Turned Down Valves for DIY Porting
04-10-2014, 05:36 PM
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Turned Down Valves for DIY Porting
I have three sets of 4 valves each for sale (1.8). Each valve has the face of the valve faced down so that it just covers the valve seat. Drop these guys in place while porting, polishing or deshrouding the combustion chamber and protect the valve seats.
I was able to deshroud the valves and blend my combustion chamber all the way up to the valve seat without worrying about the grinder slipping and messing up a valve seat.
$20 shipped per set of 2 intake/2 exhaust valves OBO.
These should obviously not be installed in a running engine!
I was able to deshroud the valves and blend my combustion chamber all the way up to the valve seat without worrying about the grinder slipping and messing up a valve seat.
$20 shipped per set of 2 intake/2 exhaust valves OBO.
These should obviously not be installed in a running engine!
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04-10-2014, 06:15 PM
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Why didn't I think of that. I have a spare complete VVT head so I could have used those valves. Would have saved me from being sooo careful with the dremel and I could have removed even more material.
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04-16-2014, 12:11 PM
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My build thread has some pics of the combustion chambers.
https://www.miataturbo.net/build-thr...ntually-57591/
Not great pics, I know. I did pretty much the standandard gasket matching on intake and exhaust. I deshrouded the valves pretty good and removed a lot of combustion chamber material up to the head gasket line/ring. If I would do it over again I would have properly CC'ed each combustion chamber to make sure I did not remove too much material. I estimated the volume and had the machine shop shave enough off so that my compression ratio would not change, but I think I underestimated the amount of material removed and still ended up with lower compression. Based on compression tests after break-in I would guess I am betweem 8.5-8.7:1 compression ratio. Not horrible, great now that I am finally insallting the turbo, but I have noticed a little drop in gas miliage and the low end is not nearly as strong as the top end power.
The ported head pulls much stronger above 4000rpm than my wife's stock 97 does.
I had the time and was willing to to try a DIY. There is no way I could afford a CNC job. Now I just wish I did all this to a NB head. The next project will be a ported VVT head, in like 5-10 years.
https://www.miataturbo.net/build-thr...ntually-57591/
Not great pics, I know. I did pretty much the standandard gasket matching on intake and exhaust. I deshrouded the valves pretty good and removed a lot of combustion chamber material up to the head gasket line/ring. If I would do it over again I would have properly CC'ed each combustion chamber to make sure I did not remove too much material. I estimated the volume and had the machine shop shave enough off so that my compression ratio would not change, but I think I underestimated the amount of material removed and still ended up with lower compression. Based on compression tests after break-in I would guess I am betweem 8.5-8.7:1 compression ratio. Not horrible, great now that I am finally insallting the turbo, but I have noticed a little drop in gas miliage and the low end is not nearly as strong as the top end power.
The ported head pulls much stronger above 4000rpm than my wife's stock 97 does.
I had the time and was willing to to try a DIY. There is no way I could afford a CNC job. Now I just wish I did all this to a NB head. The next project will be a ported VVT head, in like 5-10 years.
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