[quote name='boostcrazy' post='667111' date='Apr 22, 2008 - 2:39 PM']
Any foreign things in the combustion chamber i.e. >>coolant>>, oil, etc. can and will cause detonation.
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I hate to be an ass, but coolant can not, and will not cause detonation.
It will actually prevent it, just like water injection.
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FYI===Glycol antifreeze (typical antifreeze) will ash overtime when ignited and will cause ignition problems...... the last thing you want with any engine.... let alone a turbo'd one. One cylinder running cooler (diffently) than the others...... hmmmm .... not good. As for the water injection, water does not have any detergents or additives, therefore it causes not harm when used correctly under the right conditions. Furthermore, water injection is almost always mixed with methanol in any good setup because it mixes with water very well, it is cumbustable, will not freeze, and prevents the water corrosion of water injection and fuel system components.

Seeing as most people know coolant in the combustion chamber is bad, I figured it was a safe assumption, and didn't mention it.
The sole reason I mentioned it being like water injection is because the action of vaporizing it cools the mix/combustion slightly, preventing preignition specifically where it is. It obviously doesn't improve performance, 1 because it is cooling only a part of the combustion, not the air flowing in, and 2 because where there's coolant there's a leak, either from the HG or a crack in the engine, causing a loss in combustion pressure [which BTW would also lower the chance of preignition].
Ash in coolant is less than 5%, and leaves no noticeable residue, so it really isn't a factor for preignition.

Oh, and by the book, methanol leans out the A:F when used with water injection.

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Damn, that is cheaper than I expected. Wouldn't your discount be less than that though?
That would be just the head, you can't buy an assembled head from Toyota.
Either way you've got to reassemble the head. and if you're worried about the head being warped, and want/need to recut the valve seats, if a brand new one is close to the same price, IMO I'd go with that, especially since it comes with brand new valve guides too, and you won't have to cut your valve tips.

FOR FUTURE REFERENCE: you must have the cam caps that came with the head or the head is garbage. reason being that the cam caps and the part of the head the cams sit in are solid when assembled at the factory and then line bored through the side of the head, so each cam cap is specific to it's place on that particular head. I did not know this previously.

So, during my hour lunch break one day I went to the junkyard down the street and pulled off a 7A head from a 94 ST with 187k miles and surprisingly clean, this time taking the caps too. Brought it to the machine shop the following day and less than a week later picked it up and dropped off the $205.

Installed the new head at work on Sun June 1st. Used the whole bucket/shim setup from the other head hoping valve clearance wouldn't be too far off. Seven valves were still out. We slowly narrowed it down to one which we never did get right, it's still about 0.002mm out of spec.

Regardless, it started up just fine, actually sounds quieter than before, no rushing water/coolant noise.
Now, I've been driving it for almost 2 weeks and put just over 1,000 miles on it so far. So far so good, it feels so much better. It runs so smooth, it actually feels like a brand new motor, the way it should. Still no rushing coolant noises.

One difference is the noise it makes. It used to have 3 very distinct changes in the way it sounded. It would be quiet, then a little throaty, then over 5k RPM would scream. It doesn't make that screaming noise anymore, I'm not really sure why. Only differences in the heads are the valves were re-cut and I didn't port anything out like I did last time. I kinda liked that noise though, it sounded impressive.. haha. Oh well I guess.

Hope you don't run into anymore issues, and you can now enjoy the car! This has been so cool to follow your progress.

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sadly evilspeed is out of business so i found a cache of the website so i will copy and paste it here not that it matters but it seems like a waste to let the info die off


from the site
"Most ST Celica seem to be limited electronically (fuel cut) to 111mph as a result of the low speed rated tires they were shipped with.

To defeat the top speed limiter, you must interrupt the vehicle speed sensor signal to the ECU. This will trigger an intermittent check engine light. It may be desirable to install a switch so the speed limiter can be re-activated and the CEL extinguished. This modification will not effect the operation of the speedometer or the cruise control as long as the signal is interrupted at the ECU module and not before that point.

Locate the ECU. It sits underneath and in front of the console. Peel back the carpet from the center passenger side of the vehicle and you'll see the ECU connectors as pictured above. Locate the E7 pug. It should be the forward most plug of the three (you may have to disconnect the others to gain access to it). Locate the #11 terminal on the plug (see above). There are a number of ways to proceed at this point. The quick and dirty way is just to cut the wire and make sure that both the exposed ends are taped off. You can also install a few lengths of wire and a switch to make the feature user-controllable (thus controlling the CEL). I chose to remove the pin from the ECU plug so that I can easily return the car to stock whenever I desire.

*This is intended and designed to work on manual transmission equipped vehicles only. Attempting to do this on a car with an automatic transmission may cause your transmission to fail or work incorrectly."

also dont mind me im just getting ready to rebuild the ole 7A