300ZX (Z31) Performance / Technical Discussions related to Turbo charging, Supercharging, Engine, ECU, exhaust, and etc. performance enhancements and Techical related.

Timing, Valves, and Heads

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Old 09-01-2011, 01:51 PM
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Unhappy Timing, Valves, and Heads

ok so first off i am the proud new owner of a 87 300zx NA. i bought the car pretty cheap and the looks of the car are amazing. it did not run when i bought it, i trailered it home. the previous owner said he had it for a year and when he bought it it did not start either. he had a mechanic look at it and said it was the timing belt. ok i said. i have a close friend who is a real z enthusiest and currently owns three of them. he and i have been breacking down the engine to get to the timing belt and have come to a halt. here is the issue. upper and lower intake off, upper timing belt cover off, no snapped belt. just loose with an inch of up and down play in the middle of the cams. looking inside the intake on the heads you can see that all the valves in all 6 of the cylenders are open. where do i go from here????? pull the heads???? replace belt and respective parts and see if it will time right???? compression test?????? valve job????

please help me. i would love to not have to pull the heads.
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Old 09-01-2011, 09:49 PM
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You're going to have to pull the heads. Sounds like the tensioner stud snapped. This lead to all the valves hitting pistons and breaking the motor.

As it stands, you're going to have to finish pulling the heads to rebuild all the valves. Hopefully there is no piston damage, but it's possible.
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Old 09-06-2011, 01:31 PM
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Red face

Originally Posted by AZ-ZBum
You're going to have to pull the heads. Sounds like the tensioner stud snapped. This lead to all the valves hitting pistons and breaking the motor.

As it stands, you're going to have to finish pulling the heads to rebuild all the valves. Hopefully there is no piston damage, but it's possible.
Thank you for the advice. in your opinion would it be more cost effective to get the valves done and resurface the heads or to just get a new engine??
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Old 09-07-2011, 03:13 PM
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I've been able to find recent engine pulls from running cars for $300 or less. A full gasket kit with all the work you're going to need could easily run much more than that.
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Old 11-14-2011, 01:47 PM
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so I went with the head job option. I got a complete head job for $400 and a stone gasket kit for $160. the pistons cleaned up perfectly with very minor marks on just two of them. the cylinder walls are like glass with no scratches or burn marks. I still have not gotten all the way down to the bottom of the timing belt so i still don't know the cause of the belt failure. I bought a new 170 degree therm. yesterday. I will be getting the water pump at the end of this week. I will also be getting rid of the AC condenser and compressor. any tips for pulling the front end off the car?????? also any thing I should know when I start to put it back together??????? also any recommendations on electric fan conversion?????? your help is greatly appreciated and I hope to have the car running soon. Thank you
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