valve rattle

1980-1986 Datsun 720 forums. All 720-specific topics and discussion can be found here.
2kredz3
Posts: 150
Joined: Fri Apr 18, 2008 7:56 pm
Car: 1984 Nissan 720
Contact:

valve rattle

Postby 2kredz3 » Wed Feb 18, 2009 5:27 pm

what is the cause of the valve rattle on start up? for the most part i have eliminated it during idle (unless the engine is hot when i restart it then it rattles away until i get above 2k rpms for a while) by adjusting the valves.

so what is worn out? oil pump, lifters. . . hopefully its an easy fix.


User avatar
PEZi
Posts: 21111
Joined: Thu Dec 11, 2008 8:21 am
Car: Mitsubishi Lancer Evolution IX Mitsubishi Racing Edition
Location: Pikes Peak, CO
Contact:

Re: valve rattle (2kredz3)

Postby PEZi » Wed Feb 18, 2009 5:30 pm

its the lack of oil pressure.... mine only does it on extreme cold starts because its trying to rev too high without proper oil flow... the easiest way for me to eliminate mine is if i know its cold enough to happen i hit the throttle causing it to rev lower before it actually happens.... not exactly a good description but i hope that helps

User avatar
IMH
Posts: 352
Joined: Wed Dec 31, 1969 5:00 pm

Re: valve rattle (2kredz3)

Postby IMH » Thu Feb 19, 2009 2:21 am

Are you sure it's valve rattle? It's fairly common on these engines for a worn timing chain tensioner to cause noise at startup.

2kredz3
Posts: 150
Joined: Fri Apr 18, 2008 7:56 pm
Car: 1984 Nissan 720
Contact:

Re: valve rattle (IMH)

Postby 2kredz3 » Fri Feb 20, 2009 2:35 pm

hmm, i have done the blip the throttle to decrease the rev (also adjusted the cold idle to make sure it wasnt @ 2k) mine does it if its hot or cold every time i start it, sometimes i can hear the tapping all the time so i assumed it was valve. i proceeded to adjust the valves and that helped a lot but its still there (really bad if its cold.) this engine has 146k mi on it and the head has maybe 40k mi on it but i can not prove that. . .also i cant prove if they changed the timing change, should i try changing the timing chain just because (they are cheap)

User avatar
IMH
Posts: 352
Joined: Wed Dec 31, 1969 5:00 pm

Re: valve rattle (2kredz3)

Postby IMH » Fri Feb 20, 2009 6:54 pm

All you would really need to change is the timing chain tensioner. But that requires removing the front cover.

2kredz3
Posts: 150
Joined: Fri Apr 18, 2008 7:56 pm
Car: 1984 Nissan 720
Contact:

Re: valve rattle (IMH)

Postby 2kredz3 » Fri Feb 20, 2009 7:18 pm

IMH wrote:All you would really need to change is the timing chain tensioner. But that requires removing the front cover.
anything special i need to know about the front cover? gasket set for the whole motor is cheap so while im at it i would replace as much as i could get my fingers too. would this tensioner also cause a skip at idle?


Return to “Datsun 720”