Hey guys (and girls I assume),



My 12a Street Port (Extend Port in Australia) in a Series 2 Rx7, is starting to burn oil :( so much so I'm getting the light black look on the rear bumper bar above the exhaust.

I've got a 51 mil weber with extended fuel bowel, Holly fuel pump with fuel reg and upgraded lines. Awesome 2 1/2" mandrel bent exhaust with twin pipes and extractors. Plus I use a Series 2/3 gearbox with lightend fly wheel. The car at the moment makes about 139hp @ wheels.



Should I need a rebuild in the near future, depending whats wrong with the housings etc.. I'm considering getting the housings ported for a Periphial Port & changing the manifold to suit the 51mil weber. I've got a pair of 3mil 12a rotors which "look" perfect just need weighing and all the usual checks. I would get a workshop to do the porting to a housing & exhaust, re-jetting of weber, plus final tuning on the dyno.



Any thoughts? which apex seals would I use? would i have to upgrade radiators, oil pumps etc etc..? I've got access to people that can help with the build, I just thought I'd do some research first.



btw: car is only used for Track / weekends, so excess noise is fine https://www.nopistons.com/forums/pub...IR

cya



Craig

I think 12A's are great but, it really depends...... Doing a peripheral port setup is really nice. For this setup, why aren't you going with 13B's.? Just curious. Don't get me wrong I owned a 12A, didn't do much to it but it was a great engine no doubt. It never failed even when i tried at the end to blow it up it wouldn't. I think for the amount of effort you are going to put in, you are better off doing it to a 13B and get a huge power difference. I mean that the main reason to do a peripheral port is for power nothing more.

Being a kinda purist,I like too see a 12A where it belongs.i.e. the model car it was designed for.You can have great fun with it.We can all build 500hp plus turbo motors but there is some enjoyment in building a lil 12A that makes all the right noises and feels great to drive.



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Why 12a? simply put "money"...if I go 13b PP, I need a 13b block, S4 gearbox & lightend fly wheel (because of excess power), tailshaft adjustment?, 13b extractors (I assume)...

but with a 12a, I hope to keep the same extractors, gearbox, use my current block etc..

open to suggestions of course



cya



Craig



P.S: I probably shouldn't assume my Series 2/3 gearbox will survive even with a 12a PP?

easy...no



but, i truly believe in the 12a. shorter thicker apex seals makes it a reliable beast. you can make plenty of power with either a 13b or a 12a. people have run 8 secons and faster with 12a's in the 1/4 mile. and plenty of people run them in auto cross.



but, your real question is not weather to choose 12a or 13b. its if a PP is easy to build, definitly not. custom intake manifold. machining and welding in PP sleeves after being a tight pressed fit. custom making a intake manifold. correctly doing the exhaust ports to match your new huge PP. tuning and much more...



thousands of people have done it. but that dosnt make it easy or cheap. but very doable.

oh...but personally, i would do a semi PP with fuel injection. all the low end of a street port. and plety of top end like a PP. plus the preciseness of an fuel injection tune. PP dosnt like carb. low vacuum causes problems... dont do it cheap. you'll regret it in the end...

Go 12a, Keep it carbed, I dont know what your building this car for? first gen rearends and gear boxes in my opinion suck. I personally would go full bridge. It souds really cool and makes good power. Keep the down draft some boys here in florida are using those and turning some fast numbers. Dont let some of these fucks scare you out of what your doing, what i mean is this **** aint rocket science. if you have some knowledgeable friends go for it! I hope u bild it just as u said u wanted to. Maybe you'll get more props than i did with my project

ok thanks guys.. hmm I do love the weber.... but I have heard that the weber can have issues with a PP :( does it simply fall out of tune / start running lean etc? Because if that was only draw back I'd still do it...



other thoughts where a 12a J / Monster Port, but not first choice, would I have same issues?

mines a PP. basically its a pretty easy and basic setup, do a search and find the competition prep manual, its been posted on here a couple of times.



you can use your header, the weber will work fine, fuel pump should be ok, actually it sounds like you have a decent setup already.



you dont want to use factory steel apex seals, they just dont like to rev that high. in the US we have a choice between the mazda factory race carbon seals, or ceramics. ceramics are crazy money, but seal better and last longer.



oil pressure needs to go up to about 110psi, FD regulator is a good choice.



hardened stationary gears are a good idea, as well as balancing the rotors. i had mine done at AZ rotary rockets, and he says i can run it to 11,500, which is scary.



i would think carb needs to be rejetted. ignition timing is different too, the mazda PP housings have different spark plug locations, so their timing might be different, it depends on what housings you use.

wow that fantasic advice thanks.. something i never thought of is that I had to get official 12a PP housings, I was planning on using my current housings which i think are 12a Turbo housings, I take it they won't do the job?