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Re: A12 Engine Upgrades

Subject: Re: A12 Engine Upgrades
by Rallytwit on 2020/6/22 19:34:37

I was going to say the same but I'll throw this in. Keep in mind this is for the A12.

There are some basic routes:

1. Bolt-on parts.

a. Install a Weber 32/36 DGV down draft carb

b. Install a header in conjunction with free flow /larger diameter 1.75" exhaust.

c. Install a electronic ignition.

This will likely net you about 5-7 hp.

2. Bolt on / home mods that can be done on the cheap and without the need to fabricate things or a machine shop. These are in addition to the things listed above.

a. Clean up the ports. The valve seats as installed from the factory protrude into the port, you can
use a file or a Dremel to carefully cut down the protrusion as well as clean up the bowl area in the

b. Gasket match; match the intake manifold gasket to the head (see tech wiki for how it's done)

c. Install a moderate cam; something with no more than 280 degrees of advertised duration and
about .420 lift much more than that will make it a hassle for a street car.

d. Use dual valve springs (Isky cams still sells them)You'll need these for any cam upgrade

This level should get you around 10-12 more horsepower.

3. A moderate build that is still street-able but will require some machine work. This will also include the things mentioned in 1 and 2.

a. Source an H89 or GX head (clean up the ports in that as well).

b. Source flat top pistons or use oversize A12A pistons (.5mm and .75mm)from Rockauto for a 79-81 210
the increase in displacement is worth about 4-5hp by itself.

C. Use a .8mm thick GX or .6mm race head gasket to bring the compression up (A12A pistons are dished)

D. SI valves;these have a tapered stem and come in 37/30mm. If using a GX head it will need larger
seats installed.

E. Side draft carbs; either DCOE or motorcycle carbs, the DCOE parts are bolt on but if you have a
left hand drive car they will foul the brake master. The solution is either a single DCOE carb or
motorcycle carbs. Motorcycle carbs will require a custom manifold. You can move the brake master
cylinders but obviously there is a cost.

This should get you around 20-25hp with sidedrafts & about 15-18 with a downdraft carb.

If, and I mean if, you shop carefully for secondhand/used parts you can probably do option one for $300 and option 2 for $800. Option three with side draft carbs could easily set you back $2500. Option three with the 32/36 DGV carb may be as cheap as $1700-$1800.

So what do you get for all this? Option Three would shave 3-3.5 seconds off the stock 1/4 mile time and increase the top speed close to 10mph. While your car would still not out run a stock Miata in a drag race it would be considerably faster.