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PMRacing
PMRacing GRM+ Memberand UltraDork
8/10/21 12:49 p.m.

A couple weeks ago I drove my track rat Miata to work. On the way home I heard a noise. RPM and load dependent. Crap. It has a case of the rod knocks. After multiple seasons as an auto-x car before my ownership and 6 track seasons it's about due for a refresh. I can't complain considering this car was always driven hard and put away wet. The question is, what to do?

A. Just stick a set of bearings in it and hope it doesn't need anything else?

2. Refresh entire engine?  It doesn't burn oil and has good compression and leak down last time I checked. 

3. Swap with a running engine if I can find a good one? What other "while I'm in there" will I find?

D. LS swap? (Not practical at this time but beating you all to the punch). 

4. Light it on fire?

5. Other?

Thanks as always for the wise (and wise ass) opinions!

calteg
calteg Dork
8/10/21 12:57 p.m.

Cheap'ish easy button is the NB1 motor (99-00)   Will give you a small power bump via higher CR and better flowing head.

VVT motors are even cheaper, but you'll need a VVT controller or full standalone to control the solenoid. 

I like the idea of a K series swap, but they seem to explode on track pretty frequently. 

Ecotec swap seems interesting. Track worthy and capable of 200whp. Here's a kit, including the motor for $2500. He's had it listed for a few months, could probably talk him down

https://austin.craigslist.org/pts/d/austin-ecotec-miata-swap-kit-for-nb/7346791160.html

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
8/10/21 1:03 p.m.

All solutions involve the same step 1: pull the engine.

Then you can take the pan off and poke around inside. That's when you make your determination for what the next step is. I'd also call around to your local machine shops to see what their turnaround time is because that may be a factor in rebuild vs replace.

A motor swap is a serious undertaking and may put the rest of the drivetrain at risk. If you're enjoying it as-is, I'd just find a decent 1.8 engine, service that and drop it in. If you do find a VVT engine, you can get a standalone controller for that. 

KyAllroad
KyAllroad UltimaDork
8/10/21 1:07 p.m.

I went VVT, new turbo, standalone, and all the rest when my 1.6 gave up last year.  It's been more of a money pit than I expected but I like keeping the flavor of a Miata in a Miata.

Previously I owned a 5.0 Monster Miata and it was kind of miserable to drive.  Basically an old Mustang wrapped in a small body.

Then I had a 2.4 ecotec in an NB.  The motor was buzzy and the redline was too low for the gearing to be a decent autocrosser.  Not worth it for just 180 hp.

pkingham (Forum Supporter)
pkingham (Forum Supporter) GRM+ Memberand Reader
8/10/21 1:15 p.m.

Sounds just like what we're going through  https://grassrootsmotorsports.com/forum/grm/miata-engine-noise-diagnostics/184305/page1/

Got the engine out and pulled the pan so far.  No slop found in any bearings, but I've only pulled one so far, and it was practically new looking.  Not sure when we'll get back to tearing it farther apart.

AngryCorvair (Forum Supporter)
AngryCorvair (Forum Supporter) GRM+ Memberand MegaDork
8/10/21 2:06 p.m.

In reply to PMRacing :

You didn't really beat me to the punch because I thought "LS Swap" before reading your post. And so did everyone else.

ShinnyGroove (Forum Supporter)
ShinnyGroove (Forum Supporter) HalfDork
8/10/21 3:21 p.m.

I think the VVT swap is the best time/money/performance compromise here.  More or less a drop-in replacement with a few bits from FM and a VVtuner, substantial bump in performance and OEM reliability.

wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) GRM+ Memberand PowerDork
8/10/21 3:44 p.m.

It was pretty much 3 grand to rebuild mine, without clutch.

That's a second hand crank turned for $500, I didn't need a clutch, left the old flywheel, ground valves and surfaced the head myself, and used old pistons/con rods, etc. VRMV

 

fornetti14
fornetti14 GRM+ Memberand Dork
8/10/21 6:43 p.m.

If the motor in my '99 ever gives up, then I'll be shopping VVT Miata's on IAAI or Copart to buy an entire car & sell the bits I don't need.  I plan to take my time on my cars build, but get the donor shell out of the garage quickly.  

So a used VVT motor is my opinion because that's what I plan to do if "it" happens.

captdownshift (Forum Supporter)
captdownshift (Forum Supporter) GRM+ Memberand MegaDork
8/10/21 7:51 p.m.

Don't forget, your manifolds and oil pan are still good.

Protege lx/escort gt/kia Sephia BP engines are often overlooked and fairly readily available. 

Rodan
Rodan SuperDork
8/11/21 1:53 a.m.

Just wanted to point out that you can swap in an NB2 engine and leave the VVT inactive.  You'll miss out on a bit of midrange torque, but it won't hurt anything, and you can add a VVT controller when you get around to it.

David S. Wallens
David S. Wallens Editorial Director
8/11/21 12:25 p.m.

Honda K-series? 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
8/11/21 6:56 p.m.

Not a proper engine suggestion thread if I don't pop in and suggest a hopped up TDI.

I'll see myself out now.

PMRacing
PMRacing GRM+ Memberand UltraDork
8/11/21 7:24 p.m.

Thanks for all the feedback so far!  I am not in a rush to decide but I think VVT swap is in the lead currently. I need to do a little reading up on it. Keep the ideas coming!

Apexcarver
Apexcarver UltimaDork
8/11/21 9:29 p.m.

Double check the crank nose, had one get loose on my 95 1.8 that sounded just like rod knock

captdownshift (Forum Supporter)
captdownshift (Forum Supporter) GRM+ Memberand MegaDork
8/13/21 4:37 p.m.
bluej (Forum Supporter)
bluej (Forum Supporter) GRM+ Memberand PowerDork
8/13/21 6:16 p.m.

Duratec w/ an NC trans? Are the NC and NA/B ppf mounts the same at the transmission?

PMRacing
PMRacing GRM+ Memberand UltraDork
8/13/21 6:50 p.m.

In reply to captdownshift (Forum Supporter) :

Waiting for approval from group admins to see ad.  Thanks!

 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
8/13/21 6:57 p.m.

In reply to bluej (Forum Supporter) :

No, there's quite a difference. There's nothing about an MZR that makes it any easier to put into an earlier Miata than any other motor of similar architecture.

noddaz
noddaz GRM+ Memberand UberDork
8/14/21 10:40 a.m.

CL-S engine for the win!

PMRacing
PMRacing GRM+ Memberand UltraDork
9/1/21 12:17 p.m.

So this past week I helped my dad replace the PCV and decarbon the 3.0T in his (new to him) S4. It was fairly invasive but very satisfying when it all went back together without issue.  It has me thinking maybe I'll rebuild the engine in my Miata myself. A rebuild kit from Flyin' Miata looks to be around $700 all in. Cheaper than used VVT engines with unknown history I am seeing around.

What special tools will be needed for rebuilding the engine?  I have torn down plenty but never reassembled other than reseal and head gaskets. I'm confident I can do the build myself. I guess I'm mainly wondering about measurements for bearings, rings, etc. 

I'll take the block and head to a shop for inspection. Not sure about boring but maybe skim the head. 

What "while I'm in there" stuff should I worry about?  What are the good guides for DIY Miata engine builds out there?

Thanks!

EDIT: This engine has not had an easy life, lots of track time and now at about 110k miles Should I replace valves and valve springs?  I only want to do this once!

wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) GRM+ Memberand PowerDork
9/1/21 5:57 p.m.

If you're having a shop do the measuring/boring/etc, not much more than a socket set and torque wrench is necessary. There is a refreshing lack of torque to yield bolts and all that foolishness. I used Hondabond in place of the factory glue joined stuff (oil pan, etc.) A Haynes manual is plenty good. Honestly, it is a bit archaic compared to newer stuff. Maybe consider replacing your damper pulley (harmonic balancer), and the bolt for it. Or not. You could do it later.

ShinnyGroove (Forum Supporter)
ShinnyGroove (Forum Supporter) HalfDork
9/1/21 10:17 p.m.

The factory service manual can be found for free online, and gives very detailed breakdown/assembly instructions, torque specs, etc.  They also provide specs for valve spring free height, lifter/cam clearances, valve guide diameter, etc.  If everything in the head is still within specs you won't need to replace much.  I would absolutely replace the valve seals with OEM ones though.

codrus (Forum Supporter)
codrus (Forum Supporter) GRM+ Memberand PowerDork
9/1/21 10:30 p.m.
PMRacing said:

EDIT: This engine has not had an easy life, lots of track time and now at about 110k miles Should I replace valves and valve springs?  I only want to do this once!

I would do a leakdown test before taking it apart to see the valves seem to be sealing well.  If not, then I wouldn't touch them.

I would consider replacing the oil pump.  They're not cheap, but they're a total PITA to replace later (you have to remove the oil pan, which means you pretty much have to pull the engine again).  Replacing the water pump isn't a bad idea if it's old, but those are much easier to get at when the motor is in the car.

Flyin' Miata sells a bunch of tools to install cam & crank seals which are nice to have (but not required).  Someone near you might have a set you can borrow too.

 

amg_rx7 (Forum Supporter)
amg_rx7 (Forum Supporter) SuperDork
9/2/21 11:51 a.m.
PMRacing said:

So this past week I helped my dad replace the PCV and decarbon the 3.0T in his (new to him) S4. It was fairly invasive but very satisfying when it all went back together without issue.  It has me thinking maybe I'll rebuild the engine in my Miata myself. A rebuild kit from Flyin' Miata looks to be around $700 all in. Cheaper than used VVT engines with unknown history I am seeing around.

What special tools will be needed for rebuilding the engine?  I have torn down plenty but never reassembled other than reseal and head gaskets. I'm confident I can do the build myself. I guess I'm mainly wondering about measurements for bearings, rings, etc. 

I'll take the block and head to a shop for inspection. Not sure about boring but maybe skim the head. 

What "while I'm in there" stuff should I worry about?  What are the good guides for DIY Miata engine builds out there?

Thanks!

EDIT: This engine has not had an easy life, lots of track time and now at about 110k miles Should I replace valves and valve springs?  I only want to do this once!

Fairly easy to rebuild the Miata engine 

http://blog.miataracer.com/2015/01/lessons-learned-rebuilding-assembling.html?m=1

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