ZCar Forum banner

Status
Not open for further replies.
1 - 13 of 13 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
The images below are the result of my timing belt slipping going 70mph. I just got the heads off last night. Initially I was planning on doing a rebuild, new pistons, valves, etc. But it looks like I'm going to need to replace one of my heads as well.

What are the odds of the rods and crank being bent? Any experience or suggestions on where to go from here?

I should have the bottom end apart by the weekend, then I can assess the damage.

staylor3



 

·
Registered
Joined
·
3,080 Posts
Ususally it's just the valves that go, they are plenty weaker than the pistons. If you just replace the valves, you should be allright.
 

·
Registered
Joined
·
548 Posts
I don't know.. The pistons look like they're pretty banged up from having the broken valves bouncing around in there. I'd be looking for cylinder scoring too, just to be safe. Funny, it doesn't look like it even touched the 3rd cylinder valves.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #4
It's hard to tell in the pictures. But I looked closely at all of the pistons. Every single one touched a valve. They all have at least a small little nick on the top and the one piston is almost completely destroyed. There are gauges about 3-4 mm deep. I'm pretty sure the pistons need to be replaced.

You guys don't think I'll need a new head? Inside the one combustion chamber is really scraped up, some decent size gouges. Can those be machined out? Or is it pretty much done?

Thanks,

staylor3
 

·
Registered
Joined
·
548 Posts
That head does look pretty rough. Especially the middle chamber. Use your judgement. You might not be able to get a new valve seat in the center one. Any rough surfaces in there are going to cause hot spots and screw up combustion in that cylinder. How do the bores look?
 

·
Registered
Joined
·
782 Posts
As long as you cylinder walls were not damaged, and pistons are not cracked around the edges I would put it back together.. just surface the heads and mabey polish the chambers up just to check for damage
 

·
Registered
Joined
·
548 Posts
Since you have it apart, inspect/examine and fix it right. If you're selling the car to 300zx86t then slap it back together and tell him you just rebuilt both heads. :)
 

·
Registered
Joined
·
3,080 Posts
What I would do would just be to get new heads. There are plenty of people parting out cars on z31.com, and you've already done the toughest job, which is to remove them. Buy a pair from a not so high milage Z, and slap them on. NA or Turbo, it doesn't matter.
 

·
Registered
Joined
·
782 Posts
Aluminum heads can always be repaired ive seen alot people get there heads TIG welded and resurfaced. As long as the damage on the head is not outside the fire ring I wouldnt worry about it!! It all depends what he uses this car for if is racing yeh fix it as good as you can, but if you just need this car to run so you can drive it to work I would use what ya got. Sounds logical to me. As long as the valves are seating and the compression is building it will run fine but like the other guy said if this is a turbo car smooth the chambers back out to prevent hot spots.



Post Edited (Nov 2, 7:15pm)
 

·
Registered
Joined
·
114 Posts
Whew, that is a mess. I know where you're coming from, the exact same thing happened to me, except mine just broke almost completely off. I've had to have my heads reworked, and just to be safe, check your rings on your pistons. When mine turned loose, it managed to frezee up all of my oil rings on my pistons, which is what I'm repairing as of now.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #11
Crusader,
Did you have any damage to your connecting rods or crank shaft? Right now that's my biggest worry. I agree with 300Z86t that the heads can always be repaired. Or I even so some heads for sale on ebay (my year) for $40.

I plan on taking the bottom end apart this weekend. So everyone hold their breath. I'll let everyone know what it looks like.

staylor3
 

·
Registered
Joined
·
114 Posts
No, It doesn't look like my crank has even been touched, nor my rods. Of course your damage is far worse than what happened to mine, how fast were you going and at what RPM? Mine came off at 65 MPH and around 2500 RPM. Hopefully nothing will be affected?
 
1 - 13 of 13 Posts
Status
Not open for further replies.
Top