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The Definitive "VVT swap into 90-97 chassis" Megathread.

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Old 11-23-2016, 04:17 PM
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Originally Posted by Leafy
And you'll basically need to replace the oil pump in order to get the crank trigger on a 94-95. IIRC the boss is there so if you're a ******* judo master with a hand drill you could drill and tap it maybe.
Has anyone been brave/stupid enough to try this?
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Old 11-23-2016, 06:14 PM
  #322  
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Are you sure the hole in the pump for the sensor is not threaded? I'm like 99% sure mine was threaded on my 94 pump.
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Old 11-23-2016, 06:17 PM
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I just went out & scraped the crap of mine. It looks tapped. I couldn't get an M6 to start in it though.

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Old 11-23-2016, 06:20 PM
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Before I posted that I checked my 94 block, it wasnt threaded. The 97 block I have is threaded, well duh because there's the VR crank sensor there for OBDII cars. It should only be original non-OBDII car oil pumps that lack the thread.
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Old 11-23-2016, 06:23 PM
  #325  
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It's a '94 block. The pan sealant sure looked factory when I pulled it, but I guess the oil pump could have been replaced some time in its life. I guess the moral of the story is check first.
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Old 11-23-2016, 06:29 PM
  #326  
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Maybe I'm getting the split wrong? Maybe it was a mid year 94 change.
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Old 11-23-2016, 06:45 PM
  #327  
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When you say the boss wasn't tapped, do you mean there was just a flat boss with no hole, or did it look like the one below. That's about the best shot I could get, and I still don't see threads. Like i said, I couldn't get an M6 in there, so there could be threads buried down in there.

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Old 11-23-2016, 06:46 PM
  #328  
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Mine was flat, undrilled. From your picture it looks like you could run an M6x1.00 tap in the hole and it would work.
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Old 11-23-2016, 06:46 PM
  #329  
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Tonight or tomorrow I'll go out to the garage and check the few oil pumps I have.
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Old 11-23-2016, 06:51 PM
  #330  
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It's cool finding the little variants in mass produced things.
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Old 11-24-2016, 02:14 AM
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Along this same line of thinking, if I'm going to integrate crank sensory into a '94 block, I need to add a timing wheel. This is gonna change the stackup thickness of all the things bolted to the nose of the crank. Would I need to replace the pulley and/or boss with a NB specific equivalent? I have to think that something's thinner to accommodate for the timing wheel.

Edit: this answered my question. Boss changed in 96 when crank position wheel was introduced.

http://www.planet-miata.com/index.ph...ch-item&idn=89

Last edited by wackbards; 11-24-2016 at 02:44 AM.
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Old 11-24-2016, 07:15 AM
  #332  
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Originally Posted by wackbards
Along this same line of thinking, if I'm going to integrate crank sensory into a '94 block, I need to add a timing wheel. This is gonna change the stackup thickness of all the things bolted to the nose of the crank. Would I need to replace the pulley and/or boss with a NB specific equivalent? I have to think that something's thinner to accommodate for the timing wheel.

Edit: this answered my question. Boss changed in 96 when crank position wheel was introduced.

*Planet-Miata.com - Your #1 source for Mazda Miata new and used parts and accessories.

Correct you need the 96 or new boss.
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Old 11-24-2016, 06:43 PM
  #333  
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Tap the hole, I bet it's the right diameter for m6x1 threads. Start tapping it, once it bottoms out, grind the tap flat on a bench grinder. Then tap the bottom of the hole. Kinda ruins a m6x1 tap, but it's still useful for chasing threads and if you're careful creating new ones. Plus they're only about $10.
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Old 11-24-2016, 07:11 PM
  #334  
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The hole should be drilled correctly for M6x1.0. We had to do this on some of the very early BE pumps (like 6 years ago) before Travis started tapping them all at our request.
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Old 11-24-2016, 08:41 PM
  #335  
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Originally Posted by curly
Tap the hole, I bet it's the right diameter for m6x1 threads. Start tapping it, once it bottoms out, grind the tap flat on a bench grinder. Then tap the bottom of the hole. Kinda ruins a m6x1 tap, but it's still useful for chasing threads and if you're careful creating new ones. Plus they're only about $10.
Bottoming tap?
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Old 11-24-2016, 10:02 PM
  #336  
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Yes if you can find one that'll work. Generally when you add coating, different tips, or other features like spiral flutes and what not the price goes up.

$1.60:
https://www.walmart.com/ip/WESTWARD-...&wl13=&veh=sem

$17.22
https://www.zoro.com/osg-spiral-poin...Q&gclsrc=aw.ds
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Old 11-24-2016, 11:28 PM
  #337  
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Bottoming M6 taps are ~$7 at McMaster
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Old 11-24-2016, 11:42 PM
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I do not understand the purpose of a spiral point plug tap. A spiral point tap is made the way it is to propel all the chips forward, generally used in through holes only. Using one in a blind hole will lead to tears.

Regardless, the second tap Curly posted is not a hand tap and should not be used as such. It's made for highly rigid tapping machines, it'll break if you look at it funny.

When you grind the point off a tap you need to be sure it's done perfectly perpendicular to the threads, it's possible to have too many thread starts with a three flute hand tap if you grind the end off at an angle. It will shred stuff, quick. I do not like doing it, at all.

I'd just use a normal tap and find a slightly shorter bolt. 1.5x bolt major diameter is plenty of engagement for something like that.
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Old 11-27-2016, 12:50 PM
  #339  
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Bottom taps aren't special or exotic. They are right next to the starter and plug taps for the same price. Grinding a tap flat with out the proper end chamfer is also stupid as it always leaves the last tooth or 2 super thin, and it usually breaks off in the bottom of the hole once it starts taking a chip load.

USA made M6x1 bottom tap for $7 shipped
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Old 11-27-2016, 01:29 PM
  #340  
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Exotic bottoming tap just sounds dirty.
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