sdm9785 Posted March 29, 2012 Share Posted March 29, 2012 Alright guys, need some help. I just bought a 76 280z. The previous owner rebuilt the engine (N42/N42) recently, when he put it back together he used flat top pistons. When I bought the car it was not running and the PO said that it had bent a valve....when I took the valve cover off I noticed 2 obviously bent valves, took the head off and every piston had hit a valve. My question is, when swapping over to flat tops, does anything need to be done to clearance the pistons for the valves, or could he have had the timing off? I apologize in advance if this is a stupid question..I've looked around the site and havent found anything. Also, the PO said that the car only ran about 5 hours, until it bent the valve...unsure if that will help you guys out or not. Thanks for any info in advance. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted March 29, 2012 Share Posted March 29, 2012 Did he build it in his garage with no knowledge or experience? or did he have it assembled at a shop. Because I had my f54/e88 long block assembled at a shop and I did not bend a valve in 5 hours. Quote Link to comment Share on other sites More sharing options...
Gollum Posted March 29, 2012 Share Posted March 29, 2012 When assembling ANY engine, it's just plain common sense to clearance the motor. It doesn't take much time or effort and the process is described in many vehicle's FSM. Sounds to me like someone pulled the head and didn't make sure the cam timing stayed the same and now you're left with the aftermath. To be safe, it's best to pull the timing cover and reinstall the timing chain per FSM instructions when you reassemble the motor. There's no special procedure that I'm aware of for flat tops versus dish pistons. If the cam was fairly aggressive that could be an issue, but from what you said that doesn't seem to be likely. Quote Link to comment Share on other sites More sharing options...
sdm9785 Posted March 29, 2012 Author Share Posted March 29, 2012 Thanks for the quick reply guys. The previous owner built the engine himself, but it wasn't his first (possibly his first l series), upon first seeing what had happened I thought that he might not have been very knowledgeable on engine building as well, but after having talked with him he seemed pretty knowledgeable (I know it must not seem like it), he even stated that he did check clearances (which is what makes me think it was the timing). And no, it doesn't have a super aggressive cam, I wanna say its an A cam. With that being said I plan on using an isky .490 lift cam when I put it back together, would I have any issues with that? This will be my first engine to rebuild that has any kind of performance, so I'm fairly new to that, I've previously only built an amc 242 for a jeep and a couple of 4 cylinder low compression toyota engines. Again I apologize for being a newb! And I do appreciate all the help. Quote Link to comment Share on other sites More sharing options...
theghosttanker Posted March 29, 2012 Share Posted March 29, 2012 460 lift is the limit for stock valve springs and retainers, so if you rebuild with a 490 cam you will need to be aware that you need aftermarket springs. Quote Link to comment Share on other sites More sharing options...
Leon Posted March 29, 2012 Share Posted March 29, 2012 You'll be fine, if you time the cam correctly. The PO did not understand the importance this concept. Quote Link to comment Share on other sites More sharing options...
sdm9785 Posted March 30, 2012 Author Share Posted March 30, 2012 460 lift is the limit for stock valve springs and retainers, so if you rebuild with a 490 cam you will need to be aware that you need aftermarket springs. I plan on buying the springs and retainers from isky as well, thank you though. I'm sure I read that somewhere, but it is definitely good to see it again. And to everyone who has replied, thanks for the help, just seeing the damage on the pistons made me doubt everything I thought I knew, but you guys have confirmed things yet again! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.