No steps forward and 3 back.

[Roger P.]

Re: No steps forward and 3 back.

Hi Doug,
Congratulations on finding the problem... what a nightmare!! Now you can either get the crack fixed if possible or just replace the head. I would bring it back to the machine shop so they can stand behind their work. Like you said, it's hard to imagine that they magnafluxed the heads. They should be held responsible to correct the problem -- with or without a warranty. It's just unfortunate that you had to build the engine and tear it down 3 times. That's a lot of time & effort for you! Save me a cocktail to toast your masterpiece after you take me for a victory lap around the neighborhood

Roger

[John D.]

Re: No steps forward and 3 back.

Mystery solved. Magnaflux found a crack aproximately 1/4 to 3/8" long on the surface of the head that mates with the block deck. The crack is located between the intake and exhaust valves just inside the ring of the head gasket. It does not extend to either of the valve seats. It wasn't visible to the naked eye, or at least not to mine. Have not yet been back to the machine shop that did the work. I suppose it could be welded and pressure tested. I see used 3782461 heads on Ebay from $400 to $600 each. The problem is I have no way of knowing if they are good. Next stop machine shop. I'm not convinced they magnafluxed the heads. The crack is certainly in an area that would have been checked.

Whew!!!!! Thanks be to God. Your persistant &hard work paid off Doug. I have been worried about this issue as it's not the norm especially after a fresh rebuild.
I would look for another head and not get yours repaired.
Don't worry about getting a certain date code. Just get a good 461 and test the crap out of it. John

[Joe C.]

Re: No steps forward and 3 back.

Mystery solved. Magnaflux found a crack aproximately 1/4 to 3/8" long on the surface of the head that mates with the block deck. The crack is located between the intake and exhaust valves just inside the ring of the head gasket. It does not extend to either of the valve seats. It wasn't visible to the naked eye, or at least not to mine. Have not yet been back to the machine shop that did the work. I suppose it could be welded and pressure tested. I see used 3782461 heads on Ebay from $400 to $600 each. The problem is I have no way of knowing if they are good. Next stop machine shop. I'm not convinced they magnafluxed the heads. The crack is certainly in an area that would have been checked.

If the valve seats were replaced then one or more might have gone into water. If any of those seats were leaking, then that is the reason for your crack. Especially at shutdown/heat soak, the leaky seat insert will weep coolant into the hot chamber and crack it. If that is the case, then they can still be repaired. The seats are removed and sealant applied before reinsertion. The crack CAN be welded, but this process warps the head and requires full machining to true up all surfaces. A better option, and one which works is a stitch repair. It might be cheaper for you to find a replacement head. This time don't have hardened exhaust seats installed.

[Doug L.]

Re: No steps forward and 3 back.

Visited a machine shop on Friday that was recommended by a Corvette shop known to JD. The Corvette shop didn't do head work and told me they didn't. They recommended a specific machine shop and said they take all such work to them. Off I went to the machine shop called "John's Cages" and I was impressed by the owner. Fourty years in business. I received a detailed tour of the shop. He also recommended against welding the crack as the "introduction of more potential cracks at the weld". But he told me that if the head could be repaired he would use some sort of "J" clip to pull the crack together. He drew a sketch but I still didn't completely understand how it would work. He said he would clean the head and magnaflux everything again to determine if the crack is the only one and if it could be repaired. He said if he thinks it can be repaired and I proceed he will guarantee the repair. So now I'm waiting for his decision and the cost.

As to the shop that did the machine work on the heads, they tell me they did mag the heads before doing any work. I can't prove otherwise and the engine did run a few times before exhibiting the problem. Regardless I'm not having anything else done there. While I wait for the results of the testing I plan to rotate the engine to get the #8 piston at the top of its stroke to try to determine if the rod bent. In my favor is the fact that the rods are new Eagle units that are supposed to be much stronger than the original GM connecting rods.
Doug

[Joe C.]

Re: No steps forward and 3 back.

Visited a machine shop on Friday that was recommended by a Corvette shop known to JD. The Corvette shop didn't do head work and told me they didn't. They recommended a specific machine shop and said they take all such work to them. Off I went to the machine shop called "John's Cages" and I was impressed by the owner. Fourty years in business. I received a detailed tour of the shop. He also recommended against welding the crack as the "introduction of more potential cracks at the weld". But he told me that if the head could be repaired he would use some sort of "J" clip to pull the crack together. He drew a sketch but I still didn't completely understand how it would work. He said he would clean the head and magnaflux everything again to determine if the crack is the only one and if it could be repaired. He said if he thinks it can be repaired and I proceed he will guarantee the repair. So now I'm waiting for his decision and the cost. As to the shop that did the machine work on the heads, they tell me they did mag the heads before doing any work. I can't prove otherwise and the engine did run a few times before exhibiting the problem. Regardless I'm not having anything else done there. While I wait for the results of the testing I plan to rotate the engine to get the #8 piston at the top of its stroke to try to determine if the rod bent. In my favor is the fact that the rods are new Eagle units that are supposed to be much stronger than the original GM connecting rods. Doug

Be sure to have the head pressure tested before taking it home. This is to check the valve seat inserts for leaks, as well as checking the stitch weld repair for leaks. Watch the first and then the second video for the full process:

http://www.youtube.com/watch?v=Pq0wfU4ZaKk
http://www.youtube.com/watch?v=FIKY--USk7Y

Again, if you don't have too much invested in the cracked head, it might be cheaper to find another.

[Doug L.]

Re: No steps forward and 3 back.

Thanks for the links Joe. That was very interesting seeing how they do the repair. I get the feeling that what the machine shop described to me is a different process. I'll ask him to show me how he does it to see if it is the same. Now that I have watched the links I'm wondering if buying a new head would be less expensive. The process seems very labor intensive. I'll keep reporting back to this thread.

[Loren L.]

Re: No steps forward and 3 back.

Congratulations on finding the solution and Good Luck. For your other problem - rear gear changeover - find a buddy with a 250/300 HP and give his wide-ratio first gear Muncie a test drive.

[Doug L.]

Re: No steps forward and 3 back.

I'm back with an update and more questions. After having the head checked and told there was a crack in the combustion chamber I took the head to a new machine shop that was highly recommended by a local shop that specializes in Corvettes. I was dealing directly with the owner / operator who has 40+ years of experience. He cleaned the head thoroughly, magnafluxed and pressure tested it. The area that was IDd as a crack turned out to be a casting flaw and his tests showed no cracks. He gave me some things to look for on the block.


The block was bored and sleeved by the previous shop. The sleeves in cylinders 2,4 and 6 are flush with the top of the block but the sleeve in #8 is below the block deck by enough to catch my fingernail on. I'd estimate 1/64" below the deck. I also found that the head gasket that was on that bank has openings that are larger than the cylinder bore. I can't get a dimension because the openings in the gasket are not completely round but the outer edge of the sleeves are completely inside the impressions on the deck by the gasket's Stainless fire rings. Placing the old gasket back on the block shows that the fire rings of the gasket did not cover any portion of the outer circumfrence of the sleeve. The new shop told me to look at that area for that type of situation and that if I found this situation it was probably the source of the water. He said water under pressure and sucked in by the vacuum created by the piston stroke could travel between the block and the sleeve and if not stopped by the head gasket, would enter the combustion chamber. He also told me that his sleeving process is to stop the over bore before reaching the bottom of the cylinders, thus creating a "step" at the bottom so the sleeve could sit on this step. I asked the assembly shop to ask the machine shop that did the original work if they left such a step. I have no response yet but imagine that the sleeve being below the deck surface is a strong indication that they didn't and the sleeve has dropped to its present position.

I would like opinions of whether the situation described above could result in water entering the combustion chamber. Since there was no problem with the adaptor plate and no cracks in the head, I don't see another source for this water unless it is a crack in the sleeve. I have not yet removed the piston and can only see the upper 1/2 of the sleeve until the piston comes out.
Thanks in advance,
Doug

[Stuart F.]

Re: No steps forward and 3 back.

I hate to be the one who pointed a finger at your sleeves, and I wish I could give you some answers and insight from my experience with them on our poncho engine, but that was over 50 years ago. I vagely recall that, back then, they left the step at the bottom of the overbore, then pressed the sleeve down in to seat on the step. Now I'm not sure exactly why, whether the sleeves were of different lengths or not all the overbores were of equal depth, but the sleeves stood up above the block surface at different amounts and were then machined off as part of a "decking" process. So, they should all be perfectly flush with the deck surface. Also, if memory serves me, the block was heated in a furnace and the sleeves were chilled in dry ice before being pressed into place. It wasn't a very scientific process. I was not present for the tear down process, but I recall that it was said that the sleeves had not seated properly and several had displaced in the block. I would hope they had a better process developed since then, but I know we never considered trying to do that again after that experience. Perhaps some of the others can shed some insight on the subject.

Stu fox