superbee717 Posted January 16, 2014 Report Share Posted January 16, 2014 ive got a 73 620 with the L16 and one of the intake valve rocker arms keeps slipping out of the valve spring cap. I have the valve lash set at .008 cold on the intake and .010 on the exhaust. the particular one im having problems with is a intake rocker. also I have a junk truck with a L20 and was wondering. is the rockers and spring caps the same on these two engines ? any help with this matter would be much appreciated. Quote Link to comment
RTB Posted January 16, 2014 Report Share Posted January 16, 2014 There's an entire engine subforum. And the l20 and l16 are very close to identical. The l20 has a 2mm larger bore and is taller. The heads are completely interchangeable. Posting the lift might help answer any questions. 1 Quote Link to comment
ggzilla Posted January 16, 2014 Report Share Posted January 16, 2014 .080 Yes, that will cause the problem one of the intake valve rocker arms keeps slipping out of the valve spring cap. I have the valve lash set at .080 cold on the intake 1 Quote Link to comment
H5WAGON Posted January 16, 2014 Report Share Posted January 16, 2014 ^^^^..... .08 & .080 is the same deal? Maybe you have a bent valve? Week spring? Broken spring? Is the lash pad on top of the spring retainer? Maybe its missing on that valve..? Pics can tell us so much. :geek: google l-16 valvetrain...I would post but copy and paste not working at work...WTF...lol Most people will say HOT adjustment is best.....which might be hard in your case, but COLD should do fine. Quote Link to comment
ggzilla Posted January 16, 2014 Report Share Posted January 16, 2014 Intake should be .008" (8 thousands instead of the 80 thousands reportedly used) 1 Quote Link to comment
H5WAGON Posted January 16, 2014 Report Share Posted January 16, 2014 I was copying from olddatsuns.com I think its wrong there. I like the hot numbers Intake .010 Exhaust .012 1 Quote Link to comment
datzenmike Posted January 16, 2014 Report Share Posted January 16, 2014 That should fix it...... and the noise! Superbee as yet there is no L16B only L16. 1 Quote Link to comment
banzai510(hainz) Posted January 16, 2014 Report Share Posted January 16, 2014 I do .006 in .008 ex. the lash pad should sit flush with the retainer UNLESS you have stock retainers and a underground cam with bigger lash pads that sit above the stock retainer. Quote Link to comment
superbee717 Posted January 20, 2014 Author Report Share Posted January 20, 2014 Thanks for all the replies . sorry it took me so long to get backto the forum. I took the rocker arm and spring retainer off my junk truck with the L20 had a different casting number but looks exactly the same. seems to be working fine for now. and sorry for reporting that I set lash at .080 I actually set it at .008 my mistake. Quote Link to comment
datzenmike Posted January 20, 2014 Report Share Posted January 20, 2014 No worries. Did this fix the problem? Quote Link to comment
superbee717 Posted March 27, 2014 Author Report Share Posted March 27, 2014 im still having the problem . different valves now are coming off. especially when its cold. ive set these things now about 10 times in two months.it will run fine for a few days I will cut it off then when I go to crank it . you can tell one has slipped off again and .thats all im sure about is that they slip off when I cut the engine off. im going to try .006 intake and .008 exhaust and see if it makes any difference. im really confused why this keeps happening. really a poor design by datsun if you ask me . Quote Link to comment
datzenmike Posted March 28, 2014 Report Share Posted March 28, 2014 This design works perfectly When the rocker comes off it's more than likely that the lash pad also flies off too. The lash pad sort of helps hold the rocker in alignment. Are you setting the clearance with the cam lobe pointing up? Take care about running less clearance. The valves cool by transmitting heat to the seats when the valve is closed. Reducing the clearance reduces the cooling and can also prevent the valve closing all together which can 'burn' it. 1 Quote Link to comment
datsunwizard Posted March 28, 2014 Report Share Posted March 28, 2014 One thing that hasn't been brought up is that a loose valve seat can cause this problem. When the valve comes off the seat, the valve seat comes with it , gets cocked in the valve seat bore when the valve closes. The now hung valve and seat causes the rocker arm and lash pad to fly off. Usually it happens on the intake valves with the brass seats. 3 Quote Link to comment
datzenmike Posted March 29, 2014 Report Share Posted March 29, 2014 I'm assuming it runs fine otherwise. If the seat or seats pop off it's a one way trip and putting the rocker back on probably won't fix it. Perhaps the method for setting the lash is off??? Because this should work and they shouldn't pop off when you shut the motor off. Have a quick watch of Mike's excellent video... http://community.ratsun.net/topic/16539-l-series-valve-adjustment/ Quote Link to comment
superbee620 Posted February 3, 2015 Report Share Posted February 3, 2015 sorry it has taken me so long to get back on here . I cant get into my old account. so I got a new one. but just wanted to let anyone know that may click on this link that I fixed the problem and DATSUNWIZARD you were correct sir. it was the seats coming loose from the head and causing the valves to get hung up. had head rebuilt and now after waiting months to get my head back. im finally cruising again. thanks for all the good advice. Quote Link to comment
datsunwizard Posted February 3, 2015 Report Share Posted February 3, 2015 No problem. Was it the intake seats that where loose? If it was the brass ones, the correct repair is to replace them with steel. Quote Link to comment
banzai510(hainz) Posted February 3, 2015 Report Share Posted February 3, 2015 after waiting months to get my head back??????? alwasy have a spare ready to go!!!!!!!!!! Quote Link to comment
superbee620 Posted February 4, 2015 Report Share Posted February 4, 2015 it was the intake valves. and yes went back with steel. and yes now I got a spare just need to build it. thanks again. just didn't want to be one of those people that fix their rides after getting good advice on this site but never finish their post. thanks again to everybody that gave their two cents worth. 1 Quote Link to comment
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