The Stovebolt Site Forums The Shop Area Engine Shop Cracked block

Hello guys,
Got word from the rebuilder today that my org 59 235 (thrift master) block has a hairline crack (approx, 16") visible by magnaflux. I spoke with another 50's Chev guy who said he has seen alot of running engines that had visible cracks that ran fine for years and didn't leak water or oil. Spoke to a welding shop that told me it wouldn't be worth the effort and cost nor could they guarantee it. Engine rebuilder won't give any opinion as he doesn't want to make any calls.
1- Any opinions on how big a deal a hairline crack only visible by magnaflux is.
2- I have the 848 head(presuming it's good) are there any differences in the 235 blocks between years?
3- Do I search only for late model blocks (say 58-62). Are they better????

Disappointing news.
Thanks in advance for you replies and expertise

Where is the crack?

Going over there in another hours to discuss, i'll report back

Answer to question 3...the blocks are not too much different aside from the oiling scheme. Most people think the oiling scheme was better in the later blocks and that may be true, however I would not base my decision on that alone. Here is one notable difference: the camshaft used from 1959 and up to 1962 was better. Be it hydraulic or be it solid it was designed to produce more torque at lower rpms and it did that. Max torque was reached at 2000 rpm and the torque line is pretty level from about 1600 over to around 2600. Years ago there was a memo on the GM Heritage site that explained what they did and how it helped. They were trying to help reduce smog from bumper-to-bumper traffic and the thought that more power at lower rpms would be helpful was one of their first steps. Good luck!

It sounds like your engine builder is looking for an excuse not to finish the job. You should ask if they have done any pressure testing or other diagnosis to determine if the "crack" actually goes all the way to the water jacket or if it's just a cosmetic blemish. I'm going to guess a crack that long is the result of frozen coolant. It usually happens right at the bottom of the water jacket just above the oil gallery that runs the length of the driver's side of the block. As long as you don't run a high pressure radiator cap (4 PSI or less) a crack like that can be patched with "Marine Tex" sealant by grinding the block smooth about an inch or more wide in the area of the crack and applying a layer of the sealant. As it's curing, press a piece of 40 grit sandpaper over the patch to duplicate the surface texture of the crankcase. When the block is painted, the patch will be virtually invisible.
Jerry

Just for reference. I had a 350 block with short cracks on both sides, they were only exterior cracks into the water jacket about 1.5" long. I chose to have a welding shop make the repair only because the block was a 4 bolt, high tin, high nickel casting. I built the engine as a 355, put it in my 3/4 ton crew cab and put 100,000 miles on that engine.

If it makes you feel better, my engine has a crack that someone repaired many years ago. It's on the lower rear passenger side near the water outlet petcock.

It was a very sloppy patch job with JB Weld or possibly Marine Tex but it doesn't leak a drop. It just looks bad.

I also use a 4 lb pressure cap.

We had a similar issue, an external hairline crack. Ours was on 216 ci engine installed on our 1948 Chevy truck. We researched the issue and that there is company in California (I thin) that does Marine / Ship engine repairs and they sell a kit for repairing engine blocks. The process was beyond our technical capabilities and we didn’t pursue it. However, we did find a powder sold by a supplier in Europe and we did purchase it and added the product in accordance with their instructions. It took some 10 miles of running and the seep reduced and now so far is not seeping.

Here's the crack, about 8". He said it had been leaking coolant as evidence of rust underneath the crack. Engine sat in the truck(1959 Chev 3100) for about 25 years. So I never ran it. Simply pulled the motor and dropped it off with him. He is a very reputatble and experienced builder, 42 years in business. Seems very knowledgeable. No other major problems. He said he gave up many years ago trying to weld cracks. He never had any luck with cast. Hoping the pic loads up.

Yes, that's exactly where I expected it to be. I'm getting ready to fix a block with a crack almost twice that long, and it will be leak-free when I'm done. Too bad you're not a little closer to Tennessee- - - - -I'd be glad to take it off your hands! For a pressure-tight fix, do an internet search for the "Lock-N-Stitch" crack repair method.

https://www.ebay.com/itm/150905769851?

Jerry

That is a incredible technology Hotrod. They are based in Turlock south of me. I will give them a call and inquire tomorrow. Thank you very much and others for your opinions and help.

That is a typical crack commonly found on these engines. Since it so low on the block, it has no impact on the cylinders or anything else except a slow coolant leak. Make sure to have all of the crud cleaned out of the bottom of the water jacket.The bottom of the water jacket is rel close to where that crack is. I had a 216 crack like that after the thermostat failed to open on a hot day. the water jacket was full of crud. I had it welded, but it just resulted in more, smaller cracks going vertical. I ended up cleaning out the water jacket and Marine Texed it. I ran it for 40,000 miles like that. It still ran like a fine clock when I retired it to upgrade to a 350 and spent 20,000 to making it a show stopper and sold it for $55,000.
I'd have the machine shop finish the machine work and ask him not to paint it so that you can patch it up with Marine Tex as Hotrod describes.

Turlock- - - -sounds familiar- - - -I spent a few years doing industrial maintenance, pipe welding, and maintaining vehicles at E & J Gallo winery in Livingston. Headed back home to Tennessee in 1980, and they don't print enough money to ever get me back to California!
LOL!
jerry

Jerry
I have a question for you (after discovering a crack in my block) Does the antifreeze need to be drained from the block before using the Marine TEX epoxy? It only leaks when the engine is running.

Yes I know I am resurrecting an Old thread.

Thanks in advance!

Yes, the block needs to be clean and dry to avoid seepage from the crack interfering with the epoxy getting a good bond. I'd suggest draining the coolant and using a flap wheel on an angle grinder, or maybe a die grinder to clean an area about an inch on both sides of the crack down to bare metal. Maybe groove the crack out a little to allow the epoxy to build up a little thickness. Warm up the repair area with a Propane torch to evaporate any coolant residue before applying the filler. Just as the patch begins to harden, press a piece of 40 grit sandpaper onto the surface to duplicate the texture of the casting. Once it's painted, the patch will be almost invisible.
Jerry

Jerry
Thank you for reply. You are a great source of knowledge to this community and I (as well as many others I am sure) truly appreciate all the you contribute. Thanks again!

I'm the middle of 5 generations of wrench jockeys, from my grandfather to my grandson- - - - - -a little over 100 years of attending "Universitas Impactus Maximus" (the school of hard knocks). If I don't pass on some of that experience, it will follow me to the brown side of the grass one of these days! LOL!
Jerry

i bought a 235 locally and it was laying on the floor in this guys garage with new bore job and new pistons and a supposedly new reground crank and all new bearings, no head, what could go wrong!! after putting a rebuilt head on and in the car we started to fill it with water. to our dismay the water just poured out of a hairline crack almost the full length of the block. my dad said lets dump some Bars Leak in it and throw a blanket over the radiator and get it good and hot. this was back in the 60's i had it for about 4 years it never leaked a drop. i sold it and it ran for another 3 years that i know of, it may still be running today!!