soooo....

i am in the middle of prepping a 13b LARGE streetport(4 port) into my 83 chassis
i will be using the RB 13b->12 engine mount.

my question is about the flywheel.

the engine came into my possession with the main pulley, but no flywheel...

i have several flywheels around...

from year model 78-83.

i think the 83 flywheel should work(it will be re-machined of course)

this weighs 22lb.
i also have a balanced sa22 flywheel which is closer to thirty lbs(butt dyno LOL!)bad joke...

lemme know what your thoughts are....

 

Match the flywheel to the year/cu. in. of the engine. If this is a pre-7 flywheel and you can't locate a 74-78 flywheel, go with a lightweight flywheel and the correct front/rear counterweights.

 

Oh boy. You have to use a proper 13B flywheel. If you don't you'll kill your stationary bearings very quickly leading to low oil pressure and it will possibly vibrate right as soon as you fire it up. Since you haven't listed what year rotating assembly is in your 13B, I assume you don't know what it is. Here's to hoping you find out and can locate a correct flywheel.

 

sounds like u have a 74-78 13b as i have. if u have a flywheel from the same era u should be fine. i wouldn't chance using a flywheel from any other yr without the corresponding front counter weight. and then there's the differences in rotor weights, so if u do have a 78 flywheel, use that one. it's also a good excuse to get a light weight flywheel.

 

Both flywheels I have are from 12a engines. This is my first 13b.
I am hearing many suggestions to go with an aftermarket light flywheel.
If the lightened flywheel would work, does that not imply the balencing is all internal? Seems most lightweight flywheels are up to 14lbs lighter. If that massive a weight change is acceptable, I'm not sure I understand the importance of the potentially 6lb difference of using a different year.

The two I have are from a;
1980 12a
1983 12a

I think the 80 one is about 8lbs lighter. I have clutch/pressure plate for both.

Does anyone have weight info for a 78 13b?

The engine fell into my hands sealed, not sure what's under the front cover.

Thanks in advance!
K.

 

The issue is not the weight of the flywheel, but the balance. The stock flywheels have a built in counterweight. That is why it is important to match the flywheel with the engine.

With the lightweight flywheel, they have no built in counterweight (you have to supply your own). The counterweight again has to match the engine.

This might help sort out your flywheels:

http://www.mazdatrix.com/faq/flywheel.htm

 

there is a front and rear counter weight to balance the weight of the rotors. if you look at a stock flywheel you'll see its not symmetrical. this is there to balance the rotors.

a 74-82 12a rotor is a different weight from ANY 13b rotor, so you need either the correct 13b flywheel for the rotors, OR an aftermarket flywheel and counterweight.

the TOTAL weight of the flywheel isnt the issue here, but the offset balance weight is.

13B rotors come in 4 flavors

74-85 12lbs, 3mm apex seal

86-88 10lbs, 2mm apex seal

89-2003 9.5lbs 2mm apex seal, machined combustion recess.

and the rx8 rotors

 

Guys, he already has the correct front counterweight! No need for him to buy another one!

What he needs to know is what correct rear counterweight or stock flywheel to get.

If the OP is absolutely certain that it is indeed a '78 13B, all he needs is a cheap rear counterweight from Mazdatrix (it's the cheapest on their list, hah!) for '76-'85 13B and then a light steel or aluminum flywheel.

 

post pix of the "mazda" script on the rotor housings. if it is large letters inside a frame, it's like mine which is at least 74.

 

Good idea to post pics. Also let us know what size your apex seals are.

 

I will take pics when I get back from my business trip(Friday 4th)
the mazda script on the housings is LARGE and italics. Script takes up the whole of the flat surface there, letters being prolly a little over an inch in height. Previous owner claims 3mm apex seals.

K.

 

If it's all stock, then you've got an RX-4 / REPU engine, which will balance fine with a GSL-SE flywheel.

 

person i got it from claims all internals are stock minus a coating on the rotors and one new housing. also a pretty large streetport. both intake and exhaust ports have steel inserts.

 

but cannot recall what the engine cam from!!!! grrrr....

 

according to mazdatrix, all 13b engines share the same rear counterweight(thanks GLS SE Addict!)
however, the flywheel they offer is different for 74-88 and 84-84 13b's.

unclear as to which i am looking for...
the gsl-se was a six port if i recall... mine is a 4port.

thoughts?

 

here's a pic of mine. sorry for the size, i robbed it from a post it was in. it's out of a '74 rx4.

 

use 81-82 stock flywheel (23lbs). I have done it with no issues and many have done it too. dont listen to them, they think like a true engineer (analyze too much is no good for your health). LOL

 

I've been using a 85 GSL-SE flywheel on my 74 13B 4port for 3 years now daily driven not a single problem whatsoever.

 

I just installed a GSL-SE flywheel on a true '74-'75 REPU 13B the other day. It ran smooth as ice.

Wacky, I don't know about the '81-'82 flywheel on a 13B. It probably didn't vibrate, but have you checked the wear on your stationary bearings?

Speaking of using the wrong flywheel on a 13B, I came across a GSL-SE engine (actually an RE-SI but let's not get too technical) which had an S4 FC flywheel. No vibrations at all and ran for years like that. Upon teardown, there was significant wear of the stat bearings.

 

Yes, I did the so called mis-match parts with my light blue RX-3s 13-B streetport. This is the same block that I've used since the late 80's. When I took it apart in the 97's to use a different side plates (larger ports), I was able to re-use the housings and stat gears and to date, I have close to 100K miles of daily abuse, at least 35% of its life was with 23lbs flywheel.

 

granted a balanced rotating assy is ideal for exceptionally long life but, it's sounding like maybe it's not as crucial as once thought?

 

Racing beat sorted me on the phone, verified with mazdatrix.
The engine is a rx4/REPU

from 74-85, the same counterweights were used(for rear aftermarket)
the flywheels are slightly different weights though.

This the same flywhee(aftermarket)can be used on all NA engines. Only thing is a change of pressure plate may need to be changed. Thus I ordered a flywheel to match the brand new pressure plate I ordered incorrectly for my last 12a. The rear counterweight is the same for all non turbo motors till 85.

Wish me luck with my light steel RB flywheel!
And thanks for of your input

moderator, please close thread.

 

Good choice. Another nice thing about the lightweight flywheels is you can swap between engines and only have to change the rear counterweight. So if you decide to swap a different engine in at some point or you want to run some different internals in the current engine, you can reuse the flywheel and just grab a different counterweight.