peejay

I see that Mazdatrix lists the rotor weights to be roughly within a couple dozen grams of each other.

How much world of hurt would I be inviting for myself if I tried to run a S5 engine with a late 12A flywheel?

I found a good deal on a used S5 engine but no flywheel.

j9fd3s

iTrader: (3)

i was wondering when you'd ask that

i dont see why it *wouldn't* work, i mean the flywheel balances the rotors, and um the flywheel doesn't know you're not using the right engine.....

i've heard some specs bandied about but no concrete info

peejay

I've heard of worse things working okay.

And it'd only be temporary until I could find the proper auto counterweight so I could use my SR flywheel. Shouldn't be too difficult to do with all the 13B-RE engines running around.

j9fd3s

iTrader: (3)

i wish i had a scale handy, A i could weigh all that stuff, and B i could tell which CW's out of the pile were what!

but yeah i think an S4 flywheel on s5 rotors is a bigger mismatch

13B-RX3

iTrader: (2)

I think i have a couple RE counterweights laying around.

Jeff20B

iTrader: (13)

peejay, act like a tennis shoe, and just do it!

Forum member ArmyofOne had FD rotors with an S4 front CW and stock S4 NA flywheel. It didn't vibrate. As j9fd3s said, it's more of a mismatch than what you're asking about. Heck my 6 port 12A had a 30 pound SA flywheel that somebody put on it, but the rotors and front CW are the same as all 83-85 rotors. It ran like that for who knows how long. I'd have to look at the stat gear bearings to see if there was any excessive wear. The point is it was an even bigger mistmatch than what you're considering. And finally, I tore down an RE-SI engine that ran for years with an S4 NA flywheel. Its stat bearings were worn, but it's a lot more mismatched than what you're thinking about doing, and it never vibrated.

Jobro

iTrader: (2)

Don't do it.

I had a Top10 in the country workshop put a RX-4 13B counterweight on the back of an RX-7 12A. I could tell something was up straight away. I was new at the time and stood for it. Few years later pulled it all apart after catastrophic engine failure and found and used mazdatrix website to identify the wrong part.

For new engine I used late 12A rotors and correct balances.

I saw the 85 12A the front counterweight and rotor came from, I watched a guy pull the flex plate off a 84/85 12A (and sell me the rear counter-weight) that had a water oil cooler thing on the oil pedestal. 100% **** retentive confirmation that I now have factory rotating parts in my new engine (that has lasted 5 years of abuse so far) and I have no vibration problems whatsoever! New engine has seen 9954rpm during a burnout and I should still have the datalog to prove it.

bumpstart

i have a post somewhere oulining how to metric ID the front and rear masses and mazdatrix has the flywheel and also rear mass ID ( in imperial )

i have seen a local workshop pull the same trick and and it seemed to work OK but i have no idea how long as i did the pull down on the block
bearing wear was a little excessive but its hardly conclusive knowing the limited history of the engine

personally i would be happier if the change included the front mass from the same late 12a
the 12at and 12a 6 p front weights ( which interchange on the same, late mass 12a rotors )
are the masses with the funny 80-100 degree front mass
( one, 12a 6p has curved edges )

peejay

I'm not worried so much about the vibration as possible rear bearing problems.

And the kicker is that I DON'T want to open the engine... I just got an opportunity to pick up a good running stocker for less than what it'd cost to finish either of the two engines I'm working on right now. So my GOAL would be to just plug the turbo feed and make a blanking plate for the turbo return, pop core plugs into the rotor housing coolant passages, put my modified S4 N/A intake manifold on it, and throw it into the car so I can actually drive it now that the weather is threatening to get above freezing for more than a couple days in a row.

We'll see what happens then, eh?

diabolical1

iTrader: (3)

i say put it in and drive the car. as you said, it's just until you locate the appropriate rear counterweight. it's not like you don't know what you're doing.

way back when i didn't know about balance and such, i ran a late 12A flywheel on a S4 13B. the engine had many issues, but from what i remember of it now, none of them could have been attributed to the flywheel mismatch. however, by the time i get back to my garage and am able to find those stationary gears/bearings to inspect them closer, you'll probably have the right setup.

t-von

iTrader: (8)

I think you may be ok temporarily but, I wouldn't rev that combination to high till you get the balancing sorted. I would keep it under 4k at all possible.

j9fd3s

iTrader: (3)

actually its not a big deal to pop the rear bearing out to check/change it

peejay

No it's not... the hardest part is removing and installing the flywheel in-chassis.

trydis7

iTrader: (1)

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

I would go with an S4 CW/flywheel before an S3, if you have one.
When I measured S4 and S5 rear CW they were about an ounce apart.
The S4 rear CW had 1-2 balance holes, S5 had 2-3.

I've heard of several engines that have been run hard with the wrong CW - just don't tell the car.

Don't mean to threadjack, I could use an S5 rear CW if someone has a collection.

Jobro

iTrader: (2)

No need to have deep pockets and short arms about it. You're not dealing with a $2000 bill. Well you might be in 3-4 years of racing if you cheap on out about $50 right now.

I got a S5 turbo weight off ebay to go on my S5NA rotating assembly. Grand total $40.

I had an old RX-4 13B weight I let go to someone else for $20.

I bought my proper S3 12A rear weight for $110 from the most expensive shop in town. Didn't care about price by that stage WANTED IT DONE RIGHT.

peejay

3-4 years of racing is about 100-120,000 miles and several dozen competitions...

If I got 3-4 years out of an engine I would be ECSTATIC.

I forgot about teh e-bay. I'll give it a look, but I need something ASAP since the engine is going in this week if possible. Given the rate I go through transmissions, it's not like it's a pain in the *** time-wise to change the flywheel at a later date. Plus this engine is just a placeholder until I get another half-bridge built, and then this engine will be getting rebuilt/ported. Old T2 engines are not things to expect much from, and given how the rotor housing chrome looks "milky" I'd say it's had a good long life.

Oh yes, the engine is in my car/wagon/truck/ute right now. I just got home from a 13 hour trip to pick it up. (It returned 25mpg too, hasn't done that in forever) Fuzzy yet wired.

peejay

edit - No S5/FD/RE counterweights on eBay for under $120. I'll take my chances with a 12A unit. Given that I have to pull the front cover off anyway (feels like the oil pump is gummed up) I'll just grab the front counterweight, flywheel, and a spare e-shaft and late 12A flywheel and take it to work and see how far off it is on the balancer.

I don't think it'll be too bad, given that the rotor weight difference is less than production tolerances for a given series of engine.

Also, Mazdatrix is showing the rear counterweight to be NLA, Atkins shows rear counterweights for $140 and resurfaced stock flywheels for $125, although shipping has got to be killer for that.

Jobro

iTrader: (2)

That NLA scares me. I hope no other parts are going to fall off the mazdatrix website.

peejay

I found a good "350" flywheel locally so THE WORLD MAY NEVER KNOW.

peejay

..and it turned out to be a "326" flywheel and not a "350".

THE WORLD MAY SOON FIND OUT

ultimatejay

iTrader: (1)

^ There you go.

bumpstart

myself came across another little special from one of the locals

s4 engine with the "2" marked early 12a flywheel
and this isnt the first one i have seen run like this
there is only a handful of shops or individuals that do rotor work where i am so i will soon work out which place is pulling off the swifty


,, i reckon its been done to shortcut the process for SA22 rx7 replacement engines
--so they can run the existing clutch and say nothing to the new owner

i certainly wouldn't be happy to compromise the engine balance to save a handful of $$ on clutch or flywheel change over


in this situ i supplied an n326 flywheel and advised to purchase a 225mm pressure plate
( didnt want to give out my last s4 weight )

peejay

The epilogue is that I ended up buying a pair of nearly-new rotor housings and most of a set of FD corner seal springs and semi-decent oil control rings.

The side housings were street ported by the "bigger is better and too big is almost good enough" methodology - it looks like they were opened up slightly on the inner curve (bad) and were opened up to extreme early opening with a huge bevel which means I can't bridge port them (worse) and they close extremely late too (useless). And the rotors were milled for 3mm seals, which is fine because I can't use them anyway as the engine suffered extreme bearing failure - two spun rotor bearings and the front bearing was siezed to the E-shaft so the front rotor (the one that does not have the side and corner seals hammered into it so hard you can't tell where they are) is stuck on the shaft.

So, er, I bought the correct flywheel for nothing. But hey, even considering that, I still paid less than what the good parts I could salvage were worth, so I'm not terribly upset.

I don't know about what you guys got, but the late 12A we got (series 3 and the very last year of series 2) used the same clutch as series 4/5 N/A. 225mm disk and the pressure plate bolts to raised steps on the flywheel, which prevents putting the wrong plate on. I have successfully used the early 215mm disk on a 225mm flywheel/pressure plate combo in a pinch. (Online seller kept shipping the 215mm setup when my friend ordered 225mm clutches, and we had to get the engine in THAT WEEKEND. I had a 225mm pressure plate to donate to the cause. Worked just fine)

I think it's time to experiment with another peripheral port. I have good housings to start with this time. Actually, at last count, I think I have a dozen or so good 13B housings, mostly FC but also two GSL-SE. But I have next to zero good FC side housings! (I don't count 6-port housings as "good" )

j9fd3s

iTrader: (3)

lmao! the 6 port center irons are PERFECT for a P port!

peejay

Actually the end housings aren't too bad either, just make a dowel that you can hammer into the aux port. That's less epoxy that needs to be bought!

Really, the 12A I made probably would have worked more nicely had I had a more free flowing exhaust system, which the car didn't get until well into the car's 13B stage of life. Oh and a throttle body that wasn't small by tiny by pathetic in size.

Hmm. Maybe it is time I tried one of those semi peripheral port things.