Changing the Head Gasket on my stock FI 76

[Healeyalt]

I seem to have antifreeze leaking down the driver side of the engine under the exhaust. I was hoping it was coming from the thermostat housing and running back down along the side of the engine, but that doesn't seem to be the case. So I guess it is time to pull the head and see what is going on inside and I have a few questions for any of you who might have done this before on a 76 FI engine. BTW, there isn't any oil in the antifreeze and no antifreeze in the oil, so I'm hoping it is just a leak to the outside.

Can I unbolt the intake manifold and then the exhaust manifold and just pivot them away from the head (after loosing the exhaust hangers, etc) instead of disconnecting all the fuel injectors and other FI hardware?

Regarding the dimensions/shape of that block of wood to wedge the timimg chain with;

from the Service Manual -- 9.1" L x 1.57" W x doesn't say how thick

from Haynes Manual -- 10" L x 1.5" W x 3/4" thick

from Tom Monroe's book -- 7" L x 1" W x 1/2" thick (but his eg was on an L16 engine)

So which is it? Does anyone have a web site or post with a pic that can be printed, cut out, and traced?

Then regarding the head gasket, do most of you use the Felpro or go with the more expensive Beck/Arnley for example? Which wouldn't need gasket sealer?

Anyhow, any advice or words of wisdom are greatly apprciated.

Thanks

Gary

[siteunseen]

Here's Blue's Tech Tip for head removal, http://www.classiczcars.com/forums/tech-pubs-howto/42420-77-280z-head-removal-%5Bstep-step-photos%5D.html

When I did mine I used my longest screwdriver's handle for the wedge then pulled it out with Vise Grips. Worked for me.

And also went with Felpro, dry. You might want to upgrade your headbolts while your there, turbo ZX from MSA, seems like they were $100 though.

Edited February 17, 2014 by siteunseen

[Zed Head]

My words of wisdom would be - "do more investigating before pulling the head". Unless you've been itching to do it and this is just a good reason.

I can't remember if your engine is stock or modified but there are a few other fitting and rubber hoses up by the thermostat, on top of the intake manifold, that can leak. The heater block for the AAR and its hoses. There are also three potential leak spots at the housing, in addition to each sensor/sender/switch. The hose fitting, the gasket between the hose attachment and the hosuing and the housing to head interface.

Just saying, many of us have done the disassembly of one part or another only to find that it wasn't the source of the problem. From what I've seen and read, the typical leak spot for coolant through the gasket is at the back on the passenger side, not the front driver.

[Healeyalt]

Actually Zed Head, I dread the thought of having to pull the head. But I looked and looked and can't see where else the leak is coming from. I even pulled the thermostat housing from the cylinder head and cleaned it all up and remounted. I did check those hoses that run to the intake manifold and did replace one of them that was getting bad. The antifreeze seems to be seeping from around the middle of the engine below the exhaust manifold. Since the engine did seem to run fine, I'm hoping the gasket is just leaking to the outside. I'm really hoping I don't have a cracked cylinder head. Last Fall before putting it in storage, I did bottom out the exhaust on a bump. Has anyone ever heard of hitting the exhaust hard enough to crack a cylinder head? I never had a chance to test the compression and now that's its been below zero day after day, it'd be kind of hard to start it and warm it up to do a compression test.

[djwarner]

Have you checked the freeze plugs for corrosion, leakage? There are several on that side of the block. You should be able to see them without pulling the manifolds. If they are good, you might want to pull the manifolds to verify the source of the leak before pulling the head.

On my car, it was impossible to remove the exhaust manifold without disconnecting the down tube first..

[Zed Head]

Well, that's a bummer. If you haven't already, you might remove the heat shield from the bottom of the intake manifold. It might improve your view.

On the wedge - The thickness is not too critical, it's the width at the bottom that's key. Some people actually use a big screwdriver or other handy tool to wedge. As long as it's pushing the piston in and won't budge after setting it. I think also, that when you're inserting the wedge you'll be able to see if the piston of the adjuster is being held, if you hold your head just right and shine a light down there.

You could just do a two step operation - remove the manifolds and inspect, then remove the head if needed.

Lastly, apparently the engines are known for transporting the coolant and oil leaks around the head/block gap to new spots. It can be hard to find the source.

[Healeyalt]

I did remove the heat shield for a better view and it does appear to be leaking along the head gasket beneth the manifolds.

I'll start with a 3/4" thick wedge the same dimensions as given in the sm and trim it down a little at a time if too tight.

I do plan on doing things little by little, kind of one step at a time, looking things over good before I proceed. Last night I was able to loosen all the nuts on the intake and exhaust manifold. Because this was a southern California car, there isn't any rust and everything unbolts fairly easy. The block still has the original blue paint on it, although really faded, but there isn't any rust around the freeze plugs.

After I remove the mainfolds I'll certainly look things over better before moving on to head removal.

Thanks

Gary

[Namerow]

Re timing chain wedge: Use a piece of hardwood this. I found 2' lengths in the cabinet-wood section of the local Home Depot (1-1/2" x 3/4" IIRC).

I scaled off the dimensions from some photos of the 'official' Nissan service tool. It's a symmetrical wedge: 35mm W at the top, tapering down over 185mm to a width of 22mm at the bottom. Add a couple of inches of additional length at the top, then drill a hole and run a loop of heavy cord/string through the hole to use as a pull-out aid. Don't use wire for this, because it may snag as you're lifting the head off and pull the wedge out (don't ask me how I know this).

I was able to push the exhaust manifold off to the side without having to un-do the flange connection at the top of the exhaust pipe. Jam a length of scrap wood between the manifold and the block to hold it in position before you try to lift off the head.

[Healeyalt]

Namerow, thanks for the additonal info.

Another question I have is whether I have to take the coolant drain plug out of the side of the engine block or is pulling the plug on the bottom of the radiator going to be good enough to lower the coolant level below the head-to-block surface. That drain plug on the side of the engine has been in there almost 40 years and I hate to break, crack, or strip something!

[grannyknot]

You can run into some big headaches trying to get that block drain plug out. If you really want to get the last drop of coolant out then just lift the rear of the car as high as you safely can with the rad drain plug open and leave it for 20min.

[Healeyalt]

That's a better idea, I do have it safely supported on jack stands so I could easily lower the front some vs messing with the block's drain plug. When I tried taking that tube off that runs from the exhaust manifold to the bottom of the intake manifold for the EGR, the bolt on the manifold end of the tube twisted off. Oh well, I'll just plug it, I didn't want that EGR on it anyways, pumping hot burnt exhaust gas back into my intake manifold (yes I know it is illegal to mess with emissions). This is such an occassional runner, I won't be contributing much to global warming and there aren't any smog tests in my area.