Am I crazy for wanting to replace head gasket?

Post by **Charlie69** » Wed Mar 24, 2010 1:54 pm

There are nuts under the intake that need be loosened.

Here is a link to a 78 620 Factory service manual.

http://www.olddatsuns.com/data...8.pdf

You will need Adobe reader to view it. I suggest you download it and burn it to a CD.

Post by **justinae** » Wed Mar 24, 2010 2:26 pm

Hi Charlie,

Really! Are they bolts mounting the intake to the head, or bolts attaching the intake to something else? Of course the obvious question is how does one access them? I downloaded that manual and looked over it but it didn't say anything about those bolts.

Post by **PEZi** » Wed Mar 24, 2010 3:45 pm

basically... there are 4 bolts just like the ones you already removed... just on the bottom side of the intake... with an engine bay like yours where its 'cluttered' it can be a bit hard to reach them and you just gotta see what works for you with the tools you have

Post by **seang** » Wed Mar 24, 2010 3:54 pm

Sometimes if you just can't get at something, you will have to buy extensions and u-joint extensions for your rachet just to get at some stuff. I wonder if you can go through the wheel well at all, but you would probably still need an extension to reach them even if you could. Good job so far.

Post by **justinae** » Wed Mar 24, 2010 4:10 pm

ok who feels like a complete idiot for banging away on a presumably expensive manifold. me!

I honestly don't see how I'll be able to get to those bolts, but I'll try.

thanks fellas.Justin

Post by **Charlie69** » Wed Mar 24, 2010 6:18 pm

I have found that a 1/4 drive ratchet, 3", 6", & 12" extensions with a universal joint worked best for me.

You can see the locatotin for the bolts inthis picture. these will have thick washers on the that pinch the intake & exhaust flanges against the head surface.

On your egr pipe did you try hitting your wrench with a hammer to break ir loose?

Keep going you are doing great. And please keep asking questions.

Post by **justinae** » Thu Mar 25, 2010 5:19 am

Oh man that is the exact picture I have been searching the web for! Thanks man. So those 4 along the bottom are also for the intake? Ok, I'm on it this morning.

And I decided to cut the EGR pipe and deal with it later. If I can actually get the ends out I'm leaning towards soldering. If not I'm leaning towards using a flexible steel tube.

Thanks for the encouragement and help! Greatly appreciated.Justin

Post by **justinae** » Thu Mar 25, 2010 11:21 am

Success! The head is off and I'm on my way to the machine shop before they close. Whoever designed this engine and put those bolts under the intake manifold should be shot!

Quick question. I'm assuming I just leave the valves/cam as they are in the head and the machine shop can still do what they need to. Some of the valves are slightly open, which I also assume is what it's supposed to be.

I had antifreeze floating on top of the #4 piston, but no really obvious head gasket damage.

I'll report back with pics and results from pressure test.

Justin
Modified by justinae at 3:28 PM 3/25/2010

Post by **Charlie69** » Thu Mar 25, 2010 6:03 pm

Yes leave the cam on the head. Be sure the machine checks the head surface warpage. Also have the head magnafluxed & pressure tested for cracks.

If you remove the cam towers (the things the cam sits in) from the head it will have to checked for line bore and possibly be line bored and new cam bearings installed.

I am glad the picture helped. I would have have posted it sooner but I forgot I had it.

Keep us posted.

Post by **justinae** » Fri Mar 26, 2010 6:51 am

Ok, so I'm leaving the head completely assembled. When I took it in the guy said that they could resurface it as long as none of the valves were below the surface. But then he said that if any were they would just rotate the cam. This made me nervous as I got the impression that everything had to go back exactly as it was taken apart, hence the TDC.

I am having it pressure tested, but I read that the magnaflux was only for cast iron?

I did notice that the valves had some gunk on them. I was able to peek from above into the chamber just a little bit. But I don't think it's worth it to completely take apart the head.

thanks again!

Post by **Charlie69** » Fri Mar 26, 2010 7:59 pm

You are rite about magnaflux being for cast iron. Don't worry if they turn the cam. Just watch Hainz video a few more times and it will go back together great.

When you torgue the head bolts beasure to follow the patern and take them to say 30 then 45 then the final torque I think it is 60 ft. lb, but check here to be sure.

http://www.olddatsuns.com/620tech4.htm

Post by **justinae** » Sat Mar 27, 2010 9:43 am

The machine shop won't be able to get to my head until Monday. In the meantime I'll work on the EGR tube and exhaust manifold. Couple questions:

1. Right now the exhaust manifold is still attached to the tail pipe, though the nuts are off. It's held back away from the block with a strap. Can I just leave it like that, clean the surface, then reattach?

2. The EGR tube was cut and a guy at a local muffler shop told me I could get high temperature tubing to splice the cuts back together. This would eliminate the need to get the EGR ends out of both the intake and exhaust manifolds. Is that kosher? Sure seems easier. But just in case, I bought a torch.

3. The #1 piston seemed to have a lot of debris. Is this normal? Is it just a matter of cleaning it out and calling it good?

thanks again man. Here are some pics:Justin

Modified by justinae at 1:14 PM 3/27/2010
Modified by justinae at 1:15 PM 3/27/2010

Post by **justinae** » Mon Mar 29, 2010 10:22 am

I just picked up the head from the machine shop. He shaved off. .007". So now it is 4.244. The book said that a new head is 4.26. Do I need a shim?

Post by **justinae** » Mon Mar 29, 2010 2:54 pm

Gettin kinda quite around here.

Anyway, I'm now attempting to remove the exhaust stud that I broke. See pic. I'd like to replace all three with stainless steel studs but I don't want to risk breaking the other two studs.

I purchased a torch. Is it ok to use the torch in this situation? I'm hesitant because the head is aluminum and the bolts are steel.

I cleaned the manifold gasket surface by using a die grinder and nylon wheel attachment. It left lots of curly marks, do I need to be concerned?

What is the best way to clean the block surface? Is it ok to let stuff fall into the piston chambers and then vacuum it out?

Finally, when I got the head back I noticed there were a few shavings in the valve chambers. I'm just going to vacuum those out, but do I need to be worried?

thanks,Justin
Modified by justinae at 7:40 PM 3/29/2010

Post by **seang** » Mon Mar 29, 2010 7:33 pm

I doubt that you will need any shim, but I'm not 100% familiar with the l20b per-se, only vicariously and limited at that. There is certain amounts of valve to piston clearance that you need, that's all I know.

The swirl marks on the intake manifold gasket surface are not bad, as long as the surface is true; that is what matters.

You can just vacuum those shavings out. For cleaning the head surface, stuff rags down the cylinders.

What did you mean by debris in the #1 cylinder? Just carbon? Yes, just clean it out. If there are any chunks of carbon buildup on the combustion chamber or piston tops, I would get most of it off. You seem to understand that stuff isn't supposed to be all gouged and s***, so I think you can handle any cleaning.

Post by **justinae** » Tue Mar 30, 2010 6:29 am

Thanks man. Well I got a hold of a machine shop and they said the minimum is 4.245 so I'm .001 to short. So I need to shim it. Dang!

Post by **1995D21** » Mon Apr 05, 2010 11:09 am

Hey what did you use to clean the engine in that first pic?thanks

Post by **justinae** » Thu Apr 08, 2010 5:17 pm

I didn't clean the engine in the first pic. That's just the way it was.

Here's pics of the timing chain going back on with new tensioner and right side guide. I used the #2 position.

My notch is close to the line, not perfect, but close enough according to Hainz's video.

I did a lot of cleaning and even decided to spray pain the block and head. It's not professional by any stretch, but it's way way better than it was before. I'll post pics of the the new paint once things are back on.

Post by **breadbox** » Fri May 07, 2010 9:03 am

very nice.

Post by **Charlie69** » Mon May 24, 2010 3:40 pm

Did this job ever get completed? Does it run good now?

Post by **JasonFiske** » Sat Mar 02, 2013 3:50 pm

Justin AE - I'm fixing a very similar truck (same color even!) same repair - and I'm in Portland. If there is any chance you see this - would love to bounce a couple questions off you. JasonDanielFiske AT gmail DOT com.

Am I crazy for wanting to replace head gasket?

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