I just got done replacing the timing chain after 125,000 miles. The guides were broken, the tensioner was very worn out, and the timing chain had jumped one tooth. I replaced everything with a kit from engnbldr that includes the driver's side steel guide. I also replaced all the plugs, wires, cap and rotor while I was at it and adjsuted valve clearance. I'm not sure what the timing was set at before all this happened, but ever since I got it back together, I have some pre-ignition going on when the engine is under a load-- especially going up a hill. I set the timing by the book-- 5 deg BTDC at 750 rpm with test connector shorted. I am currently running 87 octane fuel just like I always have in this truck. I've pulled the EFI fuse several times also, to see if that would reset anything. EGR valve is functioning, too. I'm kind of stumped now. I will probably try a higher octane fuel soon, but I don't want that to be the permanent fix, because it's just covering up the real problem, IMO. I'm just wondering if there is something wrong with the advance perhaps?

Your engine was designed to run 89 octane.

I ran 87 for 2 years, with the timing set at about 2.5* BTDC.

There are your 2 fixes.

</font><blockquote><font size="1" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">quote:</font><hr /><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Originally posted by Snoopy:
<strong>Your engine was designed to run 89 octane.

I ran 87 for 2 years, with the timing set at about 2.5* BTDC.

There are your 2 fixes.</strong></font><hr /></blockquote><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Oops... wife was logged in. This came from me.

</font><blockquote><font size="1" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">quote:</font><hr /><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Originally posted by DRTDEVL:
<strong> </font><blockquote><font size="1" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">quote:</font><hr /><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">
<strong>Your engine was designed to run 89 octane.

I ran 87 for 2 years, with the timing set at about 2.5* BTDC.

There are your 2 fixes.</strong></font><hr /></blockquote><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Oops... wife was logged in. This came from me.</strong></font><hr /></blockquote><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Not denying that this could be true-- but where is this found? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> This is the first time I have heard of this. Thanks for the advice. <img border="0" title="" alt="[Smile]" src="images/icons/smile.gif" />

I think I'm having a bit of the same problem, except my engine is a completely rebuilt 20r using engnbldr parts and the new RV cam. It started out as what I thought was purely valvetrain noise, but I've slowly got myself convinced that the valvetrain noise is not excessive. I've got an exhaust leak to fix tonight, I'm hoping it is part of what I'm hearing, but I don't think so. My timing is adjusted to ~2.5*btdc down from 5*bdtc, retarding it helped a little. I'll be interested in what you find out.

I'm going to try 2.5* BTDC first, since I still have over half a tank of 87 octane in there. Then I can set it back to 5*, and fill up with 89 octane.

I dont think my 4runner will even run at 2.5* btdc it is set at 8*

</font><blockquote><font size="1" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">quote:</font><hr /><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Originally posted by firemedic:
<strong>I dont think my 4runner will even run at 2.5* btdc it is set at 8*</strong></font><hr /></blockquote><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Yeah, but how much LCE equipment is in there?

</font><blockquote><font size="1" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">quote:</font><hr /><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Originally posted by DerekM:
<strong>I think I'm having a bit of the same problem, except my engine is a completely rebuilt 20r using engnbldr parts and the new RV cam. It started out as what I thought was purely valvetrain noise, but I've slowly got myself convinced that the valvetrain noise is not excessive. I've got an exhaust leak to fix tonight, I'm hoping it is part of what I'm hearing, but I don't think so. My timing is adjusted to ~2.5*btdc down from 5*bdtc, retarding it helped a little. I'll be interested in what you find

out.</strong></font><hr /></blockquote><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">>>>*Like I mentioned today, my sevice manual shows the timing spec for your 20R engine to be zero degrees at idle.
*But note one common situation that happens with engine builders, especially new ones...
Often they will hear "noises", when the noise one hears is normal. If you are sure the noise is pinging, try the steps I outlined for you earlier..
Set the timing, follow the steps I suggested, and have faith in your own talents and ability.
I have faith in you, you asked all the right questions.
So I am betting your basic engine is not only fine, but exceptional, since I happen to know you checked everything!
Let me know if you have any more questions or concerns....*EB

Thanks for the vote of confidence, Ted. I have been driving it for the last couple of days with no problems, but "the noise" is still there although better since I've retarded the timing to spec <img border="0" alt="[Drunk]" title="" src="graemlins/drunk.gif" /> . I think this project has turned me paranoid, because I've been driving with my head out the window so I can listen <img border="0" title="" alt="[Big Grin]" src="images/icons/grin.gif" /> . Another thing I noticed last night....The vacum diagrams in my manual show different routing for the vacum advance. For the '80 it shows the vac-adv going to the the manifold below the carb, and for the '81 & up it goes to the carb (above butterfly's I think). I had found a thread where Tim@DOA had said that it should always be routed to the carb, not manifold so that is how I hooked it up. Maybe my distributor is different? Is it possible that it should go to the manifold???? OK, I have to go now- I think they're after me..... <img border="0" alt="[Alien]" title="" src="graemlins/alien.gif" />

----Sorry for the hijack Brown----