engine rebuild
 

Good everything everyone!
I recently took apart my miata motor (bp 1.8) and since I'm here at this point i would like to do something to prepare the engine for a future turbo application.

At this moment i bought a stage 2 boundary oil pump, forged rods and i planned to keep stock pistons buying them new since I had to bore the cylinder to the next step that is 83.25mm and talking with some guys, to be able to reach 220/250 horsepower it should be more than enough.
In my shopping cart there are:
-all ACL bearings and apr main studs and head studs
-the plan with the head gasket would be to run a stock one for the time being without turbo and then buying a cometic one to be able to put the thicker one and reduce a bit the compression ratio.
-As for the gaskets and seals, I'm buying everything OEM
-Reroute kit

Is there anything that I should look for in building the engine? I asked the machine shop to change the valve guides and after some reading I got into videos and discussion about the intake valves problem of shaving down after few km due to resurfacing them, should I look for some new valves since they got resurfaced in the past already? to be able to achieve the target on 220/250 hp what would be the best turbo set up which will not have much lag and start to push the sooner possible? td04?
https://cimg9.ibsrv.net/gimg/www.mia...27aa12c137.jpg
https://cimg0.ibsrv.net/gimg/www.mia...039044c25b.jpg
https://cimg1.ibsrv.net/gimg/www.mia...e148492391.jpg

• I’d say put a stock thickness cometic head gasket in it now, or even an oem gasket. It looks like you have an NA8 so stock compression is 9:1, you definitely won’t need a thicker head gasket to drop compression ratio further, plus thick head gaskets ruin your quench measurement. Stock MLS head gasket and studs is plenty of cylinder sealing for 250hp.
  
• Skip the ARP main bearing studs, they’re overkill for most motors, a lot more power (think 400+ to the tire) and/or super high RPM is when you would need the stability of main studs. For a rods-only rebuild they’re overkill and require the main tunnel to be line-honed, and it is becoming an exceedingly difficult to find anyone both willing and competent to perform.
  
• Consider looking for a 99-00 BP4W cylinder head since you haven’t bought your turbo manifold yet. They flow significantly better than the 94-98 heads.

Cant really offer much advice on a turbo specifically, I’m not very well versed in the nuances of each model number. I do know a TD04 is a pretty old turbo, unless you’re talking about a TD04-framed turbo with modern turbine/compressor design. But I also may be showing my ignorance of turbo things and TD04s are still great. Someone here with much more knowledge can help.

+1 To the 99-2000 head. for the turbo the garret 2560r is a good start if your starting from scratch, decent spool, will meet your power goal. are you using a 5 speed or 6 speed? 225 is where the 5 speed can become a consumable depending on torque.

Here in Italy its not that easy to find a head for a good price unfortunately. Its since a bit that im looking for one but no luck yet.
I am already running the 6 speed gearbox

Copy for the gasket, but having the head shaved should make the compression a bit higher. It has been shaved already once, but unfortunately i dont really know how much. At the moment the head is again at the machine shop to check if the valve guides are good or need to be changed I might as well as if the head height can be measured and then compare with the number on the manual.

And also copy about the main studs, surely its going to be a bit cheaper without the studs!

Turbo wise, do you guys know anything about garret GBC20-300? I was watching a video from sps-motorsport and they were saying that spools at around 2300rpm till the end and it should be capable for 300 horsepower even though again my goal is a bit less

As long as the head hasn't been shaved aggressively, its unlikely to significantly change the compression ratio, but measuring combustion chamber volume is the best way to confirm. To really zero in on the precise compression ratio you will need to have an idea of your piston clearance above or below the deck at TDC, which can't really be measured until the bottom end is assembled.

Spool characteristics are going to be heavily dependent on camshafts, valve sizes, compression ratio, and manifold design. I'm not familiar with that shop/video but I'd focus on builds that have been done using a stock 1.8 NA8 engine to get the best comparison.

Garrett 2560 would be a great choice of turbo. The gbc is a newer design with what looks like a smaller turbine and compressor but with new aero it still flows really well, so that would also be a good choice if you prefer response over big power.

OEM hg is probably just as good as cosmetic imo. I use a cut ring hg but I have pushed over 400hp so this isn't anything you'll really need. Also look into a better crank damper. I use a fluiddamper crank pulley along with a boundary stage 2. I also run ARP main studs, if you can get a good line hone I would run them. Do it right one time and it'll last a long time. I also run OEM valves no need to upgrade those and no need to upgrade the head for your power goals really, maybe better valve springs and retainers.

It shouIdn't be theoretically, i will ask them to measure it just to be sure about it and ask them to do do the volume capacity check if they can, otherwise I will get the tools ad do it myself.

Surely as you said the specs of the engine will contribute in different tipe of spooling and so on but im trying to get a more general idea on what to focus so I can be a bit more straight forward on the type of research I will be doing. But still thanks a lot for the great answer!

I mean, everybody told me that as soon as you get to 250 then you will want 300 and the 350 and so on and so on 😅 i honestly dont want to overshoot it spending sooo much more money that needed, at the end 900 and some kg with 250 horsepower i thing is the right balance for mainly road and hopefully few trackdays.
I think if you go over that than after all the money spent on the engine setup you need to spend a good other amount for all the chassy bracing and safety equipment.
meaning that maybe a simple roolbar and nbfl big brakes are not gonna be enough.
Main studs wise i'm gonna try to read and understand a bit more and then decide what to do.

I might have found a bp4w head for not much, im waiting for some photos. The guy said it has a small problem but didn't said what and said it would show me on pictures

Crank damper should be on your list if nothing else. The OEM damper sucks and they are old and fall apart. Main studs aren't a requirement but if your machine shop can line hone then they are a nice piece of mind upgrade. I wouldn't consider any of this stuff overspending I would consider these things smart investments.

Yes everyone wants more power you'll get used to 250. I run my car around 350whp now which is plenty and it keeps the 6 speed from blowing up so fast

Build Update:

So as said in the previous post what has been bought at the moment is:
-OEM Piston 83.25 with Hasting rings
-Boundary stage 2 oil pump
-I found a BP4W complete head (i will bring it to the machine shop to check for cracks and valve leak, I will work it as my current head removing all the burs from the casting and cleaning the intake and exhaust duct making the exhaust as shine as possible and leaving the intake a bit more rough) like this i will aslo get rid of the hydraulic lifter and use the solid ones from the new head. Another this is to do the exhintake mod since i will have 2 sets of cams
-new intake valves since mine started to have the problem that even miata dad Greg Peeters had since unknowingly in the past i made the machine shop grind them because they were leaky.
-new timing pulley since mine was in a very bad condition after the removal :vash:
-some OEM gaskets already started to arrive

In the next weeks, after the holidays, next order will probably be Maxspeeding rods and reroute kit from skidnation and probably the complete set of acl bearings.

Clutch wise, does anyone have experience with xtremeclutch brand? here the is the link for it
https://xtremeclutch.eu/product/KMZ22006-1A_2

I cannot speak to the quality of that clutch, but I know lots of people have had decent experiences with the ebay/off-brand clutches here in the States for your power goals.

Unfortunately the NA camshafts will not be compatible with the BP4W head. The ramps on the lobes are different for the different style of lifter. I'm not sure exactly what is different between them but I have always read that a hydraulic lifter cam is not cross compatible with a solid lifter cam and vice versa. The Exhintake mod is marginal at best honestly, and I think yields more gains for n/a use as it increases duration, which isn't always beneficial for turbo applications.

I read some of others experiences with ebay clutches but i think i would like to not risk to open again the gearbox to change something that broke because its low quality to be ne honest 😅
cams wise, I'll try to do some researches and see what comes out. The turbo project will probably start next year and until then the car will run n/a

a datapoint here
ive run the xtd clutches stage 1 and 2, both of which held up great. I dont launch the car but ive done lots of burnouts with them. The stage 1 started slipping at when i boosted my car, possibly because it got oily from everything leaking. The stage 2 drove fine and i could hardly tell a difference between these two clutches and the stock exedy peddle feel. These both were ran with their lightweight flywheel. The stage 3 my friend ran with their flywheel, ive driven it, and its not any more “bitey” than a person who is used to driving stick shift could handle. Even with the flywheel. That held 15psi and on a laggy ebay t3 turbo and e85 3inch hood exit. Id say 240-270 range whp.

whilst those are good experiences, like everything you get what you pay for, and there have been people who used ebay clutches that fail in spectacular ways. Delamination of the clutch material, springs coming out (which i just saw on an exedy actually) and shitty bearings supplied. If you want to go cheap you have to gamble it being bought and done twice.

Well I dont know thw price for xtreme clutch in usa, but here in Italy for a stage 2 clutch it requirest 500 and few more euro 😅 but will see

i thought you were asking the quality of an ebay clutch. But the same applies. If youre up to spending a medium amount on something you arent sure of and isnt vetted, its still a gamble and yourr spending unnecessary money to gamble. If you dont want to gamble. Why go for something medium priced and purchase something that has been proven good. Maybe happy meal?

Little update. Got the block back from machine shop and freshly repainted it light grey
https://cimg9.ibsrv.net/gimg/www.mia...32487754a4.jpg
also measured everything and its all as mazda requires in the manual.
got to weight pistons and rods to match them and they all got to be exactly the same weight so great news there!
https://cimg9.ibsrv.net/gimg/www.mia...d1003abdd3.jpg
in the meantime i found a bp4w head which i sent to the machine shop to be resurfaced and checked for leaks and i also left them my flywheel to be resurfaced and to have some weight removed (looking for removing a maximum of 2 kg form the 8.6 kg of its original form) to then get balanced together with the crank and the pulley.

The only problem im finding its with the rings. They are still in tollerance but not where they need to be. All the 1st rings measure .50 mm and mazda specs are beween .15 and .30 mm with a maximum of 1.0 mm of wear so technically they are still good but more than wanted. Same story with 2nd rings same measurment of .50 and same mazda specs fro .15 to .30mm the worse ones are the oil control rings they measure between .85 and 1.0mm and mazda requires between .20 and .70mm with a maximum of 1.0 so already at the maximum wear limit.
I sent the company an email and ill see what up with those

.5mm end gap is ideal for a turbo application.