[rthompsonjr]

So I have a 91 with only 50k miles, and instead of using that low mileage to my advantage and going turbo I went with Fuji Racing IRTBs. I have a full exhaust to match and thats about it. I'm ordering a Megasquirt this coming week to take over for the poor confused factory ECU/piggyback combo. I would love to do a fulll rebuild but that will have to wait at least a year probably more, and I am thinking about doing some head work.

I want to know how much can be milled off the head before turning the engine into an interfernece engine and when combined with porting and polishing, hw much power would this make? How much of an increase in CR does this provide?

Thanks for the info!

 

[Bryan]

Randy Stocker's site is a good place to start. The Miata Power List is also a good place to answer this, but it's an email-based forum.

 

[akaryrye]

Well you mentioned doing some head work. I am currently working on a head myself with a dremel and many assorted bits. It has taken me lots of hours and i have not done anything crazy at all. Basically my work is consisting of smoothing and surfacing intake and exhaust ports (rough for intake and smooth for exhaust), blending the bowls, unshrouding the valves, and polishing the combustion chambers.

So far I have finished the exhaust ports and unshrouded and surfaced half of the intake ports. It has been a work in progress for a few months now and I spend a half hour here and there on it and probably a total of 10 hours so far and expect another 3 to 5 to finish it off since my skills have gotten better. If you have the time, do it yourself and save some money. All the while, you will have a nice little decoration on your kitchen table for a while!

 

[akaryrye]

... or you could get the 99 head and get the same results, diy mild porting would net even better.

 

[TrophyFodder]

... or you could get the 99 head and get the same results, diy mild porting would net even better.

Not on a 1.6l block.

A 94-97 block w/99 head is the way to go!