Just got a call from my machinist today to tell me that I have a small hole in my cylinder wall. He told me it started out as a small blemish before he started the bore, and as he bored it the hole got bigger and bigger! The cylinder wall is paper thin. Is this common with these 7m blocks? Can you not bore them to 84mm? Its possible to install a sleeve in the block, but I am worried that there will just not be enough meat to support the sleeve. And the sleeves them selves are only about 1/8" thick, I planned to put 30psi on this sucker. I am considering calling this project quits, which really sucks cause I have spent a ton of time and money to get this far. Long story short...are 7M blocks not lemons? Do you have to stick to stock bore?
Bored to 84mm now have a hole in cylinder!!!!
- Thread starter PowerTrip Performance
- Start date
No, they are generally very good.
You got one with a casting defect. Sounds like an gas pocket in the cast. You can sleeve it, or get another block. Considering this one has at least one known casting defect, personally, I'd find another core.
You got one with a casting defect. Sounds like an gas pocket in the cast. You can sleeve it, or get another block. Considering this one has at least one known casting defect, personally, I'd find another core.
Sounds like you just nearly trashed the block. You can have sleeves made, but no one makes them mass produced. So be prepared to dish out some SERIOUS $.
I would ask if they could find another block for you. Since they should of had the spec's in front of them in one of the large books they usually or SHOULD have on hand.
-Jonathan
I would ask if they could find another block for you. Since they should of had the spec's in front of them in one of the large books they usually or SHOULD have on hand.
-Jonathan
84mm is usually considered a safe OS in a 7M block and it sounds like either as Mike has said a air bubble or maybe core shift... either way it's NOT the shops fault.
Forget sleeving it.
Forget sleeving it.
But was he using a dummy head to align the boring procedure? Maybe he was off a degree or two and bored it in lop-sided?
I would investigate. I have seen it way to many times out of these "hodge podge" machine shops that they really have no clue what they are doing. Go to a big city type shop and you will find dedicated and very knowledgable machinests.
-Jonathan
I would investigate. I have seen it way to many times out of these "hodge podge" machine shops that they really have no clue what they are doing. Go to a big city type shop and you will find dedicated and very knowledgable machinests.
-Jonathan
99% of the time you clock up the borning bar from the top 3mm of the stock bore as the rings never run that high so there is no wear.
Just sounds like bad luck and a dud casting to me.
(rereading his post it sounds more like a casting defect as there was a pinhole to begin with)
Just sounds like bad luck and a dud casting to me.
(rereading his post it sounds more like a casting defect as there was a pinhole to begin with)
The hole is in the number six cylinder, I can see right through the hole and it is maybe five thousandths thick. It would never hold and boost. I know it is not the machinist fault, the guy I use is VERY good, been in the business since 1975. I told him that there are lots of guys making huge power with these blocks. He does say however that the cylinder wall do seem to be very thin even before the bore. Well, I am still throwing around the idea of throwing in the towel anf starting a different project. This one will just cost me too much money and time to finish. My wife is already at her whits end with it. If I go this route, I will be wanting to sell of most of what I have for this project, including my my baddass turbo, manifold,FFIM, etc. Thanks a lot for you input guys!
siman said:
:nono:
NO cylinder repair sleeve is "mass produced"
Sleeving is not that expensive! (~$130aud per bore) (fine for gm/ford v8's)
the 7m block is not reliably sleeveable
It's a casting defect unless that magical large book has tomorrow's lotto numbers its of no use!
....Get another block and try again, 7m blocks are cheap and plentiful (good ones are not as plentiful but still out there)
Allan_MA70 said:
Exactly, you can get a block for next to nothing, bore it out, install all the parts you currently have and have a fun Supra.
Starting over is just going to cost you more, and there's no guarantee you'll have less grief with whatever you pick out next.
I have had no luck finding a block in my area (Oregon) although haven't had time to search high and low. I have looked on ebay, all I have found is complete long blocks. Most of which going for $1000+
There are TONS of sleeve kits from AEBS for hondas and nissans READILY available!
That was who I was reffering too. Sorry for being so "misleading" Allan_Ma70
And $130 AUS ( around $100 us?) is VERY expensive for what it is. For $600 you might as well buy a brand spanking new toyota short block.
That was who I was reffering too. Sorry for being so "misleading" Allan_Ma70
And $130 AUS ( around $100 us?) is VERY expensive for what it is. For $600 you might as well buy a brand spanking new toyota short block.
I have already looked into sleeving the thing, it'll cost me about $30 for the Ductile sleeve and about $80.00 for the labor, but as one of you guys mentioned as did my machinist, it will more than likely be very unreliable:1zhelp:
siman said:
Ummmm ok sence when has the 7M been an alloy block that has sleeves from the factory????
Allan_MA70 said:
again perpetuating bullshit siman, if your not sure don't chip in with "facts" that are wrong and then tell people that know about the subject they are wrong.