Turbo prepped 12A build
09-13-10, 03:33 AM
#1
Turbo prepped 12A build
I pieced this together from parts I already had here. These are the best builds.
Rotor housings from a low mileage Hayes engine that was pressure washed many years ago and water got in and sat so only the housings survived. Side plates from a Mazdas and More engine that was assembled incorrectly and ports were ugly so I cleaned them up. Rotating assembly from an '83-'85 beehive 12A that may have been dropped because the pedestal and beehive were missing (I didn't do it).
This 12A will be prepped for boost with a modded ROPR (added a couple washers to bring oil pressure up to 85-90), drilled front cover for turbo oil drain fitting, modded thermostat for cooler running ala Zenjoe, ACV port blocked with quicksteel, coolant ports blocked with 20mm freeze plugs, exhaust ports squared more than they were when I got them (to drive a turbo better), locked or semi-locked distributor eventually (after NA break in).
For NA break in, it will have these parts: Awesome '70s Nikki intake manifold that outflows the 1st gen manifolds. Oh don't be jealous. A stripped 6 port 12A Nikki or perhaps the stock carb* that came with the '70s manifold (gotta dig into it to find out its internal condition as it's been sitting as long as the thinker). A regular 12A dizzy or maybe a GSL-SE dizzy for the different mech advance curve (that would be interesting). DLIDFIS, of course. Some no-name 9 pound aluminum flywheel and maching disc and p-plate if it goes in the FB for break in. Or if it goes in the REPU for break in, I'll toss a stock 26 pound flywheel on it (look at Mazdatrix' flywheel FAQ for more info).
*I wish these carbs came with 22mm venturis like the early Hitachi 13B carbs and what Sterling does to his modded carbs, as a way to get higher air flow. Oh well, will have to make due with 20mm for now I guess.
I've always been curious to see how a 12A could perform in a rotary truck, but I've got nearly enough parts ready for its 13B build to take place, so I'll probably pass. I've already seen it once in a friend's REPU where he dropped a 12A in because his 13B finally crapped out; it was a major smoker, and he needed an engine right then. Still...
Speaking of rotary and truck, this engine is slated to go in a local guy's B2000 after break in, and he's interested in doing a turbo at some point. Not sure what type of carb he'll use, but it's going to be big and boost prepped.
So there you have it. Can you guys think of anything else I should do or add to the engine before it's fully built? So far just the plates have been stacked and end play set (.002"). I'll deal with the other front cover bits next.
Rotor housings from a low mileage Hayes engine that was pressure washed many years ago and water got in and sat so only the housings survived. Side plates from a Mazdas and More engine that was assembled incorrectly and ports were ugly so I cleaned them up. Rotating assembly from an '83-'85 beehive 12A that may have been dropped because the pedestal and beehive were missing (I didn't do it).
This 12A will be prepped for boost with a modded ROPR (added a couple washers to bring oil pressure up to 85-90), drilled front cover for turbo oil drain fitting, modded thermostat for cooler running ala Zenjoe, ACV port blocked with quicksteel, coolant ports blocked with 20mm freeze plugs, exhaust ports squared more than they were when I got them (to drive a turbo better), locked or semi-locked distributor eventually (after NA break in).
For NA break in, it will have these parts: Awesome '70s Nikki intake manifold that outflows the 1st gen manifolds. Oh don't be jealous. A stripped 6 port 12A Nikki or perhaps the stock carb* that came with the '70s manifold (gotta dig into it to find out its internal condition as it's been sitting as long as the thinker). A regular 12A dizzy or maybe a GSL-SE dizzy for the different mech advance curve (that would be interesting). DLIDFIS, of course. Some no-name 9 pound aluminum flywheel and maching disc and p-plate if it goes in the FB for break in. Or if it goes in the REPU for break in, I'll toss a stock 26 pound flywheel on it (look at Mazdatrix' flywheel FAQ for more info).
*I wish these carbs came with 22mm venturis like the early Hitachi 13B carbs and what Sterling does to his modded carbs, as a way to get higher air flow. Oh well, will have to make due with 20mm for now I guess.
I've always been curious to see how a 12A could perform in a rotary truck, but I've got nearly enough parts ready for its 13B build to take place, so I'll probably pass. I've already seen it once in a friend's REPU where he dropped a 12A in because his 13B finally crapped out; it was a major smoker, and he needed an engine right then. Still...
Speaking of rotary and truck, this engine is slated to go in a local guy's B2000 after break in, and he's interested in doing a turbo at some point. Not sure what type of carb he'll use, but it's going to be big and boost prepped.
So there you have it. Can you guys think of anything else I should do or add to the engine before it's fully built? So far just the plates have been stacked and end play set (.002"). I'll deal with the other front cover bits next.
09-13-10, 01:11 PM
#5
Have you thought about using an adapter to use a 13B intake?
Here is a link http://www.tweakit.net/shop/index.ph...sort=2a&page=2
Here is a link http://www.tweakit.net/shop/index.ph...sort=2a&page=2
Last edited by Dcashdollar; 09-13-10 at 01:15 PM.
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