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Author Topic: deciphering the bumpstick code....  (Read 4124 times)

rcicustoms

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deciphering the bumpstick code....
« on: August 06, 2010, 01:14:00 PM »

ok ive decided to try something ive wanted to for over a year now.....someone told me back in our festy days that a miata exhaust cam yeilds a power gain on our engines... i was skeptical and passed it off ... yet with russ camming the super roo it has come back up....

ive got a couple friends that have turbo 1.6 miatas and there cars build more power per psi than the b6t. i allways passed this off as the engine having a higher CR.... when i built my engine with the b6 n/a block i figured id be alot closer power to pressure...

with new events ive started researching again

first what caught me was the N/A 1.6 b6-ze makes 115hp stock where a stock capri N/A makes 100 even... so i started calling friends and low and behold my buddy nate has a 1.6 miata tore appart all over his garage... cams sitting out of the head soaking in a oil bath....Handy... so i grabbed a set of b6t cams and started comparing

first noticeable difference were the markings
the b6t uses b660 cams intake and exhaust...

the miata uses a b660 intake cam and a b61p exhaust cam... hmmm so i did some more digging..
 
 
 

b660 intake and exhaust on the b6t
b660 intake and b61p exhaust on the b6ze (miata)
now, all b660 cams weather intake or exhaust are identical (exception being the intake has a slotted drive end to run the dist.)
so i researched and came up with this nice little chart off solo miata ...

   1990-93 5-speed   
Dur @    intake    exhaust
Adv. Dur.

(.003")   236   250
.010"   220   233
.020"   210   223
.050"   192   204
.100"   170   180
.150"   147   156
.200"   122   130
.250"   90   97
.300"   37   42
Valve Timing   5 BTDC
51 ABDC   53 BBDC
15 ATDC
Overlap.   20   
Base circle Diam.   1.3"
33 mm   1.3"
33 mm
Total Lift   
.309" 7.86 mm   .311" 7.9 mm
   
now on the right is the b660 cam or intake on a miata and both on the b6t... on the left is the b61p mystery exhaust cam...
as you can see the 1p cam has a longer duration (250-236)and higher lift(.311"-.309") than the 60 cams do...hmmm

to be continued.... this weekend i will be installing the b61p cam into my high compression turbo build....we'll see how it works....
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rcicustoms

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deciphering the bumpstick code....
« Reply #1 on: August 06, 2010, 01:28:00 PM »

oh and to those saying oh no the overlap and timing are gonna go to hell....something i did not know.. the camgears on the two cars are different... the miata puts the exhaust slot in a different location to make the 20* overlap and the advanced timing on the b6ze engine
the bumpsticks and the cam gear pins on the two cams is identical. therefor by using the gtx camgears in my car i will correct the timing and overlap issues and bring them closer to the b6ts 6* overlap and 69*bbdc-1*atdc of the b6t engine...
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Rocketman

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deciphering the bumpstick code....
« Reply #2 on: August 06, 2010, 05:56:00 PM »

I believe the N/A auto capri uses a B6A7 cam on the exhaust. A lot of the 323 guys talked how the auto ex. cam would make the turbo spool faster and give a flatter torque curve.

So... I ran a B6A7 on my old B6T, i swapped it out after a while for a normal B660 cam. I did notice a little more low end grunt with it (which its supposed to do) but the top end seemed to lose a bit of its edge. The exhaust sounded a little different too.

The BP guys take exhaust cams and cut them to run them on the intake side, its called the EXINTAKE mod...check it out... wouldn't work the same on the B6 cause the dizzy is driven off the intake...interesting nonetheless though
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Rocketman

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deciphering the bumpstick code....
« Reply #3 on: August 06, 2010, 05:57:00 PM »

FWIW Russ's exhaust side was a reground B61P cam
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rcicustoms

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deciphering the bumpstick code....
« Reply #4 on: August 07, 2010, 01:34:00 AM »

i went on webcams site and russ cams are from a miata b6ze and are regrinds.(all they make) thare are two sets of cams for the miata on there and both say the use of stock springs and hla's is fine meaning there mild cams... i also went on todas site and hks site.. both make 1.6 cams but are alot more money ( toda wants 440.00 a piece for there cams) and you must use there springs and shimed lifters
meaning there "hot" cams.. hks is slightly cheaper but still "hot" cams and require springs and solid tappets... very interesting indeed...

i will be putting the cam in today so ill have more by tonight...
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Rocketman

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deciphering the bumpstick code....
« Reply #5 on: August 07, 2010, 04:30:00 AM »

WEB-CAMs has many many maaaaany more grinds available that are not listed on the site & also do custom grind. I didn't have my calipers on me to measure Russ's cams but visibly had much higher lift & the base circle was cut down a bit.

These are supposed to be the hottest cams you can run without going to solid tappets & stronger springs. I couldn't believe how lopey the idle was...sounded SICK. the GTX guys had these made back in the day.

I'd still like to go to tappets instead of HLA's, just to try, and put some stronger springs in there.

Joe, Have you looked into a MX-3 B6DE head swap? Supposed to be a better flowing head, and the intake manifold faces to the side
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rcicustoms

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deciphering the bumpstick code....
« Reply #6 on: August 07, 2010, 12:52:00 PM »

um ok yea definately do this... holy spool and torque increase.... flat torque from 4-6000 i know for a fact my car is faster, like alot faster...like im giddy like a school girl faster
i dont know if its timing or lift/duration but yea.....by far the best bang for the buck ive found for a b6t engine ... and to think ive known about this for well over a year and am just now trying it....
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azgtx

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deciphering the bumpstick code....
« Reply #7 on: August 07, 2010, 01:27:00 PM »

Got any specs for the Capri DOHC auto tranny ex cam to go off of compared to the Miata piece?
Clay
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Rocketman

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deciphering the bumpstick code....
« Reply #8 on: August 07, 2010, 05:10:00 PM »

Well he's running a B61P miata n/a manual cam... I ran a B6A7 capri n/a auto cam... i'm thinking the n/a manual capri will have a B61P cam? i'll check next time I'm in the j-yard.

Any idea how to properly measure a cam? I still have my B6A7 and a set of b6t B660's sitting around.
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azgtx

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deciphering the bumpstick code....
« Reply #9 on: August 08, 2010, 03:11:00 AM »

I am pretty sure that the Capri's used the B660 int cam on all versions.
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Chicken

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deciphering the bumpstick code....
« Reply #10 on: February 05, 2011, 12:09:00 PM »

Yes Clay, you're correct. All Capris use the 660 intake cam.  The 5-speed non-turbo head I have has the A67 on the Exhaust side.  

It sure makes more sense to reposition your cam wheel index than to try and QC numerous cam patterns from a manufacturing perspective.

CAM WHEELS  ... the next topic?
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Gaz

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Re: deciphering the bumpstick code....
« Reply #11 on: July 19, 2018, 06:53:51 PM »

Necro'd.

So, I could take the ex cam out of my n/a 91 capri, put in on the intake side of my 92 xr2, and see more off-boost grunt? Or do you replace ex cam for ex cam?
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chrispoe

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Re: deciphering the bumpstick code....
« Reply #12 on: July 23, 2018, 12:09:43 AM »

Nope, you can't put the exhaust cam on the intake side cuz the exhaust cam doesn't have the proper end to drive the dizzy on the intake side.

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Gaz

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Re: deciphering the bumpstick code....
« Reply #13 on: July 23, 2018, 11:35:12 AM »

Fail, I should have thought of that.

So, can I take the ex cam from the na and put it in the xr2, in hopes of better low end grunt?
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chrispoe

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Re: deciphering the bumpstick code....
« Reply #14 on: July 23, 2018, 12:10:05 PM »

Nope again, the N/A cam has more duration which would increase turbo spool time, but give you more top end.


If I remember correctly, the Miata cam has even more duration then the N/A Capri's for even more top end power.

Also.....the 94 Mx3's 1.6L has revised B6DE engine with the dizzy moved to the exhaust cam. That exhaust cam can used as an intake cam as long as you also use anjustable cam gear to fix timing. Some of the Miata guys have done it.
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