RichBad

1928 Series 128/129 Fast Four engine rebuild

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Oh my god!! that’s devastating. I truly feel for you after all that work you’ve done. 

Did they face the block for you?

seems a strange thing to happen. 

I saw a fast four engine at Pete’s the other day. 

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What would cause something like that?  I wonder if there was already a small crack around a stud that let loose when you torqued it?  If there was something between the head and the block, I would think the head would have gone first.  Man, I really feel for you, that motor was looking great.

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Oh Boy, I feel the pain. That dreadful sinking feeling.

 

The vertical crack is open at the top, meaning the metal is stretched laterally. The sub-horizontal crack below indicates stretching vertically. It is like the metal has pulled upwards as a bulge, perhaps due to an opening above, such as a depression in the block deck or head surface, or a too-compressible gasket?

 

You were at 35 lb.ft; what size and thread are the studs? If they are 7/16-14, 32 lb.ft is max for Grade 2 bolts; for 7/16-20 threads, 36 lb.ft is max recommended for Grade 2 bolts.

 

I see you have you have removed and replaced the studs (post #15). Is it possible the stud turned rather than the nut and you have bottomed the stud in the hole, pushing up the block metal?

 

Edited by Spinneyhill (see edit history)

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Has me baffled.  Head and block were both skimmed.  Studs were new and tightened first with stud lock so I don’t think they would have turned, I’m pretty sure all the stud holes are open into the water jacket. The studs are 7/16 unf and I was tightening progressively (with some wait time inbetween to let the gasket settle).  Maybe it was a bad gasket, I’ll pull that and have a look.  There could have been a crack initiated, the engine builder removed the old studs and said they were seriously hard to remove - perhaps that stressed it? But they did crack test and pressure test the block (but not sure if they did that before or after remiving the studs).

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7/16 UNF = 7/16-14? If so, you would have exceeded the suggest torque for that thread in Grade 2 bolts. You can put Grade 8 bolts in, but you are still in old cast iron so should stick to the Grade 2 recommendations.

 

Another possibility is that the cooling jacket is thinner than it originally was. I see there are holes beside most of the head studs. This would leave less metal to resist the torque. Remember, they only did them up "tight enough", by hand with no measurement, in 1928.

Edited by Spinneyhill (see edit history)

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I wonder if the engine guy has put to much heat around the studs when he was trying to get them out. 

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Spinney, just checked - 7/16 x 20 tpi.  I was told 45lbs for these, my plan was to go to 35 then leave until i was ready for the first start.

 

Matt, you may be right, it’s quite thin there and easy to overheat.

 

i just pulled the head off and it is quite thin in that area which probably didn’t help.  The stud holes are all open ended but I did notice the stud was slightly lower than the others (only 0.020 - 0.040) but perhaps the stud wound in more and the non threaded section of the stud ‘forced’ the hole open?

 

I also noticed that one on the front had cracked too, again it’s pretty thin there too.

 

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Black day today, my wife found my bill from the engine shop for my ‘paperweight’ and I’d promised my son it would be ready for his end of school year:(. Oh well, how does that monty python song go...

 

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2 minutes ago, Tinindian said:

Is this a case where it would be possible to stitch the block?

I don’t know what’s possible, I’m guessing not in that area but I don’t have any experience with what can be done with block repairs.

 

would be good if it could!

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Geez, what a tough story, I'm planning to button up the head on my '31 Straight 8 Chrysler and was told everything from 65 ft lbs down to 50 ft lbs, and now thinking I may go to Gorilla Glue!! No fun when this happens. I'd rather blow a head gasket than ruin a block or head. My studs are also 7/16" x 20TPI, 27 nuts on a 30" long head. Some of the studs are drilled into solid part of block, some pass into water jacket area. Those are the ones I would think are most likely to crack if any. I guess "fingers crossed" you start with a careful consistent tightening sequence and head toward 40 ft/lbs and go from there. At 40 ft/lbs, what is worst that can happen when engine is running at moderate speeds. When I took the head off 6-7 weeks ago, the head nuts seemed to come off pretty easily, perhaps 40 lbs torque, and looked to have been original , engine had 60,000 miles, and no sign head had ever been removed. Was initially concerned if the 7/16"x20 acorn head nuts would be suitable for 50lbs+ torque, and now it appears that is the least of my concerns.

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Yea, cracking was the last thing on my mind - I was more worried that I was going to pull the threads, apparently that can happen quite often on these.  I would have thought that the threads would give before something cracks but not the case for me:(. My engine was up and running 18 months ago and the only thing different since then is all the engine machining - I can’t help but think perhaps a crack was started when the old studs were removed. I didn’t pull them out as I was scared I may damage something (they were in very tight) the engine shop said they would machine them out to avoid any damage.  when I picked up the engine, the studs were in a bag with the other engine parts and hadn’t been machined (but did have some pretty large marks from some monkey grips or mole wrench).

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Took the block back to the machine shop today as I felt the way they removed the old seized studs may have contributed to the cracking (they clearly used a lot of forces as the studs were bent and had large wrench marks in them).  First thing they said was that they had seen some cracking around some of the studs before they started but they didn’t think it would be a problem because they were already there.  So why do the crack test and charge me $100 for it if they aren’t going to use it!  Interestingly, when they did do the original crack test they did say that there was a crack in the tappet area so they did a pressure test.  But that was before they removed the studs.  Anyway, they thought that they may be able to repair with threaded plugs, I’m less confident.  Will find out tomorrow.

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That’s a bit of a worry Richard I would think with the cracks going to the outer edges that would not work in my opinion. I don’t know if you could ever be  confident running around with that engine. 

For your sake I hope they can repair it successfully.  

 

 

 

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It is always the same They always come up with a load of B/S as to why their work failed  I hope tat you fond a solution to the problem

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Yup, agree Matt - I don’t think it will work in a highly stressed area but they wanted to check it in a bit more detail so I’ll give them a day.

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Called today and they are mid way through repairing it, they said it’s no problem.  Still have my doubts but they said they will pressure test when done.  I asked if they will torque it down any they said only lightly.  I asked them to fully torque it for the pressure test as I don’t want to rebuild it all only to find that it goes when I torque it up.  I’m nervous but I also don’t much like the other option of starting almost from scratch on another block.

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39 minutes ago, RichBad said:

I asked them to fully torque it

Have you given a torque specification? Do they know what might be reasonable for that engine?

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Good point - I haven’t.  The 45lbs I was told seemed reasonable any less seems quite low for a head - anyone have experience with lower torque on these heads?

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Torqued the 7/16-14 head bolts on my 32’ Olds flathead 6 to 42# with no issue but all were new grade 5 rolled thread,high head bolts made 20 years ago. Like your motor, the majority of the holes are open bottom into the water jacket. 

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Picked up the repaired block today and they said it will be all good.  They just repaired the large two cracks but not a couple of small ones on the front - they said because it was quite thin walled it would weaken it further and because the small cracks go into the stud hole which is sealed with the studs it would not leak.  They torqued it up and pressure tested it to 45psi to test the repairs so I guess it’s good.  I also spoke with the guy who did the repair and he seemed to know what he was talking about.  He was also surprised that it had cracked as he did the initial crack and pressure test - I asked him if the old studs were in when he did his checks and he said they were.  Really makes me think that removing the old studs caused the damage (or at least weakened it) as the marks on the studs look like they took a huge force to remove.  

 

Time me will tell - they did quite a neat job with the repair and luckily Matt gave me some extra paint so I could patch it up.

 

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Edited by RichBad (see edit history)
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4 hours ago, JayG said:

Is that still a crack showing left of the bolt to the cylinder wall?

No, it’s just a stain - I think from where they pressure tested it - definitely not a crack.

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Right, back to where I was a couple of weeks ago!  Have torqued up to 20lbs and will leave to settle overnight and next step tomorrow.  So far all good ?

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How good does that look!!!

thats such great news Richard. So glad they could fix it well done. 

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