Coolant issues?

[620fever]

So I recently finished changing the headgasket on my l20b, and everything is running top notch. After a few weeks I starting noticing when I started it up after sitting for a few hours a little white smoke came from the exhaust, not as much as when the headgasket blew. It goes away after I drive it for a few minutes and it primarily smokes when it's decellerating. A buddy reccomended tightening the headbolts again, they were loose, it seemed like that might have fixed it for a bit, but it is still doing it. I'm thinking about replacing the old headbolts, I thought the threads looked a little worn when I had them out. Any thoughts? I don't want to spend $100 if it won't fix the issue, but will gladly do it if it will.

[Tristin]

How long did you drive the car when you blew the headgasket? If you have all the bolts tightened, you may have lifted the head... which could have warped it some. It could be sealing up after it warms up because the metal is expanding as it gets hotter.

[620fever]

I didn't drive it too far with the blown headgasket, a couple blocks. I would think that a warped head would have shown symptoms earlier after I changed the gasket. I didn't notice the issue untill several weeks after I changed the gasket.

[bananahamuck]

You say head bolts were loose?? how loose?

 

A head gasket on a warped head will sometimes last more than a few weeks so i wouldn't `t rule that out,,Since it sounds like your taking head off in near future put a straight edge on it to be sure.

[Z-train]

Take everything apart.Forget about a straight edge,take to a shop and have them cut it to make sure it's straight.Then get some studs as i THINK new head bolts are no longer available.

[metalmonkey47]

You need to run a compression test asap. Cold though.

 

 

Then retest when its warmed up.

[Z-train]

Based on his posts,i wouldn't waste my time.THe head NEEDS to be trued.

[bananahamuck]

most likely.

[620fever]

You say head bolts were loose?? how loose?

 

A head gasket on a warped head will sometimes last more than a few weeks so i wouldn't `t rule that out,,Since it sounds like your taking head off in near future put a straight edge on it to be sure.

 

When I retorqued the headbolts they were at about 50 pounds when they're supposed to be about 60.

 

 

Take everything apart.Forget about a straight edge,take to a shop and have them cut it to make sure it's straight.Then get some studs as i THINK new head bolts are no longer available.

 

Any idea what a ballpark price for resurfacing a head is? New headbolts can be found for less than $100 I might be more inclined to try that first so I can rule that out then move on to the more expensive options.

 

You need to run a compression test asap. Cold though.

 

 

Then retest when its warmed up.

 

We ran a compression test after we changed the headgasket and everything was good then.

 

 

 

Thanks for the replies guys.

[Z-train]

Price is a local thing.As for headbolts,i used ARP studs for my build either because NOS headbolts weren't available or were so expensive,i'd be a fool not to use ARP studs.

[datzenmike]

I would try re torquing the head bolts, BUT DO ON A COLD MOTOR.

 

Did you torque them from the middle out? Like this...

 

RAD

7..8

3..4

1..2

5..6

9.10

 

If not, loosen them all but do not move the head. Using this sequence torque to 20 ft lbs, them in sequence to 40 ft lbs, then to 60 ft lbs.

 

Likely as Bill says if this 'Hail Mary' does not work it will need to be trimmed.

[620fever]

Alright well I torqued them down correctly so that isn't the issue, I figure I'll try retorqing them again, if they're loose then I'm gonna replace the bolts, if they aren't I guess the head might be warped...bummer. Thanks again guys.

[EricJB]

Summit racing has ARP head stud kits for $113.00. Part #202-4201. I used them on my LZ23 and will never go back to bolts.

[banzai510(hainz)]

I reuse headbolts all the time.

But the turbo 280zx bolts are still availible far as I know in really needed. But a milled head might be better money spent than ARP studs. and a new gasket.

 

I think 50 pounds should have sealed it and I wouldnt cinsidered that TOO LOOSE

[Z-train]

Alright well I torqued them down correctly so that isn't the issue, I figure I'll try retorqing them again, if they're loose then I'm gonna replace the bolts, if they aren't I guess the head might be warped...bummer. Thanks again guys.

 

If you are sure you've torqued them down correctly,don't try again.Take the head off,get it milled.Good fasteners and then make sure you advance the cam sprocket key to match.You can hurt these heads to the point they are FUBAR.

[EricJB]

. But a milled head might be better money spent than ARP studs. and a new gasket.

 

I agree. The head has to be straight. If it was blowing steam out the tailpipe, I would probably look at the exhuast valve and seat in that cylinder as well. A little Dykem ( or a sharpee) on them and a little lapping to make sure nothing warped. If I was going to replace the bolts due to questionable threads, I would just upgrade to ARP. If the bolts look bad, what does the block look like? Stud it and forget about it.

 

I have a ton of good head bolts in sets if you want to go that route. Or if you just need a few, let me know.

[datsunaholic]

I had no problem ordering the headbolts through nissanparts.cc. Less expensive than that ARP kit.

[banzai510(hainz)]

Remeber L20s start to crack in the center head bolt hole, there will be 2 water passages on the side. This needs to be cheaked also.

 

I seen them have cracks and be OK also. But its up to you. what you want and the money situation.

[620fever]

Drove it a little yesterday and had no problems once warmed up, only steams when she's cold, so it seems like it's likely a warped head issue. Anybody know of a shop in the Seattle area that would do a good job milling the head at decent price? Also what else is involved with this, I would need cam tower shims right? Would it effect the power of my motor?

[Z-train]

No tower shims.It changes cam rocker geometery.Use the advance holes in the cam gear.First get a measurement on how much the head will be cut to get it flat.

[datzenmike]

What year 620???

[620fever]

77 620

[datzenmike]

'78 and up have water passages in the intakes and water could get sucked up into one of the intake ports, (past a bad gasket) but this doesn't apply to the U-67 head.

 

 

I have to say that most vehicles show a white condensation out the exhaust when the engine is cold. This is totally normal and goes away once the engine and exhaust pipe warms up.