Hi everyone, I know this is Miata Turbo, and I am headed N/A, but this seems to be a wealth of knowledge.

I'm building a strong N/A VVT motor, and wanted to check a few things before I wrap up machining work and start building the motor.
This si going into my 1.6 SM racecar that am converting to VVT swapped, aero track car.

Here's my plan, this should cover engine stuff,

2003 VVT motor with 90k miles, though I am pulling it completely apart to rebuild
10.5:1 JDM VVT pistons on stock rods
Boundary engineering VVT oil pump
ACL Race Bearings
Mildly ported head with stock valves and a fresh valve job
Planning to Shave the head .020" to get to 11.0:1 comp.
Maruha VVT cams
Supertech double valve springs
MMD Solid lifter buckets
Stock cam gears
Squaretop intake manifold with cleaned up throttle body transition
Roadster sport header NA8 (basically the same as Racing Beat) - Possibly ISR 2.5" cat back
3D printed intake to run into front bumper
Flex Fuel set up ( was going to run Purple VVT injectors, but reading I need RX8 yellows now)
MS3Pro PNP for 90-93

I have finished porting the head, and honing/cleaning the block out, just about to have the valves done on the head and deck.
I was nervous last night thinking about the 0.020" shave on the head, and the aggressive cam profile.
I know Quinn went way further on head shave before having to pocket the valve, but has anyone checked a 10.5:1 JDM VVT piston for piston to valve clearance with the Maruha cams? I have everything blown apart now.

I'm also trying to get ready for setting the valves up in the head, and curious if most find they need to go with the double shim path as shown in this picture.
https://cimg3.ibsrv.net/gimg/www.mia...326cb169c7.jpg
From this thread: https://www.miataturbo.net/engine-pe...n-92281/page2/

I have built a couple SM motors that I have run over the years, but this is my first adventure in something this wild.

Thanks for any help!

 

I know there's a lot to read in the above, so I pulled out the questions

has anyone checked a 10.5:1 JDM VVT piston for piston to valve clearance with the Maruha cams? is 0.020" decking an issue?

When running Maruha VVT Cam and MMD solid lifters do you find you need to use double shims?

 

Not sure if you've seen our VVT build on YouTube (Napp Motorsports), but we did an extremely similar build to what you're listing up top. The only differences were OEM VVT Pistons and a 0.040" head shave for 11:1 compression and stock cams. I'm not sure on the valve clearance, but my suggestion, while it sucks, is to assemble the head with all the components and put some "playdough" between the valves (Full lift) and the piston (TDC) and measure how much you have prior to taking the .020" off the head. I think you'll be surprised and you'll have more room than you think. I'd bet you can take 0.060" off before you have any interference. If you want peace of mind, do the test without the head gasket in between and you'll have even more of a cushion/MOS)

This setup should net you around 160-175 whp if I had to guess. We did 150 wheel on a mustang dyno on pump gas with stock cams and a Skunk2 Intake/Throttle Body. Cams are typically worth like 15hp from what I've seen on at least 1.6 miatas. E85 only netted us like 5hp, but if you're trying to suck all the power out you can, then that'll be the way.

 

I haven't run them with 10.5 pistons, but I have run the 264s with a shaved VVT head, no interference. I only used the MMD lifters and SUB shims. On a BP4W, I did the same setup with Maruha's 272s and a .100" shaved head. ALMOST needed two tensioners, but got away with the OE setup.

You quickly make them interference engines, even with stock cams, but they're difficult to get piston to valve interference while timed. Just be sure you're building it with RPM in mind, it's best to rev these to 7600-8000.

VVT/264 combo made 165hp, BP4W/272 combo made 170. Both had ~100k bottom ends. VVT is still chugging along, BP4W blew up it's Boundry oil pump gears when he spun on track and didn't hit the clutch.

 

Curly is right, I messed up with my description. You'd want to check the clearance with the engine in proper time to see if it'll interfere before deciding the max that you can take off. It becomes an interference engine much sooner than it becomes an issue in a properly timed setup, if that makes sense.

You could also figure out how much more lift the cams you're using have, and use that and do some math to figure out how much closer the valve will be to the piston. Quinn took off 0.100 I think and had to massage the piston tops. So say 0.080" or 0.060" (for extra safety) - extra valve lift from new cams - extra piston height from 10.5:1 pistons = max you can take without having to work on the pistons.

Playdough is always safe though.

 

I can't comment on the cam and interference question other than to check for yourself. Life is full of tolerances.

If I may make a suggestion on the injectors though, get the newer ev14 injectors instead. Flowforce has them in the 380cc range which is perfect for e85 N/A engines. And $240 for cleaned and balanced injectors is a deal.

 

Circling back on this, I assembled everything with the .020" cut and it looks like there is plenty of clearance with the VVT range, I used playdoh and measured 0.235-.240 clearance on the intake cam with the intake cam timed 3 teeth advanced to simulate full advance. The exhaust was 0.378-.380"
I have a bunch of pictures I will load and share more details on. Thanks for everyone's insight.

On the MMD lifters, if you are running the Maruha cams and you make sure the machine shop does not tip the valves there is about 3.6 mm of valve above the keeper. The Supertech LC-60 lash caps are 2.65-2.8 mm deep inside, so there is a bit of clearance. I ended up just using Supertech lash caps, in a range of 2.5-2.75mm thicknesses.

Stefan, I have seen your build, and it as been a reference point for me as I have been working through my project. I like where you went with it, I am just trying to squeeze just a little more.
I hope you are right, my goal is 170, but if with E85 I can have 180hp, I am all for that. I think the E85 would help keep combustion temps down too which will be better on the pistons.
Your videos make me pondering filming my build to post, but I haven't been taking the time for that.

Curly, thanks for the insight, I plan to rev this to 7600, being its OE pistons and rods, Maybe 7700. I have heard 7800 is the line where I shouldn't cross.

Hector, I emailed Flow Force about the 380's, but they said if I might be pushing past 170 they didn't recommend the 380's as at 180 i would be hitting 95% Duty on E85. So I am still figuring that part out.

Injectors, building a 3D printed intake, and a 2.5" exhaust are the only things i still need to figure out engine wise. I hope to have it together and tuned for its first track test April 24th.

 

Any updates on this build?

 

it’s done and running.

it made 172hp on e70(e85 with 93 still in the tank)
it’s been running great so far. Let me know if you have any questions.

I put Xida’s (800/500 on Race with the top hats), Super Miata 863 Bushings, and Racing Beat large sway bar on this year. I still need to update the splitter to support the downforce of the wing. Running 15x9’s now as well.

 

Great to hear. I ordered something similar from Keegan Engineering a few months ago. Sounds like supply shortages have delayed some of the parts to get it assembled. Glad to see yours making that kind of power. Congrats!