Engine Build Opinions/Advice
 

Hi All - I blew my stock motor last week in a towing mistake. I have a friend of a friend who heard about it and made me an offer which sounds too good to be true. So good of an offer that I'm planning on doing it if I don't hear otherwise here or in my own best effort research. He's offering for me to take over a build that he was planning on doing but decided to go another way. Here's what I know so far:

• NA8 block, cleaned up
• Wiseco Pistons
• Carrillo Rods
• ACL Bearings
• Completed refreshed but OEM bp4w head with "upgraded cams" (i'm considering adding volvo valve springs)

Now he said he got the block for free from a friend that blew up his motor build and said he would give it to me for $1,200. The engine builder/machine shop he said he's used many times is quoting me $1,000 to clean up the block and put everything together. So for $2,200 (and probably a couple hundred more for misc rings etc) I'm going to have a fully built motor? Anyhow, I haven't really be down this road before and this sort of just landed in my lap. I dont have a lot of concern that the person that wants to sell this to me is in any way being deceptive or malicious, but I was under the impression from the tiny amount of effort I've done into looking into a fully built engine it would easily run into the $7,000 to $10,000 range.

My supporting mods around this are currently:

• Fab9 Tubular manifold and intercooler
• EFR 6258
• Turbosmart external wastegate
• FlowForce 640 or 900s (i have both through a mistaken order)
• Lots of cooling mods for track days like ducting, radiator, water/wetter, FM reroute, oil cooler
• Fluidampr crank pulley
• MS3pro pnp

I guess here are my questions:

1. Am I missing anything major as far as costs here? Again $2,200 +/- a couple hundred sounds too good to be true.
2. Not that I plan on running in, but any ideas how much power this thing will be able to hold on pump (93)? I was running 7psi (guessing 200whp) for track days and 10psi (guessing 220 to 230whp) for street. I'd love to get this up to 275 to 300whp for street but I'd probably run the same for track days as the roughly 200whp is all the grunt I was looking for to increase the fun coming out of corners during the track days.
3. I am planning on putting it in an '02 VVT miata. Any thing I should look out for from a fitment wiring standpoint? I feel like I'll need to do something for the ignition b/c the non-VVT head didn't have COP and my harness is wired for that. Should I try to reuse the COP on the non-VVT or convert backwards?
4. Anyone know if mounts need to be changed for putting an NA8 block into a NB2 chassis? FM's page seems to indicate mounts are matched to the block not the chassis, but I ALSO misordered NA6 mounts at one point so I have NB2 and NA6 motor mounts in possession, so I'd really love to avoid ordering NA8 mounts.
5. Assuming my VVT block is still good enough for the build any reason anything I listed above prevents me from reusing it? I've seen that the VVT block is slightly better strength wise and if it is true I need ANOTHER set of mounts, I would just prefer to run what I have.

Thanks for anyone that made it to the bottom and replies!

If you can get a good deal on used parts (or bnib parts people didn't end up using) it doesn't have to be insanely expensive to build an engine. Not cheap, but not $10K.

It won't be $2200, like you said, there are some things you're missing. Does that quote from the machine shop include surfacing the deck and block if they're not flat? Are they going to hone the cylinders? Might double check that the quote isn't just to get everything assembled and torqued.

Oil pump (OEM or do you want to spend $300 for a boundary)
ARP Main Studs? ARP Head Studs? ($250)
Piston Rings ($100)
MLS Head Gasket? ($100)
Water pump and timing belt kit? ($150)
Cam seals? Rear Main? Front Crank Seal? Valve cover gasket? Intake/Exhaust manifold gasket? etc... Adds up quickly if you're going OEM (which is what I usually see recommended).

It's up to you how crazy you go with a lot of those parts. I'm mostly playing devil's advocate here, but these are pretty common to add in when building an engine.
Also, if you're pulling the engine, are you going to put a new clutch in while the engine's out? Another thing to consider.

**I built one engine, I am far from the most experienced source. Take this with a grain of salt.

Sim's advice above is on point. I'd talk to the machine shop and get a fully broken down quote on all the work they're going to do then relay that back to this thread. My block work came out to $985 a year ago. That was for a 1mm overbore and hone, decking the block, align honing the mains, balancing the rotating assembly, doing a .010" grind and polish on the crankshaft main and rod journals (although most on here will recommend an unground crank if you want to push super high horsepower), and hot tanking/cleaning everything. No assembly, though.

Relevant to question 5, what blew on your VVT motor? That's going to be pretty pivotal regarding whether you want to reuse that block or not.

Regarding power that setup will be able hold with the parts listed, you'll be able to blow a 6 speed trans to smithereens before you hit the motor/turbo's max output. 275-300whp will be easily reachable on that setup, although I'd probably throw in some ARP head studs too even for that power level.

I estimate my built motor cost me around $4,600 all in. Bought a used VVT motor for $1,600, another ~$1,500 in parts, and I believe $1,300 in machine work. There's a lot of expenses I could have spared, though. If I were to do it again, I'd probably skip the oversized valves and just run billet gears in the OEM oil pump instead of getting a Boundary. Could probably do it for under $4k the second time around and still have a motor that made similar power and was up to the task of track use at 300whp or higher.

Like Sim, I've only built a single motor as well, so take my post with a grain of salt too.

Thanks fellas. All sound points. As all the little things have started to creep up I feel like i'm getting over $3k at this point and that's definitely more than I wanted to spend. I just redid the seals, water pump, timing belt on my vvt and I do have some spares as far as rms etc. As far as blowing that motor, I overheated it towing on a car dolly. I accidentally bumped the gear shifter into gear while fixing the soft top latch mid tow. I went about a hundred miles at 50mph. It runs now but seems like the piston rings are destroyed as it billows white smoke out everywhere. We changed oil and coolant and couldn't find any shiny bits so I dont think anything exploded. It cranks and turns over easily so I dont think there's anything mechanic. I suppose I could have warped the block, I dont really know to what extent I would have needed to over heat it to get it there, but I can still do the NA8 block if I have to which is coming from the guy selling me. I guess I need to do some soul searching because it feels more like I'm going to be closer to $3k by the end of this.

It's probably worth doing a leakdown test to see if the rings or head gasket are smoked. Given that you didn't murder a rod bearing or nuke a piston, though, I wouldn't write off the VVT block from being used. Would take a couple steps out of the equation not having to rewire anything and you'd be able to keep VVT function.

Guess that muddies the waters a bit more. But yeah, like Sim said, things add up fast. Budget dependent, it might also just be worth doing a teardown and rebuild on your VVT motor and throwing a set of forged pistons, rods, and billet oil pump gears in it while you're in there. Interested to hear others' opinions as well, though.

Aftermarket pistons rods and bearings alone for that price is worth it, and you get a spare block and a clean head!
Seems like a no brainer to say yes. But I collect as many spare parts as I can, because ... race cars.

Then dismantle your current vvt engine, and inspect the damage, or have an experienced shop inspect the damage after you take it apart.
Then use your new collection of parts to select the best parts to build your next engine.

Trying to sort out how turning over with no fire or fuel would damage the engine. Friction based heat I guess; oil pump and water pump would be spinning, but maybe not effectively enough. What gear? Unless it was 4th or 5th you probably did the equivalent of a money shift, meaning damaged valves and/or pistons, possible spun bearings.
Pull the head off, inspect, and take it to a pro to inspect if you need to. But I expect you will see smoking guns! By all means do a leak down test first.
(I've built and blown up a whole range of BP & B6 engines in race cars, though less than 10.)

Regarding points 4 & 5, the NB2 mounts extend down to link to the transmission. You can use NA8 or NB1 mounts on a 2002, it will just lack the 4th tie in point to the trans.
Or, you can use NB2 mounts on the NA8 and NB1- 8( BP4W I guess that is), along with your 2002 trans.

I'm with Icedawg here. You did an extended money shift on that VVT motor and probably have suffered some valve/ring/bearing failures. But for $1200 plus a trip to the machine shop you get a "spare" block and some new pieces to play with (I'm looking at you Wiseco pistons and Carillo rods - those are worth the "price of admission" alone).

Your only unknowns at this point are how far do you want to go with the "while you're in there" pieces. Those can add up fast. Your list of supporting mods will take you well north of $3K and you haven't even mentioned a new clutch or other fueling mods (fuel rail, adjustable FPR, fuel pump). You'll be closer to $5K above the cost of the new block and machining when all of that is added up. Ask me how I know...

Thanks for the advice everyone. I'm leaning hard into taking a chance and doing the full build. Those supporting mods are what I have already. Some of it was a little overboard for a stock block BP but I got good deals on them. The machine shop that has the NA8 block is disassembling it to make sure all looks normal to validate it is worth using both for the parts and block. I'm going to ripping my VVT out this week or next to see what I can salvage from it as I'd love to reuse my VVT. I didn't know could get the VVT mounts to fit an NA8 block so that's huge if everything else checks out.

What did you end up doing?

Great question! I ended up randoming into a facebook marketplace post for a fully built engine already used for about 10,000 miles that was being sold personally by a mechanic at a relatively close reputable local miata shop. I got the deal of a lifetime on it and now am constantly scared to do death of breaking what is probably a monster of an engine that I'm barely pushing more than what you would push on a stock motor.

what power level are you at?