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There's not much detailed info on this subject, so I figured I'd document my experience during this project. First of all, a little background...

I did the BP swap about 2 years ago. I used a '92 EGT motor, totally stock. It ran great for awhile, but recently developed a water leak. Upon further investigation, I found that my head gasket was failing, oil in the coolant, blah blah blah. In light of this, I decided to swap my EGT head for the stronger Miata head. That way, in the process or repairing the motor, I could build it up a little.

Anyway, I'm on the way to pick up the head right now. The one I chose is from a '97 Miata 1.8L. It's got the valve cover and all of the internals. I'll post an update when I get it...

I dont think there was much difference in the miata/protege heads internally.
And I dont think neither is stronger if they are all the same inside.

just to let u know there the same shyt but i have both a protege head and a 94 miata head that i converted to a fwd head for my BP MX-3. i'll take a few pic and show u what i mean since i think a gerenal pic will lead to on to a better view on what i mean. I have also converted a 94 miata BP motor into FWD form not as hard at people said it was. but there the same shyt with minor differences. (water neck, windage tray, motor mounts, water pump, etc etc, but if u run into a bind pm me or hit me up on this. done it all.

BUT GOOD LUCK TO YA

as of now im in the proccess of making a 1.8 miata diff work on the g-series trans. Blow my diff at the track this past weekend trying to quilfy for the import races. 13.6@106 wasn't going to cut it on my first pass. i got pissed off ended up racing some guy how hadn't a clue for the whole stageing up and pro tree work. so yeah wasted mins on him trying to explain how the whole thing whent and well fell asleep at the light. second pass that was it i was done trying to two step it off the line lunching with boost in other wards.

wouldn't doing that swap make a WHOLE bunch of issues for doing a turbo setup and would a custom intake manifold be required??

Just got home from picking up the head. Everything looks good. It's much cleaner than my EGT head, but that's to be expected, since the EGT head is 5 years older.

The plan is to swap in the cams and lifters from a '99 Miata to make the '97 head stronger. My main focus tomorrow is going to be cleaning up the head. I'm going to pick up the gaskets after work, so I won't have much daylight, but that's OK. All the other parts will arrive Friday. I can't wait to start ripping this thing apart...

Cy wrote:wouldn't doing that swap make a WHOLE bunch of issues for doing a turbo setup and would a custom intake manifold be required??

The '97 Miata head is the same as the EGT head, so there shouldn't be any issues with a turbo. The EGT intake manifold will bolt up as well. The only difference is that the Miata head has an extra water outlet, which should provide for better circulation of coolant through the head (that is, if I can figure out how to hook it up correctly).

You may be thinking of the '99+ head? I know that the intake manifold is different on those...

Cy wrote:wouldn't doing that swap make a WHOLE bunch of issues for doing a turbo setup and would a custom intake manifold be required??

the 94-98 miata heads have the same intake and exhaust bolt patterns in fwd and rwd form. this is how useless nonsense is started my assuming and never really doing first hand. sorry for the hrash comment no offence i know u don't mean too. how is that when i have already turned a 94 miata motor into a FWD BP form and boosted it on my MX-3 minor mods and converting miata parts to protege parts to make it work.

PoisonDrop wrote:Just got home from picking up the head. Everything looks good. It's much cleaner than my EGT head, but that's to be expected, since the EGT head is 5 years older.

The plan is to swap in the cams and lifters from a '99 Miata to make the '97 head stronger. My main focus tomorrow is going to be cleaning up the head. I'm going to pick up the gaskets after work, so I won't have much daylight, but that's OK. All the other parts will arrive Friday. I can't wait to start ripping this thing apart...

the 99 head has soild lifter and apperenty the miata guys swap in there 94-98 cams for the 99 cams. i don't think it will make much of difference but hey to each his own. im reving the damn BP up to 8,000 rpms but i got a standalone which is why im reving at the rpms. couldn't do that with my factory shyt.

but hey good luck in what ur doing in the past if i remember rite i did swap in 99 lifters and cams in a 95 head. there should be no issuse guy never complained so its gotta work.

Exactly^^^^

some of the Miata guys have seen gains of up to 50WHP from swaping a 99+ head on a turbo motor. mainly due to the solid lifters and the deg. and size of the intake ports. you can swap the lifters into any BP head. the gains are minimum unless your running big boost. thats why i just stuck to HLA's. but swaping over a 97 head will have no issues what so ever, direct bolt on. mani's and evrything.

I have done the solid lifter swap into my BP head... the only reason one would do the swap is for a higher rev limit. You won't see much gains for HP since the cam is pretty much the same lift and the duration is slightly different. This is to compensate for the hydrolic lifter...

Hydrolic versus Solid...


You will have to swap in the valves too into the head cause the '99 valves are longer than the hydrolic valves. You will also have to check the valve to cam clearance and reset it most likely.

The angle of the intake ports on the '99 head has better flow than the original BP head... that would be the HP gain. If you put a '99 head in you want to get the intake manifold too cause you can't fit the regular BP manifold on there. Except the throttle body is on the left side and you'd have to cope with that somehow.

The Miata head you got should be exactly the same, just make sure the distributor is still on the exhaust side... that would be the only difference. Also at the front of the head is a frost plug, on the Miata head there will be none cause the Miata's run the extra coolant through there... not sure how you gonna hook it up. If you decide not too, you gotta put a frost plug back in.

the miata head with a fwd protege water neck notice small water outlet next to the water neck.

this the protege water neck with it off but notice the small water outlet next to it different from the miata outlet.

Under the black sheild that is where the miata water neck is located i cut it and welded a peice of alm. to block off the water passage. miata head.

Notice on the protege head that water passage is cap off. do u get what i mean by doing some mods to convert a miata head into a fwd head.

sorry for the small pic i'll take some better pic i used my cell but i hope u get the point.

So I got the head on. Everything bolts up easily. I ended up using a freeze plug to cap off the extra water outlet. The only issue I ran into was the missing heater connection on the thermostat side of the head, as Limegreen pointed out. To correct the problem, I fabricated a "Y" connector to plug the heater hose into, basically duplicating the design of the EGT head.

a frezze plug can work too i didn't have one when i did that but thanks for the comment. glad to be of some asstance and that it all work out for you. will a lil bit fo time u can pull out them water outlets. pain in the azz.

My plans for the motor have changed a little. I figure since I'm not going to do anything with the old EGT head, I might as well take my time to build it up instead. That way, I won't have to put all the cash up front, and I can do some mods other than just the Miata internals. I'm thinking P&P, upgraded valves, and all that good stuff. It'll take awhile, but at least the MX-3 will be drivable in the mean time.

(Needless to say, I didn't use the '99 Miata stuff in the '97 head....figured I'd save them for the EGT build...)