Spec Miata head worth the time/effort to swap?
I have a 91 with a stock 1.6. I have a turbo set up with DIY MS ready to go on. However I recently aquired a spec miata head that was run for three races several years ago until the car was totaled and the head sat for a while. It was a full rebuild from Rebello so I know it is very high quality, but it is still a spec head. So the question is, will I get enough gains from this head to be worth the effort of changing it out on a non tracked car?
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If it's a shiny new part, why the hell not?
No one can decide if it's worth it or not except for you /thread |
Well, technically the dyno can.
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Ok, well I guess what i'm really asking is what kind of HP / Torque gains will I see by swapping in a Spec head on a stock miata, and will those gains be even larger when the turbo goes on? When building a spec head the components a stronger and the tollerances tighter, but is the flow really that much better if they can't port it?
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spec head maybe and probably is milled down to legal limit for spec miata, you would get bump in compression
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Go download a copy of the SCCA GCR and read the rules. When you do you will see just how LITTLE can be done to a Spec Miata engine. When you do you will realize that unless you are trying to stay within the limits of those rules a Spec Miata head is of little performance benefit to anyone other than a Spec Miata racer. They can't port it, they can't change valve angles, they have to use all factory Mazda supplied parts, they can't mill it to increase the compression ratio beyond what the factory spec was (9.4:1 on a 1.6). So what you have is a VERY well built stock head that depending on the condition of your factory head could give you a max hp gain in the 3-5 hp range. If you aren't worried about rules I would treat it like a core, have it ported by someone that knows what they are doing, have the valves back cut or consider +1mm valves, 5 angle valve job, have the valves un-shrouded, polish the combustion chamber and look at aftermarket cams. Then it for sure would be worth it.
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It also matters if its a legal spec miata head. There are definitely many spec miatas out there with worked heads not getting caught because they only race the regional level.
I'd say it's probably not worth your time/effort unless you know the head is 100%. Also, Rebello's motor quality has decreased significantly since Mike Haag left and started his own shop (http://www.haagperformance.com/). Just noticed I'm in a picture on top, silver car on the inside trying to get by P1 and P2. Edit: and it seems photos are always changing now that I visit link again. |
Originally Posted by crashnscar
(Post 729044)
It also matters if its a legal spec miata head. There are definitely many spec miatas out there with worked heads not getting caught because they only race the regional level.
TNTUBA - I was thinking of going this route, I just don't have the cash for it ATM. I guess for now I'll skip the head and start with the turbo install... |
Originally Posted by crashnscar
(Post 729044)
It also matters if its a legal spec miata head. There are definitely many spec miatas out there with worked heads not getting caught because they only race the regional level.
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