Not much of a bump, but it helps the quench a lot. The pistons are a little proud from the deck, iirc I measured .016 out, and used the same gasket, gives about .011" quench. Shave a bunch off the head while you wait for the gasket, and look for some adjustable gears.

 

Shave shave shave and get adjustable gears. Plenty of clearance. I took .060" off of my BP4W head using 10mm lift cams and still had clearance.

 

rough estimate on how much machining a head will cost?

 

I paid 120.00 for a shave and hot tank.

 

Gotta like squeezing the compression. My only regret is not shaving more. .015 thinner gasket and .025 off the head, and it is a noticeable punch.

 

I'm gonna go like .070 off my head. Maybe I'll go with this thinner gasket too

 

Is there a reason to do both and not just shave the head the equivalent of thinner HG+shave? I like this thread.

 

Bronto shouldn't it be the same? Only difference will be the shape/area around the valves.

Btw, I read somewhere there's a limit because you will eventually cut thru the water passages. Anyone?

@Quinn: how many degrees did you adjust, could it be possible to cheap out and just adjust it by a tooth?
And 2. Where did you get your exhaust as I'm still trying to find 2.3" stuff after the header.

 

I don't remember the exact degrees we ended up with because we changed them multiple times on the dyno. If i remember correctly, one tooth off is like 14 degrees of timing, so this probably won't work. My mid-pipe is a Racing Beat 2.375" race pipe and muffler section is a Jet's Integral Kobe, which is the same diameter.

Where did you find the thinner gasket kit I can only find the .040 one?

OEM Mazda 3 layer gasket is .020"

Wrong Silver. Quinn stated himself that "any head shave worth the effort would make the motor an interference application"

That doesnt mean the pistons will hit the valves under normal operation but if timing is thrown off by the timing belt breaking, the pistons will hit the valves. Mazda factory spec on shaves is pretty low...like .030 or .040

Correct. 10mm lift cams automatically make the motor interference valve to valve wise. My motor with a .060" shave and a 2002 block with the OEM 10:1 compression pistons is now an interference motor piston to valve wise as well, so if the belt breaks things will get damaged.

With my pistons, .060" shaved head, and higher lift cams, I mocked the motor up with no head gasket, which adds another .020" off to my .060" shave. With the cams and cam timing at stock, I still had some clearance. I am going to shave another .020" off of the head next time I have it off. I think you might be able to .10" with stock cams without hitting the water jackets, but gears will be a must and most likely a tune-able ECU. That is strictly at your own risk though

 

Where did you find the thinner gasket kit I can only find the .040 one?

 

sry, I meant to say I ordered the kit and then ordered the .027" one separately. my bad

 

Anyone tried the toda headgasket? Is it factory size or wassup?

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What sort of performance gains or reductions are we talking about with this engine? I haven't looked at the internals, but at what point (or does it) become an interference engine? I wouldn't imagine you could get it to that point, but... what the heck do I know?

 

^it shouldn't, even Quinn's 10mm lift and .060 shave isn't enough to touch the piston. He even stated he wouldve gone .080. So all that should be non-interference. What he was running into was that his 10mm lift valve might hit each other. Nothing to do with Honda's break your belt-break your car.

Now what do you guys know about the length of the belt, as when there's a shave timing retards as the head sits lower. I've read somewhere that there needs to be some shimming on the tensioner. If someone can clarify this.

 

Wrong Silver. Quinn stated himself that "any head shave worth the effort would make the motor an interference application"

That doesnt mean the pistons will hit the valves under normal operation but if timing is thrown off by the timing belt breaking, the pistons will hit the valves. Mazda factory spec on shaves is pretty low...like .030 or .040

 

Thanks for clarifying Quinn. And points to Spite as well.

 

I know I've asked you before Quinn through PM's but just for public informations sake, what is your thought on having to shim the timing tensioner?

I think I remember you saying to me that the tensioner has enough give in it to compensate for a .080 shave.



I'm wondering what comp numbers will be on my 01 VVT motor with a .080 shave and an OEM gasket. My JDM VVT is meant for a 10.5:1 motor so maybe it will be able to handle that shave until I get an MS3

 

I know I've asked you before Quinn through PM's but just for public informations sake, what is your thought on having to shim the timing tensioner?

I think I remember you saying to me that the tensioner has enough give in it to compensate for a .080 shave.

I'm wondering what comp numbers will be on my 01 VVT motor with a .080 shave and an OEM gasket. My JDM VVT is meant for a 10.5:1 motor so maybe it will be able to handle that shave until I get an MS3

The stock tensioner had no problems accommodating my .060" shave and has held up fine thus far. When you tension everything from the factory there is still more room for the pulley to tension. If you think about how much .060" actually is, it is quite tiny.

The JDM VVT engine got it's 10.5:1 compression from the pistons, so you're US version motor is 10:1 compression. Supposedly each .010" you shave is supposed to be worth .25 point of compression, however I don't think that anyone has accurately calculated how much is actually gained.

Quinn everywhere I look its telling me. 040 is oem for a 1.6. If your certain the gasket is .020 and i do .060 off my head with adjustable cam gears and eventually do 10mm lift cams would I be at interference with the valves in the event of belt failure. I'm sorry about the nood question but I'm really trying to get this right.

Thanks!

The OEM Mazda 1.6 gaskets are the old school style head gaskets, its not the 3 layer MIL style that the 1.8 uses, so it actually might be .040", I never measured the 1.6, only the 1.8. Also, a word of advice for you. Do NOT bother with trying to do N/A mods on your 1.6. Just save your money and buy a 99+ engine and go from there. If you want to boost, the 1.6 is fine. Look at my NA that makes 254 whp on stock internals all day long. The heads on the 1.6 just don't flow well, which is no good for all motor power. Stroke is the same on both motors, so there is no benefit with the 1.6 there either, which is a common misconception.

 

Quinn everywhere I look its telling me. 040 is oem for a 1.6. If your certain the gasket is .020 and i do .060 off my head with adjustable cam gears and eventually do 10mm lift cams would I be at interference with the valves in the event of belt failure. I'm sorry about the nood question but I'm really trying to get this right.

Thanks!

 

Yes you would. You would be interference with piston to valve too. You're going .020 over the OEM spec. The spec mazda gives is not factoring in the gasket and you are.

You need to keep variables constant through your calculations.

For example: 0 head shave + gasket = +.020, .020 shave + gasket = 0, .040 shave + gasket = .020 (The true mazda spec after factoring in the OEM gasket), .060 shave + gasket = .040 (.020 over Mazda spec), and so on.

Make sense?

 

You're the man, Quinn. I'm really glad you're on CR to share awesome info like this

 

Thank you very much Quinn, I know the 1.6 is lame but I can have the head shaved for 50$ and a gasket kit is about 120$ so for under 200$ it'll give my poor little engine some much needed help. I've yet to become faster than the car so I plan on working on that first.

Anytime fellas.

If you want to shave a little fine, but I wouldn't shave to the point where you needs cam gears and a tuneable ECU for a 1.6.

 

Thank you very much Quinn, I know the 1.6 is lame but I can have the head shaved for 50$ and a gasket kit is about 120$ so for under 200$ it'll give my poor little engine some much needed help. I've yet to become faster than the car so I plan on working on that first.

 

Is there some sort of general rule for calculating compression ratio compared to how much you shave off the head?

 

So by ".25 point" does that mean shaving .01" would increase one from say 10:1 to 10.25:1?

I must have missed that part in the midst of all the other knowledge spewed out in that post. God forbid lol

 

Obviously that's what it means. Do you need help adding?

Edit: just in case you do need help, .040 would equal 1 point of compression bumping a VVT motor from 10:1 to 11:1

 

Obviously that's what it means. Do you need help adding

Is the attitude necessary? The phrasing .25 point was odd. To someone just trying to figure it out, with no plans of doing it any time soon, .25 point is very repetitive. It would be better written as, "for every 0.010" shaved you add 0.25 compression." The point is already in there with the "."

Not trying to be a **** here, just trying to learn more. Thanks for the help despite my incompetent adding skills. It's not like I go to one of the most prestigious engineering schools in the country or anything... oh wait I do. I'm pretty sure I can do simple arithmetic.

 

If you're so certain of your math skills, why did you ask the question again?

If you're actually in a prestigious engineering University, remind me to not invest in the field you plan on joining lolol

The attitude is always necessary man. This is CR

 

lol every penny you spend on your car is the field I'm joining so have fun with a new hobby. Or every time you eat bread from McDonalds or Kroger just remember it comes from ovens that I've built. Like I said earlier if you could read, "The phrasing .25 point was odd."

 

You know..I was going to flag his first comment. Shoulda coulda woulda.

 

You'll have to ignore Cheerio; he has a permanent stick up his ass.

 

My name ain't spiteful for nothing

 

Okay, I think we maybe getting out of track. So let's focus.
To the 1.6 guy. Do what Quinn says and note that at some point you'll need 93 gas. And it'll cost ya about 3 dollars more per tank for the rest of that miata's life. Muahahah. Jk, worth the power increase.
Now, were in Cali, so..adding compression increases heat and that heat makes more NOx. Now if your a Miata nut you would know your 1.6 doesn't have EGR. This means two things. Your old cat might not be up to the task of reducing more pollutants, which means you Might have to buy an expensive Cali only cat.

Best of luck! I'm sure you can squeeze thru it. My NB can pass it's smog with anything up to 700ppm of nox. To put that into perspective a early 90's Toyota can only pass at 2/3rds those levels.