Mazda B6 DOHC 16V

[StanTheMan]

The minimum distance between Piston & head clearance is .032-.059 mm once head gasket is installed

can anyone confirm that?

I'm getting figures up to .75mm from various places

[madjak]

Are you sure that's not 0.032- 0.059 inches not mm?

It depends on a few factors. How heavy are the pistons, how many revs, rod strength.

Edit: What I wrote was misleading. Let me try again:

Piston to head: 35-40 thou, more if you have heavy pistons (up to 60thou)
Piston to valve: 80 thou intake, 100 thou exhaust. You can be a bit tighter but you need to know what you are doing.

Also FYI, my valves will hit each other too if you get the timing out. There is a cross over window where they miss each other.

[StanTheMan]

although Valve may be an issue I'm currently looking at how much clearance I have between the head & Piston. Probably closer to 0.3mm which is too close if
standard motor is be 0.75mm? pistons & con-rods are standard.

I got the figure from the 1990 Mx5 manual. It just talks about clearance.They may be talking about a different tolerance than I think they are talking about. Will check if hey talk about mm or inches

I'm talking about he minimum distance between the piston at TDC & the head bolted down on the head gasket. if 0.060" is the number that would be 1.5 mm before it hits the bottom of the head. The standard gasket is 1.2mm thick once compressed. In most cases the piston at TDC is above the deck..... I measured mine at 0.3mm and Ive read that it is normal .....

[madjak]

I'm talking about he minimum distance between the piston at TDC & the head bolted down on the head gasket. if 0.060" is the number that would be 1.5 mm before it hits the bottom of the head. The standard gasket is 1.2mm thick once compressed. In most cases the piston at TDC is above the deck..... I measured mine at 0.3mm and Ive read that it is normal .....

I re-wrote what I typed... it was wrong as I was mixing in valve to piston.

I think 35 thou would be the minimum if you are aiming for revs. 0.89mm. At 0.35mm your at 13 thou?

[StanTheMan]

Are you sure that's not 0.032- 0.059 inches not mm?

It depends on a few factors. How heavy are the pistons, how many revs, rod strength.

Edit: What I wrote was misleading. Let me try again:

Piston to head: 35-40 thou, more if you have heavy pistons (up to 60thou)
Piston to valve: 80 thou intake, 100 thou exhaust. You can be a bit tighter but you need to know what you are doing.

Also FYI, my valves will hit each other too if you get the timing out. There is a cross over window where they miss each other.

OK cheers were both editing

Its time to take the head off before it self destructs as well.

[StanTheMan]

I'm talking about he minimum distance between the piston at TDC & the head bolted down on the head gasket. if 0.060" is the number that would be 1.5 mm before it hits the bottom of the head. The standard gasket is 1.2mm thick once compressed. In most cases the piston at TDC is above the deck..... I measured mine at 0.3mm and Ive read that it is normal .....

I re-wrote what I typed... it was wrong as I was mixing in valve to piston.

I think 35 thou would be the minimum if you are aiming for revs. 0.89mm. At 0.35mm your at 13 thou?

Not aiming for revs. Just a bit more compression. and yes. very little tolerance if this is all true and most likey detrimental to the health of the piston & head

[madjak]

Its time to take the head off before it self destructs as well.

Reading up on a few performance builds, I think 25thou would be my bare minimum. It sounds like the factory 1.6 has the pistons over the deck so it's around the 32-35thou mark as stock. You need to have room for the piston to rotate in the bore a bit as well as expansion of the rod.

When I pull down my engine at the end of the year I'll measure the clearance, but at 13thou I'm thinking it's all way to tight. You will see if it's been hitting.

[StanTheMan]

Its time to take the head off before it self destructs as well.

Reading up on a few performance builds, I think 25thou would be my bare minimum. It sounds like the factory 1.6 has the pistons over the deck so it's around the 32-35thou mark as stock. You need to have room for the piston to rotate in the bore a bit as well as expansion of the rod.

When I pull down my engine at the end of the year I'll measure the clearance, but at 13thou I'm thinking it's all way to tight. You will see if it's been hitting.

I'm hearing it at 4000 rpm.......

[madjak]

yeah so it's not the piston hitting the valves, but rather the piston hitting the head. That makes more sense as I can't see how you'd hit with 272 degree cams even with a big head shave.

[StanTheMan]

Confirmed

Put the old cams back in. Noise is still there.
Lifters have plenty of oil in them. Quite smooth to move around as well.

Mind you. The 272 cams make a decent difference even with the standard ECU
Big torque difference mid range too. These are great for street

Oh well . Standard size head gasket will be on order. Hope there is not too much damage.

[StanTheMan]

OK what about Knock sensors for stand alone ECU's.

I know most ECU's will have the possibility to add a knock sensor. Ive been reading mixed reviews.
https://www.flyinmiata.com/knock-sensor-and-mount.html


does anyone have any experience with this?