Top end rebuild.

[NobleRogue]

My 97 miata is burning oil in cylinder number one. Compression tests show that all cylinders are with in tolerant range showing that my rings should be good. The compression from cylinder one and cylinder two have a variance of 10 psi. Cylinder one is also the one with the higher compression showing that the head gasket between the two cylinders should also be good. There is no oil leaking from the head to the outside of the block indicating that the head gasket should be good there to. This leads me to believe that I have a bad valve seal. I know that there is a way to replace the seals without removing the head. But I figure it would be a good idea to do it anyways. Thus allowing my to inspect and clean everything properly. While I'm at it I figure I could do a few upgrades. This is the purpose of this post. I am looking for feed back and perhaps some guidance on my ideas.

First I plan to have the heads ported. This means that I need different valves. Where could I go to get them? Would I also have to port my intake manifold? What about my Exhaust manifold? Would I need a new one and if so where can I get it? Does anyone have a line on a good place to get racing cams lifters and springs? Can I run the stock fuel rail and injectors or even the stock ECU after doing this? If I have to go with a stand alone fuel system, would my car still be able to pass smog? I know that some of thees questions may seem elementary but this is my first fuel injected build as well as my first build an anything after 1978. Also I have never ported heads on anything I built before. Thank you for reading and thank you again for any info.

[Rogue]

If I was doing that (and I am), I would source a 99/00 head.

[NobleRogue]

What is the benefit of sourcing a 99/00 head? Does it have a higher compression ratio? At the local Miata bone yard, I can get one for $400.00. Is that a fair price?

[BoBo]

The 99 head will have better flow and solid lifters. You might be able to get one for $400. However, is that something you want to do? I think you have to source a 99 intake manifold, fuel rail, and hoses as well. It's should be worth about 10hp or less.

Your other option is to have your current 97 head rebuilt. You will probably spend about $300-500 depending on what you're planning to do with your 97 head. You could port both the head and intake manifold or just the head. It's really up to you. Just don't cut too much material off, just clean it up a bit. Computer controlled porting is preferred but if you're having someone else port it, then that might be a better choice.

" stand alone fuel system?" You mean ECU? You will not pass emissions with a standalone ECU. You will have to use the stock ECU for that. However, one can swap it out before smog day. A piggy back ECU would be legit. Your budget will determine your options.

[Fishbulb]

The 99 Head moves the intake ports up, IIRC. People have built adaptors for the 94-7 intakes, or get the 99 intake.

Exhaust should bolt right up.

Solid lifters means no more ticking HLAs! :)

[kung fu jesus]

My 97 miata is burning oil in cylinder number one. Compression tests show that all cylinders are with in tolerant range showing that my rings should be good. The compression from cylinder one and cylinder two have a variance of 10 psi. Cylinder one is also the one with the higher compression showing that the head gasket between the two cylinders should also be good. There is no oil leaking from the head to the outside of the block indicating that the head gasket should be good there to. This leads me to believe that I have a bad valve seal. I know that there is a way to replace the seals without removing the head. But I figure it would be a good idea to do it anyways. Thus allowing my to inspect and clean everything properly. While I'm at it I figure I could do a few upgrades. This is the purpose of this post. I am looking for feed back and perhaps some guidance on my ideas.

First I plan to have the heads ported. This means that I need different valves. Where could I go to get them? Would I also have to port my intake manifold? What about my Exhaust manifold? Would I need a new one and if so where can I get it? Does anyone have a line on a good place to get racing cams lifters and springs? Can I run the stock fuel rail and injectors or even the stock ECU after doing this? If I have to go with a stand alone fuel system, would my car still be able to pass smog? I know that some of thees questions may seem elementary but this is my first fuel injected build as well as my first build an anything after 1978. Also I have never ported heads on anything I built before. Thank you for reading and thank you again for any info.

You really need to do a leak down test before considering a head project. This will tell you if the oil is coming from the rings or the valves. It is similar to compression test, in some regards, but a little more intricate. It is still pretty easy to do with a manifold gauge set and shop air compressor. Some places will rent you the gauge manifold. If the oil is coming from the valves, replacing the stem seals may not be enough. You could have a worn valve guide or other issue with the valve(s) themselves. It is best to verify, because putting 300-600 into head work, only to find out the rings are bad on the piston is a real bummer.

If you decide to work your current head, a mild porting and gasket matching will improve airflow a little, but not enough to expect any big gains from it. It would be shaving the head to increase compression that you will get an added benefit from, mostly. Adding cams, injectors, etc, won't help, like other mentioned, without supporting mods, like an ECU, adjustable cam gears, etc. The net return still might be what you are hoping for.

Off the top of my head, you would probably want to remove the head, disassemble the valvetrain, have the springs tested for consistency, the valves cleaned and checked for true, probably have them cut. On the head, lapping the seats, a mild porting, gasket matching, and a healthy shave to get compression near 10:1 or so. New head gasket set, new ARP head studs, new valve guides, new stems, maybe new manifold studs, timing bet, waterpump, and coolant. I would clean the piston crowns and check the bores for damage while the head was off too.


The 99 head will have better flow and solid lifters. You might be able to get one for $400. However, is that something you want to do? I think you have to source a 99 intake manifold, fuel rail, and hoses as well. It's should be worth about 10hp or less.

Your other option is to have your current 97 head rebuilt. You will probably spend about $300-500 depending on what you're planning to do with your 97 head. You could port both the head and intake manifold or just the head. It's really up to you. Just don't cut too much material off, just clean it up a bit. Computer controlled porting is preferred but if you're having someone else port it, then that might be a better choice.

" stand alone fuel system?" You mean ECU? You will not pass emissions with a standalone ECU. You will have to use the stock ECU for that. However, one can swap it out before smog day. A piggy back ECU would be legit. Your budget will determine your options.

I ran a reworked head on my 1.6 with and without a stand alone ECU. I gained most of the power from the head shave. I made similar power to a 1.8 NA motor that had I/H/E. I passed CA CARB testing, but they didn't know about the internal mods.

Honestly, if you want the most bolt on power, I would look to see how you can straight up swap in an NB motor and pass testing/inspection in your area. If the NA8 motor makes about 128hp stock, the NB motor makes 140 stock. Which would be a better platform to start from?

[Rogue]

/\ KFJ is wise.

On mine I'm using a 2001 intake with the vanes removed….we'll see how that work out here in a week or so.

[BoBo]

I ran a reworked head on my 1.6 with and without a stand alone ECU. I gained most of the power from the head shave. I made similar power to a 1.8 NA motor that had I/H/E. I passed CA CARB testing, but they didn't know about the internal mods.

Honestly, if you want the most bolt on power, I would look to see how you can straight up swap in an NB motor and pass testing/inspection in your area. If the NA8 motor makes about 128hp stock, the NB motor makes 140 stock. Which would be a better platform to start from?

Same here, I had bigger gains from a head-shave than other headwork . I got about 8hp with stock ecu on my 95, but had to adjust my cam timing cuz the machine shop shaved too much material. A year later I installed the m45 and boy I was happy. I should have kept the car.

Right now my 96 pulls about the same as the NB. 133hp plus the RB intake & Exhaust. I'm gonna have a baseline done in the future just to see the gains before I go F.I. or have the engine rebuilt. I don't know exactly what my plans are yet. I have to calculate the cost of taking my miata to the track 6 times a year in naturally aspirated form vs 8psi.

[kung fu jesus]

Definitely! I put the built head on at ~90k miles. I did a compression test and bore scope at 160k, I was around 200-205 psi across the cylinders. I put an adjustable cam gear on the intake cam.

The head work was noticeable with the turbo and later the S/C. Just the base boost on a JRSC allowed me to walk away from NCs with bolt on mods.

It was a strong engine for a 1.6 in n/a form, both on the stock ECU and a standalone. I am thinking of shaving a little more and replacing valves while it is already out of the car. The new rebuilt engine I have has excellent compression, so I think that head on it would be awesome at the track.

Pics and more info about that here:

http://mazdaroadster.net/showthread.php?3225-NA6CE-1992-Form-vs-Function-Build-and-History&p=50360&viewfull=1#post50360

[NobleRogue]

Thank you all for the advice. you have given me some things to think about.

[BoBo]

@ KFJ: Sounds like a good setup for track. It sucks jrsc stopped production on the m45 & mp62, it's great for DD. I'm upgrading my rad and replacing the T-belt, front seals, hoses in a few days. I'm looking to go to Seca this coming summer, and I have a feeling that I will make it through the day without car issues. The last few times I went to Laguna & T-hill, I had turbo manifold studs stretching, boost leak, and overheating issues. At least I'm not the only one with car issues, my track pal with a WRX STI overheats badly as well.

The Rotrex seems to be the best setup when you want to keep the heat down but it ain't CARB legal. For now all motor will have to suffice until I figure out what to do with my tired motor.

[kung fu jesus]

It's been a fantastic track and street car.

I have been curious about maybe trying a Rotrex in the future, but n/a is just so reliable that I never have to worry about it track side. I had all the issues with the turbo you described, it just became too distracting to enjoy it.

Maintenance has been something I tend to over do. I hate break downs, and I hate doing things twice because I didn't take the time to replace some seal or hose while I had the opportunity to do so. Timing belts are something that always includes seal, hoses, water pump, and gaskets. It's just how I prefer to it. It eliminates doubt and makes it easier to troubleshoot if an issue arises later.

Do I miss the power of forced induction? Sometimes, but being n/a allowed me to focus on chassis tuning and learning to drive better and faster. That has made it more enjoyable than having 200+ hp.

[BoBo]

^All the hoses and seals I bought are Mazda OEM, but the T-belt & WP are made by Gates. It's good to know that everything is in good working order.

I remember taking my Mr2T and Mr2 SC both at Willow Springs Raceway years ago, and both overheated after a few laps. I had to short shift at around 5k to keep the engine cool, even with the upgraded cooling system. When I got home I realized that my turbo manifold was cracked and the bearings on the turbo were shot. It was a sad year for me and I didn't hit the tracks for a long time after that. I love force induction and I'm all for it, but when you're limited on funds like me, all motor can be a great thing. I'm glad that I'm graduating this semester, I really need that paint job.

[kung fu jesus]

Yup. At the track with a turbo, I would drive a session, be hyper-aware of any noise, smell, or feel while hawking the gauges, maybe get a good lap or two in where I didn't worry. Then, I would spend the time between sections checking over the car, fluids, getting it to cool off, just in time to clean up and get out for the next session. It was pretty tiring and not that enjoyable.

Tracking n/a, I might check the oil once, make minor tire pressure changes, talk to other participants, enjoy the day.

[NobleRogue]

Found a head at the local bone yard. It's on a 94 Miata with a 1.8L engine. They only want $102.00 for it. All I have to do is pull the Intake off and remove the head bolts to get it off. Next step is finding an automotive machine shop that can shave and port it.

[90blue]

Porting is not something I would consider unless I intended to go FI.
If so then check here http://www.miataturbo.net (only read, do not post, far to rabid)

There is more horse power to be made with the 99 head.
There is more torque from the VVT 01-05 non MS head. Bell Williams is racing and uses a VVT head with a square top intake manifold, or at least did, successfully.
For parts and opinions check out 949 racing http://949racing.com/engine.aspx
My 2c

[kung fu jesus]

Found a head at the local bone yard. It's on a 94 Miata with a 1.8L engine. They only want $102.00 for it. All I have to do is pull the Intake off and remove the head bolts to get it off. Next step is finding an automotive machine shop that can shave and port it.

If you are having a machine shop do that, you should also have them check the springs and valves at a minimum. New valve guides are a must.

[NobleRogue]

I appreciate all of the advice on getting a 99-02 head. I would have gotten one today but the bone yard had only two Miatas. A 92 and a 94. The local Miata bone yard wants $500- $600 for them If they even have them in stock. And I hate buying used parts online. You never know what you are going to get. Most of what you find are mislabeled or give to broad of a description. I was looking at heads last night and you wouldn't believe... "maybe you would"... how many were listed as "1.8 L Head for 1990-2000 Miata" and the CPS was usually on the wrong side to be for a 1.8 L. :toomuch: :angry: . When sourcing parts, you need a lot of patience or you may end up giving yourself an aneurysm. lol.


If you are having a machine shop do that, you should also have them check the springs and valves at a minimum. New valve guides are a must.

Thank you kfj. I was already intending to replace all old parts with new including the guides. But I appreciate the advice. Please don't ever assume that I already know something cause chances are, I don't. And just to prove my point, at the risk of looking like an idiot, I must ask. What do you mean by "check the springs and valves at a minimum"?

[kung fu jesus]

Sometimes you don't need all new parts. The factory valve springs have specific measurements and allowed variances. The same goes for their spring rates. They should be able to compress them to test their effectiveness.

Likewise, valves can be measured and their stems checked to be true. If they are good, that is money saved or spent on other tricks, like valve cuts, etc.

[NobleRogue]

I was thinking about using thees. www.flyinmiata.com/valve-spring-kit.html .. http://www.mossmiata.com/Shop/ViewProducts.aspx?PlateIndexID=77140 .. and cams from HKS intake and exhaust are $355.00 each. The Cams may have to wait though because of their price.

[kung fu jesus]

Feh. I would wait until you get cams. Otherwise, unless you are going for a monster head shave, you only need one.

At this point, too, I have to point out a good BP4 motor is about 1000-1200. That's 140hp, bolt in.

[NobleRogue]

1. BP4???

2. Would that be the intake or the exhaust side if I go with only one cam.

3. How much would you recommend I shave? I do intend to keep this as a daily driver, so I'm not trying to completely ruin its reliability. Maybe just bring it up to 10:1.

[kung fu jesus]

BP4W, '99-00 engine.

Intake, stock cam.

I don't know the max amount that head can be shaved. The internetz should have some specs out there. These are all things you need to research, including a shop that knows enough about the head to do the work. The truth is out there.