7MGE Head Gasket Replacement

69ho · 08-20-2013, 01:03 PM

I am replacing the head gasket on my '89 Supra and noticed on re-assembly that the top surface of the rear timing cover is above the block deck surface from around the middle of the cover over to the left side and at or below the surface going the other way. This engine was rebuilt by the previous owner and it does not appear that the block deck was cut. I would expect to see this across the entire cover if the deck was cut and the cover was not installed and cut as well. I cannot find a good illustration that shows what locates the cover on the block. Maybe a dowel pin is missing? Is this normal? Where should the surface lie; at or below the block deck?

cre · 08-20-2013, 09:17 PM

The rear timing cover MUST be cut level with the block deck. If it's cut a couple thou too far it'll probably be fine but if it sits higher you're going to find your HG leaking sooner than later. Have a machinist measure it and cut the timing plate to match.

69ho · 08-21-2013, 12:59 PM

Can anyone tell me how the cover is located on the block? Dowel pins?

Bill UK · 08-21-2013, 09:23 PM

It`s been a few years since I removed one, but I think there are 2 dowels apart from the bolts and nuts. I also remember replacing 2 gaskets and a couple of oil seals.

Bill UK · 08-21-2013, 09:36 PM

Not sure but I think the oil sump is also bolted to the bottom of the rear timing case. At the time I was doing a total engine build so the sump was already removed.

cre · 08-22-2013, 05:02 AM

Quote:

Originally Posted by Bill UK

Not sure but I think the oil sump is also bolted to the bottom of the rear timing case. At the time I was doing a total engine build so the sump was already removed.

Yes, it is. This isn't something you want to remove with the head in place either... just in case someone thinks it's possible. (It is but it's a horror story and there are modifications and sacrifices which must then be made.)

69ho · 08-22-2013, 01:36 PM

Then if it is truly located with two dowels (I have never had one apart and cannot find any good illustrations) that tells me a couple of things. 1) that Toyota has very loose tolerances in machining the top of the cover surface and 2) in my case pulling the cover and trying to relocate will be useless. It is going to install on the dowels at the same location everytime. If I remove the cover and try to correct the surface off of the block, I will have to measure the current profile of that surface to know how to correct it. As I stated earlier, one end of the cover is at or very slightly below the block deck until you reach the middle of the cover and increases as you go from the center to the other end to approximately .010 to .020 above the deck (I have not made any measurements yet). That is going to be a challenging setup to be able to machine the part. Looks like it would be easier to correct while attached to the block so I can reference the block deck surface? Any comments?

69ho · 08-22-2013, 01:44 PM

I meant to mention that a member of another forum said he saw the same problem with his cover after removing the head. His engine had never been apart, so apparently Toyota does not control that surface very well???

cre · 08-22-2013, 05:40 PM

I've never seen it on a stock block. Yes, having it cut with the block is ideal. The issue is a little less critical with a composite HG than with a metal HG as the composite has a some elasticity and will fill in MINOR imperfections. The head gasket overlaps the timing plate and the excess height may cause issues. Over cutting the plate a little isn't a huge deal as it's just an oil galley. Dress the HG on both sides with a good sealant (Honda FIPG, The Right Stuff, etc) where it meets the timing plate and where the timing plate it meets the block (as specified in the TSRM) and you'll be fine as well.... But yes, at the end of the day getting it cut to match the block is the way to go.

69ho · 08-22-2013, 06:03 PM

Thanks for the reply cre. I think I am going to come up with a way to machine the plate on the block. I think removing it and trying to match the profile will not be impossible, but difficult to setup. This engine has very few miles since the previous owner had it rebuilt(<5K) and it seals well. I think I will be asking for more trouble (leaks) removing the plate than trying to do it on the block. I plan on using a stock Toyota composite HG which as you said can tolerate minor imperfections. I will seal the corners as spelled out in the service manual. Thanks for letting me use you as a bouncing board, so to speak. It has helped me arrive at workable solution.

08-20-2013, 01:03 PM	#1
69ho Stock Join Date: Aug 2013 Location: Huntsville, AL Posts: 6	7MGE Head Gasket Replacement I am replacing the head gasket on my '89 Supra and noticed on re-assembly that the top surface of the rear timing cover is above the block deck surface from around the middle of the cover over to the left side and at or below the surface going the other way. This engine was rebuilt by the previous owner and it does not appear that the block deck was cut. I would expect to see this across the entire cover if the deck was cut and the cover was not installed and cut as well. I cannot find a good illustration that shows what locates the cover on the block. Maybe a dowel pin is missing? Is this normal? Where should the surface lie; at or below the block deck?

08-20-2013, 09:17 PM	#2
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	The rear timing cover MUST be cut level with the block deck. If it's cut a couple thou too far it'll probably be fine but if it sits higher you're going to find your HG leaking sooner than later. Have a machinist measure it and cut the timing plate to match. __________________ 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 --->

08-22-2013, 05:40 PM	#9
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	I've never seen it on a stock block. Yes, having it cut with the block is ideal. The issue is a little less critical with a composite HG than with a metal HG as the composite has a some elasticity and will fill in MINOR imperfections. The head gasket overlaps the timing plate and the excess height may cause issues. Over cutting the plate a little isn't a huge deal as it's just an oil galley. Dress the HG on both sides with a good sealant (Honda FIPG, The Right Stuff, etc) where it meets the timing plate and where the timing plate it meets the block (as specified in the TSRM) and you'll be fine as well.... But yes, at the end of the day getting it cut to match the block is the way to go. __________________ 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 --->

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08-21-2013, 12:59 PM	#3
69ho Stock Join Date: Aug 2013 Location: Huntsville, AL Posts: 6	Can anyone tell me how the cover is located on the block? Dowel pins?

08-21-2013, 09:23 PM	#4
Bill UK AEM EMS Join Date: Jul 2006 Location: UK Posts: 891	It`s been a few years since I removed one, but I think there are 2 dowels apart from the bolts and nuts. I also remember replacing 2 gaskets and a couple of oil seals.

08-21-2013, 09:36 PM	#5
Bill UK AEM EMS Join Date: Jul 2006 Location: UK Posts: 891	Not sure but I think the oil sump is also bolted to the bottom of the rear timing case. At the time I was doing a total engine build so the sump was already removed.

08-22-2013, 01:36 PM	#7
69ho Stock Join Date: Aug 2013 Location: Huntsville, AL Posts: 6	Then if it is truly located with two dowels (I have never had one apart and cannot find any good illustrations) that tells me a couple of things. 1) that Toyota has very loose tolerances in machining the top of the cover surface and 2) in my case pulling the cover and trying to relocate will be useless. It is going to install on the dowels at the same location everytime. If I remove the cover and try to correct the surface off of the block, I will have to measure the current profile of that surface to know how to correct it. As I stated earlier, one end of the cover is at or very slightly below the block deck until you reach the middle of the cover and increases as you go from the center to the other end to approximately .010 to .020 above the deck (I have not made any measurements yet). That is going to be a challenging setup to be able to machine the part. Looks like it would be easier to correct while attached to the block so I can reference the block deck surface? Any comments?

08-22-2013, 01:44 PM	#8
69ho Stock Join Date: Aug 2013 Location: Huntsville, AL Posts: 6	I meant to mention that a member of another forum said he saw the same problem with his cover after removing the head. His engine had never been apart, so apparently Toyota does not control that surface very well???

08-22-2013, 06:03 PM	#10
69ho Stock Join Date: Aug 2013 Location: Huntsville, AL Posts: 6	Thanks for the reply cre. I think I am going to come up with a way to machine the plate on the block. I think removing it and trying to match the profile will not be impossible, but difficult to setup. This engine has very few miles since the previous owner had it rebuilt(<5K) and it seals well. I think I will be asking for more trouble (leaks) removing the plate than trying to do it on the block. I plan on using a stock Toyota composite HG which as you said can tolerate minor imperfections. I will seal the corners as spelled out in the service manual. Thanks for letting me use you as a bouncing board, so to speak. It has helped me arrive at workable solution.