In my humble opinion, Cylinder #4 must have not been tested on the compression stroke. 95% just doesn't make sense.

Me: Having a normal day Miata Dad: *Y O U G O N L E A R N T O D A Y*

This is why we love you Miata Dad. Instead of just building the NB's engine and sending it, you're teaching us every little thing that we want to know. Thanks Dad.

I think the first option of repairing the head with no mods and going back on the dyno is the best option. Add the nitrous set up after the head is fixed and then later on, swap the magical modified head on.

Rebuild the head to hit 155, then come for Quinn's record!

I think you should go with stock head fixed and continue testing bolt ons. And later on the series put modified head in and make project 2SJ 2.0

I’d love to see the modified head on there to see what you can make!

Definitely keep the head stock, I think it's great to see what you most people can realistically achieve with their car and swapping heads and some big cams is not really part of that

I'd say, repair the stock head, and see what it does then. It'll be a great source of information for everyone. Afterwards, put the modified head on it! I'd love to see how much that can do. Finally, I'd love to see a comparison between the VVT head, the stock head, and the modified head! Some mods on the VVT head (skim, port&polish, and perhaps even cams) would be amazing aswell! It would really give a great insight into the differences between the different heads!

These 18 minutes flew by! I did not notice any boringness in the editing, perfectly done imo. Also, I think doing the stock head first and the new head later is definitely the best option!

Mannn, I just found your channel. The editing you use, is very cool! Making me inspired for my Channel. Looking forward to more.

Definitely stock head back on. Cure the issues, get the results. Then superflow head down the line with fat cams and then ITBs.

The problem is lack of pop-ups! (Jk I want an NB myself)

Loved the in depth debunk in the beginning! Also my suggestion, although boring, would be to get the head rebuilt normally just to complete that data set. Then definitely use the ported head and go thru what steps make N/A power. This aligned with my current path so of course I'm being selfish but I know everyone loves an N/A built ITB setup

I dont get why people hold you to such a high level of scrutiny, you do so much for the miata community in proving and disproving the validity of mods to 100 hp cars and I'm just glad I have this resource to reference while I modify my own miata

It cant be overstated how gutted i am not to see this engine hit 155whp. I spent the last 3 days sick as a dog watching these nb1 videos and was so hyped to watch you get the car back out with the new head. I just spent an hour on the phone retelling the story to a miata buddy and when i told him he was as crushed as i. If you were going to rebuild it, i think you should. You have a lot of head content, time for some block! Lets go 155!

NA Build for sure! You definitely have the knowledge and skill to get everything out of one of these engines. We'd love to see your take on making max power on an NA setup. We decided to bail on the idea at 155 WHP on a Mustang dyno, because cams/lifters for a VVT is the cost of a self made turbo setup, which is more fun on the street as you know.

Top tip, compression test again after head rebuild, to see if there are still differences between the cylinders BEFORE the dyno.

I'd love to be able to see a re-run of you last dyno tests with the head fixed. That's the only way we would be able to truly see what the mods did.

10,000% go with option number one. I think running a stick head for a while will produce the most meaningful content for people (myself included). I'm looking to do these exact bolt ins and was super disappointed when your dyno day was a bust.

people like you are why miata modding is so accessible to newcomers, we appreciate you miata dad!

The most videos you can probably do (and what i think a lot of people would like to see) Rebuild the head to stock Put on the ported head Bigger cams VVT head Or, if u wanna build up the VVT head for the NA, once you're done put the current head of the NA on the NB and build that up. Port with big cams oversized valves etc... I have a BP-Z3 in my NB and would be excited to see how you'd do some VVT tuning with big cams.

Loving the methodology you're using on all of this taking one step at a tine learning and teaching as you go,. Thanks. This is of particular interest to me with a '95 block, 1mm bored, 10.5:1 pistons, '00 head shaved, ex-intake swap, stock header with welds ground down to open them up, 2.25" exhaust and RoadsterSport 3 muffler, with stock electronics (thanks CA smog laws) that I hope to upgrade to a megasquirt but leave the stock in place to switch between for smog (though I don't know if this is possible). Have not tuned it or touched the timing but it runs and pulls much stronger than pre-engine work. Looking forward to watching as this progresses and learn a thing or 2 for my build.

I was about to go to sleep... I guess my day is going to be 18 minutes longer.

As much as I know it’s tempting, I feel like the more methodical approach of refurbishing the stock head would provide the most data, and I know your all about the DATA!

This man doing pulls knowing there's an issue 😂 You're my spirit animal, lmao trying to figure out my pressurized crank case issue I began to race 2 mustangs and a GTI...... Needed that good data 😂😂

Repairing the head and going back to the Dyno is the best option for what you're doing, you could get a new baseline for the healthy engine and keep showing us what works and what doesn't. Awesome work on the videos! I've been following you for about 5 year and while I still don't own a miata, I'll definitely know how to set it up properly once I have it, greeting from Venezuela

First, Greg, your vids are the best, love the content! Second, getting a fresh stock head on there will definitely be the best going forward. Personally, do I want to see the magical modded head? Of course, that sound nuts. But using a stock head first would be WAY more relatable to the viewers. To me, and I'm sure to you, that's what your channel has always seemed to be. The channel has always been about learning, and that would be the best option as far as that. But hey, I'm one guy, everyone has their opinion, and more importantly, it's your car! Do what makes YOU happy! If you want to throw that magical head on there, go for it, because if I was in your situation, that's what I would do. Thanks for taking time to ask the viewers and read the comments, even after getting as big as you are! Keep up the great work!

Go the stock head, check the rings and develop the intake. Then put the nitrous then the modded head. That gives a great progression of what can be done and the Gaines that can be expected. Awesome work G

Stock head please, I’m using your vids to guide my 99 motor build for my 94 Miata :)

This series was interesting to me because it was simple hardware wise. We all know, and are already being drowned in, crazy builds on youtube. We know anything is possible if you get better and more expensive parts. Using knowledge instead of money is what made this interesting to me. Therefore my vote goes to keep it as stock as possible.

The best way to show all miata owners what "bolt-on" does what for the money you spend on it. So refurb the stock head and show dyno results with every change you make. So that all miata owners can choose their own prefered bolt-on to use. Love the content keep up the good work!!

My suggestion: Skip VVT head swap. Send original head off to get worked on. WHILE that head is being serviced, install performance head with big boii valvetrain, and get to work on the dyno. Once original head is done, swap it back in, and dyno with simple refresh AND with new 4 fogger direct port nitrous DRY system. This would allow to keep making more content, while addressing various types of builds for your various Miata kids.

Just my $0.02, I would like to see the difference with the cam/intake/exhaust mods on a stock head compared to using the ported and polished head with the same mods. I learned how to port & polish heads 40 years ago on VW Beetle engines with mild camshafts and better carbs and exhaust, and have done numerous one since. I just never had access to an actual chassis dyno to see definitive results.

I've been so excited for this video to come out...got a spare exhaust cam sitting in my garage just begging to be put in my '99 but I needed to see what happened with you first. Thanks Miata Dad!

If it's a project to learn, definitely try to narrow down the issue here, it's very interesting. Probably valves are not seating properly? Need to grind the seats or what's the procedure callled. Next the ported head would be very interesting to see. How much difference it makes across powerband with just the port.

So the stock head comparison is nice, but here(in sweden) the best mod you can get away with is pretty much a new head and N/A tuning. We have really boring laws preventing us from turboing an N/A car. It's kinda technically possible with the right amount of money, but an R32 skyline would be cheaper to buy, then to have a legal turbo swapped Miata. If it would be possible, a video on the head swap would be nice! but if there is no interest for it then its fine too, the videos are fantastic anyway :)

Well, one things for sure. Whatever you end up doing is gonna be awesome! Looking forward to the lessons. You inspired me to boost my 90 na and I haven't regretted one minute of it. I'm 50 years old and have driven many cars. My boosted red na takes the cake.

Great stuff, and this is true, we are not talking about huge cam profile differences!!! Still, I suggest to try an NA exhaust cam next time on the dyno, it has 5° less then NB (but also 0.4mm lift less). This is something to consider because we bumped from 226 duration up to 242. On m NB I did the same, with the centerline at 110 I achived a depressive 150PSI on compression test, at 95 (I was scared) I finally reached 175 PSI on the gauge, but the engine wasnt able to start. I have to try to put back the original cam and gear and check the compression. Thanks master keep on!!!!

I had the exact same problem with my NB2, cyl 1 was 50 psi under the rest on compression. Was throwing a nasty misfire at idle though, surprised yours didn't do that. When I took the head in for a rebuild they had to replace 3 valves (2 intake 1 exhaust) cause they were bent. Looks like you're leaning towards the madlad head and would like to see you smash that record or come close to it!

This curiosity and exploring of the potential in this wonderful miata platform is really entertaining to follow, thank you for sharing !

I think for sure go with the stock head before anything. Just to prove the gains you get. Then I think trying the ported head would be awesome.

Although I have sold my miata I still keep coming Back to watch your videos, they're Just pure information and entertaining and I love them! Please do a rotary swap one day 🙏

Really solid diagnosis! The hot head sounds pretty good, tough to mess around fixing the OEM one when that's sitting on your table.

Thank the Good Lord, a TCPC friday video to fix my otherwise shitty week! You rock! I'd say repair stock head and see what she would have done with bolt-ons, that's what we are stock NB Bois are here for... BUT - machining and repair work ain't free unless you "know a guy" and even then...

I'd be most interested in seeing you put the VVT head on, but there's always the risk that head isn't perfectly healthy either. It could give you content for the down time of having the BP4W head repaired though.

Awesome knowledge presented in easy to digest bite-size chunks! Love Greg's channel. All the best, Rob (2009 NC 2.0l Sport).

I say go straight for the mod head. I appreciate the step by step gains, but let’s put down 200 horses on a naturally aspirated motor already. Cheers! Excellent content as always Dad.

Fantastic info....and I can't even get mine to idle properly after cleaning the throttle body.

Thanks Greg, i wasnt watching the video really to learn something. Im loyal to your channel and i had a terrible day and you made me laugh and i learned alot. Keep it up man i love your content.

it could be the reason power was builiding as consecutive pulls were made. Something to do with seals expanding as engine was hotter

Excellent diagnosis tips for low compression!

Nitrous it's cool with a good setup . I have a 1.6 europan miata with 2 stage of nitrous and little progressif controler. If your afr, egt, fuel pressure and advanced ignition it's correct and you IS reasonable in shot . No problem!

would be cool seeing the power gains and graph comparing factory head turbo set up with the ported head. but in terms of this series i think stick with the head that came in the car just so its more useful information for others

Hey Greg not sure if you are aware but I came across a german channel called sps motorsports who claim they build 225+hp ITB MX5 engines for street/track use (fully built motors). I started digging into the specs some to see if I could tell how they're accomplishing this and saw they were using custom spec'd cams from a company called Cat Cams (also some custom wiseco pistons but no specs found yet). The site is in german but the cam spec sheet is in english. Looked into those cams and though there isn't much user info online I did find one video and a couple random forum posts so far reporting achieving over 190hp and good torque on mildly modded engines, ITBs, minor head porting and valve springs type stuff. I'm super fresh on the hunt so still learning what I can about them. I was hoping if some of the miata gurus became aware you'd look into it also and give them a real shake down. If they work as good as it seems these could be an awesome choice for the green NB project! I don't know much about cam specs so maybe they have a ridiculous amount of lift or something but the dyno sheet I saw in the video looked to have a nice curve. I'm interested in their VVT cams just don't know if a BP-Z3 is identical to a BP-6D or not. Dyno vid - 192 hp @7500rpm / 161ft/lb @5700rpm: kzfaq.info/get/bejne/Z9Kaabl62rfKk30.html SPS motorsports vid: (english) kzfaq.info/get/bejne/jtyddNB-3LCVd6s.html SPS Cat Cams: ("Sauger" are the N/A cams) sps-motorsportshop.com/teileshop/performance-teileshop/mazda-mx-5-nb-1999-2000/motor/1-8-liter/ventiltrieb/

I would love to see you just repair the stock head. It would be a great learning experience for those of us who may also have bad valves but don’t have the budget to throw a bunch of performance mods at it.

Go for stock first, modified head secoond! And rememder to walk us through the modified head in detail please! Before installing. I'm right at the point of digging into my second BP4W head with plans to do a multi angle valve job and some velocity boosting, all DIY apart from a drastic skim to raise the compression. Ah, and exhintake mod of course! Keep up the great work!

Super helpful as always Greg! My car's smoking like a clown car and I reckon it's the valve guides gone bad (I recently rebuilt the engine and didn't do these). You've shown me what a leak down test is now, so I will hopefully be doing this next!

Well lucky for you, you pretty much know it’s a valve issue I had a leak between 2 & 3 and was like oh ok head gasket. Had a weekend to do the job in my small garage with problem after problem with parts not included and having to clean up everytime to close my garage to run to the store and after everything was put back together still a leak runs better tho but I’m an idiot not thinking and just needed my car to run so I can have a car didn’t check the head or block with a straight edge and more than likely my head warp and will have to do all that work once again and send the head out for repair. Yay.....

this is super interesting, I love your level of detail w/ troubleshooting. When I achieve my dream of living in my own house and can buy another Miata, I will use this as reference

I’d like to see you run through all of the common “cheap” mods before you do anything crazier. Get your BP4W sorted with the ex-intake cam, intake, headers, exhaust, etc. While you’re on a stock engine maybe do throttle body, e85, MAF delete, VICS delete, etc. for science. Then do nitrous. I do want to see the built head with big cams eventually. But there’s so much more you can do to test message board wives tales. Honestly, not very interested in the VVT head swap. Might as well just buy an NB2 or swap the whole engine (10:1 pistons, better oil pump)

Hoping you choose the ported head and play with some variation in cams. Super curious what kind of power you can get and how the drivability turns out.

Mazdaspeed shim under buckets Heavy double valve springs "Big boy" cams = Lotta RPM's Lotta RPM's + e85 = Stock bottom end record Stock bottom end record + nitrous = Stock bottom end record × 2

This is a hard one because I want to see all three of your options! I want to see what your current setup is supposed to make, I want to know how much a vvti swap is worth and I want to see that modified head turn that motor into a screamer 😬 get to work Miata dad. I’m here for it.

I was about to say until saw the pinned comment. Gotta be tdc on compression stroke. Easy way to check is pull valve cover and watch the cams so you know for sure.

Definitely rebuild the stock, see how much power, hit your limit/pop the head and then upgrade!

Option 1 for sure, rebuikd and improve step by step! Maybe even try porting it yourself when all other things are done!

Notifications enabled, gotta see you chase that na nb record ;)

Thank you for all your work from the Miata nation!

I think rebuilding the head to stock fits the most with the goal of this project, but I definitely would like to see some awesome vvt head swap stuff in the future!

I honestly hope you keep the stock engine or find another 1.8 from the same models.. the VVT really did make the rebirth series impossible to follow on anything but a VVT turbo due to the tuning aspect! But Either way Ill watch and follow along!

VVT block, 272 cams, shave head to the max, itb’s, E85, Quinn style please (you know you want it).Dude! I wrote this before you said it.

Most realistic dude on the internet. Do the modified head.

I learn more than I can retain every video I watch on this channel and I love it.. My brain is curious, but it hurts. lol

Thanks for all your help over the years!

Excellent video and just in time. My headgasket recently blew. Hope you gonna show us how to install a head. Keep up the good work and take care.

VVT head swap on an nb would be very informative. Good content.

Definietly I wan't to see the improvements of the second Head!! From a didactic point of view fix the leak issue and continuing with your step by step mod test will be more interesting that drop all de meet and potatoes at the same time.

I’m just watching this and giving sideways glances at my Miata knowing damn well it’s low on compression. I haven’t tested it but I feel it in my bones

Let’s see that stock head replaced first. I wanna see what those mods were worth on the dyno.

IMO just install the madlad head, I think you can skip the stock head, because we already know it made more power with the mods, and you cant actually confirm that the head was in complete good shape when you did the stock runs, maybe the stock runs would be affected as well but less than the exintake swap.

I'd love to see you top Quinn's 185 by using the ported head - it'd be an amazing feat! Hey, what about ITB's too.......

Umm maybe valve angles being different matters eg. Triumph motorcycle old twin we use to run 2 inlet cams but intAke and exsaust valve Angals are 45degs so swap works put a Westlake 4valve head on it valve angles are maybe 60degs intake 40degs exsaust...? So valves same length so if run same cam in both sides one will have less lift than the other because of the valve Angals is this what happening with the mx5 when you put exh on intake = less lift

Your problems are real world and really helpful to learn from. Would be really interested to see how you tune this car with a NOS set up for daily driving. Ie it’s on tap when you need it only. I fancy trying this set up for my mx5 kit car as an alternative to the usual turbo route 😁

Thank you for the goodies! 🙏 Much appreciated! 👏

Go for option one! Just make it work and finish what you started! After that’s finished and done, go for the record 😌

In your last video, you went over how tuning VVT could see awesome gains across the power range. It would make the nitrous build an absolute beast.

Please Greg, go for the stock NA power record !🙏🏼

I really would like to see the built head with itb’s, but I feel like the stock head would be better for community knowledge.

Put the madlad head with new cams on there and send it!

You could do the first option first then down the line go for the third.

Im just here to say no matter what you do with the head I just cant wait for a new vid so I dont have to rewatch your older ones 😄

And id say port that bp4w head since they are the best flowing already. Port the crap out of it and go to town! Maybe a turbo fed into individual runners into itb's. Ive always wanted to see someone do this on a miata. Would sound sexy.

Amazing video, I love this series. Things are getting interesting. Looking forward to see the results after problems will be fixed and wondering how many whp it will make.

Thats perfect. Time for a porting job and new valves for even more power =)

Not related to this video but can you do a quick video explaining why Gingiums 1.6 can make nearly 400hp with a Miata trans and diff, but your 1.9L VVT ate the Miata trans for breakfast, lunch, and dinner? Love your vids, dad!

Glad you found the problem! waiting for a engine disassembly and rebuild video now.

I think in the end you should put the vvt head on so that you makes as much power as you can on the bottle but maybe save that for the final iteration.

Hey man, congrats on finding the issue. 👍 What do you think you gonna find wrong with valve train? As for next option, i'd love to see vvt head swap. I didn't find this info anywhere. And the nasty head with exhintake sound fun too. Could be interesting how much power you can make usig dramel tool and not spending money on cams. Looking forward to whatever option. :D

I like the stock head idea! But you do you man, love the content, excited for more!!!