valve work

[ZTEC]

hello z fourm, i am posting because I need help in pointing me to the right direction in doing a valves & lifters job on my 77 280z. I need to do this because first off my z wont run, it cranks and bumbles a bit but will not stay running, so I pulled off the valve cover to find that i am able to move the arms from side to side by hand(this cant be right) so I figured i need to do a valve job.

p.s. the reason i say its the valve work because i have previously owned a 76 and i had a burnt valve in it causing it to run off. The 77 is running the same but a lot worst(I had it running at one point of time for a whole min but it eventually died out)

[IdahoKidd]

The poor start and running conditions you describe are not symptoms of valve trouble but sound like fuel issues. Before you get carried away with an expensive valve job, check things like the compression, the color of the plugs, etc. Check fuel pressure and fuel flow. It sounds more like a clogged fuel filter or a gummed up gas tank. Be sure your timing is correct and your cap, plugs and wires are in good shape. You may dive into a head job and find it is no better than before. Go to the "search" function at the top of the page and spend an hour chasing threads about fuel pressure, gas tanks, fuel lines, no start issues, etc. It will save you hundreds of dollars and give you some great knowledge.

Give more background on the car too please, such as, how long have you owned it, when was it running well last, how long has it sat, any mods that you know of, etc. All of these things can trigger responses from members who have 'been there, done that' and will keep you from re-inventing the wheel.

Let us know whay you find out.

Leonard

[Pop's Z]

Also, if you can move the rocker arms around by hand they are probably in serious need of a valve adjustment. Cars with badly out of spec valve/rocker clearances don't run right. It is not a difficult job, just tedious if you haven't done it before. After you have done it a few times it gets easier and goes a bit quicker. You can get a video of the proceedure from ZTherapy. Try doing a complete tune-up before thinking about a valve job. Fix the simple things first.

Cheers, Mike

Edited April 10, 2010 by Pop's Z

[Z train]

Also' date=' if you can move the rocker arms around by hand they are probably in serious need of a valve adjustment. [/quote']

Not true.If the arm is on or close to the heel of the cam,you will be able to move it side to side.

To the OP-get the FSM and start reading.You knowledge level is at a point where it's ggonna cost you serious $$$ for NOT fixing the issue.

[olzed]

Correct! You will be able to move each rocker ,and should have some clearance in each one in turn, as you rotate the crank shaft by hand.

Some will be tight and others loose depending where in the cycle the crank and camshaft are at that moment.Get a spanner on the pulley nut and turn the crank from there,and you can watch the cam rotate, opening various valves.When the valve is in the open position the rocker will be under tension .When the valve is closed there is no tension on the rocker so you should be able to move it.Get a home workshop manual pertaining to your car and it will help.You can check the rocker clearance yourself if you own some feeler guages,and no it's not the side to side clearanceyou check. The rocker clearance/tappet clearance/valve lash(all the same thing) is .008-.010 inch,or .20mm-.25mm on a cold 240 or 260 motor(don't know about 280 but i'm guessing the same) Rotate the crank until you can see the lowest part of the cam(the heel) against each rocker in turn.That is the position where each one becomes loose,and the same position where you do any checking or adjusting.See the two nuts one above the other,These are the adjusting nuts and this is where you slide the feeler guage.

[ZTEC]

Well I just bought this car a few weeks ago, the owner did not know what was going on with it, and it sat up for a bit (it did not run when I bought it) and been trying to get it running since. The work that I've done to it so far was replace the fuel pump, because i did not know the condition of the one that was on there, I've checked that fuel was getting to the engine by pulling the fuel hose after the fuel filter(good).FOLLOW UP* I got the car where it starts for a min on crank, runs for a bit (very roughly) when i get it to rev by holding on the accelerator rod(it take a sec to get it to rev), i can here loud machanical ticking, I believe from the arms, and also backfire in the are intake area. HELP! HELP! HELP

P.S. It doesnt stay running, it dies out after playing with it a bit, probaly after 2-3 mins

Edited April 11, 2010 by ZTEC

[ZTEC]

Ok z fourm, I figured one problem. Today I pulled the rocker cover and found that four of the lash pads had fell out which was causing first the loud ticking and second the arms to move from side to side, I put evrything back as it should be and cranked it up. It took a bit to get it started (which I will talk about in a sec) and it ran a lot smoother. (it only runs for about 2 mins and dies, when I go back to start it it just turns over)

Ok the problem, when pushing on the accelerator rod it does not rev right up, also I pulled the fuel hose again (from the top of the fuel filter) and SPLASH, fuel came out but pressurized(more air pressure than fuel) so I figure that there is not enough fuel getting to the engine. Like I said before I was sitting for a while and I belive the tank is trashed, so I will be dropping the tank to get it cleaned and probaly will either get the fuel rail cleaned or get a new one. Will follow up. Thanx!