It occurs to me that I have a bare block in the garage right now, that's never had a BHG. I should take a look and photograph the thing up close.
Dealing with the 7M Block Crack
- Thread starter TONY!
- Start date
GrimJack said:
If it hasn't been machined it wouldn't matter. I looked at 3 of the 7 cracked blocks before they were sent out quite closely and the crack was NOT apparent until it came back
soooooooooooooo....the crack only appears after machining? hmmmmmmmmmmm......mayhaps they are being machined incorrectly?
I'm pretty confident that if you clean the deck with rubbing alcohol, then swab it with dye, any cracks will be easy to pick out.
Could be something in the machining process, too. I wasn't planning on having my spare one milled, I am going to find a shop with a surface grinder and have them use that instead, so no ginuea pig with my block.
Could be something in the machining process, too. I wasn't planning on having my spare one milled, I am going to find a shop with a surface grinder and have them use that instead, so no ginuea pig with my block.
Hey guys, I originally learned of the crack through a thread on SF and when I got my JDM engine I very closely inspected the block deck and sure enough there was a crack between the center head bolt hole and the water jacket. The engine was a 40 thousand mile JDM engine that I decided to rebuild with all forged internals. The crack became more apparent after machining but I could faintly see it before.
I was obviously very concerned about the crack and did fairly extensive research on how to deal with the situation. My machinist said that it was a fairly common problem on some domestic engines with similar water jacket/ head bolt hole layouts. I also spoke with one of my engineering professors and he said that complex iron castings are generally designed to withstand small cracks and the crack did not appear to be in a critical place as far as structural integrity of the block was concerned.
It is my opinion that this crack is caused by thermal expansion and contraction of the block and head bolt. My crack was so small that it would not be possible for coolant leakage to occur along the deck suface. The crack can only travel a short distance as well, since the plane that the crack occurs on is cut off on all sides by the water jacket hole, the head bolt hole and a freeze plug. It seems that a large number of people who actually closely examine their blocks discover this crack on one or more head bolt holes, leading me to believe that a very large number of 7M's are running around in this condition. Being that I have never heard of a crack related failure of a 7M I am assuming that this is really a non issue anyway. This does not change the fact that a great deal of 7M's seem to have this crack. I thank Tony for the excellent writeup, and the more information on this subject the better.
I was obviously very concerned about the crack and did fairly extensive research on how to deal with the situation. My machinist said that it was a fairly common problem on some domestic engines with similar water jacket/ head bolt hole layouts. I also spoke with one of my engineering professors and he said that complex iron castings are generally designed to withstand small cracks and the crack did not appear to be in a critical place as far as structural integrity of the block was concerned.
It is my opinion that this crack is caused by thermal expansion and contraction of the block and head bolt. My crack was so small that it would not be possible for coolant leakage to occur along the deck suface. The crack can only travel a short distance as well, since the plane that the crack occurs on is cut off on all sides by the water jacket hole, the head bolt hole and a freeze plug. It seems that a large number of people who actually closely examine their blocks discover this crack on one or more head bolt holes, leading me to believe that a very large number of 7M's are running around in this condition. Being that I have never heard of a crack related failure of a 7M I am assuming that this is really a non issue anyway. This does not change the fact that a great deal of 7M's seem to have this crack. I thank Tony for the excellent writeup, and the more information on this subject the better.
Well, I went out to the garage and examined my spare block. Cleaned up that area until it was shiny, then swabbed it with some blue ink, and even direct sunlight shows no crack at that location.
I'll check again after I get it ground down, just to be sure, of course.
I'll check again after I get it ground down, just to be sure, of course.
I had a problem with this, years before...
I rebuilt my supra engine.I Was aiming for 600 hp....
Sent my block to the machine shop which i was told was a good one.
After they machined the block and I took it home and inspected it I noticed a small crack going from the rear location pin to the cooling jacket. I complained about it and after a week or so they took it back and pegged the crack. I was told if the pegging was done correctly it would stop the crack from increasing. Well I installed the block and ran it...It blew white smoke like a bhg....I removed the head and saw that the crack had increased in length...
I was so pissed and complained again....The shop told me that it wasnt thier fault and other bullshit...I found a good mechanical design engineer who studied the crack and wrote a 5 page report on it...I submitted the report to the automotive company and submitted a personal letter saying i would take them to court. The engineer spoke to them and then finally after what seemed to be a nightmare ended....they gave me another block which i used.
My lesson learnt...Always research companies before givin them your block to machine...
Cheers,
Roy
I rebuilt my supra engine.I Was aiming for 600 hp....
Sent my block to the machine shop which i was told was a good one.
After they machined the block and I took it home and inspected it I noticed a small crack going from the rear location pin to the cooling jacket. I complained about it and after a week or so they took it back and pegged the crack. I was told if the pegging was done correctly it would stop the crack from increasing. Well I installed the block and ran it...It blew white smoke like a bhg....I removed the head and saw that the crack had increased in length...
I was so pissed and complained again....The shop told me that it wasnt thier fault and other bullshit...I found a good mechanical design engineer who studied the crack and wrote a 5 page report on it...I submitted the report to the automotive company and submitted a personal letter saying i would take them to court. The engineer spoke to them and then finally after what seemed to be a nightmare ended....they gave me another block which i used.
My lesson learnt...Always research companies before givin them your block to machine...
Cheers,
Roy
I had a problem with a chipped deck when I was putting some ARP head bolts in a block that was sitting in a junked car for good 2 years. The guy who I got the car from had a BHG and he took the head off and left it in the hatch. The bare block had made home to All sorts of Wasps and other animals 0ver a period of time. The Machine shop cleaned it as best as they could.
I installed the ARP head bolts into the block without the head first to make sure the threads were clean. THe first few went on Ok but then the rest started to get tight.
So I took em all out and rechased the threads, Turns out the holes had mud or sand inside it from what ever the hell had made a home in it. and the deck chipped. Insted of screwing around with it more, I just tossed that block and started on a cleaner one.
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Now, On my cressida block, I was putting my blitz oil pressure gauge so I was trying to take the old oil sending unit off so I can put a T-Fitting in. Well the damn sending unit broke and the threads got left inside the block..
I broke out the ol extractor and put it in the hole and the goddamn extractor broke inside the hole. So I took my dremel and drilled a hole just a little bigger so I can put a bigger extractor in it without the other extractor falling into the block.... Son OF A Bitch, That bigger extractor broke.
I put some JB Weld on the Broken bastard, let it sit over night.
Next morning I took the car to a friend of mine who's got a welding shop.
Showed him the mess. Oil was leaking out of that hole slowly.
He used a screw driver/hammer and broke the JB Weld off of it and then broke out the Torch and some Brass solder. and filled the rest of the Brass fitting hole with Brass. So I have no more oil leaks. Its holding pretty good for now.
As for the oil sending unit and the T-Fitting. I used the hole closer to the front plate right behind the power steering pump and that took care of this problem.
CAUTION:- IF YOU DO ANY WELDING ON THE BLOCK WITH OIL STILL IN IT, MAKE SURE YOU DRAIN THE OIL, POP THE OIL CAP AND DIPSTICK. THE HEAT GENERATED BY THE TORCH CAN BUILD ENOUGH PRESSURE TO POP YOUR VALVE COVEFRS RIGHT OFF THE HEAD
I installed the ARP head bolts into the block without the head first to make sure the threads were clean. THe first few went on Ok but then the rest started to get tight.
So I took em all out and rechased the threads, Turns out the holes had mud or sand inside it from what ever the hell had made a home in it. and the deck chipped. Insted of screwing around with it more, I just tossed that block and started on a cleaner one.
------------------------------------------
Now, On my cressida block, I was putting my blitz oil pressure gauge so I was trying to take the old oil sending unit off so I can put a T-Fitting in. Well the damn sending unit broke and the threads got left inside the block..
I broke out the ol extractor and put it in the hole and the goddamn extractor broke inside the hole. So I took my dremel and drilled a hole just a little bigger so I can put a bigger extractor in it without the other extractor falling into the block.... Son OF A Bitch, That bigger extractor broke.
I put some JB Weld on the Broken bastard, let it sit over night.
Next morning I took the car to a friend of mine who's got a welding shop.
Showed him the mess. Oil was leaking out of that hole slowly.
He used a screw driver/hammer and broke the JB Weld off of it and then broke out the Torch and some Brass solder. and filled the rest of the Brass fitting hole with Brass. So I have no more oil leaks. Its holding pretty good for now.
As for the oil sending unit and the T-Fitting. I used the hole closer to the front plate right behind the power steering pump and that took care of this problem.
CAUTION:- IF YOU DO ANY WELDING ON THE BLOCK WITH OIL STILL IN IT, MAKE SURE YOU DRAIN THE OIL, POP THE OIL CAP AND DIPSTICK. THE HEAT GENERATED BY THE TORCH CAN BUILD ENOUGH PRESSURE TO POP YOUR VALVE COVEFRS RIGHT OFF THE HEAD
PIONEER said:
I did exactly the same thing on a perfect M-EU engine in my MA45, i junked the engine
and got a free 5M-E i re-located the oil pressure sender and have done on every M series engine sence!
as for cracked blocks i have never seen one in person and i have seen ALOT of M series engines over the years!!!