gtred

I've been looking for camshaft data on my existing OEM set up with the intention of getting a re-grind that will get me to 7500rpm... but I've only been able to find bits and pieces of info... and worse yet, the data didn't specify how the cam was measured. In order to get a baseline, I measured this yesterday on my trackday car. It's a 2004 msm. The deck is measured square, but not milled. The head is skim cut .003". Cometic .036" thick head gasket. Timing marks are aligned using OEM cam gears. TDC confirmed. Measured from the lifter @ zero lash. *The measurements in inches are:

EO: 0.040 = 40 degrees BBDC
0.050 = 36 degrees BBDC

EC: 0.040 = 4 degrees BTDC
0.050 = 6 degrees BTDC

Exhaust duration @ 0.040 = 216 degrees
Exhaust total lift = 0.360" (lifter @ zero lash)
Exhaust lobe centerline = 112 degrees

IO: 0.040 = 7 degrees ATDC
0.050 = 10 degrees ATDC

IC: 0.040 = 44 degrees ABDC
0.050= 39 degrees ABDC

Intake duration @ 0.040 = 217 degrees
Intake total lift (lifter at zero lash) = 0.370"
Intake lobe centerline = 115.5 degrees
Lobe separation = 114 degrees

* note that 0.040" = 1mm

StanTheMan

that's really confusing. They use 0.040 & 0.050 as a base measurement. I get the 0.040 as its metric and japan is metric. But trying to compare that to other-cams where the standard is 0.050 makes it difficuilt
but on top of that......they also use the 0.050.....

gtred

I was just really surprised at how small these camshafts are. I'd never degree'd in an OEM cam before. Prior to this, I've only degree'd in aftermarket camshafts as per their supplied cam card.

I understand the 114 degree lobe separation (because of the turbo), but the intake side seems quite retarded with a 112 degree centerline... and there is no overlap at all, in fact negative 11 degrees overlap.

I think that it is important to get a baseline on what OEM lift/duration/LC/LS in order to get baseline information to a knowledgeable cam grinder about any changes you want to make.

I wish some of the more experienced miata builders would chime in and give their perspective... which is why I posted this; ...hoping for some discussion/miata specific education.

StanTheMan

I just ran this through a cam lobe calculator. The results I get are reasonably aggressive.
I did the numbers at 0.050....cause thats what I understand. It must be said. I'm a weekend warrior. not a pro.

Intake Duration is 229.00 degrees.
Exhaust Duration is 222.00 degrees.
Installed Intake Centerline is 104.50 degrees ATDC.
Installed Exhaust Centerline is 105.00 degrees BTDC.
LSA is 104.8 degrees
Overlap is 16.00 degrees.

Now Mazda speed has the BP-4Z head right? No VVT. If Ive put the data supplied by you in correctly and the calks are correct. I'd say that's reasonably aggressive. The assumption is also that you are also using the non adjustable cam sprockets?

StanTheMan

I used this online calculator....

Camshaft Calculator - Wallace Racing

maybe have a go yourself. to make sure I got the numbers in the right place.

sixshooter

iTrader: (12)

229/222 at .050? I'm going to say that something is wrong with the calculations. A cam with that much duration would not idle smoothly on an engine this size. I seem to recall the specifications being listed somewhere and they were far less than that.

gtred

Thanks for chiming in. My numbers look a little small to me. Just because they were repeatable doesn't mean that they are reliable... I'm going to re-do and re-post if there are any errors.

Things that I had done differently than in previous engine build were: 1) There is no rocker to adjust out the lash on a miata motor, so I used a feeler gauge to zero the lash... I'll make sure it didn't interfere with the dial indicator extension. 2) because of the close space, it was difficult to get the dial indicator perpendicular to the lifter bucket... I'll try to make a better effort on lining these up. 3) As I had already installed my ATI damper and torqued with a new bolt, I didn't want to remove the bolt to mount the degree wheel. I mounted the degree wheel to the flywheel and was trying to be careful not to confuse the numbers. I'll mount it to the front this time. Oh, and the 2 glasses of red wine... Might be a factor. I'll switch out to beer for the next go-'round.

StanTheMan

https://forum.miata.net/vb/showthread.php?t=288089

since its a post by Emillio....its probably on this site as well...

sixshooter

iTrader: (12)

Says 174 @ .050 at that link, which is quite a short duration cam by muscle car standards. I thought stock specs were closer to 185 on the Miata but I'm not sure where I got that idea.

gtred

I did re-measure. Changing from wine to beer didn't change the numbers much. I did find an irregularity with my "IC @ .040" number; which reflects a minor difference noted below... the rest were unchanged. 'Gonna have to face the fact that we have baby cams.
EO: .040 = 40 degrees bbdc
.050 = 36 degrees bbdc
EC: .040 = 4 degrees btdc
.050 = 6 degrees btdc
IO: .040 = 7 degrees atdc
.050 = 10 degrees atdc
IC: .040 = 37 degrees abdc
.050 = 39 degrees abdc
Intake duration @ .040 = 210 degrees
Exhaust duration @ .040 = 216 degrees
Intake lobe centerline = 112 degrees
Exhaust lobe centerline = 112 degrees
LSA = 112 degrees
Overlap = -11 degrees

Stan: Be sure use note that EC = BTDC and IO = ADTD are negative entries in the cam calculator program. Thanks for re-posting Emilio's cam doctor data.

sixshooter

iTrader: (12)

Also this, for information's sake: Solomiata : Engine : Camshaft specs

StanTheMan

well youre pretty close there gtred

216 @040
on solomiata its at 215 @040

maybe chase that beer with a nice Tennessee Bourbon whiskey shot. LOL