Head Gasket Questions!

[nkopp]

Hey all. Had a coolant leak and some work to do behind the timing belt (heli coil on the water pump bolts), so decided to take off the head gasket and take a look. car is new to me, so I figured it would be worth investigating anyway.

Here are a couple of photos. Two questions:

1. How does this look? The second cylinder has some soot by the valves which matches deposits in the exhaust manifold as well. Four and five have more gunk on the block. 

2. I was expecting the first cylinder to be up. Cylinder 4, though, is up instead. Have I messed up the timing?

planning to clean off as much of the gunk as I can. Looks like quite a bit of rust from the coolant, in particular, anything else I should be looking at as I put things back together?

Thanks, as always!

 

Edited November 27, 2022 by nkopp

[Zed Head]

What do you know about the engine?  It has studs and non-stock pistons and a mish-mash of valves.  It looks like somebody ran straight water for a while the passages are full of rust.

Did you jam the timing chain?  If not you'll probably need to reset timing anyway.  Could be that your damper is broken or the wrong one also.  You should probably get Monroe's book.  https://www.amazon.com/Rebuild-Your-Nissan-Datsun-Engine-ebook/dp/B006VUICHG

[Zed Head]

p.s. does anybody know why I can click on the first picture and have the ability to magnify immensely (just keep clicking and it keeps growing) but cannot do the same on the second picture?

[nkopp]

1 hour ago, Zed Head said:

What do you know about the engine?  It has studs and non-stock pistons and a mish-mash of valves.  It looks like somebody ran straight water for a while the passages are full of rust.

Did you jam the timing chain?  If not you'll probably need to reset timing anyway.  Could be that your damper is broken or the wrong one also.  You should probably get Monroe's book.  https://www.amazon.com/Rebuild-Your-Nissan-Datsun-Engine-ebook/dp/B006VUICHG

Yeah, not much on it's history. Previous owner had put a turbo on it is all I know, he said it ran though I didn't hear it. I attributed the studs to him, but don't know about the valves and pistons. It seems to have a mix of original parts, OEM replacement, and other aftermarket parts. I replaced some 280z components in the cooling system.

Are there any visible issues on the pistons and valves? Or anything I should look for while I've got it apart? Looks like maybe the pistons are these?

Just grabbed the book, thanks. Wasn't expecting to get into the engine on this pass, but one thing led to another. Was hoping to get it running and then come back around to look inside.

1 hour ago, Zed Head said:

p.s. does anybody know why I can click on the first picture and have the ability to magnify immensely (just keep clicking and it keeps growing) but cannot do the same on the second picture?

Having the same issue myself... Should be fixed now, it seems like it uploaded a smaller version of that one somehow.

Edited November 27, 2022 by nkopp

[Zed Head]

What is the engine supposed to be?  You just kind of appeared from nowhere.

There are some not-so-good things in the pictures but it's hard to tell what they are.  You might clean up the piston tops and post another.  Detonation can cause damage that looks like foreign object damage.  It can also break rings.

 

 

[nkopp]

Ah, its a 240Z L24. Will do on cleaning tomorrow and re-post. Thanks!

[Patcon]

The rust in the jackets and head needs attention. A pressure washer would be good for that

[Racer X]

First, the engine doesn’t have a timing belt, it has a chain. And whoever pulled the head didn’t block the chain, and the tensioner, so before the head can be reinstalled, the front cover will have to come off, and the tensioner reset, as well as the timing.

The pistons and combustion chambers look like they don’t have a lot of time on them, but the top of the cylinders look like they do, and the cooling passages towards the front of the block look clogged and the rest of the visible cooling passages look too corroded. There does appear to be something not right, like Zed pointed out, but I’d rather not comment based on pictures alone. Detonation will burn the tops of the pistons, eventually burning holes through the piston tops. Detonation can also break the ring lands, and rings, something that may or may not be visible without removing the pistons.

The part of the valves that need inspection can’t be seen while they are installed in the head.

I see someone spent a bit extra and sprung for head studs.

You mention a turbocharger.

What kind of fuel delivery? Carburetor? Injection?

The pistons don’t look like the kind used in a turbocharged engine. Usually a dished piston is used, not a flat top. Tuning a high compression turbocharged engine is difficult, eliminating detonation requiring very high octane fuel, ultra precision fuel delivery and ignition timing.

Looks like you have some work to do.

 

 

 

 

 

[Diseazd]

Looks like the PO replaced the valves in the number one cylinder. The exhaust valve in the number one appears to be an L28 valve…..looks larger than the rest. The block definitely needs a boil out……looks like the PO filled the radiator with saltwater lol…….I can’t imagine why it’s so rusty. Regarding the exhaust valve…….could just be an illusion. If the head is a late E88, I believe they came with the larger exhaust valves.

Edited November 27, 2022 by Diseazd

[dutchzcarguy]

On 11/27/2022 at 1:08 AM, Zed Head said:

but cannot do the same on the second picture?

I can... so you should be able too. (in the middle do a click, sometimes it switches to a other pic..)

btw.. the 2 oil holes between the cyl.3 and 4 ... one looks blocked that's a bad thing!

Also the 1st cyl exhaust valve appear to lay a bit low/deep into the head.. investigate.. (new seal maybe needed?)

Edited November 29, 2022 by dutchzcarguy

[Reptoid Overlords]

Those pistons have valve reliefs in them.  The Nissan factory flat tops for the higher compression F54 engines don't have valve reliefs.  I may be wrong, but aftermarket pistons with valve reliefs are normally used when shaving a good bit of materiel off of the bottom of the head to get higher compression.  As mentioned, this is counter intuitive to building a turbo motor(at least an L series turbo).  I think I would measure the head to see if any material has been taken off by a machine shop and see if that cam is stock or not.  After sorting the above mentioned issues of course. 

I have DSI pistons and my head is shaved .080" for higher than stock compression.

Edited November 27, 2022 by Reptoid Overlords

[Zed Head]

1 hour ago, Reptoid Overlords said:

The Nissan factory flat tops for the higher compression F54 engines don't have valve reliefs.

The pistons combine with the head's combustion chamber volumes to determine compression ratio.  The F54 used the P79 or P90 head.  It has a larger volume than the N42 and N47 heads.  The F54 and the N42 L28 engines have similar CR's.  8.8 and 8.3.

The engine in this thread looks interesting, probably has more interesting parts.  Probably should be rebuilt but if it ran okay before it could just be reassembled with a new head gasket.  All from a tiny leak...