Well, from my experiences...

If you make a change and a problem develops after the change, it is a pretty good bet the problem is related to the change.


You need to make sure the head gaskets are properly instslled. There is a front (forward) and back (rear) to them. All FE gaskets I have ever seen are marked "FRONT". Depending on the gasket manufacturer it may appear that one gasket is "upside down" when they are properly installed.

There are coolant passages on one end of the gaskets and the passages must go to the rear of the engine.

Improperly installed head gaskets will cause overheating.

 

Okay, so here goes a question as I have never experienced this with a 390... IF you flip a head gasket and get it wrong, how does it react? Do you just get temps that are too high or do you hear popping and boiling from the head that is not right? Is there a way to tell without removing the heads? From memory, I had one gasket that was flipped over so the holes and dowels would line up. Does misinstalling a head gasket create a super noticeable heat issue or is it more insidiously subtle?... like my heating issues?

 

If a head gasket is installed incorrectly, then yes it would explain a few of a symptoms your truck has for overheating issues. Pulling the heads to check the head gaskets is likely a great idea at this point in time.

If a head gasket were installed incorrectly, you would essentially be blocking off a lot of the passages in the block that contain coolant and restrict coolant circulation through the engine.

Take a look at the picture of my 351W block I just posted in my build thread (ignoring the pastewax [film/greasy-looking-stuff] on my head surface and cylinders).



If any of those coolant passages are blocked around the outside of the cylinders where the head mates to the block, you're restricting coolant flow. You're allowing your block to keep more heat instead of passing it on to the coolant which is then dissipated when the coolant circulates through the radiatro. Those passages are small enough as it sits, so restricting even 1-2 of them by blocking them off has the potential to get VERY hot.

 

And actually, not blocking ones that should be blocked has the same risk. The head gaskets on a 302/351W intentionally block off some cooling passages at the front while leaving the rear open, to prevent the rear cylinders from being starved for coolant. Not sure if the same is true on the 390 or not.

 

FE's are similar.

Look closely at the picture and you will see "front" in the red circle. Installed as shown the gasket forces coolant through the block into the head and then to the thermostat.

If the head gasket is installed backwards the coolant will bypass the rear portion of the block and head.

As I posted earlier, when properly installed the head gaskets might look like one is installed up-side down. If you installed the gaskets so they looked the same there is a pretty good chance one is installed backwards.

I can't say that I know of a sure fire way to tell if a gasket is installed backwards.

 

Very interesting.

 

Actually, the head gaskets on the 390 do not block any passages. Or, at least mine did not. That is what had me thrown as I recall verifying that every passage had a hole in the gasket and with one flipped the wrong way, the cylinder bore holes do not line up so I had to flip it over.

The bad news is... I found out exactly what is wrong. I did some more testing and by fluke found out that there is a crack in either the head or the block that does not show up until the engine hits about 150 degrees. At that time, a cooling system pressure tester gauge starts to slowly build pressure. It took about a minute for the pressure to hit 17# and I shut off the engine. I cracked the valve to release the pressure and heard a bunch of air bubbles come from the engine to the radiator. I restarted the engine and the pressure built again, more air air bubbles. Once the crack opened up, the temps went through the normal quick rise process I had experienced before. So... I will be putting an engine in it.

My understanding now is that everything is fine and ducky until the engine temp gets to 150 and then the crack(s) open and start to flood the engine with compression gasses. That allows the coolant to boil and steam in the areas of the block and heads that the combustion gasses pool causing overheating. Yes, I know... it's not new nor is it rocket science and has probably been explained in other posts. My situation just involved a crack that would stay sealed at cool temps evading being found. I just learned a little more about troubleshooting overheats.

 

The 390 head gasket does block the front most coolant passages between the block and heads, similar to the Windsor gasket shown in Bkaul's previous post. There is a front and back to the head gaskets and they must be installed accordingly.

Your new findings are helpful and conclusions are correct, as far as they go. A blown of improperly sealed head gasket will cause the same problem.

You stated in an earlier post that your rig didn't overheat before you did the top end work. I stand by my comments that the root problem lies with the top end being reworked. Cracks in blocks and heads don't just appear and in my experience FE's are typically not prone to cracking.

With a head gasket being installed backwards and the engine being run for any length of time there is a very good chance that the severe overheating seen by the rear portion of the cylinder bank and head that didn't receive cooling could have been damaged. This could be anything from a blown head gasket or cracked block or head, to scored pistons and damaged rings.

Since you are planning on an engine swap, per your last post, pull the heads while the engine is still in the truck and confirm the head gaskets are installed properly. It might save you some time, work and money.

Some other things about trouble shooting any problem...Confirm when the problem started, look for any work performed at that time and go with the simplest fix first.

 

To clarify, I have no idea if the truck had overheating issues prior to me taking the top end off. I got the truck and it did not run hardly at all. The reason it didn't run is that cylinders #3 and 4 intake valves had stuck in the guides and bent the push tubes. This being because the engine sat for 10 years or more without being turned over. I started out taking the top end off so I could clean up the heads and inspect the cam.

The engine has not been run extensively and never into a full blown overheat since I got it running. The plan was to do a long block but the engine really only has 50k on it and cylinder bores are clean with no ring grooves so I am going to strip it and send in the heads and block and have them boiled and fluxed. If I need to replace one of them to make it good, I will. I can rebuild it stock for cheaper than buying a long block and stock is all I need. I will be taking the heads off and confirming the gasket install.

 

My misunderstanding. I understood you to say in a previous post (#29) that you did not experience overheating prior to having the top end off.

Good luck.

 

If you want to verify a combustion gasses in the cooling system NAPA or any other parts store worth going to should carry a Block Test kit. It contains a blue liquid, a clear plastic tube with a rubber cone on one end, and a hand pump/air bladder for pulling radiator gasses through the fluid. If said fluid changes color you have a problem.

 

Coolant pressure should build as the engine warms up, up to whatever pressure the cap will vent it - I'm not sure what you're describing there is indicative of anything other than a normally functioning cooling system. If it was building pressure before warming up, I would think it could easily be due to a cracked head, but if it does it only as it warms up, that's normal.

Now, the bubbles could potentially be an issue. It would be worth checking with a test kit as 54Hydro suggests.

 

I finally gave up on the old engine and pulled it out. After stripping it down to it's undies, I figured out the answer to a lot of my questions... Why if the PO said it is only 50k original is everything wore the hell out? Cuz he is liar. The timing chain had enough slop to run a screwdriver through the gear teeth while turning the engine over. That was the ONE THING I never checked when I was troubleshooting... timing chain slop. Now that I feel totally stupid, I am long blocking the old boy and it oughtta run like a new truck.