Blown head gasket

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LowFlying720
Posts: 34
Joined: Fri Aug 15, 2014 10:24 pm
Car: 85/86 Nissan 720

Blown head gasket

Postby LowFlying720 » Mon Oct 05, 2015 11:07 pm

Hi all

Well a few months back my engine started running rough like it was running on three cylinders and anytime i put a load on it I'd get a loud knocking like detonation.

I ran a compression test and the back two cylinders only pulled about 30 psi. so I ran a pressure test on each of those cylinders to see where the air was going and it was going smartly out intake valve of #3, or so I thought. I figured at that point I don't need to go any father I had a bad valve and pulled the head off. What a surprise when I got the head off and looked at the head gasket, it was blown between third and fourth cylinders. DUH

Both the head in the block miked out flat and don't appear to be damaged in the area where it was blown.

So, two questions.:
Can I just throw on a new head gasket and put it back together or should I have It milled?

In the process of removing the intake and exhaust manifolds I broke that pipe that goes from the end of the exhaust manifold around to the intake manifold at the fitting where it goes into the intake manifold. I'm guessing that's another part of the omissions Control, so can I just plug both ends and toss that or do I need to get a new part? I have installed a weber carburetor and have removed all the other emissions control stuff.

86 (85 1/2) 720 pickup Z24 engine.

Thanks


User avatar
waynosworld
Posts: 232
Joined: Mon Aug 24, 2015 11:10 pm

Re: Blown head gasket

Postby waynosworld » Tue Oct 06, 2015 10:04 pm

The Z24 is famous for blowing headgaskets, if the deck and head are flat, I would just put another headgasket on it and call it good.
The Nissan fix for the headgaskets blowing is to re-torque the head bolts every tune-up, it doesn't matter the order they are re-torqued, as long as all of them are done.
I don't know a lot about removing the emissions hardware, perhaps someone with more knowledge will chime in.

LowFlying720
Posts: 34
Joined: Fri Aug 15, 2014 10:24 pm
Car: 85/86 Nissan 720

Re: Blown head gasket

Postby LowFlying720 » Sun Oct 18, 2015 11:51 pm

Yeah both the head and block are perfectly flat so i went ahead and threw in a new gasket and put it back together.

I tapped out both manifolds where the EGR was attached and put a plug in them. I'm guessing that since I have already removed the vac hoses that use to actuate the valve on that pipe that it won't make a difference. I guess I'll find out the folly of that logic when it burns my valves or burns a hole in one of my pistons.

BranS
Posts: 10
Joined: Wed Apr 20, 2016 8:42 pm
Car: 1985 nissan 720 4x4 z24

Re: Blown head gasket

Postby BranS » Sun Apr 24, 2016 11:50 pm

So how did it work out? I've tried a Lotta crap and still detonating.... gotta get compression test..... hope it's not blown H.G.


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