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Fixen block cracks ... 4 Attachment(s)
Hey guys, I just cant catch a brake, I bought 2 more blocks.
The first one I took apart, has a crack in the #6 exhaust port, starting about a inch down in it, running through the seat and down in to the cylinder. The second block I actually pressure tested it before I magnafluxed it. It pressure tested good at 40 PSI, but when I maged it, I found a couple cracks, they aren't leaking, so there not through, I'm thinking, maybe I can "v" them, and braze them.. Any thoughts ? Thanks.. |
Re: Fixen block cracks ... Elwood
Can you preheat the block to @400°, weld, pein, and then slow cool over 24 to 36 hours? That is how we had Cat blocks repaired in the old days. Maybe a blacksmith shop? Bruce |
Re: Fixen block cracks ... Thanks for the Idea Bruce.
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Re: Fixen block cracks ... We drill the ends of the crack, thread the holes, then insert threaded plugs. Then we resurface the deck. This works best in the usual places between the valve seats..
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Re: Fixen block cracks ... These cracks are down in the runners, dont think I can get in there to do that supereal ..
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Re: Fixen block cracks ... I'd be afraid if you heated it up enough to brass it the crack would go further. I've drill and taped and screwed in special plugs in some ports but some you cain't get at. I think on intake ports if you V out the crack use J-B weld it will hold, but I don't think JB will hold in an exh. port. Walt
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Re: Fixen block cracks ... For your consideration. One guy up in my area was taking apart engines with a low success in finding perfect blocks. He started buying good running engines from restored cars and when he freshened them up, he would still find small cracks in them although they were running just fine. Many of the blocks he junked most likely would have run just fine. I couldn't find a head for my farm diesel tractor that had a crack in head right through to a seat. Head shop shop told me to junk it. I took it part because of broken valve spring. Its been back on tractor for 10+ years now and have no issues with leaving the crack alone. I'm not saying to spend tons of money on engine and disregarding details but sometimes if the slight crack didn't cause previous issues, it probably won't be an issue later . Every hole handle just a tad over 10 hp so unless you supercharge it what I see in the picture doesn't look too troublesome. If you find a perfect one fine ,but don't toss the one with these little crack lines.
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Re: Fixen block cracks ... Did you pressure test with air or water? I use air or nitrogen @60 psi and bubble soap. leaks always show. that is a bad spot if it is not leaking at 60# you have 2 choices put it together or scrap it?
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Re: Fixen block cracks ... If you can drill the ends of the crack to keep it from running further you could pin the area you can reach and then sleeve the hole and turn a valve guide down to fit it. A stainless sleeve is how I fixed a hole that was in the #5 intake valve pocket in my pickup motor. I have put several thousand miles on it with no problems. I have another block that I intend to repair the same way.
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Re: Fixen block cracks ... For the 'leave-it-alone' folks... It was about 14 years ago that I had my 59A apart for a valve job, and a couple other repairs. I found one of the 'part-number' cracks, #6, from in the port, across the deck, and starting on the cyl wall. Who knows how long it had been there. It never gave any problems that I was aware of. I agonized over repairing it for awhile, and in the end, just put the engine back together without doing anything to it. So, it's been that way for at least 14+ years, and maybe much longer. The engine is not doing anything bad - no overheating, does not use coolant (can run couple years without adding coolant), doesn't smoke, doesn't use oil, etc.
What more could I ask for? My point - maybe I've been lucky - don't know. But, in this case, doing nothing is working ok. |
Re: Fixen block cracks ... Walt is absolutely correct.
Intake ports respond well to the JB Weld trick. It is unaffected by gasoline, but will degrade with alcohol. If alcohol is present in the gasoline, you can use a product called "Splash Zone" or "Belzona". Both a bit expensive. The only epoxy type product that will withstand the exhaust (other than some NASA ceramic products) is called "ThermoSteel". It will withstand 2000 degrees. To use any of these products, the surfaces must be clean, real clean. |
Re: Fixen block cracks ... Well I did pressure test this block up to 40 PSI, before I maged it, so to start i think Ill mark the cracks and re pressure test it up to 60 PSI and pay close attention to the marked cracks, and If it doesn't leak, I think Ill put it together,
This block is I think the 8th block I have bought that has cracks, but this is definitely the best one so far, This is the first one that didn't leak on the pressure test. |
Re: Fixen block cracks ... I'm pleased to see this thread and the entries to it. I have always felt we tend to overreact to the cracks we find. When they happen, they usually don't get any worse, and a significant number of good running engines are found to have cracks when taken down. The concept of pressure testing is most helpful in isolating those engines you can just leave be. Even cracks that do pass water, can most often be delt with with Bars or water glass.
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Re: Fixen block cracks ... I recently picked up nine flatheads from a local guy for $1K. Two are Mercs, three or four are 59A blocks and the rest are 8BA or 8RT blocks I pulled one of the 8RT's apart the other day and found what appears to be two cracks running from valve to cylinder or water jacket to cylinder. I was planning on scrapping it. Should I reconsider? I plan on selling some of the good stuff and keeping a few parts for my projects. Thanks.
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Re: Fixen block cracks ... I can't see the purpose of pressure testing to such high pressures. The cooling system isn't going to be more than 7 psi at most in operation, why put so much stress on an already suspect block?
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Re: Fixen block cracks ... I found a crack free block and built an engine around it. 1000 miles later I had to take the heads off and there were 2 of the 'part#' cracks in the deck. Crack free now doesn't mean it will stay that way ...
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Re: Fixen block cracks ... In the old days before portable sonic testers I ported through many many blocks. After practicing on a few junkers, I became very adept at silver soldering holes and cracks. All this became a big necessity because it usually happened after you had 40 or 50 hours in the port job.
If you can gas weld, you can learn to sliver solder cast iron in a reasonable time. The big trick is to NOT get the base metal red. And yes it will stand up in exhaust ports also as long as there is water behind it. Cracks are easier to fix than holes which sometimes require backup slugs. |
Re: Fixen block cracks ... I like the silver solder idea Pete.
Ive got a couple blocks that leak under a pressure test, I think Im gonna do some practicing.. |
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Re: Fixen block cracks ... Quote:
Karl |
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