Megiddo Posted January 23, 2022 Share Posted January 23, 2022 I was changing my header gaskets today to get rid of a small exhaust "tick". I was very surprised when I pulled out one of the header bolts and a stream of coolant came gushing out. Apparently, when I had my engine and heads rebuilt last year the machinist ran a little deep when chasing the threads on the head. Anyway, can I use RTV on that as a thread sealant or do I need to do something more involved? Thanks, Tom Link to comment Share on other sites More sharing options...
mat in tn Posted January 23, 2022 Share Posted January 23, 2022 try whatever. but you need new heads Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 23, 2022 Share Posted January 23, 2022 I wouldn't use RTV. Instead I'd use a thread sealer, like Loctite 56747 PST. Had the same issue on a 351M and that's what I used. Worked well. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 23, 2022 Share Posted January 23, 2022 try whatever. but you need new heads I disagree. As said, I had the same issue on a 351M where someone drilled too far in to install a helicoil. The Loctite PST did the trick. And, as Bill/85lebaront2 pointed out to me back then, the 383 in my SuperBee came from the factory that way. Link to comment Share on other sites More sharing options...
mat in tn Posted January 23, 2022 Share Posted January 23, 2022 try whatever. but you need new heads I disagree. As said, I had the same issue on a 351M where someone drilled too far in to install a helicoil. The Loctite PST did the trick. And, as Bill/85lebaront2 pointed out to me back then, the 383 in my SuperBee came from the factory that way. I have not found a need to drill when chasing threads. it's more likely a crack. it's true that you can seal threads that enter a coolant passage. outer head bolts for example. but when it's a fault I don't trust it. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 23, 2022 Share Posted January 23, 2022 I have not found a need to drill when chasing threads. it's more likely a crack. it's true that you can seal threads that enter a coolant passage. outer head bolts for example. but when it's a fault I don't trust it. In my case the PO wasn't chasing threads. He was drilling out the hole to tap and install a helicoil and somehow went too far. And in that case there isn't anything wrong with the head. But I agree that if it is a crack then the head is bad as it'll probably continue to crack. So I recommend that Tom checks to see if his head has been drilled too far or if it is cracked. I'd think that would be easy to ascertain by sliding a drill bit in to see how far it goes in comparison to the other holes. Link to comment Share on other sites More sharing options...
Megiddo Posted January 24, 2022 Author Share Posted January 24, 2022 In my case the PO wasn't chasing threads. He was drilling out the hole to tap and install a helicoil and somehow went too far. And in that case there isn't anything wrong with the head. But I agree that if it is a crack then the head is bad as it'll probably continue to crack. So I recommend that Tom checks to see if his head has been drilled too far or if it is cracked. I'd think that would be easy to ascertain by sliding a drill bit in to see how far it goes in comparison to the other holes. I'll try that, but the volume of fluid that came out made me think it was more than a crack. I think its drilled too deep. I don't know if my header bolts vs. the original manifold studs could have contributed. My machinist did do some extra work on the head as a different bolt hole had been drilled crooked for an easy out and had half a bolt "keyed" into the head with half an easy out. He then ran a tap through the the rest of the holes to make sure the threads were solid Will the locktite sealant make it difficult to get the bolt out next time? I don't plan on taking the headers off in the near future, but I seem to be good at twisting bolts off. Link to comment Share on other sites More sharing options...
Megiddo Posted January 24, 2022 Author Share Posted January 24, 2022 I'll try that, but the volume of fluid that came out made me think it was more than a crack. I think its drilled too deep. I don't know if my header bolts vs. the original manifold studs could have contributed. My machinist did do some extra work on the head as a different bolt hole had been drilled crooked for an easy out and had half a bolt "keyed" into the head with half an easy out. He then ran a tap through the the rest of the holes to make sure the threads were solid Will the locktite sealant make it difficult to get the bolt out next time? I don't plan on taking the headers off in the near future, but I seem to be good at twisting bolts off. The hole in question is about 3/8 inch deeper than the rest. I'll try the sealant. Thanks. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 24, 2022 Share Posted January 24, 2022 The hole in question is about 3/8 inch deeper than the rest. I'll try the sealant. Thanks. That sealant won't make it very difficult to get the bolts out. It is kind of a cream and sets up a bit, but not hard by any stretch. I use it on lots of things and really like it. Link to comment Share on other sites More sharing options...
mat in tn Posted January 24, 2022 Share Posted January 24, 2022 The hole in question is about 3/8 inch deeper than the rest. I'll try the sealant. Thanks. 3/8" deeper is significant, that is easily the casting thickness behind the bolt. that sounds like they drilled too far for certain. in this specific bolt position, is it possible to use a stud with a nut to tighten instead of a bolt? I know header bolts with reduced heads are the norm but some positions are tighter than others. in fact, fords factory mustang headers are clearance'd so full-size bolts can be used. I know they don't flow as much but they fit so much better Link to comment Share on other sites More sharing options...
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