jungle New Reader
July 2, 2013 5:19 p.m.

So I am debating about picking up a '97 Miata, there is a hole in block, and a bent exhaust valve. I also found a C.L. add listing a '99 motor & trans. I found out that the '99 has better flowing head, uses different intake manifold, fuel rail, and cam sensors. The pistons are also "crowned" for an extra 0.5 compression ratio.

So are the transmissions the same?
Can I get '97 head repaired and put it on the '99 block w/o any extra issues?
Will another Miata guru notice the block is from a different year? This motor has been sitting for 2yrs in the guys garage, if it spins over is there anything to worry about?

TIA!

Keith Tanner MegaDork
July 2, 2013 5:30 p.m.

Easy. The transmissions aren't identical, but interchangeable. Better 3rd gear synchros with the NB one, although by this point in their lifespan the difference will probably be more closely related to the life the transmission has led. Get the NB starter if you can, it's lighter.

You can put the NA head on the NB block, no problem - although I wouldn't.

It's tough to spot different blocks. I'm not sure I could tell the difference offhand.

codrus Reader
July 2, 2013 11:17 p.m.

Other minor differences -- you'll want to keep the NA alternator, because the NB one requires computer control. The NB head is better, but you'll want a simple RPM-based switch to flip the solenoid for the 99 VICS intake at the right point. I'm not sure if you can use the 97 fuel rail on the 99 intake -- you might need to use the 99 rail and modify it to use on a return-based fuel system. There are lots of writeups on this kind of thing on miata.net.

Keith Tanner MegaDork
July 3, 2013 12:01 a.m.

The 99 fuel rail modification consists of: mount the FPR from the NA on the end of the rail.

PeteD New Reader
July 3, 2013 7:30 a.m.
Keith Tanner wrote: The 99 fuel rail modification consists of: mount the FPR from the NA on the end of the rail.

I think the devil is in the detail wrt. the fuel hoses & connectors. Here is the best explanation I've seen on it: Update to '99 Miata Head on '94 Engine - Fuel Rail Issues. Summary is: get SAE 30R9 fuel hose (I could only find this at NAPA) and the special connector (DORMAN 800-081) to the fuel rail.

The only other thing I found is the EGR ... the '99 EGR valve [BP4W-20-300A-9U] has a different electrical connector than the '94 EGR valve [B6BF-20-300-9U]. I re-used the '94 EGR valve on the '99 intake so it would plug into the car's existing harness.

-- Pete

EvanB PowerDork
July 3, 2013 7:40 a.m.

I have a 99 fuel rail with 94-97 FPR in my car. No issues with standard fuel lines clamped onto the inlet and outlet with the stock hose clamps. I have put ~10k miles on it without a leak.

Apexcarver PowerDork
July 3, 2013 7:49 a.m.

On-topic, but a bit a a derail. I have a friend who just got a 97 miata with a 99 head on it.

It is megasquirted and turboed, he needs to get it through emissions, which if I am not mistaken, around here means OBD2 plug-in and has been asking my advice.

I was thinking the best route might be to zero the boost and put a stock computer on it for emissions day, but is that possible with the 99 head? (97 OR 99 computer?)

whenry HalfDork
July 3, 2013 8:20 a.m.

I installed 1.8 in a early 1.6 car years ago. The only problem was back dating the intake and FI system; sounds like this proposed swap is very similar.

Keith Tanner MegaDork
July 3, 2013 8:45 a.m.

Fuel lines are easy. You can either just slip regular lines over and clamp them on, or you get a "fuel line repair kit" from your local auto parts store that consists of the clip-on connector with a hose barb on the end. Not difficult at all. Almost every "high pressure fuel line" is the clamp-on style.

Leafy
Leafy New Reader
July 3, 2013 10:10 a.m.
Apexcarver wrote: On-topic, but a bit a a derail. I have a friend who just got a 97 miata with a 99 head on it. It is megasquirted and turboed, he needs to get it through emissions, which if I am not mistaken, around here means OBD2 plug-in and has been asking my advice. I was thinking the best route might be to zero the boost and put a stock computer on it for emissions day, but is that possible with the 99 head? (97 OR 99 computer?)

If he knew he needed to pass OBDII tests he should have bought a parallel install megasquirt instead of an PNP. He'll need to put in the stock injectors, wire the wastegate open. Trouble will be getting all the readyness monitors to set while driving in a way to not hurt the car like that. I'd throw the stock header back in to make it easier. I'm assuming that because he's using an MSPNP that he's running a stock CAS on the back of the head and the 97 crank sensor rather than using the better 99 cam sensor.

Apexcarver PowerDork
July 3, 2013 1:21 p.m.

Car was just purchased with the modifications in place.

Will send you advice on to him.

codrus Reader
July 3, 2013 4:56 p.m.
Leafy wrote: If he knew he needed to pass OBDII tests he should have bought a parallel install megasquirt instead of an PNP. He'll need to put in the stock injectors, wire the wastegate open. Trouble will be getting all the readyness monitors to set while driving in a way to not hurt the car like that.

I can't say about the 97 computer, but the 99 one is happy to set all of the readiness monitors with a single drive from cold, never going over about 30% throttle or 3500 RPM.

You'll need to log in to post.

Also on Grassroots Motorsports

Follow Us to the Nürburgring

14 hours ago in News

Follow along as James Clay from BimmerWorld contests his first ADAC Zurich 24-Hour race at the Nürburgring.

Shark Bite: Back in 1997, Hyundai Was Into Rally

14 hours ago in Articles

A Hyundai Tiburon as a rally car?

From the GRM Vault: Our First Drive of the Original BMW M3

1 day ago in Articles

We tested BMW's E30-chassis M3 back in 1989. Here's what we thought.

Great Moments in $2000 Challenge History: Minor Gasser

1 day ago in Articles

Here's what happens when you put a Chevy 350 in a Morris Minor.

What’s the Soonest That You Have Raced Your New Purchase?

1 day ago in News

This BMW M3 was wearing numbers 24 hours after getting registered.

You Need This: 2005 Lotus Elise

2 days ago in News

A Lotus Elise looks so right in British Racing Green.

2017 Mazda MX-5 RF

2 days ago in New Car Reviews

We're big fans of the Mazda MX-5. Now Mazda went and put a retractable fastback on their fourth-generation car. So, ...

Project Ramp Truck: Installing Sound Deadening

2 days ago in Project Cars

Time to cut down on heat and road noise making its way into the cab.

Eric Foss Sets Fastest Time Ever at the Tire Rack Ultimate Track Car Challenge

3 days ago in News

47 of the country's fastest cars battled it out for track supremacy.

Who Wants to Design the Next GRM T-Shirt?

3 days ago in News

Blipshift is involved, so you know that it will be cool.

Reader's Ride of the Week: Improving Upon the Ultimate Driving Machine

3 days ago in News

This E36-chassis M3 just keeps getting better.

What Was the Most Powerful Car at the Grassroots Motorsports Dyno Day?

3 days ago in News

What if we told you it was an Audi?

OUR SPONSORS

Grassroots Motorsports Magazine

Subscribe Today

Also get your instant access to the digital edition of Grassroots Motorsports Magazine!

Learn More
BMxJ1OgkrSqdPZCNsrE4fNjWETcOJ11x