aarang Posted December 30, 2005 Share Posted December 30, 2005 Just wondering guys, I was putting a new engine together and am having a problem pop up that I haven't seen before. I have put numerous timing chains on L6's, so it is not a new procedure for me. I have the straight and curved guide installed and put the tensioner on. With a smooth transition on the slack side guide and the slack in the chain removed, the plunger on the tensioner has about 1/4" of piston exposed! I Know of the minimum of plunger exposure, but can't seem to find the maximum allowable. The head and block maybe have a couple thou's removed between the two and I am using the HKS 1mm HG. Seeing how my deck height isn't radically changed and the timing marks ( set it on #2 hole) line up where they should, what do you think the problem is? Am I missing something?? Also this is an aftermarket timing set I got through Vic Brit. Should I fork out the cash for genuine Nissan? If someone could point me in the right direction, it would be much appreciated! Thanks in advance Aaron Quote Link to comment Share on other sites More sharing options...
dapiper Posted December 31, 2005 Share Posted December 31, 2005 The important thing is to assure that cyl #1 at TDC, that the cam sprocket notch is aligned with the oblong groove on the cam thrust plate. Alternatively, the two bright links on the chain should be aligned with the dimpled marks on the sprockets which should also correspond to the above condition. Quote Link to comment Share on other sites More sharing options...
RedNeckZ Posted December 31, 2005 Share Posted December 31, 2005 You may have to add some cam tower shims to take the length out of the chain. Don't know how much shaving of the head you did. But it can cause the problem with to much chain. Most part stores have them. Good Luck, Rich. Quote Link to comment Share on other sites More sharing options...
zcarnut Posted December 31, 2005 Share Posted December 31, 2005 I have always found it necessary to elongate the mounting holes of the tensioner and the curved side guide as outlined in the “How to Modify your Nissan/Datsun OHC Engine†book. According to the FSM (and other texts) it is very important not to have any of the tensioner piston exposed. If modifying the mounting holes does not accomplish this then you can shim the piston shaft. I have found that spark plug washers are the correct size for this. I also recommend re-drilling and tapping the curved guide mounting bolt holes to 8mm. I have seen the stock 6mm bolts shear off on some engines. Quote Link to comment Share on other sites More sharing options...
aarang Posted December 31, 2005 Author Share Posted December 31, 2005 I did elongate the holes in the slack side guide to try get the best overall curve, etc. every combination I try doesn't seem to do any good. I don't think I want to get into shimming the cam towers as the head and block haven't been radically altered. The engine was a low mile F54/P90 that wasn't molested, I just had the head and block resurfaced which was only a couple thou's off of each. I don't think the 1mm HG would alter it that much as I have used them before with no probs. I think for safeties sake I will just get a genuine Nissan timing set. Does Courtesy Nisssan have the best price on these, or does anyone know where I can get a good deal? Thanks Aaron Quote Link to comment Share on other sites More sharing options...
jeffp Posted January 1, 2006 Share Posted January 1, 2006 You may have something there with the chain being to long. BUT, the FIRST thing you need to do is establish if you can acheive the correct cam timing with the current setup. I realize Nissan tried to make it easy, and to be honest, I NEVER paid any attention to the lighter links on the chain as it really means nothing to me. The important thing you need to check is the cam position to the piston. Meaning, if the cam is specified to open @ 10 degrees BTDC, then make sure, no mater the length of the chain, make sure with the degree wheel the cam starts opening @ 10 degrees. Then you can atend to the slack in the chain issue. Make sure that when the chain is taught, by turning it with the crank, that the right side chain guide is not making any contact with the chain, or at least, VERY little. The chain guide introducing an angle in the chain by rubbing it, WILL change the cam timing, and after it runs some the chain will rub itself to where it wants to be, but you will again have to adjust the cam timing. So if you can getthe cam timing correct with the timing holes then you can then make adjustments to the left side chain guide by like you said elongating the mounting holes. The tensioner, you can also do the same thing to to move the piston back into the holder. I would first start with a Nissan part, just to be sure, but the degree wheel and cam timing will verify wether the chain will work. Quote Link to comment Share on other sites More sharing options...
Here comes trouble Posted January 1, 2006 Share Posted January 1, 2006 If you have the old chain...slap it in there to check for slop as opposed to the after market chain.for comparison..I see nothing wrong with with the shaft of the tensioner showing a 1/4 inch..... in the #2 spot means a little slop at TDC... I used #3 spot at 150,000 on an L20 B with no problem for anorher 100,000 miles.OEM does not wear out that quick..... Like DAW sez if it don't feel right... go with the OEM. your time and your labor and your cost when something goes wrong Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 1, 2006 Share Posted January 1, 2006 Pretty Simple to figure out how much was machined: Take a caliper amd measure from deck to top of the head, measurement is somewhere around 4.250" or there abouts. When checking in the junkyard that is what I chek for, and it hasn't steered me wrong. I usually check the spec before going junkyarding for the day---it's in the Blue Nissan "How to Modify" booklet. That will tell you exactly how much has been removed from the head. As for how mch out of the tensioner---till it pops out. The NISMO catalog formerly had a chain tensioner LIMITER that would stop the thing form popping out, but short of measuring that distance on someone's engine that has one the only thing I can say is so it's stable, doesn't cock, and doesnt' pop out. An L20B set would be WAY too long. 10mm too long! Your tensioner would be popped out if you used one of those. They move out with 30 to 100 thousandths milled off the head, with almost TWICE that, the thing literally slaps all over the place, and I don't think that's what you have. Quote Link to comment Share on other sites More sharing options...
katman Posted January 1, 2006 Share Posted January 1, 2006 Pretty Simple to figure out how much was machined: Take a caliper amd measure from deck to top of the head' date=' measurement is somewhere around 4.125" or there abouts. When checking in the junkyard that is what I chek for, and it hasn't steered me wrong.[/quote'] Stock thickness on factory L6 heads is 4.248 inch give or take a few thou. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 1, 2006 Share Posted January 1, 2006 Stock thickness on factory L6 heads is 4.248 inch give or take a few thou. I edited. I was thinking 4 1/4", ended up decimalizing 4 1/8". Damn, why can't we all go to the metric system?!?!?!?!?! 108mm? Quote Link to comment Share on other sites More sharing options...
aarang Posted January 2, 2006 Author Share Posted January 2, 2006 I'll try to measure the head today and see what I get. When I put the cam sprocket on #2, the timing mark on the cam was exactly where it should be, off to the side of the notch, so I didn't think about it too much until the tensioner problem. How much tension can I put on the chain on the slack side? I always thought you just wanted it to "guide" the chain, not actually put tension on it. Quote Link to comment Share on other sites More sharing options...
katman Posted January 2, 2006 Share Posted January 2, 2006 Damn, why can't we all go to the metric system?!?!?!?!?! 108mm? Yeah, really. It's not in any FSM near as I can remember but a factory repair document says 107.9mm unmolested, which is what we used as a thickness substantiation for ITS racing. Most original heads will measure closer to 4.250, and some as thick as 4.253, so you had it right. Rarely get one less than the 4.248 dimension. Quote Link to comment Share on other sites More sharing options...
aarang Posted January 3, 2006 Author Share Posted January 3, 2006 Measured the head thickness using dial calipers in various places I got 4.245". I don't know if this amount would radically alter my timing chain slack, I tend to doubt it. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 3, 2006 Share Posted January 3, 2006 Thanks Katman, that was what I thought. I looked in the "Blue Book of How To Modify" and in there it says 4.218, but everyplace other I have cehcked says 4.250" So that measurement of .003 "off spec" is nowhere near you need to be to casue a problem with chain length. Quote Link to comment Share on other sites More sharing options...
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