So the is no longer about "info on the most hp you can get out of a A12"

But now is: info on the most hp per ascf sedan racing class rules

RPM is your frined, build it for high rpm and thats where smaller ports and carbs work well in motorbikes.
Aim for the highest comp possible using custom single valve springs made for the cam and rpm you are choosing.
Diff is a given go as over 4.88 if possible someone called Cameron datto had a 6.1 to 1 or similar I think it was a combo of R & P that where diff lapped or a forklift ratio.

Use the best oil you can afford to throw away after each race and make sure you run a magnetic sump plug for metal removal from the high rpm.

whats the carb filter requirements? can you run somethig through the bonnet? or long velocity stacks?

Ignition what is allowed?

Make sure none of your brakes are gripping or causing unnessesary friction

finally weight is the key, stay away from high calorie foods and do your best to keep everything light

Are Daihatsu Charade 1.3 allowed or suzuki swifts allowed? I know the civic with the eb1 or eb2 engines are superior to datsuns in every way but very rare nowdays although you do see them at wreckers once a while.

two things that might be worth a look there - there's probably a couple of tyres out there that are legal that are a lot more effective than others (I note they don't allow race or off road specialist tyres of course). As to which tyres they might be, I have nfi. Do they allow retreads at all? Some of them are occasionaly pretty decent at moderate speeds on surfaces with less than ideal traction, but obviously not good for anything seriously high speed.

Secondly - diff ratios are free. I reckon you might find that (hypothetically) a diff ratio that lets you run in 2nd and 3rd for most of the time (or even 3rd and 4th, though that's probably a stretch) instead of 1st and 2nd (again, hypothetically) will have an advantage. that's because there's a much bigger rpm drop shifting from 1st to 2nd than 2nd to 3rd or 3rd to 4th, so if you could run 5.2 diff gears (if you can find em) or 4.88s and run in 2nd and third, or 3rd and 4th (I don't even know if you'll be shifting gears at all to be fair, once you get up to race speeds) would keep the motor in its 'sweet spot' easier than 3.9 gears and 1st and 2nd.

They say you have to run a set venturi size. You could probably very carefully rework the carb around the booster to get a little more flow without going to a bigger venturi, and similarly, you could look at slightly thinner throttle plates themselves, that won't obstruct flow as much when fully open. It might only add a little bit of flow, but you'll need as much as you can get if you have to use the stock carb.

yes they are the specs, ascf sedans

My apologies to Carter, who is JuniorSedan, I've misread .06 as being 6 thou, whens it's 6 100ths, or 60 thou. So did you get some nice 74.5 mm Hepolite pistons like I did once, with flat tops. That motor was a revver,too, with a 54/86 cam & some webers. Had to do some serious persuading of scutineers that it wasn't an A15 in disguise, it really was only 1220 cc's. It did in fact go better than the 1570 cc A15 with the same cam I had, because the valve springs in the A15 were stuffed & had been from the start. Worst saved $80 ever, cause thats how much new ones would have cost me.
the page for the tech specs for Juniorsedan are
http://www.speedwaysedans.com/tech-specifications

I did a google search for the regs for a Junior Sedan. They list 1200's 120Y's & Sunny's as eligible running an A12 motor, so no A15's. Its basically standard bore A12, with a 0.06 thou overbore allowed, & a 0.06 thou limit for maching the crank,only single valve springs,a standard carby that they specify the throats for both primary & secondary's at 20/26 & that can have the choke butterfly removed, standard exhaust manifold, standard ports, balancing allowed but only on the crank & only in the factory style, so no adding counterweights. Flat top pistons are acceptable, & camshaft & compression appear to be free. So a good set of outers from a twin valve spring set, a set of flat top A10 pistons & attention to detail in the build that nothing is binding, etc. The web site I viewed specifically mentioned that several competitors had been caught cheating & were dealt with by termination of license, etc.
The Junior Sedan class is a speedway category for 10-17 year olds, that started in Western Australia. Races are run in every state except NSW, where the minimum age is 12 by law & so the category can't be run here. Interesting class with what looks like an even playing field & a variety of cars you can run.
So a good A12 with a cam matched to the carby size, flat top pistons & a good set of single valve springs would probably make about 80 HP at the crank. If everybody else is making about the same, then a few HP one way or the other is going to be the winner. Hope Ernie can point you towards somebody closer to you for advice.

Sikyne's A12 was recently dynoed at 160+ rwhp. And that with a stock block.


Quote:A12 normal block can rev past 8k. Even an A15 stock block will do it. The main requirement is valve springs that are capable of high rpm.

in reference to question of thread,
the people who are most likely to try and extract the most hp from their NA race a12 1300cc would probably be from japan,have deep pockets and also access to very high quality parts that were developed just for racing.i.e nismo,tomei parts etc etc.Chances are they are not on forums to answer this type of question.i.e japs 1200 tomei owner.and if they are,they will be on japanese forum.Most hp from an a12 will mostly depend on how much your willing to spend.

that said, japan 1300cc ts cup a12 engines claim 170ps.this is what i refer to as "worked" a12s !!!

If it's anything like ministock racing here, you aren't allowed to do bugger all to the motor. I once browsed the ministock rules, and to get an edge, you'd really need to build the engine clever. (I can think of a few small things that could be done)Downsize the rocker shaft a little bit, and fit offset bushes to the rocker arms to gain a little extra lift. (and if they ask to check your lift, remove the rocker shaft, so they can measure it at the push rod) Can you run flat tops? If not skim a few thou off the crowns, (To widen the squish bands on the pistons a bit) and then zero deck the block. Back cut the valves. Since you're gonna be stuck with a small cam, get that bit more flow at low/mid lift. Plus the valves only see peak lift once, but they see the mid/low lift twice during an intake cycle. is painting/polishing/coating the engine internals allowed? Coat the crank and rods with the oil shedding film to cut down on windage losses. use a lower profile lock nut on the tappet adjustor. That tiny bit less weight means the valve train can accelerate just a wee bit quicker. Make some lighter weight valve reatiners. Probably not legal, but done right it'd be hard to pick.
Since you're hamstrung by the rules, you have to do lots of little things to gain just the slightest edge. I wonder it you could use ring spacers, and run super thin rings for less drag on the bore wall?

I was revving my A12 to 8600 pretty regular...............they start to where out quickly with that kind of treatment.

Peter Zekert has said his full race A12's are right at 100 HP at the wheels, the engines are gone through pretty often. Think 6-8 hours. Another US racer Dave Patten's A15 (without the restrictor) managed 156hP at the wheels..................14-1 one compression, Revved to 9K and all sorts of other goodies..............nowhere near streetable.

Grover I started with the SCCA in early 1989, new lots of SD Region folk, mostly corner workers. The old 200SX emergency car we used was donated by San Diego Region.

Junior Sedan sorry for Hijacking the thread.........

Tom