REVENGE of the L20b

[BRuZED]

1st it was the camshaft sproket being a pain now this....

 

I got everything re-assembled, looking good and now for some odd reason it just won't start up!?

 

I mean, it tries like the dickens...it wants to! But it just tries and doesn't catch...

 

This L20b was running fine up to my overheat/blown headgasket...i haven't messed w/ a thing. I have taken it in to the machine shop got it purdddy again and rebuilt it(properly) from there.

 

Now.

I had a buddy look at it and the only 2 things that he can come up w/ is "spark issues(we tested all plugs/wires -n/p) or compression...?"

 

So far:

No discolored smoke is firing out the tail.

But!

After testing the coil the spark is BRIGHT but YELLOW...is that enough to lite up the fuel?(i mean BLUE = good YELLOW = Bad = right?)

That i figure would be a good place to start...

 

I haven't compression tested it yet(as I need to find my tester in storage) but outside of the Head and cyllanders where else could there be a compression issue? -while testing the plugs the 'out' plughole seemed to be pushing air....???!

 

ANY help what-so-ever would be GREATLY appreciated as I need desperately to get my only car running...my beloved "BELLA" 1977 710

 

-thanks!

[RacnJsn95]

I can't really understand... Did you rebuild it or now? If you did, I assume you took the timing cover off, right? Think you might have installed the distributor shaft 180

[BRuZED]

nope.

 

After the overheat, i removed the head, had it machined and then re-installed.

 

No other major work on it outside the changing gaskets and new thermostat.

[datzenmike]

Did you set the motor at TDC compression when you took the head off?

Did you put the sprocket back on the #2 position?

Did you have the distributor out?

[BRuZED]

how do you set the motor at TDC compression?

and #2 sprocket position?

 

erm?

[SHADY280]

the fact you asked that scares me. you need to have the valve timing in the right spot for the engine to run. i think thats your problem.

[datsunfreak]

the fact you asked that scares me...

 

Me too. :eek:

 

FYI, if your timing is off by enough, you may have bent some valves too.

[BRuZED]

Valve timing?

Like valve clearances?

-I set those...

 

but seriously.

I'm very novice, w/ a good understanding of mechanics...

I just need a push in the right direction...

 

So valve timing...?

[BRuZED]

ok...

TDC

no, i didn't.

*i wish i knew to.*

 

As far as sprocket on #2(i need to confirm -but i'm pretty sure.)

[datzenmike]

TDC top dead center. Piston is at the top of it's travel...what else? It does this twice on every 4 stroke engine so we need to get it on the compression stroke and NOT the exhaust.

 

Remove the valve cover so you can see the cam lobes. Disconnect the coil wire to the distributor so there is no chance the engine will start while you are turning the engine over by hand!! Use a 24mm wrench on the crankshaft nut and turn the engine clockwise. You could take the plugs out to make it easier to turn over.

 

If you look down the passenger side of the timing cover you will see a small metal tag close to the crankshaft pulley with timing marks on it. It will read from left to right and may say 20 15 10 5 0 (which is TDC) As you continue to slowly turn the crankshaft clockwise, (it might be easier to watch from underneath) a small notch on the outer edge of the rear pulley will come into view. It's hard to find so mark it with a crayon or piece of chalk. Keep turning until it passes all the numbers and stop at 0. The motor is now at TDC.

 

Now look at the cam lobes on the #1 cylinder. If both are pointing up, and evenly spaced to the left and right of the cam centerline, with the intake in the 10 o'clock position and the exhaust in the 2 o'clock position, you are at TDCCompression. If not, you may be on the exhaust, so rotate the crankshaft one turn and line up the pulley mark with the 0 on the timing plate again. Check the position of the valve lobes. Are they in the 10 and 2 position now? If yes then you are NOW at TDCCompression. If it is even slightly off, OR not even close, then the chain will have to be locked in position, the cam sprocket removed and the cam turned into the correct position and the sprocket put back on. This will place the cam in the proper position relative to the crankshaft at TDC.

[Bleach]

I bought my old truck from a guy who did just what you did... destroyed the engine. :(

 

maybe you'll be lucky and the valves missed the pistons

[RacnJsn95]

Well... if it turned over, and didn't suddenly stop, or make any scary bending noises, your engine may be ok still... But before you go any farther... I suggest you watch this video by Hainz...

 

http://www.guba.com/watch/3000024223?duration_step=0&fields=23&filter_tiny=0&pp=40&query=datsun&sb=10&set=5&sf=0&size_step=0&o=1&sample=1189832394:9f57b72b069cbeb8c29a09fbcd9b930e5b107393

 

It's worth watching if you're a n00b. Do it... It may save your life...

[tnip]

def watch the video. it is a huge help.

 

it sounds to me like these are not the issues tho, well... def issues, but not the reason it's not actually firing. right? even with bad timing, even 180 out, shouldn't it attempt to run, albeit very rough and backfiring and sputtering and not for long? and the fact that he's able to turn it over pretty freely would suggest, to me anyway, that he hasn't had any problems with bent valves. i'm not saying he shouldn't check everything again, since he fully admits to being sorta pwned by his motor.

 

and i'm not much above him as far as noob status, but i'm a quick learner and have done my lil share of wrenching, but still VERY open to information and criticisms. so please correct me if i'm wrong.

[BRuZED]

Well... if it turned over, and didn't suddenly stop, or make any scary bending noises, your engine may be ok still... But before you go any farther... I suggest you watch this video by Hainz...

 

http://www.guba.com/watch/3000024223?duration_step=0&fields=23&filter_tiny=0&pp=40&query=datsun&sb=10&set=5&sf=0&size_step=0&o=1&sample=1189832394:9f57b72b069cbeb8c29a09fbcd9b930e5b107393

 

It's worth watching if you're a n00b. Do it... It may save your life...

 

do you have a direct link to this for d/l?

I'm on PDX Metro Wi-fi and it's painful to watch...

I KNOW I must watch it.

 

Thanks Everyone for comming to my aid.

As soon as I get some light I'm off to attack her.

[spiffinspudater]

I can make a link for you later. I am the one that posted it up. What I would suggest if you dont want to wait a couple of days for me to find the video and put it on an upload site, then download it in the mp4 format (for ipod/psp) and download VLC media player and watch it that way.

 

If I dont post a link for it message me and remind me. I have a very short term memory.

[RacnJsn95]

do you have a direct link to this for d/l?

I'm on PDX Metro Wi-fi and it's painful to watch...

I KNOW I must watch it.

 

Thanks Everyone for comming to my aid.

As soon as I get some light I'm off to attack her.

 

If you look right above where it plays the video, it says "Select your download format, choose the ipod format, and its an .mp4 file, which most video players support. It's a big file so it might take a while.

[BRuZED]

Ok.

 

Got it at TDC, marked it.

The cam is NOW in proper position relative to the crankshaft at TDC.

 

However.

The sproket was on post hole #1 NOT #2.

-So I corrected that and expected it to start...

*NO DICE*

 

Even further it made a bunch of slack in the timing chain after inspection.

 

Sooooo...

I'm back at square one in needing to remove the timing cover and attacking the tensioner.

 

?I think?

 

...any help is greatly appreciated.

[tnip]

... are you not wanting to take the cover off or something?

[BRuZED]

Well...

Being that the engine is in the car and parked in the street....not really.

But it's reality.

 

I'm figurin' that's what is gonna have to happen.

[datsunaholic]

TDC #1 or TDC #4? The crank pulley is the same for both... You could have the distributor off 180 degrees now (well, the cam off 180 but it's the same diff).

[BRuZED]

TDC #1 or TDC #4? The crank pulley is the same for both... You could have the distributor off 180 degrees now (well, the cam off 180 but it's the same diff).

 

#1

but there is a HUGE difference in slack now(more)

 

I haven't messed w/ the Dist. at all.

[banzai510(hainz)]

if it was in #1 or 2 or 3 it will still start if evrything is timed.

The valve lash set

and distributor timmed also

 

if you can get that vid started it will help or a book but shounded like you had it already just maybe the dist was off if you pulled the front cover off and reinstalled the oil pump wrong.

 

The dowel is alwasy in the 12o clock postion (head)

#1 piston up.The one closest to you by the radiator

[BRuZED]

if it was in #1 or 2 or 3 it will still start if evrything is timed.

The valve lash set

and distributor timmed also

 

if you can get that vid started it will help or a book but shounded like you had it already just maybe the dist was off if you pulled the front cover off and reinstalled the oil pump wrong.

 

The dowel is alwasy in the 12o clock postion (head)

#1 piston up.The one closest to you by the radiator

 

I haven't messed w/ the oil pump nor the distributor.

Could the distributor be out-of-whack even tho' it was running fine before pulling the head?

 

The video just finished!

I will watch it tonight...

 

What could be making the timing chain so gimp?

[datsunaholic]

#1

 

I haven't messed w/ the Dist. at all.

 

 

Doesn't matter. The crank turns 2 revolutions for every 1 of the camshaft. The distributor also turns at 1/2 crank speed. But the cam and distributor are not timed together- the dist is times at the crank worm gear, and the cam via the chain.

 

So... if you turn the crank to TDC, after having the head off, you need to know where the distributor is timed. It will either be pointing to #1 or #4 when the crank is at the timing mark. If you set the cam at TDC with the dist pointing at #4, it'll be 180 degrees off.

 

BTW, if you had the head milled the timing chain will be a bit more slack than before- by twice the amount shaved off.