Tip & How-To about Mazda B-Series Truck
These days most small cars have aluminum heads and the number of blown head gaskets that I have seen has increased a lot.
Rule number one if you want your head gaskets to last is to not let these engines overheat. With the iron heads you could let the heat gauge run into the red with no real lasting or catastrophic damage - most of the time.
With these aluminum heads you cannot do that. Whether you run out of water due to a leak or your 10 dollar thermostat sticks shut, you have got to pull over and stop the engine. If you don't, that 10 dollar thermostat could cost you over 900 dollars.
To cool the engine as fast as possible just raise the hood with the engine off. DO NOT POUR WATER OVER THE ENGINE!!! That is very very bad and could easily junk your engine.
Ok lets say that for some reason you do blow a headgasket because the bolts were not originally tight enough or some other reason.
You have some options as to repairs. You can go used from a junkyard or new. Used will be lots cheaper but harder to find a good one. Always take the used head to a reputable machine shop to be checked. Almost all used heads are already warped to some degree. Less is better and one that hasn't been milled before is lots better. Your machine shop should know how to bend aluminum heads so that they are really close to being straight. If they dont then the cam bearings wont be straight for the came. Remember both sides need to be straight. top and bottom. In most cases it is possible to straighten it enough that the cam area will not need to be rebored oversize, and the bottom can just be touched up with the milling machine.
Next important bit is to not use Felpro gaskets. Use Corteco head gaskets on aluminum heads. Felpro works great on iron heads but most of the headgaskets I have seen blown were Felpro and very few were Corteco and of those few Cortecos blown, the engine was grossly abused where some Felpro ones had no history of abuse. Just trust me on this one.
Now here is a tip that your mechanic may not like at all. Some of these gas engines have the head bolts right at the edge of the head. Usually two at each end and we wonder why all the heads are warped? Lets think about this a bit. If the torque specifications for a head say 160 foot pounds and the distance between head bolts is roughly 4 inches what is happening at the ends of the heads where there is half as much surface area clamping the gasket? Yep you guessed it. There is nearly twice as much pounds per square inch squishing the gasket at the ends. With time and heat this will warp the head.
Now the part your mechanic may not like. I don't torque those 4 head bolts as much as I do the ones towards the center of the head. If it says to torque the bolts to 160 foot pounds then that's what they get except the 4 end ones will only get say about 145 or close to 10% less. Now I did not actually do all the math to compute the torque necessary to keep the pounds per square inch even for the end bolts but rather estimated. If you are or know an engineer that can compute that feel free to let me know the results.
Posted by Bryan... on
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