hey guys im just finshing my series3 7 at the moment ive done the body -suspention -and just finshing the interior. which is all sweet but i still havnt got a motor the only mechanical gear ive got is a rebuilt lsd

my plan is to get a engine get a large port job-48ida- exhaust...etc
what would be better engine to use? are 13b's noticabilly better than 12a's?
and parts and emissions arent a worry as im rota-friendly new zealand

 

There have been several previous threads on this subject, so I suggest you do a search.

However as you are in New Zealand I suggest looking for an early 4 port 13B, slightly more weight but it will give you around 8-10% more power than a 12A with the identical set-up.

 

Yes, a 4-port 13B is your best bet. A newer 6-port doesn't respond well to stuff like Half Bridges and the likes, so a 12A or 4-port 13b is the WQAY

 

cheers for the info, the 4 port come from the rx4's right?

 

Yes, the 13B four port was used in the RX-4 and RX-5.

 

cool mazda nz sells them as n.o.s

 

Depends how much you wanna spend. If you want the best platform and don't mind spending a bit extra you could use a Series 5 Turbo block with n/a rotors. All you have to do is slap on a 1st gen front cover and sump.

 

^ what Revhed said ...

 

Revhed I think the problem is that practicaly every rotary item in NZ is imported secondhand from Japan[as is nearly every car newly registered!]. Getting a s5 turbo engine is reatively easy but NA parts are more difficult/expensive. I have heard of imported 13BTs being backdated to carb NA still using turbo rotors as a very cheap option, not certain if they are even opened up.

 

im confused? i assume you mean the series 5 13bt would be a better choice if i was leaving the internals standard due to factory larger ports- right?

 

less miles, better ports, better bearings,and hardened stationary gears, better apex design (for boost anyways) the list is endless......74~76 cosmo/Luce 13b 4port, and 89~91 rx-7 4 port = a lot of design changes in the middle.

kenn

 

no. i won't speak FOR Revhed, but i'm fairly sure he meant what i meant, which is to get the S5 13BT block and swap in the S5 13BE rotors (and counterweights), thus creating an N/A motor with serious potential.

 

hey cheers for the info but my only thoughts on this is are that the engine is getting a large bridgeport (maybe a pp )-so the size of the factory ports dont really mean much -and as for the km's the engine has done also doesnt matter as building the engine from new parts from mazda.

so guess im just after a idea of which block would be ideal to use as a starting point-and the 13b n/a are hard to find as most later models are all turbo's

cheers for the info you guys

 

You are considering installing a bridgeport carby enginein your s3.

First 12A or 13B? 13B would be the best choice.

Second which 13B, 4 or 6 port? The 4 port is the best choice.

Third which 4 port? The options are a 70s RX-4 engine, or a 80s RX-7 engine. You ask which is the ideal, the answer is a hybred as mentioned by Revhed- 13BT housing. 13B rotors, etc. with a 48 IDA. This is of course the ideal high budget solution. The second best is an old 13B and rebuild/port as you intend. Design wise it will marginally outdated but in practical terms there will be little difference in power and reliability.

Only you can make the final decision depending on three criteria:- how much you want to spend, if the car will be used in competition, and the availability of parts in NZ.

 

Yep, that would be the ideal starting point.

But, even without N/A rotors I think the S5 Turbo block is still the way to go. There is only a small difference in compression ratio compared to the old N/A 13B's (9.2 compared to 9.0) and the S5 rotors are almost 1kg lighter.

 

excellent point. one which many, inlcuding myself, often overlook when thinking about using a T2 block in a normally-aspirated setup. the weird thing is i ALWAYS remember when giving compression options to T2 guys ...

 

cheers for the info revhed -by the sounds of it ill go with that