Would like your $.02 please.

[travlnman]

I have a '78 Z , all stock with supposedly 93k original miles. Looks like I have a head gasket change in my near future. My current setup is N42 block (stock) and N47 head (stock).

 

My main fear is, that in pulling the head and having it resurfaced and sealed with a new gasket, I may open another can of worms. I know that sometimes when a fresh new seal is applied to a 30+ yr old cylinder , the rings may be the next to go. I could pull off a gasket change in a day, no problem, but has anyone ever had a problem with piston rings failing on a newly sealed head ?

 

I have read every thread having to do with heads, detonation, etc, but no mention of ring failure. My local salvage yard has a complete '78 , from which I could acquire the whole engine , tear it down and give it a complete freshening up . It's just my project car/toy, so no big deal on being down for a while. Not looking for a big HP gain, just want a reliable weekend driver. If no one has had ring issues, my just pop for the gasket swap, otherwise, I'm off to the salvage yard. Thanks in advance.

[gregkring]

Rings would not be next to go. Your engine may be more likely 193K miles, but not too big of a deal for a Z motor. if you can get a core cheap, however why not start from scratch and build a motor you know is good.

[travlnman]

I have seen the ring issue on chevy's and ford's , but have never heard of it on an L6. Otherwise, this engine runs great, just eats coolant. No external leaks, and yesterday added some stop leak to radiator, on the off chance it was a small high pressure leak I missed. As soon as the thermostat opened, and started to circulate the stop leak, I began to see a light blue puff of smoke out of the tail pipe when i would blip the throttle. The car uses no oil otherwise.

[macambra]

Don't compromise, I found a free n42/n47 set. Cylinder walls still have the cross hatching so I changed the bearings, new head gasket. Went cheap and didn't change the rings. 6 mo.s later I am blowing by. Checked compression-#5 is 85, 1-3 are 155-160. Don't waste your time.Do it once!!! $150 at napa saves alot of time.

[Tony D]

Questions back before guessing:

1) why is a 'head gasket change in your future'?

2) what is the current compression and leakdown per cylinder?

3) why do you assume the head needs resurfacing?

 

Without those being answered, anything is a guess and may not be remotely applicable to your situation. All tools needed to properly diagnose these items are less than $100 at Harbor Freight.

[GrayZee]

I would just fix the problem at hand, my experience is that the top end goes long before the bottom end does. Besides, how much do you stand to lose if something goes wrong in the near future? A few hours of your time and a head gasket. Sounds better to me than spending alot more time and money on rebuilding a whole engine that probably didnt need it in the first place.

[BRAAP]

3. Please make a good effort to post a topic "subject" title that is pertinent and descriptive of the subject that you want to convey. When you post a thread with a title like “I need help” this makes it harder for the next guy to find what he is looking for when they try to search the database. It is impossible to know what that thread is about so it must either be skipped over or opened to check the content. The title of your post is not the place to be VAGUE!!!

 

Aside from that' date=' my input parrots Tony D.

Questions back before guessing:

1) Why is a 'head gasket change in your future'?

2) What is the current compression and leakdown per cylinder?

3) Why do you assume the head needs resurfacing?

 

Without those being answered, anything is a guess and may not be remotely applicable to your situation. All tools needed to properly diagnose these items are less than $100 at Harbor Freight.

[steve260z]

I replaced the head gasket with a new cam. Left the bottom alone and compression has remained the same...160...for the last 5k miles.

ss

[travlnman]

Tony D and Braap,

 

I know a head gasket is in my future. My car drinks coolant with no external leak. It will pressurize the overflow tank and blow the top off of it. After adding stop leak the other day, immediately upon the thermostat opening, I almost immediately got a light blue smoke out of the tail pipe, and the car does not burn or use oil otherwise. Also, I doubt anyone here would pull a head to replace a gasket on a car with 92k/192k (take your pick) and not have it surfaced , at least I would not. Did not check compression , as the above reasons are enough for me, I'm not a pro like some here, but not a novice either. I could easily pull down my engine or a salvage unit and build it from the top down , and I plan on just that, just not this soon. The budget is a little tight as lots of folks are. The long range plan is to take it off the road and overhaul the entire drivetrain. I also have a small leak on my rear main, so all of the above may well just answer my question. One responded that his rings had failed, on had not. As of now I have a 50/50 shot with the responses so far. That coupled with the rear main and such will probably justify at least a bearings , rings, and gaskets.

 

All that being said, WHEN I pull the head and have it surfaced, since it's an open chamber head, how much can I shave without needing to shim cam towers and such ? May even throw in a small cam while I'm at it, and along with the "krylon rebuild" just call that my engine overhaul for a while.

 

As to the posting rules, sorry, did not violate on purpose, more out of ignorance. I frequent many forums for Z's and other vehicles, as many do, I don't read the "rules and regs" as well as I should, just "agree to" and keep going. I don't even try to keep them all separate , not that much room left in the old hard drive.... you fellas go easy on the coffee now

[jc052685]

Ok, the head gasket needs to be replaced......now what was the cause? Fix that!

 

If its a stock build just throw a head gasket on there.

[travlnman]

I have already fixed the cause. The previous owner was trying his best to turn it into a "ricer" clone. Gauges screwed onto the A-pillar, that lit up, but were attached to nothing ?? Cut the original exhaust off, and ran a straight through 2 1/4 " pipe all the way out the back , big coffee can tip, no muffler. It was so loud it hurt to drive it. I'm all for to each his own, but wow. The timing was cranked way up, and it would detonate on 93 octane, he just could not hear it over the exhaust.

[Ineptitude01]

I'm with BRAAP and Tony D, but if all you do is a head gasket, even if there's still some underlying problem, a head gasket is a pretty cheap part, and this would give you a good excuse to do the manifold gasket, valve cover gasket, and have the head checked. If it's good, you don't need to resurface it, and having that knowledge is always a load off your mind.

 

And if you do... Good machine shops shouldn't charge too terribly much for a refresh, especially if you supply your own stem seals, which you'd get in the head set that included the gaskets I just mentioned. My local shop, Lynn Automachine in RWC, charges $10 a valve, and there's just nothing like seeing the head completely clean. Then you're a valve adjustment away from fun times (potentially).

 

A compression check is a good idea, too. The more you know about your engine, the better equipped you are for whatever it might throw at you (rods? ) in the future.

 

Bottom line: Changing the head gasket won't make it run *worse*.

[BluDestiny]

I've changed a head gasket and then drove cross country 2 days later. The rings probably won't go. Just get the head milled to freshen it up a bit. Don't go shaving a ton off

[BRAAP]

If you are wanting just a quickie temporary fix to get you by as you start acquiring the bits and pieces for a more permanent long term powerplant;

 

1) Run this one till it dies then park it till it the long term powerpalnt is ready.

 

2) Find another running core for cheap, swap that in for the time being, though you could end up inheriting other issues.

 

3) Just as BluDestiny said, pull the head, clean the block deck really good, surface the head, but only enough for 100% clean up, so long as it wasn't a ton of material removed, just bolt it back on and go. If the head is warped excessively, you should also finish dissembling the head and have the top decked as well as the cam line wont be straight, or find another useable head core.

 

4) If this is the long term powerplant, you best bet is just pull it and rebuild it.

 

 

Hope that helps.

[travlnman]

Thanks guys. Like I said , it's not my primary means, so down time is not a big deal, just love driving the thing. I originally bought it to have to fix up with my son (15) and if he's really lucky, maybe let him drive it one day.

[Tony D]

"Also, I doubt anyone here would pull a head to replace a gasket on a car with 92k/192k (take your pick) and not have it surfaced , at least I would not. "

 

I think me an Blue Destiny are two that won'tresurface a head unless there is a REASON to do it. Channeling, warpage, something.

 

I pulled my head at 243,000 miles because I was SURE the 3/4 cylinder fire rings had blown and either the head or the block had channelled (by compression test alone 150, 150, 100, 100, 150, 150)...

 

Pulled head, NO channelling, nothing. Lapped the valves, and found they were not well seated. Drove the car 18,000 miles in the next three weeks (from SoCal to Kingston Ontario Canada, Boston, around most of the PNW, and the Great Lakes Circly Route)---no resurface of the head whatsoever.

 

Matter of fact, LAST WEEK I finally pulled the intake-exhaust gasket (FelPro Rectangular Gasket on a Roundport N47 head with the Rectangular Port Stock Exhaust Manifold on it) now 10+ years later after no issues whatsoever. Pulled it because the MSA collector flanges caught on something, jerked the exhaust, and broke the manifold...

 

Now it has a round port header which I will never use on anything else once that E88 gets here from Mr. Shewbrook.......

 

But I digress. Because it's off does NOT mean it needs surfacing! Doing maintenance for maintenance's sake just wastes your time and your money. Like BD and Braap mention, there ARE instances were it may be called for, and then it's due more than just a simple decking on one side....likely you are better finding another example in that case.

 

The heads surfaced start getting less and less serviceable. Shims only go so far. Eventually you end up with a head that can't be shaved at all any further.

 

The economics of just letting it run and replacing it are hard to beat compared to 'interim' repairs.

[Ineptitude01]

Again, I'm with Tony D. I didn't resurface my head at all for my build. I checked it for warpage or other damage, and it passed by any metric. Strong degreaser and a razor blade got the deck surface smooth and clean, and a toothbrush got the nooks and crannies. The only time I've ever resurfaced a head was for my CRX Si, which overheated badly in a previous life, and even then, it wasn't warped by much.

 

"If it ain't broke..."