L20B intake/exhaust gasket replacement

[650savag]

My stock, low milage, '78 620 has developed a pretty nasty exhaust manifold gasket leak at the #4 cylinder and I was hoping that some of you guys here would give a newbie some advice on the change out. I located a Beck-Arnley gasket for $16.99 and I'm considering undertaking the change out myself. I have read up on both repair manuals and feel pretty confident about doing it, although I'm not the greatest mechanic around. I know I can run into problems with the studs breaking, etc, when dealing with exhaust systems and I was also wondering about removing the stock carb (de-smoged) or leaving it mounted and pulling the whole assembly together? Any and all comments would certainly be appreciated. Thanks in advance. Dan

[DanielC]

Here is how I put an L-16, or L-18 manifolds back on the engine. I assume the head manifold surface is clean, and the manifold to head surface is clean on the manifolds. There is three studs on the head that hold the exhaust manifold only. One on the center, one on each end. Put the studs in if they are not there. Put the gasket on. Put the exhaust manifold on, tighten the nuts finger tight. Just start the four bolts, with the big thick washers, that hold the exhaust and intake manifolds, without putting the intake manifold on, yet. Pull the large washers out to the end of the bolts. Carefully slide the intake manifold down on to four bolts, try to not touch the sticky stuff on the gasket if you are using a stock gasket. Start the four top intake manifold bolts, they center the intake manifold. Now all the bolts, and nuts should be started. Tighten the four top intake manifold bolts finger tight. Tighten the four lower intake manifold bolts finger tight, you need a socket, a universal joint, and a long extension to reach the inner ones. Now torque everything evenly to specs, I do not know what the torque is, my manuals are out in the garage.

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[datsunaholic]

The '79-80 L20Bs are a bitch to get the middle combo bolts out. You WILL need at a minimum a shallow socket and a universal joint- you cannot get them straight on due to the manifold design. It works better if you have a swivel socket.

[Jason]

I just did my head gasket on the L20b in my wagon. I had to take off the intake and exhaust manifolds first though. I used a Felpro gasket on mine. I have the SU's on so it's even harder to get at the middle combo bolts because they're stuck behind the heat shield, so like Doug says, get a shallow swivel socket to do it with, works way better though still a pain.

[dat521gatherer]

not recommended but i have taken all the top bolts/nuts and lower outer bolts/nuts and manifold mating bolts then taking a pry bar to lift the intake manifold off the bottom inner bolts/nuts. forcing the manifold up off those last bolts might not be something you want to do and you can damage something if not careful. done it twice at the junk yard as a experiment to save time and it worked both times. even less fun with the pollution pipes in the way. had to hack those off. good luck!:)

[banzai510(hainz)]

The L20 with the emissions is a PAIN!!!!!!!!!!

It was hard to do and my motor i got FREE and wasnt installed 78/79 l20.It was in my gagrage and found it hard to get those bolts lower inner exhaust bolts.

shit even the carb nuts were kinda a pain.

Im used to L16 intake or exhausts.

 

then getting those bolts/with the exhaust washer back in is another proplem and hop not to put it in at a angle and stripp out the aluminum threads

 

your going to have a bent BACK(pain)!!!!!!!!

[hang_510]

I know I can run into problems with the studs breaking...

... leaving it mounted and pulling the whole assembly together?

 

it will be easier to do w/the more parts you remove, but isnt required.

 

also a l o n g extention helps w/the center bolt.

the OEM gasket should still be avail from nissan, around the same price too.

 

i recently redid my HG and about 100mi later the back stud broke :cursing:

luckily i was able to squeeze my drill around everything and used a EZ out sucessfully :thumbup:

 

i recommend replacing all the studs at this time, especially if they are rusted.

something i shoulda done mysef :poop:

[banzai510(hainz)]

ANTISEIZE is your friend!!!!!!!!!!

[650savag]

Thanks to everyone who has posted to this thread so far. All the good advice will be heeded. I just came in from work and sprayed about half a can of "Corrosion X" on all the bolts and studs that i could reach. I will let that sit for a day or so and spray them all again before I start to dissasemble everything. This Corrosion X is the best penetrating oil that I have ever seen so hopefully that will keep me from stripping or breaking any bolts or studs. I will replace the studs before I go back with everything. Does anyone remember what size swivel socket I will need for the middle, bottom, combo bolts? Is there two of those or just one? I will check with the nearest Nissan dealer about OEM gasket but that would be about an hour away. I can get the Beck-Arnley here in town for $16.99 or a Fel-Pro set for $11.99. I will probably go ahead and remove the carb and related stuff first. I just recently put this rebuilt Hitachi on that I got from Lance Kilgore (one of the guys here at Ratsun) so it's not much of a chore for me (about 30 - 45 min.). I will post again when I get finished and I welcome any other helpful hints. Thanks again, Dan

[hang_510]

IIRC its 12mm

 

ive been happy w/ PB blaster :D

[Jason]

I bought new studs for the head when I did the head gasket and intake/exhaust manifold. I also used a ton of anti seize on them too! I also bought new spacers as the ones on didn't look right either....

[banzai510(hainz)]

nissan is going to have to order those intake gaskets mostl likely

Felpro is fine. I use them for the intake. Matter of fact they are the same size as the SSS intake gasket. 1.5 intake holes

Victor renz (Napa) is fine

[650savag]

I want to update everyone who is helping me on this project and ask a couple more questions. I started pulling everything off this afternoon when I got home from work. I worked on it about an hour and got pretty far along. I got the carb and related stuff off and got about half of the intake/exhaust bolts out without a problem. I still haven't removed the two exhaust bolts at the rear (they seem to be seized pretty good) and I did not want to break them off. I did not get the two combo bolts underneath the middle section because I'm waiting on those until I can buy a swivel socket when I'm off tommorow. I sprayed everything good again with Kroil oil and corrosion X. The question I have is about the EGR tube. I haven't been able to loosen either end of that big, metal tube. What funtion does this play and do I need it if I'm not using the EGR valve (blocked and plated) (de-smogged). If I have to hacksaw it, can I just plug both outlets with a pipe plug once I get the manifolds off and remove the fittings? Or does this tube play an important part that I'm not seeing? Thanks again for everyone's help and I will keep updating. Dan

[datsunaholic]

Depends on what you mean when you say blocked and plated...

 

With the EGR valve removed, the tube is doing one of 2 things:

 

1) Nothing

2) Providing the intake manifold with a massive vacuum leak through the now open (but plated) EGR valve seat manifold (which is the part the upper end of the tube is on)

[650savag]

Depends on what you mean when you say blocked and plated...

 

With the EGR valve removed, the tube is doing one of 2 things:

 

1) Nothing

2) Providing the intake manifold with a massive vacuum leak through the now open (but plated) EGR valve seat manifold (which is the part the upper end of the tube is on)

 

When I got the truck the EGR valve was blocked (small tubing was cut and bent and the vacuum hose was off and plugged. So it's not really connected or doing anything but just sitting there and blocking the hole where it mounts on the intake. I was planning to build a plate and bolt on in place of it but haven't built it yet. The spring diaphram inside of it works and keeps it sealed off so it doesn't leak air and the truck runs great. If I'm not able to loosen the fittings on the big EGR tube, will it hurt to cut the EGR tube (big tube from intake to exhaust) and just plug the outlets in the intake and exhaust ?manifolds with pipe plugs?

[650savag]

I'll post an update and ask a stupid question. I finished tearing down everything yesterday and I'm cleaning the mating surfaces today on the head, and both manifolds. I picked up the gasket yesterday and I'm wondering if I need to use any kind of gasket sealing compound on one or both sides of it? Also I was wondering about the 2 small gaskets that came in the kit? I believe they are for the connection between the exhaust manifold and the exhaust pipe but I don't know why there is two of them? Is that correct. Also do I need to change out the doughnut looking gasket on the exhaust pipe before I put it all back together? It looks OK but I don't know for sure if it was sealing good. Please, someone or several someones reply ASAP if you can answer these questions. I want to start back together with it today. Thanks again, Dan

[Jason]

It's all in the prep work 650, make sure that you clean the surfaces well, I like to scrape down the surfaces with a single edge razor and then scrub off any bits left over with a with a 3m pad until everything is nice and shiney. The 2 small gaskets, are they for the thermostat housing and cover?

[650savag]

Good news to report. I finished the gasket job yesterday and drove it to work yesterday afternoon. (12 hr. nites). Thanks to DanielC, Datsunaholic, Jason, Hainz, Hang10 and everyone for the good advice, expecially about the 12mm swivel socket. I had to drive to Shreveport to get one at Sears (2 hr. round trip) but I sure could not have done the job without it. Thanks again! Dan

[hang_510]

:thumbup: