how much power would i be looking at if i rebuild a 12a and street port the engine, RB street port exhaust , and a RB street port intake system vs a 13b ported rebuilt with street port exhaust and street port intake system??
would it be worth the wait to save for the 13b??

 

It really depends on the carb and EFI modifications.
However you would be looking at about 180bhp for the 12a and 210hp for the 13b.

This is order of magnitude and expect 10-15hp variation depending on how good your tuner is particularily with the 12a carb system. In reality the difference in cost is going to be minimal so on balance the 13b is better with slightly more power and more certainty of obtaining it.

The method of installing a 13b in a 12a engine bay is well covered on this forum so there should be no trouble in the update.

 

What carb would you suggest for the 12A?

 

Street porting would be pushing it to the limit of a modifird Nikki which would be the cheapest and simplest way.

I suggest you look at a Weber 48IDA, a second choice would be a Holley using Racing Beat components. Use the search feature on this forum to hear competing claims from'experts' !

But whatever carb is chosen upgrading the fuel pump will be essential, and check out the state of your fuel filter.

 

Your going to make more power with the 13b... if you do do it make shure you get a 4 port motor... I would just build it up for nitrous apps...

 

Horsepower, shmorsepower, the 13B is just so much torquier than the 12A, there's no contest.
And the 4-port motors are the easiest to set up.

Just my opinion... -WG

 

I think that the other thing to consider is torque. You can get a whole lot more torque out of the 13B.

 

If I had the money to do either setup, it'd definately be the 13B, but carbed... much simpler But yeah, a 13B is a far better engine to start with

Jeff

 

im planning to just buy the full RB exhaust system for now for the 12a, but if i do upgrade to a 13b would i ahve to buy a whole new exhaust system??

 

no ... just get a 13B header front section

 

The stock 12a fuel pump is actually fine for a street ported 13b with a weber. I use it and it's also in Racing Beat's manual.

 

13B over 12A anyday

 

I have a chance to buy a 13B, rebuilt, for $1000, and I'm very tempted because the price is so good. Fiure to put ir into my 83GS, carbed (what carb)?

How big a job is the fit?

JH

 

Where can I find it?

 

ok i read this link: http://lancaironline.net/lists/flyro...ssage/506.html
comparing 12a's to 13b's
is this guy full of it in the comment on the bearing sizes being the same. the comment on apex seals makes sense to me though
found the link when researching turbos, figured this would be a good thread to bring it up

 

well heres a dumb question.... are there any benifits to a 12a over a 13b???


EDIT: D'oh..... I guess my question would be valid if the post above me didnt appear when I was typing mine....

 

Gamble, that e-mail or letter is written by Leon .P.

He is a legend as far as I am concerned, and is one of the real smart guys when it comes to rotaries in Australia, MUCH MUCH more so than the current crop of "*******" that rate them selves so highly from my country.

He is the only person I knew over 10 years ago who could properly describe a rotary engine in many technical aspects, while the current crop of "world experts" were doing their apprentice trades. He is a very smart guy. Some of his quotes from magazine features of the day were genuine, smart & original, where a majority of others could only quote things from other sources like Racing Beat tech manuals !

Very smart bloke in my books

No amount of methanol/C16 and truck turbos can replace inteligence, and that guy has plenty of it.......he would be pretty old now ?

 

In this thread, is the 4-port 13B being referenced or the 6-port? I have the opportunity to get a running '87 for $500, and I'm thinking of putting the engine in my '82, as opposed to building up the 12A. If the gains are going to be small (10-15hp, according to someone above), I can make up that power with a little more money into the 12A.

 

The reason the 6-port makes more power is because the 6th ports have a lot more timing (later closing) than the 4-port 12A, so 135 Hp vs 103 Hp is a much larger increase than just the displacement story tells. The older 4-port 13B only made 115 Hp or so, which matchs more closely the displacement story (1308cc is only 14.2% more than 1146cc) The reason 4-ports can make more Hp, is due the the amount of porting that can be done to them. But still expect only a 15% increase compared to that of the 12A of similar tune.

Thought is seems general consensus that the 13B has a wider powerband than the 12A.(again this may or may not be due to the 'variable' nature of the 6-port configuration)

 

Someone from Racing Beat told me they didn't offer much in terms of manifolds (intake or exhaust) for a ported 6-port 13B, as opposed to the 4-port or 12A, because they didn't find significant gains for the ported 6-port, since it already breathed much better, unless you went all out for high RPMs and race driving.

This has me wondering if the 6-port 13B will put out basically the same amounts of power as a streetported 12A (or 4-port 13B), without the porting job.

Of course, this is all assuming proper FI and/or carb tuning, as well as a mild porting job.

Anyone have any thoughts? I'm just trying to decide whether to put a 6-port engine in, as opposed to rebuilding the 12A, including porting, with a goal of 200hp, and reasonable torque.