L20b cam sprocket help

[Knox]

Hey guys, I am new to this forum, I am currently in the process of installing an A87 head to a recently rebuilt L20b block but I'm having a heap of trouble installing the cam sprocket and timing chain onto the cam:

With the timing chain already attached to the crank sprocket, I try to lift and lever the sprocket and timing chain onto the camshaft dowel but I can't get it close enough to slip onto the end of the camshaft. It doesn't feel like its really caught on anything, it just doesn't seem to reach, the closest I can get it is about 8mm, and by that point it really feels like I'm going to break something. I am using the same chain the l20b had with the previous head installed, has anyone else had this problem? the tensioner still seems to be in position, is usually this hard to install the sprocket under tension? -let me know if pics are needed

[datzenmike]

Oh oh...

 

 

Sadly you didn't block the chain tensioner from falling out.  When the cam sprocket is removed the spring loaded tensioner pushes out of it's holder and like toothpaste... once out it is impossible to put back in.

 

 

 

 

Get one of these next time....

 

 

For now you will have to remove the fan belts, rad, crank pulley, oil pump, distributor and the drive spindle between them and the water pump. Now remove the two small bolts between the head and the top of the timing cover and the bolts in the front of the oil pan and half way down each side. Now you should (with great difficulty) be able to unbolt and remove the timing cover to get at the chain and tensioner. No one who has ever done this, ever lets it happen a second time.

[ggzilla]

It can't be done unless the tensioner is blocked before the timing cover is put on (or before the old pulley is removed).

 

Time to pull the cover off ...

[Knox]

Alright, I suppose I'll get to pulling apart the front cover.

[datzenmike]

See bottom picture

[ggzilla]

This is where consulting a repair manual would have saved time and money.

[Knox]

I forgot to mention I'm in the process of an engine swap (l18 to l20b) so I'm doing all this with the engine out and pretty much completely stripped.
Does anyone know how to remove the crank pulley while the engine is out?

-I also followed the manual as well as I could, I even made a chain tensioner stopper out of wood and wedged it in, though due to the fact that when I pulled the sprocket off in the first place, I was reading one of the two crank-pulley timing plates, which just so happened to be the wrong one and I ended up with the crank in the wrong position, which then involved me hand-cranking the engine whilst pulling up on the chain with the sprocket, with the stopper tool removed.

[ggzilla]

Does anyone know how to remove the crank pulley while the engine is out?

What I do is wedge an old bearing shell (half-round) between the flywheel teeth and a single trans bolt. Then use a long pipe over the wrench on the crank pulley and quickly pop it off.

[Ranman72]

impact wrench for the pulley 

[Knox]

Yeah I'll give that bearing shell method a go, and yeah, an impact wrench for the pulley should do the job, I shouldn't have any problems then. Can you use RGV silicon gasket maker to seal the front cover for installing?

[ggzilla]

Can you use RGV silicon gasket maker to seal the front cover for installing? Yes, if you are careful to use only a small amount and let it tack up per directions. After all Nissan uses it on some of their newer engines. But many people put it on thick which causes problems so you may hear from other Ratsuns to not do it at all.

 

Use RTV as a gasket replacement or to seal the corners. I would not use it as sealer for a regular gasket - although if spread very thin and applied carefully RTV will work here too.

[Knox]

Yeah, alright I'll try that then, I'm also a little worried because I had already used RTV seal on the sump, basically because I didn't have a proper gasket. So I'm not sure if I should redo the entire sump seal.

[EricJB]

If you are doing this on a stand, and need to rotate the motor, and your block of wood is in the way, tie a zip tie around the tensioner. Then cut it off when you get everything right.

[ggzilla]

RTV when applied per directions is superior to a regular gasket. But it also far easier to do it wrong. If rtv can be seen dripping from the pan rails then I would do it over.

 

Nissan put "liquid silicone gasket" on the factory KA24 engines and other engines. It seems to be O2 sensor-compatible rtv.

 

[Knox]

Ok, I should probably redo it then, initially I wasn't very confident with it, especially since the oil pan had already been bent out of shape around the bolt holes when the previous thick rubber gasket was installed, and there were drips coming out in a few spots. I wasn't even sure that you could use gasket maker on the oil pan because of the outward ridges on the mating surface.

[ggzilla]

Yep it can be use on ridged pan flanges.

 

For timing cover which normally uses a thin paper gasket, thin RTV should be applied. However to replace the thick sump gasket RTV can be applied thick if allowed to tack up properly just be careful.

 

Whatever you decide, beat the pan back to shape around the distorted/overtightened holes.

[Knox]

Alright, I'll give that a shot. I'll pick it up tomorrow and let you know how I go, hopefully I don't run into any problems. I was thinking about whether or not to just make up a gasket for the front cover out of some oil grade gasket material, hopefully to avoid trying to hinge/beat off the front cover, if I should expect to have to pull it off again.

[difrangia]

Knox,

 

Right off the bat, I want to stress that this will not be for everyone. As I get older I tend to work like electricity. I take the path of least resistance.

 

 I put new valves in my 620 last Summer and though I blocked the chain with a homemade wedge, somehow I let the tensioner spring out. I pulled my hair out studying the forum here and all I could find was ‘Off with the front cover’ except one post. Can’t remember who the poster was, but he related that he had fished the tensioner back in from above with a couple of long screwdrivers.  I thought, what the heck have I got to loose?  

 

  I got the crank on TDC on cylinder #1. Got out couple of long screwdrivers and the headband LED light. Wired the chain up tight toward the driver side and went to work in the tiny space on the passenger side of the chain. I was able to lift the tensioner head with one screwdriver and push it back in to the tensioner cylinder with the other. Held it there as I unwired the chain and kept it pulled up against the tensioner to hold it in. Used the other hand to put the sprocket on and fit it to the cam. Probably be a lot easier with two people.

 

  I took extra precautions to have the cam positioned with intake & exhaust lobes on #1 at 10 & 2 o’clock for TDC position of the crank. You can’t use the timing links on the chain to check if  timing is correct as you can’t see the position of the bottom one on the crank sprocket and need to check proper timing through the cutout in the top sprocket. There are threads showing how to do this. You can search it or I’m sure that someone on Ratsun can go right to the thread and post it.

 

  I rolled her over carefully half a dozen times by hand to insure that the timing came back at TDC on #1 cylinder. Roll slowly and stop if anything even slightly interferes. Very easy to bend a valve. TThen it’s heads off. I’m not saying that this will work every time for everyone, but I’d do it again prior to dismantling the front end.

 

Steve

[difrangia]

I failed to stress in the previous post that if you try to do this and didn't have #1 piston at TDC prior to first removing chain, and the cam to correct position for #1 TDC, you'll need to release all contact between the cam and valves before turning crank or the cam, or next stop is a bent valve.  

 

Here' slink to a thread with the cam position when #1 is TDC.

 

http://community.ratsun.net/topic/56093-help-l20b-timing-cam-dowel-on-bottom/?hl=%2Bcam+%2Btiming

 

In the instance that you do try what I've suggested, I'll stress again; be sure that you've studied the whole situation have your brain around what you're you're doing and proceed slowly. Be sure to take all the plugs out to rotate engine in order to make rotation smoother with no compression to deal with and remember 'almost any contact between valve and piston is quite likely to result in bent valve.

[Knox]

Yes! this is exactly what I tried this morning, after thinking it through I decided to commit to pulling the front cover assembly off completely. I was about midway through getting the cover off when I undid the oil pump bolts and removed the oil pump and distributor drive assembly, at this point I realised I could look up through the hole to see the state of the tensioner to discover datzenmike was completely right, totally identical to the picture; the tensioner shoe/guide had been booted up in between the chain guide and the chain, with the bottom of the spring and plunger visible. So I started trying to push down on the tensioner shoe, whist loosening and slacking the chain, all while making totally sure that the tensioner couldn't come out completely. After about an hour of not quite getting the tensioner in the right position to slide in, even with my Dad helping me, I bit the bullet and decided to take the cover off completely. With taking the front cover off, I decided to take the sump off aswell, to redo my sketchy gasket job with the silicon gasket.

Now that I finally popped the tensioner back in, I tensioned the chain and wedged in my dodgy chain stopper tool and started to sort out the timing. With the head install, I thought I'd keep the rather ambitious reground camshaft (280degree with asymmetrical lobes and the highest possible regrind lift (not sure) my Dad put in the l18 when he owned Datsun back in the 80's) to keep the journals happy along with all the broken-in parts of that particular head. I thought I'd use the l20b factory set no.#2 dowl positioning hole on the sprocket, to keep on the safe side, especially with the high lift cam. The only thing is I am not particularly sure where TDC is without the front cover and pulley assembly installed, is there some kind of hidden mark and method of accurately finding TDC with the front cover off?

[banzai510(hainz)]

If using the chain wedge. What I do is rotate the cam in the direction it will give you slack in the chain.

Hopefully you marked the link where the chain goes to the dimple on the cam sproket.(this is done forest before tear down)

[Knox]

Alright, I fixed the tensioner problem and sorted out the timing, now I've assembled the engine; RGV sealed the sump and bolted it in, cut out some gasket material for the front cover and put that on, bolted on the rocker cover to a fresh cork gasket, ready to put back in the engine bay. 

The process of putting the engine back in wasn't as easy as I hoped, for someone who had never done anything like this before, apart from taking the engine out in the first place, this was very difficult. The first problem was when the engine-gearbox mating plate wouldn't clear the steering linkage, after a good hour of lifting and angling the engine we cleared the steering linkage and slid the clutch over the input shaft only to find out a good 5 hours later after ramming and shifting the engine, that the clutch thrust bearing assembly had come off its part of the input shaft and was getting pushed against that section of the shaft. After we fixed that the engine slid straight in, and wobbled the positioning dowl into its hole. Bolted in the engine-transmission bolts and knocked it onto the engine mounts, started working on the plumbing and bolted on both manifolds and called it a night.

With the engine hopefully running soon, I'll be able to install my boot seal and custom ordered door belts, sikaflex the windshield, put on some cheap new tyres and she should be able to get registered for the first time in 16 years, this week sometime hopefully