mystery cam? or did I break it?

[TheBirdistheWord]

So, I bought an L20b with a w58 smog head from a local datsun guy a while back, I took off the oil pan and valve cover It had obviously been re-gasketed as well cleaned inside and out and painted. The seller informed me that he didnt perform this rebuild, and suggested to open it up and check everything to make sure all was well. I decided that someone wouldnt go through the trouble of taking it completely apart just to do nothing and re gasket it on such an inexpensive motor so I decided to just put the motor in because the original L16 was on its last leg.

 

After getting the motor in and set up to run, I adjusted the valves after the first start because of the crazy marble sound indicative of bad valve clearance. Adjusted them to .008 and .010 for intake and exhaust respectively (cold) and while it helped alot with the chatter it didnt come close enough to alleviating it all the way. Yesterday, I tried to adjust them after the motor warmed up and it made running conditions and the sound worse, so I will have to go back and adjust them to cold specs because that has yielded the best results so far.

 

Im pondering two different scenarios at this point, scenario 1: this is an aftermarket cam and I have know idea of how to determine that much less get the proper valve clearance specs for it, scenario 2: the lash pads are worn beyond usable specs and those should be tended to, to rule it out before I move on. My question is, can I use the lash pads from the L16 that I pulled? It wasnt chattering at all when removed it, the head was failing so I figure thats the closest thing to stock that is accessible to me on short notice. If that doesnt do the trick should I install the L16 cam to eliminate the potential variable of this cam not being stock? When I drove it for a short period the motor had no power whatsoever but it WOULD idle relatively smooth. ANY input is greatly appreciated as I am driving my motorcycle until this gets worked out and its no fun in 40 degree weather. any ideas? things I may have overlooked? Should I install the known good lash pads for good measure either way? could I have hurt anything in the valve train by driving it for about 5 miles? I apologize if this is a bit scattered.

 

::edit:: I used 5w-30w on the initial start up and that is what is still in the motor, I know thats not recommended and I didnt learn that until after I had poured it in, but could it create/exacerbate this issue?

[erichwaslike]

sounds like timing chain death rattle

[Sealik]

Measure the cam...and see what pads are in there

Could be an aftermarket cam (higher lift) with stock lash pads..????...which could also give you that 'sound'

[Sealik]

Subtract the smaller/narrow part of the cam lobe from the larger(widest) part of the lobe, then multiply by 1.48

 

Mine as reference....

1.536-1.209 = .327 x 1.48 = .48396 lift

 

Aftermarket lash pad on right

 

[DanielC]

This is what a loose timing chain looks like.

And this is a tighter timing chain.

Pretty much the same parts, just the curved guide is moved in to the chain. Look close, and you can see the curved guide has slotted holes in it.

 

The above pictures are of a L-16, but the L-20 is similar. Notice how the chain tensioner at the bottom is more retracted in the second photo. This tensioner has a spring in it, and is also supplied with oil pressure. A used engine, with too thin of an oilo can cause the oil pressure to drop, making a timing chain rattle more.

 

You will need to drop the oil pan to get the timing chain cover back on, and it will be easier remove the timing cover with the oil pan dropped. With some luck, you may get the oil pan to drop without destroying the gasket. You can also get the pan gasket only, from Nissan.

[Sealik]

Yeah.. check chain stretch.

 

 

Notch on back of cam sprocket will be to the left (CCW) of this setting...relative to the mark on cam thrust plate

 

Engine was carefully rotated to 0 degrees TDC...without going past

If you do go past 0 degrees, rotate engine back a couple of 'inches' and try again

[TheBirdistheWord]

Ok, first off, thank you for all the prompt and detailed responses! So before I take the timing cover off, can i use the lash pads from the L16 in the L20b? What weight oil should I use? I figure ill start with these things to potentially save some labor time. and I ill attempt to figure out the cam timing. That process is still a bit unclear to me.

[datsunaholic]

You can use the L16 lash pads as long as they're the same size or the correct size. They're probably ALL stock (and hence the same) but without a micrometer measurement of every one you won't know.

 

Don't run 5W-anything. Minimum 10W-30. I use 10W40, 15W-40, 20W-50, Straight-30... depends on the weather.

[TheBirdistheWord]

Does anyone know the stock lash pad size? Most of the info I've found through searching has yielded modified cam pad sizes

 

 

Edit: as well as stock cam lift? I know that's available here but I'm on my phone so its not so easy to find it.

[Sealik]

Does anyone know the stock lash pad size? Most of the info I've found through searching has yielded modified cam pad sizes

 

 

Edit: as well as stock cam lift? I know that's available here but I'm on my phone so its not so easy to find it.

 

The stock pad (mine/used) is around .165...but...it's dished....sooo...actual 'thickness' is around .120

I believe the stock cam is around .415???

 

EDIT

 

Just measured the stock lash pad

The total thickness of pad is .165

The dish/recess on the bottom of the pad is .069

Sooooo...that means the pad is only .096 ... a little less than the .120 I mentioned earlier

Edited March 8, 2012 by Sealik

[TheBirdistheWord]

Thanks Sealik! I am probably going to install the lash pads tonight if the tick doesnt subside more

 

I added 10w-40 and it damn near eliminated the tap, but there is what sounds like one valve in the rear of the motor that is getting intermittently stuck open/closed at different RPM. Will I be risking breaking something if I try to take out the car to cycle the heavier oil into that valve? Better question is, does that sound like it will help the issue?

[Sealik]

Just confirm that you don't have a aftermarket cam...swapping stock pads won't improve anything, unless they are totally NFG

Could be some crud in the seat of that valve...?...many possibilities

 

 

Another way to determine weather you have the 'correct' pads would be to do a wipe pattern.

Wouldn't have to take anything apart...lobe up/set valve lash...with a clean rag...wipe off a rocker.

Stick a felt pen under cam and mark each end of the rocker....at least 3/16" if possible

Rotate engine and see what pattern you come up with.

 

See here on right rocker.....after rotating cam...pattern is missing on pivot side

 

[69srl311]

Another trick is to shim the tensioner so it can't retract and you won't get the "death rattle" when started and the cam won't jump forward or advance until the oil pressure is built up. Usually not a concern but if you have a radical cam or like in my case with a U20 engine that has two chains, you could nick valves with the pistons. If the lash pads were the wrong thickness it is possible the wipe pattern on the cam followers could be so far off the cam is coming off the follower insert.

[TheBirdistheWord]

Engine did sit for an extended amount of time, not sure how long. Is there anything that I could use to alleviate a stuck valve? Seafome is supposed to help with that, that might be a good thing to try.

 

So with the wipe pattern am I looking for the pen marks to be completely gone to indicate there is contact throughout the entire rocker surface? If that is the case, how do i determine how much thicker of a pad to use? Would I measure the cam at that point and calculate lift?

[Sealik]

Engine did sit for an extended amount of time, not sure how long. Is there anything that I could use to alleviate a stuck valve? Seafome is supposed to help with that, that might be a good thing to try.

 

So with the wipe pattern am I looking for the pen marks to be completely gone to indicate there is contact throughout the entire rocker surface? If that is the case, how do i determine how much thicker of a pad to use? Would I measure the cam at that point and calculate lift?

 

You can try some seafoam after you figure out your cam/pads

For the wipe pattern.....You want a little bit of felt pen left on each side...of the rocker surface

If nothing is left on one side..... or it is not symmetrical (both sides have the same amount remaining)....that means the pattern is not centered

 

Try it...and let's see a pic

 

Usually people mark the whole rocker...but...there is no need...most of it's coming off anyways

[Sealik]

Here...just did mine

 

 

 

See the pattern that remains on the rocker?

'Exactly' the same on the other side.

[docbainey]

Before you screw with anything, I would say a compression test is in order. You'r dealing with an unknown as far as if this motor is any good or not. After all, you said the motor had no power whatsoever. Don't be chasing your tail on a bad engine.

[Sealik]

Before you screw with anything, I would say a compression test is in order. You'r dealing with an unknown as far as if this motor is any good or not. After all, you said the motor had no power whatsoever. Don't be chasing your tail on a bad engine.

 

 

Correct...and or a leak down

But...it takes less than 10 mins to measure the cam, see what lash pads are in there (stock or aftermarket), and if need be... a wipe pattern on 1 rocker

[docbainey]

Correct...and or a leak down

But...it takes less than 10 mins to measure the cam, see what lash pads are in there (stock or aftermarket), and if need be... a wipe pattern on 1 rocker

 

I know, but how many people have micrometers or digital calipers, or can use them correctly for that matter, or understand the whole point of it?

[TheBirdistheWord]

I could more or less wrap my head around measuring the cam. But as stated, don't have the proper tools to do so. I will do a leak down if need be. my reasoning for not doing it before the motor went in is that i couldn't see why someone would pull apart, clean, and re gasket a motor that's only worth $100-200. I definitely can believe that person may have done something wrong with the re assembly of the motor. And I'm almost certain that is what I am dealing with now. Going to test the wipe pattern right now than take her for a spin to see if that valve loosens up and to see if the oil pressure was improved by the heavier oil. because that could have been my power problem.

[TheBirdistheWord]

Wipe pattern was good, did it one two different lobes to make sure both times I was left with marks that were very close in size, almost identical to the naked eye. HOWEVER, I found one of the retainer springs on the rear most valve was off completely. So going to throw everything back together and see if that was my "one" valve tick I was hearing when I last ran it. ::crosses fingers::

[flatcat19]

Why clean stuff?

To make it look good.

 

Easier to sell a "good" motor if it looks good.

 

Would you have bought the motor, for the same price, if owner said something is wrong with it?

 

Go look at used cars.

Open the hoods. See any dirty motors?

Why do you think that is?

[datzenmike]

::edit:: I used 5w-30w on the initial start up and that is what is still in the motor, I know thats not recommended and I didnt learn that until after I had poured it in, but could it create/exacerbate this issue?

 

Get 10W30 anything to get the oil pressure up at idle speed. This will increase the tensioner pressure.

[TheBirdistheWord]

Why clean stuff?

To make it look good.

 

Easier to sell a "good" motor if it looks good.

 

Would you have bought the motor, for the same price, if owner said something is wrong with it?

 

Go look at used cars.

Open the hoods. See any dirty motors?

Why do you think that is?

I definitely agree with that, but this motor hadn't just been cleaned on the outside, it had been panted and re gasketed all the way around. I'm not holding to my previous assumption, it just seems like a lot of work to go through for an extra 50 to 100 bucks. Everything is pointing to my assumption being wrong at this point. I understand I took a risk, and evidently lost, was just trying to rationalize it.

 

Get 10W30 anything to get the oil pressure up at idle speed. This will increase the tensioner pressure.

 

10w-40 in it now. Helped quite it down a lot. Just sounds like there is one last valve sticking, couldn't even get the thing to idle today much less drive it. I need to get a light to time it properly, have done it by ear up to this point.

 

Verified that the valve lash and clearance are both to spec, I suppose a leak down/ compression test is the next order of business. If that checks out than it looks like ill be taking the pan and timing cover off. I will.get some pictures of the cam gear ASAP to reference it here because I'm still not sure what needs to be lining up.

 

::edit:: when im looking at the timing chain, I know how to identify if it is to loose but how do i correct it?

[banzai510(hainz)]

I'm still not sure what needs to be lining up.???????????

 

 

 

 

watch this naked 1000 times