head gasket failure- something sinister or just 7M?

[mark_vdh]

pretty sure the topic was on http://www.supramania.com/forums/
but I'm not a member and can't search

found this on the cressida forums tho
http://forums.toyotacressida.net/for...r+passage+head

[cambelt]

Yep thats it , I originally did it because id see corosion at that spot that wasnt drilled , the air formed a little pocket that had knowhere to go.
7M,s have terible water flow and must be improved for better cooling .
All the earlyer M engines had much better water pumps on them and flowed so much more water than a 7M one .
A way i improve a 7M pump is machine the step off, around the outer of the pump bringing the impeller closer to the housing.
They really need a 8 vane impeller like a 5M.
Dave

[allencr]

head was retorqued after 500kms with no boost, and again 500kms with minimal boost
fretting....

I think it should be a regular maintenance item, especially if these 500kms increments were during a break-in that was babied & never once got even close to stinking hot.
The after-market gasket might be an exact copy of the original factory gasket but the factory may have 1 or more newer/improved(?) versions to replace it, with strengthening or progressive coolant passages, materials, whatever.
The water-pump would help at idle, but I'd go for opening up the passages towards the rear, or even just keeping a high idle for faster flow to equalize things after hard use. Short term hard use probably won't heat up that intake side like a 4000-rpm for an hour on the highway run will.

[JZA70R_92]

will a 5M pump fit on a 7M though? Mines only NA but I like to improves its durabilty!