1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Piecing together a motor and have some questions.

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Old 12-18-07, 08:41 PM
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Piecing together a motor and have some questions.

How hard would it be to piece together a motor?

I was thinking about slowly gathering these parts:

12A irons
GSLSE housings
FD rotating assembly

I have a very limited budget and really i am just dreaming right now, but what else would i need here considering i would be also buying a rebuild kit? I mean, i know i need a intake system, water pump, alternator, etc etc. I am just talking about the motor itself.

If this is a retarded thread and it has been discussed before, i am sorry and by all means close it!
Old 12-18-07, 08:45 PM
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Curious as why the FD rotating assembly...

Make sure you have the right tools for the job first.
Old 12-18-07, 08:50 PM
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FD rotating assembly is lighter than the TII rotating assembly i believe

I probably dont have the right tools yet and there is no time limit for this build, basically i would just collect the right parts as i go and then build it up when i had the knowledge and time. I have the rebuild DVD, but would really like someone to be there with me and hold my hand as it was rebuilt. Might enlist the help of ManInBlack as he is pretty close to where i live.
Old 12-18-07, 09:09 PM
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why not use the rx8 shaft. its the lightest isn't it?
Old 12-18-07, 09:27 PM
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good idea, but i have no clue
Old 12-18-07, 11:47 PM
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If you are on a budget why are you considering fd internals? get a good GSL SE core, rebuild it with streetported 12a plates, then get the racing beat intake and exhaust. The SE internals are a little heavier and same with the flywheel, but that will cut cost and provide better torque and midrange anyway, great for a street car.
Old 12-19-07, 12:30 AM
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domokun!

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hey i have a question for you not pertaining to the motor question. how did you get the rear to lower more?(car in your sig) im having problems trying to bring the rear down.
Old 12-19-07, 10:01 AM
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S5 rotating assembly, not FD. While the FD may be lighter, the S5 NA rotors are higher compression, unless you plan on turbo chargeing. Only FD internals, I recommend are the corner seal springs.
Old 12-19-07, 10:39 AM
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Yes i do plan on turbo charging the car, so S5 TII internals then?

And budget wise, that is the genius of slowly putting together a motor, you dont have to shell it all out at once, lol
Old 12-19-07, 10:46 AM
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If you're turbocharging, then you can use FD internals, though the S5 parts may be easier/cheaper to find used.
Old 12-19-07, 10:49 AM
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thanks, yeah i am just trying to get an idea of what i am going to need then slowly attack and find pats as i go along
Old 12-19-07, 12:13 PM
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S5 T2, 13BRE, 20B, FD all have 9.0 compression rotors. I'd avoid FD rotors because they tend to be weak.

I'm building a new engine for the GLC. It will consist of GSL-SE or earlier rotating parts. Wanna see who builds theirs first?
Old 12-19-07, 02:51 PM
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i am betting on you

mine is really waiting funding because i cant find a job in this darn **** poor economy in michigan
Old 12-19-07, 03:47 PM
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whats your goal for the engine/car? power and use wise
Old 12-19-07, 04:42 PM
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Planning on a Judge Ito extended port
RB wrap around sidedraft intake
tweakit FI setup
stand alone
turbo hat from rotary shack
and a turbo of undecided specs at the moment, suggestions?

Power??? I have no idea and really dont care, lol. Anything over 300hp is gonna be gravy in the FB

Oh and i plan on it being the ultimate street car. As it is right now i drive the FB about 600 miles a year so it sits in the garage a lot. Truth be told i love showing it off more than i drive it, but i am sure that will be different when the frankenrotor is in there
Old 12-19-07, 04:47 PM
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Originally Posted by FBsliderseven
hey i have a question for you not pertaining to the motor question. how did you get the rear to lower more?(car in your sig) im having problems trying to bring the rear down.
Racing beat springs, but I wish it was a bout 1-1 1/2 inches lower. Didn't change much in the back vs stock other than stiffening things up.
Old 12-19-07, 04:50 PM
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Turbo widebody FB

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Ummm I don't understand why you guys are recommending using a S5 rotating assembaly. The S4 rotating assembaly is slightly heavier, but it has a lower compression (what really matters for power and reliability in a turbo setup). You then need a S4 front counterweight, and a lightweight flywheel and a rear counterweight (if you are using an aftermarket flywheel, which will probally end up being lighter than the S5 rotating assembaly anyways...).

I do agree with Scott that you should use the S6 corner seal springs (they are a wedge shape rather than a wire) they are a much better design. Other things to consider are a RX8 eccentric shaft (1 pound lighter) and RX8 stationary gears, they are hardened and come with windowed bearings.

Back to the compression ratio situation, think about it like this, a lower compression ratio means that you have a LARGER dish in the rotor and can put more air and fuel in the engine at a give time. Therefore you get more power because more charge is getting into your engine at any given time...
Old 12-19-07, 05:09 PM
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good to know!
Old 12-19-07, 05:20 PM
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Im getting ready to built another motor. RX-8 rotors, eshaft, front/rear counterweight. thats a real high compression set up.
Old 12-19-07, 05:27 PM
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are you gonna carb it?
Old 12-19-07, 06:19 PM
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NA or S4/S5 TII rotors, it's all in the tuning. Fwiw, starting with the S5 engine, the stationary gears were hardened since the NA version has an 8k redline. Hardened gears and 3 window bearings are backwards compatable too.
Old 12-19-07, 06:28 PM
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not to hyjack but whos a good rotarded porter in the seattle area? and would
12a irons, SE housings, and renesis internals work?
Old 12-19-07, 06:34 PM
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Originally Posted by Dan_s_young
Ummm I don't understand why you guys are recommending using a S5 rotating assembaly. The S4 rotating assembaly is slightly heavier, but it has a lower compression (what really matters for power and reliability in a turbo setup). You then need a S4 front counterweight, and a lightweight flywheel and a rear counterweight (if you are using an aftermarket flywheel, which will probally end up being lighter than the S5 rotating assembaly anyways...).

I do agree with Scott that you should use the S6 corner seal springs (they are a wedge shape rather than a wire) they are a much better design. Other things to consider are a RX8 eccentric shaft (1 pound lighter) and RX8 stationary gears, they are hardened and come with windowed bearings.

Back to the compression ratio situation, think about it like this, a lower compression ratio means that you have a LARGER dish in the rotor and can put more air and fuel in the engine at a give time. Therefore you get more power because more charge is getting into your engine at any given time...
true but i used s5 na rotors for my turbo motor. the idea being that spool is much quicker and you can run lower boost numbers to get the same hp. i love this setup. my t04e hybrid spools as fast as the stock s4 turbo and out spools my brothers hybrid on the turbo motor. we are both running half a bar and i can walk him by 2nd gear.

use stock corner seals and replace the rubber insert but def get the s6 springs. for seals i would get the rotary aviation. i have never broken one and have been through a few sets of the atkins and oem seals. one tuning mishap and resulting detonation will blow the atkins/oem seals to bits.

get s5 rotors, na or turbo. s4 is heavier. s5 housings. on the s5 housings the spark plugs are farther apart vs the s4 resulting in being able to run more advanced timing. renesis e shaft and stat gears.

man i cant find the exact compressions for the different year rotors but i think this is right

s4 turbo 8.7:1
s4 na 9.5:1
s5 turbo 9.0:1
s5 na 9.7:1
Old 12-19-07, 09:52 PM
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ill be building a 300 or so set up for my SA. to me it seems like youre going through WAY too much trouble, and WAY too much money.

you can easily hit 300hp with a S5 T2 swap and still keep the S5 ECU. ill be doing tha initially. then i may swap it over to SE rotors and a standalone, just for a little more spunk. whenever i break it apart itll also get port work.

you could EASILY spend a crap load less than youre looking at spending and have A LOT less trouble. the perks of your idea is itll look more "old school" to the untrained eye, but the untrained eye probably wouldnt even know what they were looking at anyways.

also, on the debate about rotors. S5 all the way. yes the S4 T2 have a lower compression, but that only matters if youre wanting extremely high numbers. theyre SUCK when not in boost and wont be as responsive as the S5 rotors.
Old 12-19-07, 11:23 PM
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Turbo widebody FB

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I dunno I just figure that if you are using a turbo that is reaching full boost potential quickily and you will make more power with s4 rotors. I can deffinately see where your coming from. When I discussed my setup with my friend (has been building rotary engines for 20ish years) he also suggested the s4 rotors for a setup like mine.

But like the other guys mentioned it depends on your goal. If you want more HP go with the S4 rotors, and if you want a very responsive setup go with the S5.


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