I've been tackling a lot of problems with my 78' 280z's inconsistent idle and timing, etc... I recently ran some seafoam through my system to try to clean any gummed up lines or pathways that might be causing issues with fuel. I actually ended up discovering something else that makes me feel that my issues might be due to vacuum leaks. I found white smoke that appears to be leaking from in between the intake manifold and the engine block. I'd imagine that this could pose a significant cause for my vacuum issue. I plan to remove the intake and exhaust manifolds to replace that gasket and hope that might solve my issues. But I started thinking... if i'm going so far as to disassemble the entire side of the engine block to replace a manifold gasket, it'd probably be the ideal time to go one step further and replace the head gasket as well. I found instructions for disassembly, but i'm a beginner and was hoping to get some advice... Once i have the head removed to replace the gasket, is there anything else I should plan on doing? As far as upkeep or cleaning inside? Like I said, I'm new to this, so if there's anything more I might be able to do, I'd like to do it now while everything is apart. Lemme hear your thoughts.. Thanks!

Check chain slack. You may move the sprocket to the next hole or replace all that while you're at it. New head bolts too. Hopefully you won't snap one of the old ones. A lot more to say but I'm on a quick break now. Others will chime in.

I'd get the tom monroe how to rebuild L motors book from Amazon. Best $20 you'll spend.

 I'd do a compression check before pulling the head. If the compression is good, I wouldn't open that pandora's box. 

27 minutes ago, Mark Maras said:

 I'd do a compression check before pulling the head. If the compression is good, I wouldn't open that pandora's box. 

Rlly? I guess that would save me some time. I'll do that.

Yep, big step up from changing a manifold gasket to changing the head gasket. Not the sort of thing to do as a "while I'm there" if there's no problem and you're not so confident.

 

44 minutes ago, Mark Maras said:

 I'd do a compression check before pulling the head. If the compression is good, I wouldn't open that pandora's box. 

Wait. Wouldn't a leaky manifold gasket result in low compression? I'd have to put everything back together anyway to test compression.

 
Wait. Wouldn't a leaky manifold gasket result in low compression? I'd have to put everything back together anyway to test compression.

No. The valves that seal compression are in the head, not in the manifolds.

don't pull the head off unless its a problem. If you suspect a issue with the head gasket, start with checking for exhaust gases/oil in the radiator, and oil in the pan. If those are ok then leave the head alone. Typically I would expect an exhaust leak to present as a noise, and intake would be hard to notice unless it was pretty bad. You can smoke out intake leaks with a cigar and a hose after blocking the TB with a cup.

IF there is a manifold leak its likely the exhaust on the back of the head. That is were one of the bolts typically breaks off, leaving #6 with just one bolt holding the manifold up tight to the head. After a while the hot exhaust will eat up the gasket and you will get a loud "tick" sound. You can find it easy with a 1/2" rubber hose hold one end to your ear, move the other end around the exhaust and listen for the tick.

 

White smoke can be just something burning off, have you sprayed any chemicals around the engine?

Here are a few things I like to do just to base line an engine, after its warmed up take a vacuum reading note the vacuum numbers as well as any erratic movement of the needle, do a compression test write the numbers down for future reference. Put in new plugs, drive it 10 miles pull them and take pictures for future reference.

 

 

3 hours ago, moozieman said:

. I found white smoke that appears to be leaking from in between the intake manifold and the engine block. 

If the white smoke appeared while you were "Seafoaming" it would be an exhaust leak.  But there could still be an intake leak in that area.  The way to test would be to start the engine and spray some carburetor cleaner at the spot where you saw the smoke.  If the intake gasket is leaking the idle speed will change.  Probably increase.  Spray, listen, spray, listen.  Confirm an intake leak first.

You're right on the edge of creating a non-running car.  Even changing the intake/exhaust gasket can be difficult, with broken bolts and ez-outs and drilling.  Removing the head gets you in to timing chain issues, with the potential for dropping the chain and needing to remove the timing chain cover.  Big hairy problems....

What's the history of the motor?  A lot of miles or pretty fresh rebuild?  Does it smoke on start-up?  You like driving it or working on it?

It may be time to freshen it up but that's what I always do, get it roadworthy, dependable.  I'd rather work on mine anyway.  I guess it's time to buy another one instead of talking other people into working on theirs.  

1 hour ago, siteunseen said:

What's the history of the motor?  A lot of miles or pretty fresh rebuild?  Does it smoke on start-up?  You like driving it or working on it?

It may be time to freshen it up but that's what I always do, get it roadworthy, dependable.  I'd rather work on mine anyway.  I guess it's time to buy another one instead of talking other people into working on theirs.  

It has 121k on it but I honestly don’t know the history too much.

1 hour ago, Zed Head said:

If the white smoke appeared while you were "Seafoaming" it would be an exhaust leak.  But there could still be an intake leak in that area.  The way to test would be to start the engine and spray some carburetor cleaner at the spot where you saw the smoke.  If the intake gasket is leaking the idle speed will change.  Probably increase.  Spray, listen, spray, listen.  Confirm an intake leak first.

You're right on the edge of creating a non-running car.  Even changing the intake/exhaust gasket can be difficult, with broken bolts and ez-outs and drilling.  Removing the head gets you in to timing chain issues, with the potential for dropping the chain and needing to remove the timing chain cover.  Big hairy problems....