My friend has a 425 nailhead block with a about a 4"crack in a water jacket. Is it worth fixing and if so how would you do it?
It all depends on where the crack is...in the head bolt area would be possible with risks. Down low just to hold water is no problem. You must "V" the crack, keep it clean, preheat prior to the weld, and peen the hell out of the hot weld as it cools, to spread the metal as the weld contracts. Weld about 1 or 2 inches, then peen the hell out of it. Airco had a great cast iron welding rod, but I've been away from that work for 20 years and forget the number (310??). Nailhead 425 blocks are 40+ years old and getting hard to find, so I'd sure check it out. Good luck! Frank *************************************************
There's a process caled "s***ching", uses pressed in pins that overlap so one holds the next one in. Do a search here, it's been talked about.
A friend of mine used something called Block-weld(?) or something like that for an auction car he bought, and then discovered exactly why it was auctioned. Had a crack down low on the outside. The Block-weld worked by itself without actual welding!!! He used the car for almost a year before trading it in. I think if you rewelded as Buford said and then used Block-weld just to make sure, you'd be about as safe as you could be. I wasn't there when he used the product, but if I remember correctly, he said he had to loop out the heater core to prevent blocking (because it can't be easily drained once the product goes in it.), add the product to clean water in the well rinsed block...run it for awhile and then completely drain the rad and block. Left it overnight to cure...next day, problem GONE! He WAS nervous for a couple of weeks...LoL Wild how it worked...but maybe he was just lucky...I dunno! I do know that the leak was bad once the pressure went on the system and the Block-weld stopped it completely. YMMV...
Two ways; Weld it or Plug it. Either way takes skill. Welding, I'm not that good at. Fact is, most of the people I know lack the skill, or the machine. At the shops, they always say it's easy, but when the chips are down they say, "can't guarantee". My way is drill/tap/plug. It's easy as pie and fun to do if you're a mechanic. It'll cost you about a C-note to buy the drill, tapered tap, and tapered cast iron plugs. For car motors get the small size. For Diesel Locomotives the large size. REGIS. http://www.regismfg.com/ Being patient is key, get in a hurry and break off the drill or the tap. Put lock-tight on the threads of the tapered plug, screw it in until it pops off. Overlap each plug, just enough to catch the last one. If you're cheap and don't want to buy the tapered tap and plugs from Regis, I've seen straight thread work. You can get a box of 100 for about $4.00. Use 10-24 bolts about 1-1/2" long, at least long enough that there is a shank(not the ones where the threads go all the way to the head). Drill and tap for one, beyond the end of the crack. Don't run the tap all the way through, just in enough to where the bolt binds up right near where it shanks. Experiment on a piece of s**** 1/4 inch plate to nail that technique down. Put locktight on the threads, turn bolt in until it shanks, just snug. Then cut the bolt off flush. Drill next to it, just so the next one overlaps into the edge of the first. Repeat drill-tap-plug, until you've laced the entire length of the crack. There are a lot of people that have an aversion to using stop-leak, I don't know why. I've used it in almost every car I ever had for the last 50 years and it never hurt one of them. Go figure. Anyhow, If you get a seep after plugging a crack throw some stopleak in, it will never leak again.
The Jalopy Journal
