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Intake Exhaust cam swap

Old 02-21-2013, 10:39 AM
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Default Intake Exhaust cam swap

K...I know everyone has heard of it but who has tried it? I have been searching the forum and cant find anything on it.

I saw the mod in diymiata.com and it says redrill cam gear to 197.5 degrees.

No go. The car is way out of time by the sound of it. It wont even start. I later get to looking and someone says drill it at 249 degrees. If I do that it will be drilling through the 270 degree slot already in the gear. Would have to put it in the mill for that one and make a "plug" for the gap.

Oh...all of these measurements are from the "I" mark.

Any help would be great.

Thanks "B"
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Old 02-22-2013, 10:11 AM
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Does this info in this spreadsheet make sense to you?

OEM Cam Gears - Miata Turbo Forum - Turbo Kitten is watching you test compression.
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Old 02-23-2013, 07:27 PM
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Wow. That has a lot of info.

I believe by doing the math, I drilled the hole wrong. Close but not right.

Thanks for the spreadsheet....I think ill give it another shot.

-B-
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Old 02-28-2013, 07:06 AM
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Good luck.
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Old 03-08-2013, 10:49 AM
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Too answer your question has anybody done the swap, yes we have. Diesel_Miata had a cam he already prepared and we through it in Schadenfreude's '95 last summer. It's very easy if you drill the hole correctly. I gotta say, I didn't really notice anything at all. I think it's something a tune needs to really take advantage of and even then gains are small.

I have the Mazda speed cam in my 00. It wasn't intentional though, I'm just a moron and ruined my cam when doing my timing belt by not torquing down the sprocket. Always torque your nuts!
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Old 03-18-2013, 11:43 PM
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K....I swaped the cams back to stock and still wouldnt run right...I began to think i messed something up but being a zero clearance motor what could I mess up.....Well....Maybe I should have tentioned the timing belt right. It had jumped about 6 teeth and of course wan way off. I got it back and runs like it used to....Low rpm miss sound and screams after 3500 rpms.

My guess is that is the same problem I had with the other cam...I checked and it was drilled right.

My question now is did the swap give you any more low rpm power? I raced an auto-x yesterday and the track was tight so I had to stay in low rpm second gear....no power till mid range or higher....I might as well been in 5th gear comming out of the turns.

When I was on power for a breif second the car pushed like a bread truck going in to the corner...another discution for later though. Rain then later snow. Car covered in white now. I cant wait till spring time.

Thanks for the help guys....I appreciate it.
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Old 03-19-2013, 05:43 PM
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Try a compression test to check for bent valves if you think you might have bent one. The BP engine is non-interference in stock form but I don't know if the added lift of the cam swap changes that.
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Old 03-21-2013, 11:44 PM
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So....what your saying is that if I have bad/bent valves or even low compression on a cylinder than I will have the no power at low rpm issues?

I have been using a little bit of water/coolant for a while....wonder if I have a blown head gasket?

Guess it couldnt hurt to get a new one...I have a head/intake port match almost done....would be a great time to swap.

lemme know if Im way off in my power loss assumption.

Thanks
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Old 03-22-2013, 05:49 PM
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If you have poor sealing at the valves or the piston rings (or even the head gasket) it is a little less evident at higher RPMs because it takes time for the gasses to exit through the opening. At higher RPMs there is less time for it to escape.

This isn't to say that you might not have some other problem at play but some diagnosis through a compression check might prove useful.
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