WizardBlack Posted April 2, 2009 Share Posted April 2, 2009 I have a question about the timing chain system since I suspect an issue. Basic configuration of my car: '77 L28E with N42 / N47 setup Holset with Megasquirt and EDIS-6 I have been running 15 psi and it holds together OK, but I suspect it's a bit weak. It would probably just keep up with a stock STi. Given that I weighed it and it's 2500 pounds dead on, it has a good weight advantage. I have been concerned that the P.O. didn't get some stuff right with the headstuds and HG, so I decided to pull it apart. With the valve cover off, I can look down to the chain and see that the chain running along the straight guide is loose and doesn't lay along the guide. I can reach down and jiggle it; it is LOOSE. Is this common? Correct? I turned it over and over and it shows that the notches are lining up correctly according to the Haynes manual, but that amount of slack is disconcerting. I assume this would retard the cam quite a bit and play heck with spool and powerband. This is the first and only Datsun I've played with so nothing to judge by. Quote Link to comment Share on other sites More sharing options...
Xnke Posted April 2, 2009 Share Posted April 2, 2009 Replace the timing chain, chain tensioner, and the chain guides, at least. The tensioner is likely worn way out, mine was down to the metal backing and still held the chain in tension. the guides are likely beaten to death by the chain, so I'd replace them too. Might as well, since you have to take the timing cover off. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 2, 2009 Author Share Posted April 2, 2009 Replace the timing chain, chain tensioner, and the chain guides, at least. The tensioner is likely worn way out, mine was down to the metal backing and still held the chain in tension. the guides are likely beaten to death by the chain, so I'd replace them too. Might as well, since you have to take the timing cover off. Yup, I already have all the parts on the way, but just curious if that was normal or not. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 2, 2009 Author Share Posted April 2, 2009 Just as an update. I got into the head a bit to clean it up and noticed a few things. First, I can manually spin some of the valves while they are on the seat. Second, I can press down on a retainer with a flat blade screwdriver and press it down a good 1/4 to 1/2 inch. That is without leaning over top of it, etc. I guess there's where a lot of that power went. I can't hear a dang thing when it's on the road with the whining diff (soon to be fixed also). I ordered ISKY springs and retainers. I'll hold off on the cam until I have an intake manifold on the car. Quote Link to comment Share on other sites More sharing options...
Xnke Posted April 4, 2009 Share Posted April 4, 2009 whoa...might want to check the valves too, the retainer groove may be worn severely, as could the valve seats. of all the heads i've worked with, (probably 40) that only happened on one head, with the softer bronze valve seats, and the seats were eroded back. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 4, 2009 Author Share Posted April 4, 2009 Well I've pulled it apart. How might I tell if the retainer groove is borked? I have the hardened seats, so I hope I am good there. Quote Link to comment Share on other sites More sharing options...
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