Found this while replacing head gasket

[Silky_Johnson]

So, I am a novice mechanic with (I would say) decent skills. Thanks to Ratsun I have the information I need to be prepared for my projects!

 

I finally decided to try tackling a head gasket replacement on my L18, and I expected to find some things when I got the head off. I'm also putting in a new radiator and some other items while everything is apart. I think compression is low on cylinder #1, So I figured I would find something there.

 

To start off the oics, I guess the good news is that I can finally confirm that my A87 is a closed-chamber head!

 

 

And here are some close-ups of what I found, valve-wise:

 

#1

 

 

#2

 

 

#3

 

 

and #4

 

 

 

 

Given the suspected low compression at #1, I was hoping to find something wrong with the valves so that I didn't have to mess around with the bottom end. To me, it looks like the exhaust valve has some damage, and the intake valve looks to be really crusty, if not also damaged?

 

Maybe you guys can help me know what I'm seeing? I took the head down to the machine shop (Clackamas Auto Parts), and the machinist isn't going to be in until Monday morning, so I'm hoping that you guys can help me know what to ask for when I talk to him. Should any valves be replaced? #2 valves look awesome to me, and the others don't look bad. What needs to be done, if anything? If you guys say they look good, I'll throw on some new valve stem seals and call it good.

 

 

 

KEEP READING:

 

You may be wondering what I found block side? I've had this annoying ticking sound since I've had the car, kinda like a diesel, but not quite. I thought it was valve train related, or ignition, but everything seemed healthy as far as I could tell. I did all of the regular tune up procedures, but nothing would get rid of the ticking sound. Actually, before I blame my problems on the following pictures, I suppose it could be an exhaust leak, but I don't know that yet. If and when I put everything back together, and if it is an exhaust leak, maybe the ticking/clatter will go away?

 

Anyway, here's what I found block side:

 

 

Cylinders #1 and #2

 

 

and Cylinders #3 and #4

 

 

My guess is that the "reliefs" in the pistons for the intake valves we not meant to be there. My question pertains to what should be done? Anything? Is it possible that the intake valves caused this damage without damaging the valves? Did the PO intentionally make his own "reliefs?" What the heck is going on? Is the ticking noise that I'm hearing the valves hitting the pistons?

 

I'll thank you in advance for your help. Let me know what you guys think. I'm just trying to figure out whether or not I should go cheap and just slap on another head gasket and go, or rebuild, or swap in an L20B block... If anyone wants to sell a verifiable non smoking, even compression L20B short block for $200 - $300 in the Portland area, I could be persuaded to swap it in.

[ggzilla]

The valve heads look fine to me. When valves are bad, compression won't be a little bad, but a lot bad. A little is almost always ring wear.

 

 

The pistons look fine. Someone put reliefs in, but it should cause zero problems.

[flatcat19]

So...before you tore it apart, did you verify cause of low compression?

[ggzilla]

Good question. It's actually easier to diagnose when the head is on. If compression is low, then wet compression test will tell you if it's the rings or not. You can't tell by looking unless something is obviously broken which doesn't appear to be the case here.

[Silky_Johnson]

So...before you tore it apart, did you verify cause of low compression?

 

*Novice

 

Nope. I was reading about leak down tests and mistakenly figured that I would just take the head off and go from there. The gasket that I took off didn't appear to have blown.

 

By the way, this was more just a trial run at mechanics than trying to fix the compression issue... I'm thinking a block swap would probably be cheaper than new rings if that's the case anyway, right?

 

So by the way, what do you guys think about those dang pistons? It's not normal, right?

[Silky_Johnson]

The valve heads look fine to me. When valves are bad, compression won't be a little bad, but a lot bad. A little is almost always ring wear.

 

 

The pistons look fine. Someone put reliefs in, but it should cause zero problems.

 

Got it. So the reliefs are fine. When I saw those I thought, "I'm screwed."

 

And maybe I should just wire wheel the heck out of #1 intake and call it good on the valves? And maybe I'll put the head back on and diagnose the compression issue further...

[datzenmike]

I don't get the valve relief cuts at all. Must be for some other head with big overlap cam and larger valves.

 

Check the valve lash on the #1 valves. If ok pop the valves out and look at the valve faces and seats.

[Silky_Johnson]

I don't get the valve relief cuts at all. Must be for some other head with big overlap cam and larger valves.

 

Check the valve lash on the #1 valves. If ok pop the valves out and look at the valve faces and seats.

 

Valve lash is good. I did it once per spec (.008 and .010, cold), and then another time per Hainz spec (.006 and .008, cold) Head is down at the shop right now, so I probably won't be able to do anything until at least Monday.

[wayno]

Can you wiggle the pistons in their holes, every block I have ever used without doing anything to it, I could not detect any movement while trying to move the piston tops sideways.

Do you know how the cam was timed, and what cam you have?

[ggzilla]

I wouldn't bother to wirebrush the valve heads. If I was a commercial shop I would do it, but really -- it won't change anything. They look fine.

 

It's hard to tell from the photos, but the valves appear to be recessed. They should stick up over the seats a bit. If they are almost level they may have been ground to much. Like mike say, pop em out and check the seats. It should have the standard Datsun 3-angle grind according to the specs in the factory service manual.

 

You can also check the valve faces of the valves that are open. If there is a groove on the face that's bad. It should have a shiny ring around where it seated, and a bit of carbon on each side of the shiny ring.

[ggzilla]

Bring it to Bluelake tomorrow, we'll inspect it for you. Then you can still deliver it to the mechanic -- if needed -- on Monday.

[Silky_Johnson]

Bring it to Bluelake tomorrow, we'll inspect it for you. Then you can still deliver it to the mechanic -- if needed -- on Monday.

 

I left the head at the shop, and they're closed on Sundays. :crying: Thanks for the offer though. What I noticed on all of the valves is that the exhaust valves all look more recessed than the intake valves - close to level. Right now I have a Godfather line repeating over and over again in my head... "Why didn't you come to me first?"

 

Can you wiggle the pistons in their holes, every block I have ever used without doing anything to it, I could not detect any movement while trying to move the piston tops sideways.

Do you know how the cam was timed, and what cam you have?

 

I tried wiggling the pistons, and there is no play that I can detect. I have a cam with U20 stamped on it, but I don't know whether it's a regrind or not. The cam sprocket and oil pump spindle were both right on. I did notice that when I cranked the engine over (by hand), I would move it to TDC mark on the pulley, but then it would move itself back about 5 degrees? In other words, to get the pulley to stay at TDC, I would have had to move it to 5 degrees ATDC first and then let itself move back.

 

Maybe the chain was mistimed? The distributor is nearly maxed out on advance, so I've always suspected either the timing was off or the timing chain was worn. If I advance the distributor as far as it can go on both adjustments, it would only put me at about 18 degrees BTDC. Not much room there...

[datzenmike]

First of all the distributor is driven by the spindle not the chain. You could have a worn chain or no chain at all and it would still read where it was set and never change. If the dizzy is at the end of the adjustment range then it has either been replaced with a different one or the engine was apart and the spindle installed one or more teeth off.

 

The dizzy only needs to be advanced to 12 degrees so 18 degrees is 6 more that you don't and will never use.

 

The crank backing up 5 degrees... is this with the head on???? If so it could just be compression in the #1 acting like a spring? Hold it at TDC until it escapes.

 

U20 is a stock L20B cam casting

[banzai510(hainz)]

exhaust valve will alwasy recess as they get hot and over time will sink. Esp the older heads. Eventually to the point where you cant set the valve lash anymore and just gets tight then loose compression.

You have to see how much the pivit ball end can go down. otherwise youmigh be on the close end of its limit anyways and new new seats?????new seats you better hope ethe guy is good as if done wrong they can/will fall out.

 

Unless you see a obvios crank in a valve or in #1 piston everything look good on a digtital camera over the internet.

 

as for the distributor your supposed to look for the 11.28 setting on the spindal. This will be obvious if things were messed with. Maybe wit was set off cause a differnt Matchbox was installed or a wrong timming plate.

 

also back side of the dizzy is a 8mm bolt where you can move the timming plate to get it more in the midde. This could be it also thinking your maxed out.

[I'm BLUE]

exhaust valve will alwasy recess as they get hot and over time will sink. Esp the older heads. Eventually to the point where you cant set the valve lash anymore and just gets tight then loose compression.

You have to see how much the pivit ball end can go down. otherwise youmigh be on the close end of its limit anyways and new new seats?????new seats you better hope ethe guy is good as if done wrong they can/will fall out.

 

Unless you see a obvios crank in a valve or in #1 piston everything look good on a digtital camera over the internet.

 

 

Agreed !!!

 

This is extremely important !

I had 3 valves that "sunk" into the valve seats/head ,,, on my e88 240z car head ( 6 cylinder )

Had BARELY if any adjustment ,,,

I cheated to get by ,,, ( am shamed to say how nor do I recommend ! )

Than when I had enough money ,,, I took it to a machine shop and had the valve seats replace ,,, and valves re-ground.

It CAN be expensive though necessary unless you have another good shape head you have access to !

 

On a side note ,,,

I would look at the #1 exhaust valve very closely ,,,

Take it out/clean it/inspect it ,,, or roll the cam over to "open" position then clean it well and inspect it very closely

if it were me I would probably consider replacing it ,,,

It may not be leaking or bad ,,, but it looks like ( to me ) you might be pulling off the head to replace it in the near future.

Valve should cost like $10-ish bucks.

looks pitted ?... See how the edges are not "sharp" anymore yet jagged and does not have that defineing smooth edge rather "rough" ( hard to tell from photo )

 

For peace of mind ...

You can have a "leak down" test performed at a machine shop for about $45.

They will check for leaks in the valves and cracks in the head itself.

as well as warpage ( if any ).

 

Always perform at least a compression check if not a leak down test ,,, first before tearing anything down.

So you won't be chasing a ghost

Saves time and in some cases money ! :)

 

Good luck !

[rayven14]

From one novice to another, since you got the head off and Im assuming you dont the history (last rebuild) Id go ahead and have it rebuilt.

[Xnke]

Looks like the #1 cylinder has been seeping oil into the chambers, that's what causes that kind of grunge pattern on the exhaust valve. Wire wheel will scrub that stuff off and it'll look fine after...but measure your valve margins and check for worn out parts.

 

The valve reliefs were probably cut because you probably have an engine that at one time had a big cam in it, which would also explain the extreme amount of timing advance being run...if the engine was being run with mechanical advance only, then you could dial in more idle advance and install tighter springs in the dizzy to limit the max advance...very commonly done to enhance the power gains from a larger camshaft.

 

Got any photos of the cam lobes? Just photos of the top side of the cylinder head would be enough; you can spot a cam big enough to need valve reliefs that largfe pretty quick just by eye.

[datzenmike]

 

 

I had 3 valves that "sunk" into the valve seats/head ,,, on my e88 240z car head ( 6 cylinder )

Had BARELY if any adjustment ,,,

I cheated to get by ,,, ( am shamed to say how nor do I recommend ! )

 

 

Removed and ground some threads off the pivot, maybe ground down the lock nut as well.

[Silky_Johnson]

I love Ratsun...

 

Thanks for all of the replies guys.

 

exhaust valve will alwasy recess as they get hot and over time will sink. Esp the older heads. Eventually to the point where you cant set the valve lash anymore and just gets tight then loose compression.

You have to see how much the pivit ball end can go down. otherwise youmigh be on the close end of its limit anyways and new new seats?????new seats you better hope ethe guy is good as if done wrong they can/will fall out.

 

Unless you see a obvios crank in a valve or in #1 piston everything look good on a digtital camera over the internet.

 

as for the distributor your supposed to look for the 11.28 setting on the spindal. This will be obvious if things were messed with. Maybe wit was set off cause a differnt Matchbox was installed or a wrong timming plate.

 

also back side of the dizzy is a 8mm bolt where you can move the timming plate to get it more in the midde. This could be it also thinking your maxed out.

 

I have played around with valve lash a little, and as far as I can see, I still have plenty of adjustment left.

 

The spindle is clocked in at 11:28. If anything, it's closer to 12:00, but definitely not retarded. And yes, I found the 8mm bolt on the backside of the dizzy, and it is also maxed out on advance. Like Mike said, I have it advanced enough right now, I just don't have any room for further advance adjustment. FYI: I'm running the early 510 single-point distributor with a Pertronix kit. It was set up with points when I got it, on the same early distributor, but I ended up buying a rebuilt distributor because the mechanical advance on the old unit was shot. Is it possible that I have a dual point pedestal? The engine is a late model JDM L18.

 

For peace of mind ...

You can have a "leak down" test performed at a machine shop for about $45.

They will check for leaks in the valves and cracks in the head itself.

as well as warpage ( if any ).

 

I talked with the machinist today, and he's going to do a leak down test (for $20), as well as clean the head (also cheap), and check for warping and resurface if necessary. In my opinion, the guys down at Clackamas Auto Parts are awesome. They're honest, economical, and they do good work. As it turns out, my father-in-law knows the machinist, Art, who has apparently been working there since at least the '70's.

 

Got any photos of the cam lobes? Just photos of the top side of the cylinder head would be enough; you can spot a cam big enough to need valve reliefs that largfe pretty quick just by eye.

 

I don't have any available yet, but I should be getting the head back tomorrow afternoon. I'll snap some more oics for the pic whores at the next opportunity. But fair warning, based on the pictures that I have seen of different cams, I don't think I've got a real wild cam. On second thought, the top end is awesome, and I have no power before 3K, so maybe it's a regrind? I don't know, I'm just shooting in the dark.

_______________________________________________________________________

 

On another note, assuming that there are no compression issues in the head (which I expect), and based on the fact that there isn't any damage to the piston, I'm probably looking at piston rings or damage to the cylinder wall for the cause, right? I have access to an engine hoist and stand. How easy would it be for me to re-ring the piston? I don't see any how-to's on here, but I do have Hayne's, Chilton's, and the Keep Your Datsun Alive book. Should I do all of the pistons while I'm at it? Should I just pull the block out and have someone else do it?

 

What's your advice?

[banzai510(hainz)]

My advice to L motor guys:

always have anotther L motor ready to go in.

 

But if motor is going to be open up might ass well do them all.

But then again it might be nothign your worrying about. L got oil oozing out of my head also on my Banzai car.

 

On timmin of the distributor spindal its pretty close to 11/28 when the crank is at ZERO.

if you have a scrrw driver and place it across. the screw driver will be right of the top hole and left of the bottom. Then install the dizzy. I pout the timming plate loose and rotate them to the maximun on both sides.

 

Now far as I know the L16 dizzy will ONLY fit the L16 mounts/pedastals. The 10mm screw will only go in to them as the tang on these is slightly shorter. Than the later ones(L18/20). as the timming plate slot will not line up LONG WISE(slot wise). You can tell if its been hacked up.

 

L18 dizzys where closer to the L20 mounts and timming plates.

 

Only you can tell us if anything looks hooky on it.

Take photos.

[Silky_Johnson]

Looks like the #1 cylinder has been seeping oil into the chambers, that's what causes that kind of grunge pattern on the exhaust valve. Wire wheel will scrub that stuff off and it'll look fine after...but measure your valve margins and check for worn out parts.

 

The valve reliefs were probably cut because you probably have an engine that at one time had a big cam in it, which would also explain the extreme amount of timing advance being run...if the engine was being run with mechanical advance only, then you could dial in more idle advance and install tighter springs in the dizzy to limit the max advance...very commonly done to enhance the power gains from a larger camshaft.

 

Got any photos of the cam lobes? Just photos of the top side of the cylinder head would be enough; you can spot a cam big enough to need valve reliefs that largfe pretty quick just by eye.

 

At long last, I got the head back from the shop. The head tested out perfectly and didn't even need resurfacing. I guess that means I'm rebuilding the bottom end. Do I copy Jacob's L19 and put 280zx flattops in? Just re-ring? Drop in an L20B? Here come the oics:

 

 

 

 

 

 

 

 

My cam is definitely stamped with U20, but based on other photos, I'm thinking this could have been a regrind? There isn't anything written on the back of the cam. What do you guys think? Hot cam? Big cam? Do I need the valve reliefs? If I don't need the valve reliefs, I think it's time to throw in some flattops...

[flatcat19]

Grab your How To Rebuild An L book and a feeler gauge.

I'd say re-ring it for cheap. Then build a motor on the side if finances permit.

 

Cheers on having good head.

A lot of men pay good money for that.

[Silky_Johnson]

Got any photos of the cam lobes? Just photos of the top side of the cylinder head would be enough; you can spot a cam big enough to need valve reliefs that largfe pretty quick just by eye.

 

Paging Xnke:

 

Here's the deal. Based on some good advice from DatzenMike, I think it would be awesome to throw in some ZX flattop pistons. Based on Mike's calculation, the end result would be 1853cc's of displacement and a 10.7:1 compression ratio. Because of the peanut head and "swirl" effect, the engine would resist pinging better than an open chamber head of the same compression ratio. Mike thinks it would run on premium pump gas just fine. If not, a little timing adjustment would take care of things. Feel free to chime in if you disagree, but I assure you that I will likely respect Mike's opinion above just about everyone else on here. :thumbup: Besides, he's usually pretty conservative when it comes to engine builds.

 

BUT! I still have this cam issue. Are the valve reliefs in the pistons there because they need to be with this cam, or were they put in for a previous big cam? If my cam is too gnarly, I can't just swap out pistons and call it good, because the valves would hit, right?

 

So, does this look like a stock cam, or mild enough cam for this project? Is there a way that I can "test" to see if valves would hit? I imagine a person would have to finish block work, bolt up the head and then slowly turn the crank and wait to feel for a "stop?"

 

If this cam just won't work, should I just go junk-yarding for an L20B and rip off the cam, rockers, lash pads, and springs? Or maybe I should get a stage 1 Isky or Comp cam?

 

As you can see, those dang homemade valve reliefs are freaking me out a little.

[banzai510(hainz)]

That is NOT a stock cam. Its a regrind.

You can tell by how much of the back side of the cam is ground almost flust with the cam barrel its self.

 

I persoanlly would pull one rocker arm out and ink pen the rocker arm then put it back in set to say .008intake/.010 exhaust and turn the cam over a few times then pull rocker back it back out to make sure the wipe pattern is on the center. then you know you got the right lash pad set up in there and such. No tthat tha machine shope would know this or not.

 

How i do this is bolt the head to a emply block or another block with the pistons half way down that you can bolt the head on a rotate that cam around using the cam bolt sprocket back on and use aq big breacker bar and turn it.

 

When dont set it back up to TDC or the dowel in the 12oclock postision.

 

This is also a asymetric cam as you see the opening is faster and closing is slower(Its good)

 

I think I would bolt this to a L20 with stock pistons (11.35cc dish)to be on safe side But I dont know if you have the same clutch set up flywheel at home.So you would need to buy this.

 

L18 with flattops might be cutting it close with valve overlap or more whats the spec on the Lift of this cam and if oversize valve installed(44mm??) You could put it together and turn it a few tims and youll tell if it hits but cant gareentee at 6k rpm. a l20 bottom end would be good with this head and sidedraft set up.

 

http://vimeo.com/19077890

[banzai510(hainz)]

I cant tell if that is aftermarket valve retainers. as aftermarket one look like the stock ones that wht I say do a Rocker arm wipe pattern ck.