the valve and the toe got pushed into the spring, then the cam lobe pushed it down hyper-compressing the valve spring and popping off the collets - remember that this is a newly rebuilt head, so the collets wouldn't be stuck in position like they are after a few years. 

 

the evidence: the valve guide seal is torn and the little spring that wraps around it holding it onto the guide seat was popped off (that's the little "needle-like" thing in the picture. this makes me believe something pushed down on it hard enough to blow the spring off it and tear the top.

 

anyway, i'll know more tomorrow and will report what i find.

[71Nissan240Z]

Pressurize that cylinder where the valve prpblem was. If that valve holds up there then it's not leaking and your fine. If it leaks air your valve is bent. A little tap on the piston is fine as long as the valve still seals. No need to look with a camera or anything if the valve is sealing.....

[siteunseen]

No need to look with a camera or anything if the valve is sealing.....

 

 But he's got that cool colonoscopy camera already.  I'd bet his wife insists that it stays in the garage. 

[rossiz]

well, i dug into it on friday afternoon and unfortunately, no love.

 

put on a new valve guide seal, installed the springs and did a compression test - nothing in #2.

i used the camera in the spark plug hole and saw the evidence of serious impact. there was clearly quite a bit of commotion in there when things came apart, as was evidence by some marks on the inside of the cam cover and it looks like the spring keeper took a beating. 

 

so it's "off with her head!" and i'm hoping that i might get away with just replacing the valve. 

stay tuned...

 

 

piston impact

 

valve cover

 

valve spring keeper

[EuroDat]

You are getting to be an expert at removing datsun heads for all the wrong reasons. Its sad this job is not working with you. Respect that you remain calm amungst it all.

Small marks on a piston crown should not be a problem for a street car. This looks like it took a couple of hard hits and the effects could be more than just piston crown damage. It might have compressed the top ring groove and the groove is now too tight on the top ring.

I would add the piston to my list of parts. I don't think I would feel confident driving with it.

Chas

[Captain Obvious]

Bummer. Off with her head!

 

If we weren't so far apart, I'd be more than happy to give you a hand getting this thing into tip-top shape.

[siteunseen]

I'm sure your puppy training is going better than your green eyed lady. 

[Mark Maras]

 Rats! Looks like thrashing on green-eyed Lillith is to become your Super Bowl tradition. Sorry to see the damage. Don't know if it will help, I have a spare L26 & an E88 that could give you a runner until the new build is complete. Let me know if there is anything I can do to help out.

Mark

[Zed Head]

Bummer.  Is that really a colonoscopy camera?  I want one.

 

Did you check any other cylinders?  Still curious about cam timing and valve clearance.  Although getting the rocker arm lodged on top of the retainer as it wiggled its way out seems reasonable also.  There was probably a short period of time where the valve was still held up by the seal when piston damage could have been avoided.  Sorry, I'm sure that doesn't make you feel better.

 

Don't forget though - the Seahawks are playing in their second Super Bowl.  A little bit of feel good.  Unless you're from Wisconsin.

[rossiz]

thanks for all the kind words - although a disappointment, i'm not crushed by this as i've gotten to the point where removing the head is about a 1 hr. project now.

all the other cylinders had between 165 and 175 lbs compression, so i'm thinking it's just the one that i have to worry about - but once i flip the head over and see the chambers the truth should be revealed.

 

i'm really not interested in pulling the piston out - takes the project to a whole other level of PITA... my fingers are crossed that i can get away with leaving it as is...

 

and yes, i will be wrenching on green-eyed Lillith during the superbowl. last year i was re-wiring the primary power and relay circuits during the seahawks win, so i have been instructed to continue the tradition lest my change in game-day habits upset the outcome...