rigo Posted May 13, 2011 Report Share Posted May 13, 2011 Hey guys I'm in the middle of re building my l20b and I ran into a little issue. I was starting to torque the bolt for the cam gear, so I started moving the cam untill it reached the desired marking for the timing.. well while I was turning it it started getting really really hard to move it to the point were it felt it would not move no more almost as if one of the lobes could not move the valve spring down.. the lobe was the one for cylinder 1 intake.. also the chain is not installed ao its not like the chain is getting stuck.. any help with the problem? Thanks in advance - Rigo Quote Link to comment
Z_Rac3r Posted May 13, 2011 Report Share Posted May 13, 2011 Is it on an engine? or are you rebuilding it on a bench? If on an engine, possibly hitting a piston? Probably something silly like that. Are they new valves? one possibly bent? Quote Link to comment
rigo Posted May 13, 2011 Author Report Share Posted May 13, 2011 Yea its on a engine stand.. I got the head re done at a machine shop, valve job and everything.. the pistons and connecting roda amd bearings are all new.. in sure I put everything back by the book.. Quote Link to comment
Z_Rac3r Posted May 13, 2011 Report Share Posted May 13, 2011 What I mean, is, if the head is on the engine, and one of the pistons is at tdc, the valves can hit it if your just rotating the cam. Don't force it, or it will bend the valves. turn the crank so the piston moves down, and then the top end should be able to rotate. That's the only clearance issue I could see if everything else is done by the book. Quote Link to comment
wayno Posted May 13, 2011 Report Share Posted May 13, 2011 If the cam was not in the correct position before you bolted it to the engine block, and the engine(crank and pistons) are at top dead center, then a valve is more than likely hitting a piston, hope you didn't force it to hard, you can bend a valve that way. Quote Link to comment
rigo Posted May 13, 2011 Author Report Share Posted May 13, 2011 Ok so yea I moved the crank around a little bit then rotated the cam it it moved! So this means I'm cranking the piston up too high? Sorry I'm so dumb about it this is my first build.. Quote Link to comment
nismo dr Posted May 13, 2011 Report Share Posted May 13, 2011 stop spinning it without the chain! I hope it was positioned correctly before you bolted the head down. Do you have a manual or are you winging it? Quote Link to comment
rigo Posted May 13, 2011 Author Report Share Posted May 13, 2011 I have an original datsun manual for the 76 datsun 620 truck. Something wrong? Quote Link to comment
ggzilla Posted May 13, 2011 Report Share Posted May 13, 2011 Any engine will do that if the timing belt (or chain) is not connected. The problem is forcing it. Quote Link to comment
rigo Posted May 13, 2011 Author Report Share Posted May 13, 2011 So I should aligne the cam pulley were its suppose to go first for base timing amd then put the piston at tdc so I don't deal with that first issue?? Quote Link to comment
john510 Posted May 13, 2011 Report Share Posted May 13, 2011 Do not turn the cam without the timing chain installed especially if you arent sure where the pistons are.Your rebuilt engine may need to be fixed before you finish it.Read the manual.I would get the chain on correctly before tightening the cam bolt.You should of had the #1 piston at TDC and the cam at TDC before you put the head on.Then timing chain without spinning anything. Quote Link to comment
rigo Posted May 13, 2011 Author Report Share Posted May 13, 2011 Damn well thanks for all you guys help.. guess I got some more work to do. Quote Link to comment
D52E Posted May 13, 2011 Report Share Posted May 13, 2011 I agree the best thing to have done would have been to align the cam to TDC (Top Dead Center) before bolting the head on the block. No worries, we have all be there before having trouble with our project cars. This is one of the reasons we come here - to share information and experiences. You can try turning the crankshaft a few degrees from TDC to lower the piston slightly from TDC (I would guess 30 degrees of crank rotation) but just beware that the tool you have holding the timing chain tensioner can move and let the tensioner piston out which would require you to remove the timing cover in order to get it re-aligned again. Once you have the pistons slightly down from the top you can proceed to align the camshaft to TDC. After that return the crank back to TDC. You did use a tool to hold the tensioner piston in? You can watch this set of informative videos from ratsun member Hainz for timing chain setup Timing Chain Videos Link. There is some good information there on this process. Take your time, read the manual and watch the videos. With a little patience it will all come together. If you have any problems with the way it runs after putting it together check the compression on all cylinders to make sure none of the valves were bent. If you do find a cylinder that is way low on the compression you may have to pull the head back off to replace a bent valve (don't beat yourself up over it - shit happens). Valves should be available from sources like rockauto.com and they are not too expensive. It's just the pain in the but to take it all apart again. Good luck man! Quote Link to comment
rigo Posted May 13, 2011 Author Report Share Posted May 13, 2011 Thanks a lot man. I don't have anything on the block. No chain, tensioner, or guides.. I baugt this l20b bottom block re done from hopsing machine down here in san diego ca.. so I'm just putting everything back together from the ground up.. I'm just gaa keep studying everything amd make it right (this is gana be my daily driver once I'm done) ima post up pics of my 510 wagon build in a few days .. this timing thing is just setting me back. Quote Link to comment
wayno Posted May 13, 2011 Report Share Posted May 13, 2011 How hard did you push on the bar/breaker bar/wrench? It's not that hard to bend a valve, I did the same thing a while back and removed the head to adjust the cam as I had the timing chain pinned, I reused the head gasket as it was only torked for 5 minutes, and when I pulled it apart, it came off clean, I have been using that engine daily since, it's been a couple months now with no problems yet. Needless to say I am hoping it doesn't become an issue reusing it. I hate to say this, but if you pushed say a hundred pounds trying to turn the cam, you should probably pull it apart. I have bent 2 valves just laying the head on its face because the cam was holding the valves open, so the weight of the head was resting on the valves. Quote Link to comment
rigo Posted May 13, 2011 Author Report Share Posted May 13, 2011 Honestly, I think I put about 60 lbs or pressure but I am gana take it off and re install it.. I hope the ARP studs are still gana be good.. they are brand new.. Quote Link to comment
yello620 Posted May 13, 2011 Report Share Posted May 13, 2011 There is no reason to be torqueing the cambolt yet anyways. The cam bolt has to be removed to install the timing chain anyways. Unless you got some cheap chain with a master link. You need to de-adjust all your valves, and then set crank and cam to TDC, then install chain, guides, and tensioner. Now you can torque the cam bolt. Quote Link to comment
banzai510(hainz) Posted May 13, 2011 Report Share Posted May 13, 2011 WTF!!!!!!!!! you watch this http://www.youtube.com/view_play_list?p=8EF51386855F2B58 Quote Link to comment
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.
Note: Your post will require moderator approval before it will be visible.