White smoke after running on 3 cylinders

[rundwark]

Got some serious white smoke after running on three cylinders today.

 

Stopped the car on a drive when I noticed a lot of smoke from the tail pipe.

 

I found out at home that cylinder 4 wasn't firing, messed with the spark plug a bit and then replaced it. With the second plug I swapped in, it fired again. Now I'm getting some serious white smoke. It smells pretty sweet so pretty sure it's coolant.

 

What are the odds this is merely a head gasket failure vs/ something worse like a warped or cracked head or block?

 

'70 510, stock L16 with dual SUs

[rundwark]

Did a compression test too, 170psi on all four.

[datzenmike]

No reason for it to warp unless there was a previous condition or it was seriously over heated. Most likely the head gasket.

[rundwark]

Thanks Mike, that's reassuring.

 

I still feel like an idiot for driving it on three cylinders ("it sounds funny, oh whatever, it'll be fine"), but at least I'm a slightly less hopeless idiot now. :)

[flatcat19]

Why can't it be the intake gasket leaking to the exhaust?

 

 

 

Compression tests are horrible for diagnosing head gaskets. 

Cylinder leakage FTW. 

[wayno]

If it has 170 across, I would first look at the intake gasket, maybe coolant is leaking/being sucked in that way, bad intake gasket between the water jacket and #4 intake, but that would depend on what head it has.

[datzenmike]

An L16 always had 210 heads and they always had water ported intakes.

 

 

 

Why can't it be the intake gasket leaking to the exhaust?

 

 

 

Compression tests are horrible for diagnosing head gaskets.

Cylinder linkage FTW.

Would you bet an internet beer on that? Intakes rarely leak unless a header installed. Flanges never match the intake flanges and the bottom bolts that bridge across both don't tighten properly. Second would be a GM owner slathering a good gasket with RTV.

[rundwark]

When compression testing I also noticed some vapor coming out of the cylinder 4 spark plug hole whenever I had cranked the engine.

 

I'll check what head it has when I get back home. It is probably whatever it came with stock when new (in the US). Either way, I'll definitely check the intake gasket, I'll have to remove all that anyway on my way to pull the head... I recently replaced it (when I replaced the intake and exhaust manifolds when swapping my single downdraft carb for twin SUs), so it's possible the new gasket was bad or I messed something up (maybe didn't torque it properly) while doing that.

[datzenmike]

Actually the easiest way to remove the head is to leave the manifolds on. Disconnect the down pipe, throttle cable, choke heater wires and the intake water jacket pipe hose. If you don't find the gasket blown then remove the manifold bolts. At the least put the head back on with the manifolds in place and save yourself the frustration.

[rundwark]

What's the advantage of leaving the manifolds on? I've never done this before but intuitively, it seems more straightforward to pull the head without all that other stuff attached to it..

[banzai510(hainz)]

what I do is pull the intake off ad a whole unit.

then pull the exhaust manifold out and off to the side if possible. Might have to move the crank case tube. then i pull the head.

Mikes way of pulling the y pipe is good also but I never trust those bolts as they are rusted and may break.

[datsunaholic]

Some L-series (particularly L20b's with the full smog setup) are really hard to get the lower manifold bolts loose in the car (it can be done, a 12mm swivel socket makes it a lot easier).  But in my case I always remove the manifolds first.  Too damn heavy to lift the whole mess out as a unit, and it makes lining up the head dowels a lot easier without that extra weight when assembling.

[rundwark]

Yeah, won't be too difficult on mine. I recently installed different intake and exhaust manifolds. Sadly no time this weekend, but should get all the gaskets I need in by next weekend.

[flatcat19]

Yeah, won't be too difficult on mine. I recently installed different intake and exhaust manifolds. Sadly no time this weekend, but should get all the gaskets I need in by next weekend.

 

Did this puff of white smoke happen right after you replaced the manifolds?

 

 

Are all the bolts evenly torqued? Are they tight?

[rundwark]

Nah, it happened gradually..

 

I did a pretty spirited mountain run with it after the conversion and it ran great. After another week it started running on only 3 cylinders every now and then. I didn't think much of it first until it started happening consistently.

 

I am going to take the carbs off and check the bolts, because I don't trust I did that right anymore after this thread. When putting everything together I was really surprised how low the torque spec for them was (like 12 lb/ft if I remember correctly) in the Haynes manual. What would you suggest I torque them at?

[datzenmike]

FSM says 9-12 ft lbs. Don't forget this is an aluminum head. It expands twice as much as cast iron or steel so it tightens as it expands and aluminum is soft, don't strip them..

[flatcat19]

Every bolt in the aluminum on that head strips out so easily. 

 

I rebuilt a head not too long ago...every bolt hole is now reinforced with heli-coils with JB holding them down. 

Shitty day. 

[rundwark]

That sounds painful flatcat, I'll be careful.

 

A few nights ago I pulled the manifolds, hoses, plugs and other stuff off the engine prepping to pull the head. I figured that since this is the first time I pull a head, I'd rather make it as light and detached from other stuff as possible.

 

Intake/exhaust gasket looked perfect so pretty sure there was nothing wrong there. I have new gaskets ready to go, just need to fab a piece of wood to jam the timing chain tensioner in and off we go. Wish me luck :)

[rundwark]

Pulled the head, pretty sure it was the gasket.

 

Piston 4 is squeaky clean from it's high-pressure steam bath:

 

Looking closer (hard to tell in oic) you can see that the gasket was blown between the cylinder and the biggest coolant passage next to it:

 

Head looks pretty dirty but no obvious blemishes or cracks:

[Nuclear Water Boy]

I can see the break in the HG where water got sucked in. Can't tell if detonation played a part or not as I can't see if the fire ring on the HG if it has damage or not. Sometimes really old HG's develope cracks where you get steam or white oil because time, heat/cold and pressure makes them brittle. May as well do a valve job.

 

Lou

[datzenmike]

Usually on tear down there is some sign of (green/yellow) antifreeze coolant, I don't see any and this can be a problem. Anti freeze prevents corrosion and rust and I see lots of that. Once fixed be sure to run 50/50 mix. This will keep your rad abd cooling system protected better than straight water. BTW replace lost water with distilled, not tap with disolved minerals in it.

[rundwark]

Yeah, I've been running 50/50 and only added coolant and distilled water since I got the car. Had to replace the stock rad soon after I got it, it was totally clogged up and a two night CLR soak didn't change much. Pretty sure the original owner ran tap water in it for quite a while... Bummer.

 

Anyone have experience adding rust-removing agents to the cooling system to clean it out?

[rundwark]

@Nuclear, I had some overheating early on as well as more recently after screwing up filling up the coolant properly. Also had some detonation/pinging when the engine was out of tune. So I think all of that contributed to the head gasket failing (plus the fact that it's probably 40-odd years old, I don't think it's ever been replaced before; and from conversations with the original owner, I'm pretty sure he kept it going in its overheating condition – with the clogged up rad – for quite a while)..

[rundwark]

Installed a new head gasket tonight but I'm a little concerned about the quality.

 

The openings for the cylinders are quite, erm, not round.

 

What do you guys think? Fine, or buy a better gasket before I reassemble everything?

 

 

Detail pics:

 

 

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Moar oics:

 

Pre-install, as clean as I can get it (smooth to the touch but still looks grimy)

 

 

[banzai510(hainz)]

just put the other guide dowel in place before butting the head on.

gasket looks fine. Its not near the piston so I assume this is still a L16 block.

 

I just buy the walmart(supertech 50/50 mix antifreeze)