Hi guys Iv been reading post for awhile now thought if ask a few q's, Iv got a 1980 rx7 that I have a 12a bridgeport in , it's so loud that Iv bought a 13b with a rather large extend port ! I will run my Ida webber ( 48) , but should I run dizzy locked or unlocked ? If I want power out of this high rise intake manifold or low , I was thinking low after the reading Iv done on here .... ? And exhaust headers to twin 2" to collecter or headers to 3" or suggestions that would work well for extend port I don't want it really loud as this engine should be quieter .( hopefully ) as I'm growing up lol , any other advise on what would help my old beast go well please let me no , aiming for 200 hp

 

I have a 13b extend port with weber in my 1980 rx7.I used to run a locked dizzy set at 23 degrees.I later changed to run the ign only from a michrotech.complete with a tps on the carb.We dynoed this when engine had 100 000 km on it. made 150hp to the wheels,so maybe 200 210 flywheel . Hp curve went up at 45 degrees angle no dips up to 7000rpmI run a heavy flywheel makes this setup driveable.Engine now has done over 160 000 km
Have to check exhaust but muffler has 21/2 inch in/ out .Hope this helps

 

my thoughts are:

1. you shouldn't need more than 2.5 inches. that's more than enough for flow and a civil-minded tone.

2. intake length will come down to your use for the car. i will assume since noise level is an issue for you that you intend to use the car in a capacity other than racing, so you may want to go longer. however, you could also go with a short one and use spacers to play with length. it's up to you.

3. i won't comment on the locked vs. unlocked dizzy. i see the merits of locking the dizzy in forced induction applications, but i do question it in a setup like yours. perhaps i lack understanding of it in that context though so i will let you get that particular information from someone smarter and more experienced than myself.

 

So I already have a 12a set of 12a headers 1 3/4" quite long joins under drives seat to one 2.5" exhaust with a res then over the diff to a big boiler style muffler at rear May just alter this then and try it ??? Yes I want it on the street , for day trips to beach summer cruises , and rota events over here , may use at odd track day and bit of drag racing and drive home ! Iv had car since 2000 and just had it painted original white all trims back on again , that's why I'm not going turbo want more old school look , but want it to go as good as possible ! Engine all new bits housings etc carbon seals should be good

 

Aw and how heavy do ya recommend , ! Everything I see over here is only 10 12 pounds ? And what intake manifold any recommended ?

 

1. i like the idea of a shorter intake manifold, and then using spacers to get the length in the engine's happy spot.

2. someone just posted all the stock ecu timing maps, and basically you could lock the dizzy and do ok... an S5 T2 is running 20degrees off idle and at wot... you'd gain at cruise with the vacuum advance, and it might idle better with an unlocked dizzy.... i'd say start with your locked dizzy, and if you get bored, throw in an unlocked one, and start playing

 

If you are running a webber a locked dizzy will help to eliminate the flat spot if you jet it correctly as oppossed to rich on the idle circuit . I experienced this first hand Other weber mods inluded extra progression holes, longer accell pump stroke. drilled holes in the butterfly
The flywheel i ran was a std rx4 -yes its heavy but suits me.
ill post my michrotech ign maps shortly you will see how much timing you can run when its not being scatterred through a dizzy cap

 

RPM 8000 31degrees 2 degrees split inches merc
7500 31 2 30 plus 3 degrees


7000 31 2 25 + 3 degrees
6500 33 2 20 + 3 degrees
6000 32 3 15 +3 degrees
5500 32 3 10 + 1degrees
5000 32 3 5 0
4500 32 2 0 0
4000 32 2
3500 31 2
3000 30 2
2500 27 2
2000 25 2
1500 22 1
1000 20 1
500 18 1

 

I run my bridge unlocked and it was set at full advance 24 degrees , it still idled ok never got very carried away with the timing it stil went good tho , so I mite start unlocked then and see how it goes on dyno ?? The fly I currently have is a 12a turbo factory one with the step in the back if you know the one I mean ?? Don't know how heavy it is never weighed it. Maybe I should just run it , are they safe at big revs ? I don't want it to fly apart I like my feet. !! Exhaust over the diff or under ?? Currently it's over but Iv noticed over here a lot under as it straighter but looks a lil ruff to me. ?

 

I don't think your 12a header will connect to the new 13B engine, but a like the 2.5" exhaust size. Maybe add a presilencer or resonator pipe after the header and ahead of the muffler to help quiet things down.