Blown Head Gasket :(

[Mike_The_Grad]

Well the title says it all.

1972 c10 with 350SBC and th350. Engine details: I have about 20,000 miles on the rebuild I did about 4 years ago in my garage. The reason for that rebuild was a blown head gasket. That one was because the head gasket and engine were 20 years old and had sat for 8 years in my driveway with tap water in the block and not being ran.
So I bored the block out to 0.040 over, installed rebuilders pistons, zero decker the block, installed a comp cams XE250H cam kit. Roller topped rockers, a set of remanufactured 882 heads. Stock qjet and stock iron intake. Since then a lot has changed. Ran a 2101 intake for most of the time up until about a month ago when j found out my qjet had cracked venturi booster walls. So a buddy gave me a brand new 2701 edelbrock performer EPS intake with a brand new 1406 performer carburetor. I had to recalibrate the carb which I just had gotten dialed in when this happened. Which was lastnight.
The gasket I'd blown on the driver side cylinder head. I know this for sure because I have true dual exhaust and I have the exhaust crossover ports blocked off.
So I have my work cut out for me this weekend. The only positive I can see in all of this is that I was planning on changing my oil this weekend anyways. Theres always a positive in any situation. The thing I'm wrestling with in my mind is that I'm supposed to get a set of 041 casting cylinder heads from a buddy of mine. But they need to be overhauled and stiffer valve springs installed. But that's at least a week or two out if I were to get them today and get them to the machine shop. This truck is my daily driver so that's not an option. So I will have to just go ahead with the gasket replacement and do it again if and when I get those other cylinder heads.

The other crazy thing is, I have a job interview on Tuesday morning. That's not the crazy part. The crazy part is that I had this exact same job interview last year in March for the same position with the same company. Obviously I didnt get the job, but one week later to the day after the interview I wrecked my truck. It was out of commission for 8 months. But I got it back on the road. Now to have this kind of repair ahead of my scheduled interview is Kind of strange that's all. Lol.
Oh well. It is what it is. And nothing to it but to do it.

[geezer#99]

So, did you get bubbles in your rad and clean looking spark plugs to indicate a blown gasket?

[Mike_The_Grad]

Hey Geezer,
Yes I did have bubbles in my radiator. Plus about half of my coolant "disappeared". The number 7 spark plug was soaked with coolant. Another weird thing is, this is the same cylinder I blew the head gasket on last time. Different set of heads this time. Same block.

And a question to anyone with an opinion. Should I bring the engine up to TDC#1 on the compression stroke before i remove the pushrods? I'm thinking it wouldn't be a bad idea so that when I put this all back together it'll already be on the #1 cylinder so I can begin adjusting the valves.

[geezer#99]

Sure. Put it on #1 tdc compression.
When you pull the head check to see how accurate it is.
Then leave it there.

[Mike_The_Grad]

Sounds good. Thanks Geezer.

[1972RedNeck]

Before you just go put a new gasket in it, I would want to know why it failed. Overheating? Detonation? Bad machine work? Cracked head?

What's going to keep the new gasket form failing in the near future?

[Mike_The_Grad]

1972RedNeck,
I agree with you. I'm fairly certain it failed because of my recent issues with fuel. I had my original 1972 qjet 4mv on there from day one. Well I started experiencing issues with performance so I bit the bullet and pulled the airhorn of it. The float was saturated for starters. But i also discovered my venturi booster walls were cracked. I have a thread up here on it if you wanna check it out. Anyways, a buddy gifted me his brand new 1406 edelbrock performer carb and his brand new performer EPS intake. So I swapped them out. And right off the bat I knew it wasnt right.(the 1406 is calibrated lean from the factory.) So I bought a calibration kit for the carb. This was all within the last month. I began swapping rods and step up springs and got it pretty close to dialed in but it would still get warmer than normal after sustained driving on the freeway. So I took it to the next step and changed the primary jets. The floats in the carb checked out fine. But i also swapped in a new mechanical fuel pump. The airtex brand pump i installed lasted about a week or so, I know this because of the new liquid filled fuel pressure gauge I installed at the carb. The gauge is accurate because my parts guy hasn't had one returned to him in 25 years. Built in America in Anaheim CA. So I installed a Spectra Premium mechanical fuel pump and it works as designed, but it's to high pressure for the edelbrock carb @ 7 psi at idle. These carbs need around 5.5 psi. So my next purchase is a regulator. I digress, my parts guy thinks the failure is due to running lean for to long a period of time. And I agree. My spark plugs are almost pure white and the plug from the #8 cylinder has its electrode partially melted away from the ground strap. Here are some pics. The last pic is withe the number8 cylinder towards the left and the number 2 plug to the right.

[Mike_The_Grad]

Any tips for prep and reassembly? Cylinder heads, block, etc.
I'm heading to the auto parts store to pick up a can of copper-spray-a-gasket to cost the head gaskets. And a tube of high temp thread sealant for the head bolts. The intake manifold gaskets are fine and sealed to the heads still. My exhaust flange gaskets are fine also. I probably should get a new set of spark plugs though. I have everything to do an oil change also.

The gasket blew in the exact same place as the 20 year old gasket did about 4 years ago. Different set of heads this time same block though. It's right below the outer head bolt on the number 7 cylinder. Not one of the ones between the rockers but rather one of the "middle" head bolts. I'll post a picture when I get back to the house. No coolant in my oil. How can j tell if my coolant is still good? I run dexcool and at $18/Gal. The stuff ain't cheap. It looks fine except for the one dead fly and moth floating in it.lol.

[AussieinNC]

I never use any thread sealant on SBC head bolts...

the holes in the block are blind in a lot of locations and a heavy application of sealant can cause a hydraulic lock and prevent the bolt from achieving full torque load...

Worse case I have seen them crack blocks !

Run a tap down each bolt hole in the block to clean out any debris and then use a little anti seize smear on the bolt threads...

I would be checking that bolt hole next to where the gasket blew for cracks...or pulled threads...

I would also not install the Dexcool on the rebuild until you are totally sure the blown head gasket issue is corrected...just fill it with normal tap water and run it for a few days.

[Mike_The_Grad]

AussieinNC,
That's an interesting thought on running straight water. I'm working on cleaning the block surface and I noticed some junk in the coolant jacket on the passenger side. So I started poking at it with a skinny stiff wire a lot of crap became dislodged. So I grabbed my set of mechanical fingers and I was able to pull a few chunks of junk out of there. The rest i blew out with my hand held Hudson sprayer pump. A lot came out.

The bolt hole next to that area that blew out of the gasket has oil in the threads. I noticed on the small block chevy(or at least mine) that the 4 outside middle head bolts are different length(2 per cylinder head, front and back of the head) vs. The short ones that run along the bottom edge and they're not as long as the upper four bolts that are between the rocker stud bosses. I bring this up because on my engine all four of those bolts had oil soaked threads while all of the others didnt.

[Mike_The_Grad]

A few pics.

[geezer#99]

Mike!
You did know know that 9 out of 10 pro builders say use a sealant on steel shim gaskets only. Put the composite ones on dry.

As for water use. I always fire a motor back up with straight water in it. Less mess if you spring a leak.

I see another heat source in your pics.
Wrapped headers.
I’ve heard They can cause the heat in the head to stay higher. Higher heat can blow gaskets.

[AussieinNC]

Mike, your last pic posted shows me the water port at approx 11 o clock location has a small crack at its head bolt hole, that hole does extend into the water gallery space. Can almost guarantee the block surface area between the hole and the cylinder wall is warped....and may be the source of the leak. I downloaded the pic and enlarged the image.

The presence of water in cyl 7 is obvious due to the reduced amount of carbon present on piston top.

If it were mine I would be pulling the engine and have it checked more closely for cracks...if good have it decked, then install studs instead of bolts...studs can achieve much better clamping force over a bolt.

The lower outer row of head bolt holes with oil in them seems strange...you sure you didnt put oil on the threads when installing them? There is no oil pathway to those bolts in the block.

If time and money are a concern, grab some composite style head gaskets and use lots of brush on sealant on both sides of the gasket when installing.

One thing to check real close is that corresponding area on the head that matches where I indicated....check for cracks and warping....much easier to machine head now while it is off....

[Mike_The_Grad]

To confirm what I found and what I did when I assembled the engine. I had the machine shop "Zero Deck" my engine block. Well they reinstalled the original dowel pins back into the block for me. I just took some measurements with my digital caliper. The total depth of the dowel pin recess in the cylinder head is 0.433 inches. The "crushed" thickness of my head gasket is approximately 0.046. The dowel pin height above the engine block surface is about 0.308. The dowel pin diameter is roughly 0.310. Which is exactly the id of the cylinder head dowel pin recess. Also there isnt really any type of chamfer on these dowel pins. The cylinder head has a slightly smaller diameter towards the bottom of the dowel pin recess which starts to taper at 0.250 below the head surface. Basically what I'm getting at is I need to chamfer the dowel pins in the engine block because they are interfering with the cylinder heads ability to sit flush against the block. So, I believe that this is the reason the head gasket was more prone to blowing out. In addition to a lean running condition which is apparent due to all of my cylinder head valves are white as chalk.

[Mike_The_Grad]

Broke out the harbor freight dremel and cobbled this together to put a chamfer on the cylinder head dowel pins. I guess one way to check it is to set the cylinder head directly on the engine block right? Or maybe not incase it's not exactly correct and then the head gets seated to the block and then I'm looking at a new problem. Decisions Decisions...

[AussieinNC]

The alignment studs are just that, only used to align the head during install...

I would just cut the top 1/8" off of the stud and round off the top edge...strange though that the same area failed before the deck as milled and the stud replaced.

What style of gasket did you use? Am I seeing some witness marks on the top of the pistons. Zero decking leaves only the thickness of the compressed gasket to provide quench area under the non chamber areas of the head....your .046 gasket thickness is appropriate to your street engine, but I suspect the thickness is greater where it failed due to lowered clamping pressure.

Lean conditions would provide a "white" residue on the valve heads...it also will contribute to an excess of cylinder heat and will lead to eventual failure.

Say safe...

[Mike_The_Grad]

Well the last time this happened it was inevitable, I believe.
My truck sat in my driveway for 8 years with no hood and only tap water in the block. At the point in time that it was parked, it already had 80,000 miles on the rebuild that was done in 1992, truck was parked in 2005 until 2013 when I got it back on the road. I only regasketed it, valve covers, oil pan, intake manifold, new timing set, and balancer installed. I got 4,000 miles out of it when the gasket blew. Then I rebuilt the whole thing and here I am about 4 years later and 33,000 miles later.
When i rebuilt the motor i did everything myself that i could possibly do in my garage. Installed camshaft, pistons, crankshaft, heads, adjusted valves cut my own spark plug wires. Hei, all for my first time. Oh and I rewired the truck with an American autowire kit while the engine was out. Never done that before either. Took me 40 hours mostly because j didnt have the correct crimp tool in addition to soldering and heat shrink tubing every connection. Anyways. I turned the key after it was all back together and it started on the second turn of the key. I broke in the camshaft and drove it to get a burger and a milkshake 2 miles away because I felt I had actually achieved something on my own for myself for once in my life. The truck ran like crap. Timing was close but it was running lean and the valves needed to be readjusted so I took it to my mechanic for a "tune-up" when I went to pick it up he asked me where I got the motor. I told him I built it myself. He asked who helped me. I told him nobody, besides a couple of buddies for the heavy lifting. He just stood there and said, i have to admit you did a good job for your first motor. I cant say if you'll get 100k out of it, and he said he wasnt sure he would let me do it in his shop. I told him he didnt want to hire me, im to slow a mechanic. I just do it out of necessity and now more as a hobby. There, I think that sums up my c10 experience.
Heads are back on.
Should i install pushrods and then retorque the cylinder head bolts? Or wait a while longer and retorque them and then install and adjust valves?

[geezer#99]

Or finish getting it togethor, run it through several heat cycles and then check the torque.

[Mike_The_Grad]

Hey Geezer. Thanks. I'm thinking I should get this wrapped up. I dont think I'm gonna go with "the right stuff" gasket maker on my valve covers just yet. In case they need to come back off. The stuff is a PITA to clean off parts. But I hate leaks more than enough to use it whenever I can. Lol

[Mike_The_Grad]

Well I got it all back together. It took me 5 days by myself, well including the help I got here. I also came down with a nasty head cold. And nearly depleted my bank account. Not like there was much in there to begin with. But I also managed to miss a job interview I had scheduled yesterday. And my girlfriend is kicking me out of the house. So, life can get interesting pretty fast. At least I have a running truck that I can move all my things out with. And a way to get to work. So things are a little tough right now. But sometimes you have to work for the things you want.

[AussieinNC]

Sorry to hear about the past week or so...chin up young man, things will get better....

It took me two marriages before I found the right one....just stay the high road and you will be fine.

You did a great job to get it running again...and dont worry about how slow you might think you are...there are lots of folk on here that take years to get their projects done...

Keep us in the loop young man...we are here for you...

[Mike_The_Grad]

Thanks Aussie
I'll be alright. I was fine before I met her, I'll be fine after. 6 years is some time invested though.

I appreciate all the input. I think I might have a air bubble trapped in my cooling system as my temp gauge looks to be reading a lil different and if I remember correctly this was an issue I had a long time ago. One way I fixed it was to back my truck down one of the loading docks behind the grocery store and pop the cap on the radiator. 2 big gulps of air came out and after that i was fine. I am running tap water in the block. How long would be considered long enough before i switched back to dexcool? I do have the brand new EPS manifold but that's the only aluminum component of my setup. I dont have a heater core installed. I need to get the leaks fixed before that can go back in.

[Grumpy old man]

I have to ask Why are you using Dexcool ? I remember back in the 90's all it did was cause problems . I've never used it , Just regular Prestone green and I've never had any cooling or head gasket problems ...Ever


https://www.consumeraffairs.com/news...m_dexcool.html

[clay68c10]

X2 on the Dexcool.
Good old green stuff works just fine and no weird problems with it turning into goo.
My 93 has had green coolant in it for years now, no problems.

[AussieinNC]

Ditto on nixing the Dexcool....can cause some issues with some metals and can also just turn to gruel over time...

Just use the auto parts stuff...50% will work fine....

I would leave the plain water in for a few weeks to see if anything else crops up....

On the gauge issue...did you wrap the threads of the sender unit if PTFE tape?

If you did it can cause the erratic behavior...use the metal particle sealer available at auto parts stores....

You did install a thermostat in the engine when you put it back together?

Air has a bad habit of getting stuck in the back upper areas of the cylinder heads....your idea of elevating the front of the truck is a great one....I have sometimes installed bleed valves in the rear manifold areas to ensure the air can escape. (Like a radiator drain valve...)

Stay with it young man