I have a crack in the lifter gallery of my 1967 427 block, casting number 3904351 with two bolt main caps. The crack does not presently extend very far into the casting and has been filled with a JB Weld-type material. The crack has not resulted in the deformation of the lifter bore although it looks like it has in the attached photo. Are there any recommendations about anything I can do to prevent the crack from spreading or other precautions I should take before I rebuild the engine?
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Re: 1967 427 Cylinder Case Crack
John-----
You can prevent the propagation of a crack like this by drilling very small holes at the end of each crack-line. The holes must intersect the crack-line with NO amount of the crack-line on the both sides of the hole and you really need to drill them right through the casting section in order to ensure the complete containment of the crack. In your case, one end of each of the crack-lines terminates at the lifter bore. The lifter bore, then, terminates" that end of the crack-line. So, in your case, you need to drill the holes only at the other end of each crack-line.
I would drill the holes about 1/16" OD after PERFECTLY center-punching the hole center with a SHARP center punch. After drilling, you can fill the holes with an epoxy like JB Weld. No strength is necessary, here; you're just sealing the holes and the JB Weld (although it is strong, too) will work just fine.
The above procedure will prevent any further propagation of the cracks. However, it will not repair the existing cracks. In your case, I don't think that it's necessary. However, if you wish to repair this sort of crack, I'd find someone expert at "pinning". "Pinning" or "stitching the crack" involves the tedious process of drilling and tapping a hole at one end of the crackline, installing a special tapered, threaded pin, drilling another adjacent hole overlapping the installed pin and the crack-line and continuing until the entire creack-line has been pinned. Due to the location of your crack, this will be an especially difficult process, but I think an expert could do it. It will also involve honing of the lifter bore due to the protrusion of the adjoining pins. Another option would be to drill out and install a sleeve in the lifter bore after the pinning was performed first. I'd recommend this, actually, as I think you'd have a stronger overall repair.
Lifter bore repair sleeves are available for your engine under GM #14044875.
I would not recommend any sort of weld repair, at all.In Appreciation of John Hinckley -
Re: 1967 427 Cylinder Case Crack
John,
Joe has covered this subject well however I would like to vote for the process of drilling out the lifter bore and replacing with a sleeve. Most machine shops that build racing motors perform this process as routine. It squares the lifter bore with the crankshaft and produces less friction and more horsepower. In your case this would be perfect to address the problem. If you cannot find this service locally, I can provide you with the number of a local machine shop that will provide the service along with any other machine service needed. It would be a PITA to ship the block but the results would be well worth the effort. I am assuming this is the original block for your Corvette. If it's not, just chunk it and find another block without a similar problem.
The machine shop is Cabot Automotive at 1 501 982-4930. Ask for JD Wooley the owner and cranky old fart that runs the place.
Regards,
JRComment
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Re: 1967 427 Cylinder Case Crack
Joe ----
Thank you for the very detailed recommendation. I would like to do the right thing the first time as my instinct tells me that the crack could get worse and the casting might become unrepairable. The cost and effort of pulling and tearing down the engine after rebuilding is also a factor. Is this something that you would send to American Cylinder Head Repair in Oakland (that I beleive you have mentioned before)? Might be a good excuse for me to attend the Western Regional in April. Would drilling the ends of the cracks and sleeving the lifter bore be a reasonable first step or would this be just a cost compromise in lieu of the better approach of pinning? Thank you again, Joe, for sharing your knowledge.Comment
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Re: 1967 427 Cylinder Case Crack
JR----
Thank you for your thoughts in addition to Joe's. Is Cabot in Arkansas?Comment
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Re: 1967 427 Cylinder Case Crack
John,
Yep, All the way to Cabot AR.
JRComment
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Re: 1967 427 Cylinder Case Crack
John, there should be some engine builders in you area that specialize in high performance engines. Misaligned lifter bores was/is a problem with all engines therefore creating the need for shops to be able to correct this. The standard practice to remedy this is to bore/sleeve. I would check around your area before that I shipped my engine a long distance. No problem with the shop that JR recommended, but just trying to save you a dollar or two on the freightDick WhittingtonComment
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Re: 1967 427 Cylinder Case Crack
Dick ----
Thanks for the recommendation. It's a long way from here to JR's neck of the woods and I do like to save money if I can. I also feel better about shipping it myself in the back of my truck.
JohnComment
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Re: 1967 427 Cylinder Case Crack
John-----
American Cylinder Head Repair is still in business and they've been around a LONG time (like, maybe about 50+ years). However, I don't know who's running it these days. The fellow that ran it for years was Einer Elbeck. The last time I was there, he was still in charge. But, that's been a long while and he was no kid then. So, I don't know if he's still there, or not. For a shop like this to stay in business, though, I would expect that there's some sort of "continuum of experience". If I were you, I'd call first and discuss your situation with them and describe, in detail, the crack that you have. You might ask for Einer and see if he's still there, or not. If he is, you should have no trouble. If he's not, you might want to "feel out" whoever you talk to in order to discern if he sounds like he's someone that knows what they're talking about. A guy like Einer will leave no doubt in your mind.
In my mind, a repair like I first described (i.e. drilling the small holes in the end of the crack to prevent further propagation, filling with JB Weld, and installing the sleeve in the lifter bore is a permanent solution. It might seem a little bit "hokey" to drill the holes and fill with JB Weld, but I really think that this will be a perfect repair. You'll absolutely stop the propagation of the crack and, limited to what exists now, I don't think that the crack will be any problem. The lifter bore repair with the sleeve might be a bit of "overkill", but it will absolutely ensure that the crack is permanently isolated from the lifter bore. Of course, the lifter bore sleeve, by itself, will not prevent propagation of the crack. So, it's the COMBINATION of these 2 repairs that, in my opinion, will render the situation adequately and permanently repaired. I really don't think that the "pinning" is necessary. I suggested that only because it might make you feel better. That's about all you'd get out of it compared to what I've suggested.In Appreciation of John HinckleyComment
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Re: 1967 427 Cylinder Case Crack
Joe ---
Thank you again for taking the time to post such a detailed response to my questions. You always impress me with your responses which are precise and clearly understandable. You are right that there is an element of feeling good about the repair, particularly when it is a major component. Preventing further propogation of the crack is clearly the first priority as it appears to be confined to the area shown in the photograph. If it spreads any further, it will be very difficult to drill. Sleeving the lifter bore will eliminate my concern about changes in the shape of the bore as the area around the crack is heated and cooled. The JB Weld does sound kind of "hokey" but seems to make sense if you think of it as a filler. I also appreciate your evaluation of the additional benefits of "pinning" the cracks as that would be a major undertaking in terms of crating and shipment in addition to the cost of the work.
Thank you again, Joe.Comment
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Re: 1967 427 Cylinder Case Crack
John-----
One other thing: if you drill the holes I suggested to prevent propagation of the crack, make sure that the holes don't go through any oil galleries. From the picture, it's hard for me to tell if this would occur. However, it shouldn't be too difficult for you to tell by "eyeballing" it and noting the position of the cam tunnel oil passageways. Even if you do have to go through oil passages, that doesn't mean you can't do it. All it means is that you need to do something else besides the JB Weld to seal the holes. In that case, I would drill and tap both sides of the hole for small, short machine screws, installed with sealer. That will resore the integrity of the oil passages while the crack will be completely "terminated".
If the holes don't go through any oil passages, then you really don't even have to use any JB Weld if it bothers you. The holes really don't need to be sealed in that case. Personally, I would use the JB Weld to do it, anyway, but you don't have to. In this case, the JB Weld sealer is really just "frosting on the cake".
By the way, JB Weld is used in many industrial applications to repair heavy machinery and, even, industrial engines. It's very versatile stuff and it's very reliable. Personally, I would not use it for any high strength application, but filling these holes requires no structural strength, at all. You're just filling the holes. The JB Weld is impervious to all engine chemicals and it will withstand heat significantly greater than it's ever going to have to. If the engine ever gets hot enough to break down the JB Weld, that circumstance is going to be the least of your problems.In Appreciation of John HinckleyComment
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watch the water jacket
Be careful about drilling at an angle toward the cylinder or you may get into the water jacket. Take one of those pocket lights with the flexible end and stick it through one of the bigger deck water passages to light up inside the jacket. Then you can look through the water passages and head bolt holes to see where the water passage goes (you can use a coat hanger to measure the depth of the jacket by sticking it down the hole, can also look for casting core shifts). This part of the block casting is hard to sonic test for thickness. Found out about that years ago from someone building stroker motors.
Good luck,
MarkComment
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Re: 1967 427 Cylinder Case Crack
There is an oil passage running parallel to the crank which intersects the center of each lifter bore at a ninety degree angle. I assume that the lifter bore sleeve is, or will have to be, drilled and properly aligned so that this passage is not blocked. Other than that, I don't see any other oil passages in the immediate vicinity of the cracks. The crack on the right in the photo has a terminus just below where the lifter gallery part of the casting abuts the cylinder portion. The terminus for the other crack is in the lifter gallery itself and can almost be discerned in the picture. I have had very good luck using JB Weld in anumber of different applications and understand why it would work well in this repair to "fill" the holes. Thanks again for your help, Joe.Comment
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Re: 1967 427 Cylinder Case Crack
John------
The GM lifter bore repair sleeves are not pre-drilled for the oil passages. However, this obviously has to be done as part of the installation. There are 2 ways to do it. First, the sleeve can be installed as-is and then the holes drilled after it is in place. This is the best and most precise way to do it, but it requires tools that many machine shops might not have. The second way to do it is to precisely locate where the holes need to be drilled prior to installation. Then, the holes are drilled in the repair sleeve prior to installation in the block. It's then necessary to very precisely install the sleeve. This is really not all that difficult, though, if one is very careful. If very slight "mis-alignment" occurs, it won't cause any problems.In Appreciation of John HinckleyComment
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Re: 1967 427 Cylinder Case Crack
Joe ---
Thank you again for the additional advice. Upon further study, it appears that the crack continues through one side of the lifter bore and is rather shallow (about 3/8 of an inch at its maximum depth). It certainly seems logical that the steps you have outlined will isolate the crack without any other adverse consequences and without having to ship the casting out of state.Comment
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