But come on, how could you not love Bertha?
My last entry ended with a puddle of coolant on the garage floor. Some investigation traced the coolant from the floor up to the oil pan, up the side of the oil pan to the engine block, and up the side of the engine block to the passenger-side cylinder head. At first I thought maybe it was coming from the sender for the temperature warning light. Or maybe "hoped" would be a more accurate word than "thought." The temperature sender would be easy to tighten up, or even to remove and re-install, if that's what it took. It wasn't the temperature sender. A little further looking traced it to one of the head studs. "[Expletives.]"
The head bolts on a Chevrolet Mark IV big block thread into through-holes which pass into the water jacket. Because of this, it is necessary to use some type of thread-sealer on the bolts in order to prevent coolant from leaking out of the water jacket past the threads.
When I used Bertha's block to build Matilda's engine, I decided to use ARP head studs, instead of head bolts. I didn't really need to use studs, but I guess I wanted to use some neat-o race car stuff. Anyway, ARP is a widely-respected manufacturer of automotive fasteners, and they suggest that you use their brand of thread-sealer on their head bolts and studs. It's easy to cynically imagine that the main reason they specify that particular sealer is because they make it, so they can get some more of your money if you buy it. But, I also know that there are a lot of engineers in the world who work at determining the best way to do things, and work at fixing problems that have already occurred elsewhere, and sometimes that's why particular products are recommended. So I try to make it a point to follow manufacturers' instructions. And so I got a tube of ARP thread-sealer.
And the ARP thread-sealer worked just fine, on about 29 of 32 head studs. But three of them were leaking. One outside the rocker cover, which is the one that leaked onto the garage floor, and two more that I found after I pulled the rocker cover.
I'm not saying that I think there's anything wrong with ARP's thread-sealer. By the time I found the coolant leaks, it had been over a year since I had installed the cylinder heads, so I didn't really remember the details of how I installed the head studs. But, the instructions for the ARP thread-sealer say to knead the tube, in order to mix it before using it, and referring back to an old blog entry, I could see that I'd installed the passenger-side head first, so the studs that were leaking may have been the first three I installed. I developed a theory that I either hadn't mixed the sealer before using it, or at least hadn't mixed it well enough. I have no reason to think that the ARP sealer wouldn't work fine if used properly, but on the other hand ... once bitten, twice shy, I guess, so I started looking for other options.
Years and years ago, my dad got me a Haynes book on overhauling Chevrolet V8s, and I referred to that book quite a bit while building Matilda's engine. It suggested using Permatex No.2 on the head bolts, but I had used the ARP sealer because that's what ARP recommended. After finding the leaks, I asked a few people what they recommended, and checked the halls of internet knowledge. That resulted in a few suggestions of various RTV products. But the Permatex No.2 documentation states that it is "non-hardening," which authorities seem to agree is important for sealers used on head bolts, and I have a positive history with Permatex, so I decided to try using No.2.
I didn't want to pull everything apart if I could avoid it, even though everyone says that's the smart way to do it. I decided first to try re-sealing the threads with the engine in place in the car. I figured that if it didn't work, I'd be no worse off and I could still pull everything apart for the final fix. If it did work, I'd save a lot of time and effort.
I made a plan, and first I drained all the coolant, by pulling the lower radiator hose. Then on a Saturday afternoon I started by de-tensioning all the passenger-side head studs. Then I removed a head stud, and prepared to clean the threads in the block. I was surprised, however, to find that there was still a lot of coolant trapped in the engine block. I didn't want to try to seal the bolt holes while they were wet, so I got a hand pump, stuck a piece of 3/8" hose into its end, stuck a piece of windshield washer hose into the 3/8" hose, and wrapped the joints with electrical tape. The windshield washer hose would fit into the bolt holes, so I could stick it down into the engine and suck the coolant out of it.
After the coolant had been sucked out, I proceeded with cleaning the threads for the stud that I had removed. The Edelbrock heads that I used came with some long head bolts, because there are four (I think) bolt holes per head that require longer bolts than the stock bolts. But the stud kit that I got was made for the Edelbrock heads, so I didn't need the long head bolts. So I took one of those long head bolts and used an angle grinder to cut grooves through the threads, to turn it into a sort of a shadetree tap, so that I could use it to try and clean the threads in the block. I ran that tap down into the hole, used a wire brush to clean the threads on the head stud, then I applied Permatex No.2 to the stud threads, re-installed the stud and snugged the nut down on it. Then on to the next stud, and repeated the process for all sixteen studs.
I went through that process, one stud at a time, removing the stud, cleaning the threads on the stud, cleaning the threads in the block, applying No.2, re-installing and snugging the nut. All in all, it took about three hours. Enough time to play Days of Thunder twice on the TV in the garage. Cole Trickle won the Daytona 500 both times.
Only one thing left to do, just torque the head studs back to spec, to finish the job. I felt really good about how the whole deal went, and I was feeling confident that there would be no leaks when I was done. And then, on the last stud in the torque sequence ... something didn't feel right. And when I say "something didn't feel right," I mean "I immediately knew that the thread had pulled out of the engine block, but I was hoping in the name of everything holy that it hadn't." But the stud never got tight, and eventually some investigation determined that, yes, the thread had pulled out of the block. Having worked through denial, that only left anger, bargaining, depression and acceptance to go.
It seems stupid now, but when I started the project, I had thought that it would probably take two years, and I hoped I could have it done in one. I was four years in at the point when the thread pulled out of the block. After four years, I had thought I was on the verge of finally getting the car running and driving so I could take it back to the body shop for them to finish the paint. Now instead, I would have to, at an absolute minimum, remove the carburetor, intake manifold, and one cylinder head. More likely, I would have to remove the entire engine from the car. It seemed likely that this would set the project back at least six months, if not longer. Depression came easy. Acceptance would be more difficult.
I started considering my options for thread repair. I have used Heli-Coil in the past, and Keensert. But there was also the question of how much to disassemble the engine, whether to attempt to do the repair in the car, or whether to attempt the repair myself at all. My main concern with doing the repair myself was that if I didn't drill the hole square to the deck of the block, then I might just create more problems in the future. I knew that there was a magnetic base drill at work that I could probably borrow, but the bolt hole that needed to be repaired was at the end of the block closest to the firewall, and under the low end of the open hood, so it would be very difficult to maneuver the large and heavy mag base drill into that space. I could remove the engine from the car and use the mag base drill outside of the engine bay, but by the time the engine was out of the car, it seemed like it would be easy at that point to just get a machine shop to do the repair. I definitely didn't want to pull the engine, attempt the repair, reassemble the engine, reinstall it in the car, and then find out that it still leaked.
One thing that helped to make the decision was a conversation I overheard at work. I heard one of the technicians talking to someone else about an engine he was working on for a friend's mud truck. He said something about "We told him he better take the bottom end and get it balanced, but he didn't want to spend the money on it, so we said, fine, but you're going to regret it later." I felt stupid when I heard that, because it had never occurred to me that I should get the bottom end of my engine balanced. I had just figured that if I was buying parts that had been individually balanced, and which were all intended for the same model of engine, then they should all go together and work fine together. As I started to research the subject, I came to learn that I didn't even understand what it means to balance a bottom end, or why it's done. It goes to show that, no matter how much you might know about a general subject such as engines, there's always more to learn. Anyway, I think this article was very helpful in filling in several gaps in my knowledge. In hindsight, it makes sense that aftermarket parts suppliers can't know what other aftermarket parts you'll be combining with their parts, so they can't know how to balance their parts to work with whatever else you buy. It seems so obvious now, I feel pretty stupid for not having known it before.
Anyway, I overheard these comments at work, and my mind went back to the camshaft break-in for Matilda's motor. There had been a low-frequency vibration that I could feel through the floor of the car. I didn't know what to make of it at the time, but now it seemed likely that it was because the engine hadn't been balanced. At this point, I had already committed to the idea that the engine would have to come out of the car to repair the block. It would be another setback on top of that one, but just one more step to commit to the idea of completely disassembling the engine so that the bottom end could be balanced. And since I would be taking the crank, rods, pistons, etc. to the machine shop for balancing, I decided that I might as well have the machine shop repair the block, too.
I called my favorite machine shop and talked to the owner. When I told him that a head bolt thread had pulled out of the block, he asked if it was one of the doweled holes. There are two holes on each bank that are countersunk to take a dowel sleeve which the bolt passes through. The dowels accurately locate the head so that the valves and sealing surfaces are in the right places relative to the block. I told him, yes, it was one of those doweled holes. He explained that, because those holes are countersunk, there is less thread engagement there and it is common for those threads to pull out of old blocks. That made me feel a little better, as I had never heard of such a thing before, and I was wondering if I had done something wrong that had caused the thread to pull out. Interestingly, several months later, after the repair was completed, I saw this article, which explains why threads pulling out of blocks is becoming a more and more common problem, so that made me feel even better still.
Anyway, the machinist said it was no problem to repair it. I was feeling a little paranoid about the rest of the bolt holes, though. I once rebuilt a Holley carburetor, and when I went to put it back together, one of the threads for one of the float bowl screws pulled out of the main body. This was another case where I was worried about getting the hole drilled perfectly square with the surface, so I had that repair done by a machinist also. He fixed it, and I took it home, went to reassemble it, and another thread pulled out. I was using a nut driver, with a screwdriver-style handle, so I hadn't put hardly any torque on it, but it just pulled out. And it hadn't even gotten hard to turn with the nut driver, it just went soft and pulled out. So I took it back to him, and he fixed that one. I took it home, went to reassemble it, and a third hole pulled out! I couldn't believe it. In this case, my stages of grief were trending strongly towards the "anger" end of the spectrum. I took it back to the machinist and when he saw me walk in with it he said, "Are you using an impact wrench on this thing?" I tried to force a polite laugh but just said, "Just do all of them." So he fixed the one that needed fixing, and the last hole, too, even though it hadn't pulled out (yet?). Ever since then, when I have a thread pull out of a part, I start to get paranoid about all the other threads in the part. So when I talked to the machinist about the thread repair on the Impala engine block, I asked him what he thought about just Heli-Coil-ing all of the head bolt holes in the block. He said that would get pretty expensive, since it's 32 holes in total, but that he would suggest just doing the four doweled holes. That made sense to me, so we agreed on that plan.
So, it was a very discouraging turn of events, and really hugely disappointing. In fact, words don't even really begin to capture the feeling of discouragement I had after the thread pulled out of the block. The only saving grace was the incremental way in which the situation developed. First, I had some coolant leaks. Eventually I accepted that, and made a plan to repair them. Then a thread pulled out of the block. I accepted that, and made a plan to repair it. Then I realized that I should have had the bottom end balanced and the whole engine had to come apart. At that point, it was just one more step.
However, in hindsight, things really worked out for the best. If I hadn't had the coolant leaks (or even worse, if the leaks had only been coming from studs under the rocker cover, and I didn't find them), or even if I had been able to repair them with the engine in the car, I might have been tempted to just ignore or "live with" the vibration in the engine, and hope for the best. And maybe it would have been fine. Or maybe it would have resulted in catastrophic engine failure, who knows. On top of that, there were a few other things that had been nagging at me which I was able to address when the engine was disassembled. So in hindsight, the coolant leaks and the thread pulling out of the block appear almost as if Bertha's engine block was saying, "Wait a minute, slow down, buddy. This isn't right. This needs to come apart, and do it right this time."
So, like I said at the beginning of this entry: How could you not love Bertha?
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| Engine comes out. |
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| Empty engine bay. |
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| Engine disassembled, parts boxed up and loaded in the Charlie-10, to go to the machine shop for block repair and balancing of the rotating assembly. |
