Any consensus as to whether or not the 01-05 motors are more reliable than the 99-00 motors? In particular, im referring to the bottom-end. I only got ~140k out of my `99's BP bottom-end before I wore away #3 rod bearing. Took the entire motor apart for a rebuild.

I installed ARP head studs and like a moron, did not bother installing ARP main studs and now its too late.. I dont want to tear it apart to line-bore the main journals.

Then I keep going back and fourth as to whether or not I should buy a MBSP and 01-05 oil pan. It seems that the wisest choice would be to (in hindsight) install the ARP main studs as everyone I've spoken to thinks the MBSP is too flimsy to do much of anything.

I'm not building for major power, just high RPM reliability.

Anyone care to chime in?

 

No difference aside from 01+ pistons having a bigger bump in the middle to bump up the comp ratio. IIRC
Its been discussed and general opinion around here is that the mbsp doesn't help ****. Though if someone has some good info/proof proving otherwise I'm all ears.

 

dont the 99-00 bottom ends have thrust bearing issues? or is that something else?

 

I'm not aware of this.

 

i can remember who was telling me about this, but they said the 99-00 bottom ends have a flaw in them...... (it may very well not be true, just throwing it out there to see if anybody knows of this)

 

I think some early 00's had some issues. can't remember specifics, but I think I know what you're talking about

 

i think the thrust bearing problem was a manufacturing defect where they did not machine the tolerances properly, too much play, but i cannot confirm that. fortunately my motor did not show any symptoms of wear with the thrust bearings.

the problem i ran into, however, was con rod bearing #3 which wore away badly. the motor would knock over 3k and would stop if you mashed the gas pedal. i diagnosed the bearing by manually turning the motor and upon downstroke, i could shove a metal rod into the compression chamber (remove sparkplug) and you could actually push the piston down a mm or two.. you would feel/hear the play.

so i guess the MBSP is overrated.. and unfortunately i didnt install the ARP main studs. :(

oh well, another 150k, hopefully i can squeeze more juice out of this lemon.

edit: i may just drill, tap and plug the oil pan, that way going turbo will be a cinch in the future if i decide to go that route.

 

Here is what you're looking for:
http://www.miata.net/solo/99miatathr...ngfailure.html

As for the MBSP, Mazda put it there for a reason, although most earlier BPs have been running fine without stronger ARP main studs OR a MBSP. The newer MZR engine also now has a single complete assembly to support all the main bearings, so there has to be good reasoning for supporting the mains. My personal opinion is that you will be fine without either; the BP has been able to withstand >7000rpm even after rebuilds without either. Oh yeah, don't worry about line boring... the block itself is very stable and will generally maintain the proper bore for the main journals indefinitely, or at least I have never read of a clearance problem.

Keep in mind if you ever decide to install BOTH the ARP main studs AND the MBSP, you will either have to file the studs (not recommended) or drill the pan out for clearance because it won't fit.



The BP is an iron horse. As long as you have your tolerances in check, there will never be a reliability issue.

 

I've killed both a '99 and '03 stock blocks.

The 01-05 MBSP should yield a tiny amount less crank play/vibration in high RPMs.

The ARP main studs are definitely more beneficial than MBSP... As previously mentioned Mazda screwed up the thrust bearing tolerance on 99-00's (too loose.)

If your building for reliable high RPMs, an ATI Damper & Boundary Engineering oil pump are worth looking into. A balanced/forged rotating assembly would be smart too... Honda VTEC's these engines are not.

I still have the '03 block (pan, MBSP etc) if your interested.

 

Al nailed it. Pretty much if you think your engine is going to be used for high stress applications, it would be wise to invest in the above mentioned. If you are just daily driving with the occasional fun run, you shouldn't worry about it, although it doesn't hurt to have insurance. I am not sure about your #3 rod bearing failure, however. That's peculiar.

 

hey al, regarding the oil pan and MBSP - can you shoot me an email to: mike@clearcorners.com

my low post count restricts me from being able to PM.

thanks for the input guys. i assume we can all agree though that if one is to install the arp studs, the block NEEDS to be line-bored right?

mike

 

Another thing you might want to look into is possibly using a 94 block if you are going turbo simply for the easy oil pickup point on that side of the engine.

 

at moderate turbo power levels (250rwhp), the rods in both NB blocks will turn into wavy gravy. I'd bet a lot of money that those of us without boosted NB motor failures have at least one or more non-straight rods in our motors--even if they appear to work fine.

Now... I wonder if that slight bend in a rod in a working motor can upset the bearing surfaces enough to cause significant wear on the bearing before any rods fail. Once the rods are not cylindrical to the crank, it's recipe for ... well, a new motor.

 

I dont know about that^^

I made 270 and change on a mustang dyno and my rods were perfect in every way when i took em out of my motor

 

i've got four rods from a 250 whp motor that are ever so slightly twisted or bent in some direction. they'd probably all still work fine but....

 

Leather was running on a MSM though correct? With the lower redline (at least with the stock ecu) the forces on the rod can be decently lower than running a different BP up to 7000rpm. IIRC the loads on the rods have a squared relationship with the engine speed.

 

im willing to bet that leather's car has seen higher than the factory red line...

 

oh it definitely has. 7700 rpms

 

the thrust bearing issue is not that big. By now the motors have either been fixed under a FSB, or are dead.

 

the first 98 (built for the 99 release) motors had a issues but Pitlab77 they are all dead or been replaced.