Crack!! (not the drug lol )

itsjustsway · 02-28-2011, 10:21 AM

Horrible news/ needing advice... So I pulled the motor out of my mk3 turbo and noticed something bad.. There was a very small crack by 2 coolent channels by cylinder 2.. They don't appear 2 be leading into the cylinder how can I fix this? I was going to get the block pressure tested then weld the cracks it has then shave the block to ofcourse resurface and smooth it out.. Is this worth it? Or will the compression and force of the engine f-up the welds and moter if I take this route? .. Should I look into a 1jz swap??

cre · 02-28-2011, 05:08 PM

If the cracks are in the head, you could have it welded but it's probably going to be cheaper to just source another.

If the cracks are in the block, it's trash. You can't weld cast iron blocks with any reasonable reliability.... Not saying it can't be done but it usually fails gloriously in no time at all.

btwilson86 · 02-28-2011, 05:17 PM

Please don't post in the MKIII FAQ. That's for frequently asked questions only. Thread moved to the MKIII general discussion forum.

itsjustsway · 03-07-2011, 04:16 PM

Quote:

Originally Posted by cre

If the cracks are in the head, you could have it welded but it's probably going to be cheaper to just source another.

If the cracks are in the block, it's trash. You can't weld cast iron blocks with any reasonable reliability.... Not saying it can't be done but it usually fails gloriously in no time at all.

So I would b better of buying another block or a whole new engine? The welds won't hold because there's 2 much pressure right

cre · 03-08-2011, 03:40 AM

Welding cast iron is a bitch, welding old cast iron can be hell and very unpredictable. There are a couple reasons why most welders will even tell you to forget it... I just can't remember the reasons. :P It's more a matter of penetration and inconsistent density. It can definitely be welded (I suppose that's up for argument but it's not my argument to make), but the couple people in that industry with whom I've spoken on the matter have all said that it's a waste of money and effort.

You'll usually have a horrible time finding a professional welder who will weld a cast iron manifold; Those are small and require less precision. It's not unlike when you crack the exhaust side of a turbo... it's trash.

If you can find someone who's willing to weld it the odds are that after the welding and all the milling and boring and flushing that it would still be cheaper to buy a used block and only do a mild rebuild.

itsjustsway · 03-08-2011, 09:08 AM

Quote:

Originally Posted by cre

Welding cast iron is a bitch, welding old cast iron can be hell and very unpredictable. There are a couple reasons why most welders will even tell you to forget it... I just can't remember the reasons. :P It's more a matter of penetration and inconsistent density. It can definitely be welded (I suppose that's up for argument but it's not my argument to make), but the couple people in that industry with whom I've spoken on the matter have all said that it's a waste of money and effort.

You'll usually have a horrible time finding a professional welder who will weld a cast iron manifold; Those are small and require less precision. It's not unlike when you crack the exhaust side of a turbo... it's trash.

If you can find someone who's willing to weld it the odds are that after the welding and all the milling and boring and flushing that it would still be cheaper to buy a used block and only do a mild rebuild.

Yea ur right .. Where can I find a block? Will it have to be used or is there a site I can order 1 from?

cre · 03-08-2011, 12:16 PM

Do you already know yours is bad?

As far as I recall they're no longer available new from Toyota. Used it the only option and there are a number of places you may acquire one. As I would be planning on rebuilding regardless of where it came from I'd look locally for one which I could inspect and measure myself. If you want one that's already rebuilt check the classified ads on the various Supra sites (I think someone posted here with a freshly rebuilt one recently). You could also try contacting Aaron at www.driftmotion.com to see if he has anything.

If you're planning on upgrading to forged pistons you may also use a GE block. You lose the oil squirters which are there to cool the stock cast pistons... not a big deal with forged though. You'll also need to have the block drilled for the oil return and supply for the turbo. If you go this route make sure you run a GTE oil pump and not the GE pump.

itsjustsway · 03-15-2011, 05:09 AM

So I took the block 2 a machine shop and they told me it was fine.. So I'm getting the block shaved and honed.. I want stock oversize 40 over pistons with rings.. Anyone have brand suggestions?

cre · 03-15-2011, 05:53 AM

Don't go 40 over unless you have to... on a turbo block bore it over as little as possible. That extra .15 liters (No, I didn't bother with the calculator for that number, but if you need we can) isn't going to gain you anything that's worth the extra meat between the cylinders... the 7M's cylinder walls are fairly thin as it is. I'd keep the walls meaty and add the whopping 1/2psi it'll take to make the same increase in power with a manual boost controller.

If you just want stock, Toyota or NPR are good. The NPR are available with a molybdenum coating too. Personally, at this point I'd put in something forged (never know how power hungry you'll feel in a couple months

).

02-28-2011, 10:21 AM	#1
itsjustsway Stock Join Date: Jan 2011 Location: Kissimmee Florida Posts: 27	Crack!! (not the drug lol ) Horrible news/ needing advice... So I pulled the motor out of my mk3 turbo and noticed something bad.. There was a very small crack by 2 coolent channels by cylinder 2.. They don't appear 2 be leading into the cylinder how can I fix this? I was going to get the block pressure tested then weld the cracks it has then shave the block to ofcourse resurface and smooth it out.. Is this worth it? Or will the compression and force of the engine f-up the welds and moter if I take this route? .. Should I look into a 1jz swap??

02-28-2011, 05:08 PM	#2
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	If the cracks are in the head, you could have it welded but it's probably going to be cheaper to just source another. If the cracks are in the block, it's trash. You can't weld cast iron blocks with any reasonable reliability.... Not saying it can't be done but it usually fails gloriously in no time at all. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

02-28-2011, 05:17 PM	#3
btwilson86 Super Moderator Join Date: May 2007 Location: Billings, Montana Posts: 1,034	Please don't post in the MKIII FAQ. That's for frequently asked questions only. Thread moved to the MKIII general discussion forum. __________________ 1989 7MGTE R154 Targa Top White Package w/Blue Interior Driftmotion 57trim CT26, Upgraded Intercooler, 2.25" Hard Pipes, 3" Turbo Back Exhaust with Test Pipe, HKS VPC w/GM 3 bar MAP sensor, APEXi S-AFC, Walbro 255lph fuel pump, ProSport EVO Series Boost / Fuel Pressure / AFR gauges, Lotek a Pillar Gauge Pod, HKS Type 0 Turbo Timer, Eibach Lowering Springs, Tokico Illumina II TEMS struts, custom powder coated Motegi Racing TrakLite wheels

03-08-2011, 03:40 AM	#5
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Welding cast iron is a bitch, welding old cast iron can be hell and very unpredictable. There are a couple reasons why most welders will even tell you to forget it... I just can't remember the reasons. :P It's more a matter of penetration and inconsistent density. It can definitely be welded (I suppose that's up for argument but it's not my argument to make), but the couple people in that industry with whom I've spoken on the matter have all said that it's a waste of money and effort. You'll usually have a horrible time finding a professional welder who will weld a cast iron manifold; Those are small and require less precision. It's not unlike when you crack the exhaust side of a turbo... it's trash. If you can find someone who's willing to weld it the odds are that after the welding and all the milling and boring and flushing that it would still be cheaper to buy a used block and only do a mild rebuild. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

03-08-2011, 12:16 PM	#7
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Do you already know yours is bad? As far as I recall they're no longer available new from Toyota. Used it the only option and there are a number of places you may acquire one. As I would be planning on rebuilding regardless of where it came from I'd look locally for one which I could inspect and measure myself. If you want one that's already rebuilt check the classified ads on the various Supra sites (I think someone posted here with a freshly rebuilt one recently). You could also try contacting Aaron at www.driftmotion.com to see if he has anything. If you're planning on upgrading to forged pistons you may also use a GE block. You lose the oil squirters which are there to cool the stock cast pistons... not a big deal with forged though. You'll also need to have the block drilled for the oil return and supply for the turbo. If you go this route make sure you run a GTE oil pump and not the GE pump. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

03-15-2011, 05:09 AM	#8
itsjustsway Stock Join Date: Jan 2011 Location: Kissimmee Florida Posts: 27	Reply So I took the block 2 a machine shop and they told me it was fine.. So I'm getting the block shaved and honed.. I want stock oversize 40 over pistons with rings.. Anyone have brand suggestions?

03-15-2011, 05:53 AM	#9
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Don't go 40 over unless you have to... on a turbo block bore it over as little as possible. That extra .15 liters (No, I didn't bother with the calculator for that number, but if you need we can) isn't going to gain you anything that's worth the extra meat between the cylinders... the 7M's cylinder walls are fairly thin as it is. I'd keep the walls meaty and add the whopping 1/2psi it'll take to make the same increase in power with a manual boost controller. If you just want stock, Toyota or NPR are good. The NPR are available with a molybdenum coating too. Personally, at this point I'd put in something forged (never know how power hungry you'll feel in a couple months ). __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar ---> Last edited by cre; 03-15-2011 at 05:56 AM.

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