Motor building quesitons
 

So my s4 t2 let go acouple of months back. When it let go it took both rotors and housings. I purchased a used jdm s5 t2 engine that was known to be smoking but had good compression. I tore the s5 down tonight hoping to make use of everything. But found the irons to have worn less then favorable.(They could be potentially lapped, maybe, but then I would need to find someone who was able to do that.) Both housings are in good shape and both rotors are in good shape. I know the s5 irons are more favorable due to the thicker irons. So, my question is, can I use the s4 irons with s5 rotors and housings or a I asking for a timing nightmare between the different gears in the housings?

yes you can, but, make SURE you use the s5 e-shaft, flywheel AND counterweight

other than that, yes you can mishmash the irons and housings

Wasn't going to mix match eshafts when I knew the eshaft was good on the set of rotors, it will be getting a new flywheel on my s4 one was had seen better days. An when you say counterweight you are talking about the front counterweight or the rear at the flywheel? My Jspec had no flywheel so I was going to go lightweight with a counterweight for the s5 engine.

if you use s5 e-shaft and rotors, you must use the s5 REAR counterweight, same with s4. you can put s5 internals into s4 housings and irons and vice versa, but you need to keep the e-shaft, rotors, and rear counterweight the same per series of engine

again, not all S5 irons are the updated cast, some just have the reinforcement rib that does little to nothing for integrity before they actually beefed up the size of the casting even later in production.

lapping irons isn't wise or cost effective, since lapping irons usually takes away most if not all the nitrite anti wear surface, properly renitriting irons including re-coring and machining costs almost as much as new irons does.

all eshafts are identical from 1986 through 2002.

depending on how bad the wear is, the factory specs are actually quite unforgiving to wear on the irons, you're better off using the finger nail scratch test. i've run some fairly worn irons in my own engines and they didn't give me much drama.

Mazdatrix still laps housings. $90 a face so $360 for all faces. Shipping will eat you up though due to weight. I'm on the fence about it currently. My first rebuild I lapped my housings. This one I didn't( used a different set from my parts car). My housings outlasted an apex seal that tried to roll out of the groove( apparently a know issue once 3 piece seals get around 150k on them). At 146K they had significant wear marks compared to the ones I used next that had114k on them but the car ran fine other than smoking on startup. I figure it's better initially due to everything being smooth. Long term I'm not so sure unless you have them re-nitrided. As far as rotors. As said use the counterweights that match the series of the rotors you are using.

1. Lapping removes the smooth surface from the iron that helps the engine seal bed in quicker. New factory irons are not polished smooth, just as new piston builds are left with a honed surface. It aids oil retention.

2. New irons for an S5 turbo are around $1500 for all three. You can get all of the plates lapped and nitrided for $500-700. Three used turbo irons are around that much.

3. Nitride and Nitrite are different. Iron is nitrided.

If you know someone that works in a machine shop with a large enough surface grinder, you can have them surface ground and source a local heat treater for for the nitriding. You might want to put a bit rougher surface on the plate before nitriding by hitting it with a 150-120 grit polishing stone and some oil. If the shop does a bit of nitriding, see what they want for the whole deal.

Freeze plugs will need to be replaced and most likely the oil galley plugs.

once the irons are worn beyond spec, lapping them will remove all the nitride(so i misspelled it, sue me).

solely lapping irons with that scenario results in severely worn irons in a short period. to do a nitride job as good or better than the factory requires drilling and retapping all the brass drift plugs in the irons, as well as replacing all the core freeze plugs. doing so for so cheap, i would be weary of the results because i have a feeling the nitriding either isn't thorough or one or more of the recoring steps was ignored which results in oil and/or coolant leaks. additionally, if enough material is taken off then the coolant seal passages need to be remilled if the wear is severe enough.

after all that you still have a used iron that is prone to coolant seal wall failures.

you're all free to do as you wish, i'm just giving you my experience with trying to recondition irons to at least factory specs and why i chose to just not put people in the position of using overpriced and unreliable parts. rebuilding an engine is already a time consuming and costly venture as it is without having to redo your work. in most cases just using some semi worn parts is better than bashing your head into the wall, you're rolling the dice with anything aside from new parts.

1. You can lap to remove the glazing without taking off all of the nitride penetration. This will not remove the ridges, but will help make an engine with new side, corner, and oil control rings seals bed properly. Most prominent racing engine builders recommend this.

2. How used an iron is does not affect the coolant wall seal life. I've had a brand new iron fail, and mazda remans fail in short order.

3. It goes without question that a half-ass lap and renitride will result in less than desirable results.

I am stating that for the cost of buying used irons, you can have your perfectly salvagable but worn irons reconditioned to as-new condition... or you can spend the same amount of money on used irons with worse results.

4. there is no way to measure how much nitrite layer is remaining before or after the service.

5. cut the face and the wear existing at the 3 and 9 will just spread much quicker from the now thinned anti wear layer.

course you can assume the iron has never been lapped before, if it has... as the parts get older their history is less known, unless you have a known never rebuilt engine.

4. Again, nitride.
And there are ways to measure, actually.

5. If you lap the face only to remove the glazing, you won't remove the wear grooves.


What it comes down to is that I would prefer to recondition irons to OEM quality for the price of used irons, and you would prefer to rebuild with used parts with a head-start on being worn out?
Makes sense.

If I were the OP, I would sell his S4 irons, refinish the S5 irons with the money, and build a better engine.

But to each their own.