The 521... OK, after eliminating all the other culprits... valves???

[hessianben]

The 521's L16...

 

 

Well, after replacing the stock carb with a weber,

replacing the intake/exhaust gasket to eliminate possibility of coolant into intake,

replacing fuel pump, filter, lines,

replacing a faulty vacuum advance unit and vacuum lines,

and tuning the carb to spec...

... it still will only idle-

upon acceleration, it skips, bogs, and pops white smoke out of the carburetor.

Under load, it will chug and bog until it slowly reaches higher rpm, where it will run ok until deceleration. If, while accelerating, I give it any gas, it will almost die.

 

I ran compression on all four cyl's:

 

1. 170

2. 85

3. 77

4. 150

 

Not good.

This means I have some shot valves, right?

Or, does it mean rings?

 

Another thought: do the L series motors have adjustable valves? (and how do I check?)

 

The ultimate question:

If it needs a head rebuild, is it more economical to pay someone to do it,

or for me to buy the parts and attempt it myself? (taking into account the fact that

I am only mildly technically inclined, and will most likely break and replace a few things in the process, and say lots of swears...)

 

If having a shop take care of it is the answer... does anyone know somewhere in SoCal that is knowledgeable in older motors?

 

Thanks guys.

Sincerely,

pooped...

[Cuts metal like mad]

you need a book... Since the comp numbers are so wildly diferent I'd guess valve adjustment. It's easy, 17mm and 14mm, .008 feeler gauge. Start here...

[Pacific coast Datsun]

Im no pro but here are my thoughts...

Adjust the valves on #2 & 3 & then redo the compression test. The numbers should go up.

You "may" have a partially damaged head gasket causing compression to be low on those 2 cylinders.

Its not that hard to replace the head gasket yourself. Main thing is to make sure when reinstalling the head the head bolts are torqued to specs.

Adjusting the valves is'nt hard. I did mine in 15 minutes. Use 2 wrenches...a 17 & 14 mm if i remember right. & youll need a feeler gauge to measure the gap. Basically you loosen one nut,then move the other to get the right gap.

[420n620]

cold intake valves .008

cold exhaust valves .010

hot intake valves .010

hot exhaust valves .012

[hessianben]

Ok, I'll check the valve adjustment before I do anything drastic...

I found this on NWDE:

 

http://www.nwde.org/extras/forum/forum_posts.asp?TID=3582&PN=1

 

looks easy enough...

question: is it necessary to replace the valve cover gasket if it is in decent shape?

 

Thanks

[datzenmike]

Head gasket blown between 2 and 3.

 

 

Won't hurt anything the check and set the valve lash and when you take the head off the settings won't change.

Edited January 8, 2009 by datzenmike

[lynchfourtwenty]

i notice everyones replying about the low compression in 2,3 but i dont think that really explains why its running so rough?? or does it??

 

i was kinda thinking maybe checking the timing an such..

[hessianben]

Well...

just adjusted the valves to spec:

 

.008 intake

.010 exhaust

 

#2 and #3 were really tight.

the intake on #4 was too snug as well.

 

 

Put it back together and started it up...

 

It idles a little smoother,

but, it still won't accelerate- and it skips and bogs and backfires out the intake.

 

I'm going to borrow a timing light tomorrow and set that to spec, but when I drove it home, it ran like a champ!

 

This whole problem began after about an hour on the 101 at about 60mph with some mild grades, on which I dropped down to 3rd gear at about 45mph.

 

 

 

 

On another note-

 

I finally cleaned my garage enough to fit the truck in and work at night!!

whee!!!

 

[ggzilla]

I'm surprised it runs at all with compression that low. Almost for sure that's a blown head gasket (two adjacent cylinders are very low).

 

 

But it could be burnt valves, or bad rings. But two together is usually head gasket.

[hessianben]

My first thought was head gasket- but,

it's not making any white smoke...

 

is that an 'always' type of symptom?

[Bugeye]

the white smoke will only be present if the head gasket blows at a water jacket, but if it blows between cylinders you get low compression on the 2 cylinders its blown on,

[Pacific coast Datsun]

Curious..when you were on the 101 what temp. did it get up to?

[lynchfourtwenty]

when i first got my truck it had a u67 head on it, the between the middle 2 cylinders was a notch an the head gasket was toast right there too.. it puked water big tim the first time i got it started, which was when i knew it needed some work, but i bought it knowing it supposedly had a bad gasket.. well it was even worse then that..

Edited January 8, 2009 by lynchfourtwenty

[hessianben]

The temp gauge stayed at about the first third of the face for almost the whole drive. The only time it moved was when I was climbing the grade West of Beullton on the way to Gaviota. It never passed the halfway mark, and dropped as soon as I was going downhill.

 

Is there anything else I should check or do before I begin pulling the head?

Should I check to make sure I'm not getting blow-by from shot rings?

 

Any tips on changing the HG?

 

Thanks everyone.

 

[lynchfourtwenty]

hey if my dumb ass can doit, anyone can doit... no real secrets.. might i reccomend replacing the timing set while your at it?? or possibly lookin at the water pump real good to make sure its still all good.. an check the timing cover for cavitation... just a thought... its always good to check into these things... as for bad rings... i dont know much bout that man... maybe do another compression check since u adjusted the valves and let us know if anythings changed.. i believe a leak down test would be better???? or do both..

[Cuts metal like mad]

yes, definately recheck the compression. If it soMe how makes it back up over 100 (doubtful, but cross your fingers anyway)... But IF it does, check timing... Tdc on crank, cam, oil pump spindle/dizzy.

[ggzilla]

Is there anything else I should check or do before I begin pulling the head?

Not really. You *can* do more, but at this point it is shot. To tell if it is valves, hook air compressor up to the bad cylinder, see where it leaks. Take off the radiator cap

* Hissing from the carb or exhaust manifold indicates a burnt valve

* If you can't tell or if it's coming from the oil cap, it indicates broken rings.

* If the radiator coolant starts burbling, it's blowing out into the coolant

 

Agreed, sometimes a blown head gasket it won't suck water into the engine creating white smoke. Sometimes it won't leak water into the oil.

 

I think once you tear it down, you'll see if the valves are bad, and if the cylinders are scratched. Probably just clean up the block face and head face real good, stick a new gasket on, use a torque wrench and it'll be good to go. For those scaredy cats, check the head face with a straightedge and if it is out of spec, have the head milled flat. That's rarely needed after a blown gasket, but happens occasionally so professional mechanics will *always* have it done - it's you paying, not them so why not?

[banzai510(hainz)]

makse sure the accell pump works in the main barrel of the carb.

Make sure it squirts in there when you cycle the linkage.

 

Have you messed with the distributor or anything? Pull out the oil pump and install it correctly? Change distributors from a L16 to a L20b or something?

 

yeah adjut the valves that should help but usally when a motor cuts out when you push the gas is

Acell pump on carb

Main barrel transition circut plugging up

condensor bad if still using point distributor.

Vaccum adv on distributor or dist off a tooth.

also a worn point dizzy where the shaft is so loose it wiggles side to side to make the point open when you dont want them. But this happen all of a sedden so it might not be it.

 

head gaskets are ez to do

Didnt I send this to use on how to do the valves and headgasket?or Iam I flogging a dead horse??? go to olddatsuns.com

http://www.guba.com/all/search?query=hainz&set=5&x=34&y=3

 

 

If you have blow by the valve cover port or the crank case block vent will be really stinky!!!!!!

 

I seen cracked exhaust valves.

 

 

I can sent the full DVDs if you sen me your full name and adress

Edited January 8, 2009 by banzai510(hainz)

[Fineline]

Throw a couple of squirts of oil in the cylinders and re-do the comp test. If your #'s go up its the rings. If no change it something else.

 

I'm with Hainz. Sounds like timing or fuel to me.

[hessianben]

Hainz:

 

Thanks for the reply-- I tried to watch the video,

but I got this message:

 

You have requested a page that no longer exists on our site. Our pages change so often that you really can't bookmark any of them for long, aside from the front page or your My GUBA page.

 

 

I've been searching "hainz video" through the Ratsun posts for half an hour now,

and everyone talks about it- but I can't find an original link!

I would love to watch it-

Please send me the link again.

Thanks!

[banzai510(hainz)]

I can get the link ok from my work computer.

 

But that carb looks new so I will assume its good!!!!!!!!!

Is the choke plate fully open after its warmed up??? I will assume yes also as it would usually still be driveable.

 

you could have cracked exhaust valves. as the compression number state its very low.

 

Most good head machine places can redo a L head for a reasonable price.

But if you know somebody near you ,you could get a working L16 head for almost FREE. I have one here I use for trouble shooting but you live to far away to use it.

 

 

ck the point gap again

[hessianben]

Thanks Hainz- got the video to play

Now its homework time!!

I have a feeling it's a HG or valves, since I've tweaked almost everything else,

with the same symptoms remaining...

Gonna watch the video and start the teardown tonite!

Thanks.

[hessianben]

WOW.

 

Hainz, that video is awesome.

You done this before once or twice?

It is now in my permanent bookmarks.

 

Going to go run comp test again.

-then add a few drops oil and run comp again.

-check points

-pull valve cover, recheck valve lask

-pull the cam sprocket and head to examine and replace head gasket.

 

Question:

 

once I get #1 to TDC, should I see the 'bright link' on the chain?

should I keep turning it over until I see that link, and then make sure it coincides with TDC?

 

Question too...

 

What's a good way to hold the chain out of the way while I pull the head, so it doesn't fall into the cover and maybe jump a tooth on the crank?

 

Thanks!

[lynchfourtwenty]

well a wooden wedge is most commenly used to keep the chain tight.. but in my opinion its better to just pull the timing cover so u can examine it an see if its cavitated at all.. plus i'd just replacing the timing set if u havent done it before or dont know the last time it was done.. maybe never.. a gasket set is like $60 an the timing chain set is some where around that also i think.. the chain maybe streched or something ya never know an its better safe then sorry.. i replace all gaskets.. just because.. lol, another reason for pulling the timing cover is to check out the timing guides an tensioner..

 

as for pullin the head i believe u need it TDC on compression stroke so the cams are at the right angle when u wanna bolt the head back on.. as noted in the video the dizzy shaft will be at the 11:28 position ect ect.. forget the cam angles an such its been so long.. but i think u get the hint and im confident u can do this with out problems.. :) good luck buddy

[hessianben]

Well I ran a compression test after adjusting the valve lash.

The numbers came up just a bit- about 10 psi in 2 and 3, but still not right.

1. 120

2. 100

3. 90

4. 120

 

I'll put a dab of oil in each and see if that changes anything.

if it the compression improves...

that means shot rings, right?