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Re: straight vs. split pattern cams [Re: Tig] #880793
12/20/10 03:27 PM
12/20/10 03:27 PM
Joined: Feb 2007
Posts: 6,295
U.S.
M
moparniac Offline
master
moparniac  Offline
master
M

Joined: Feb 2007
Posts: 6,295
U.S.
My desktop dyno says my new split cam makes more power


Mopar Performance
Re: straight vs. split pattern cams [Re: Tig] #880794
12/20/10 03:34 PM
12/20/10 03:34 PM
Joined: Jan 2003
Posts: 9,870
Weddington, N.C.
Streetwize Offline
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Streetwize  Offline
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Joined: Jan 2003
Posts: 9,870
Weddington, N.C.
Some of the EM combos run very big intake lobes and advance the heck out of them to maximize (use up) the airflow potential of the heads by the 6500 rpm Cap set by the rules...Bishoff's 433" CHI headed Ford had a 106 split in at like 100 as I remember and Kasse built a motor that had (IIRC) a 98 degree ICL...and these guys have access to anything they want.

It's an over generization to say that advancing a cam to work well means you have the wrong cam....in an overported motor it can be great way to fill the holes well and still keep the Intake closing 'streetable'. an 8 degree larger intake lobe in 4 degrees earlier will have the same closing event, so if sized right for the port and as long as the roll on torque is sufficient down low it will probably make more top end power...won't it?

Ultradyne has ground tons of 108 spread cams that went in at 102 for years and years


It's dangerous and misleading to do more than generalize, all cams are application specific and more than 1/2 of the things I've learned that worked well or better for YEARS (particularly with strokers) seemed counter-intuitive to many 'experts'....but in recent years much of what has been flushed out of these jaw dropping engine-masters contests has made me feel a lot more open about talking about them.

Lobe spread and durations with a typical pushrod single cam motor are always at best a trade off....you have to give somewthing somewhere to get more somewhere else....and as correctly pointed out with a race app in a way it's easier because the clutch/cionverter and gearing can side step over the low efficency parts of the curve....in that respect a ture street motor is a lot more difficult to get as right as possible. Ask yourselves why have all the major auto companies spent umpteen millions develop their own forms of Variable cam timing (VTEC effects lift AND durations) and variable lobe spread tuning technology over the years? To improve VE across the powerband and make more power and/or torque with less cubes.


WIZE

World's Quickest Diahatsu Rocky (??) 414" Stroker Small block Mopar Powered. 10.84 @ 123...and gettin' quicker!

https://www.youtube.com/watch?v=-mWzLma3YGI

In Car:

https://www.youtube.com/watch?v=PjXcf95e6v0
Re: straight vs. split pattern cams [Re: Tig] #880795
12/20/10 07:43 PM
12/20/10 07:43 PM
Joined: Dec 2008
Posts: 1,200
UK
6
602heavy Offline
pro stock
602heavy  Offline
pro stock
6

Joined: Dec 2008
Posts: 1,200
UK
Quote:

FWIW this cam 320 / 320, 288 / 288 @ .050 .691 when installed 4 degrees retarded (@ 112) from the recommended 108 picked up 2 tenths. We were just looking for a little more top end and it worked but what was that telling us?





......could be one of four thing....or maybe two of four things........heck it could be all of the four differing valve events.

just messing , would'nt like to speculate. ........would take a bet idle was lumpy.

Last edited by 602heavy; 12/20/10 07:45 PM.
Re: straight vs. split pattern cams [Re: 602heavy] #880796
12/21/10 12:04 AM
12/21/10 12:04 AM
Joined: Mar 2006
Posts: 9,815
MI, usa
dvw Offline
master
dvw  Offline
master

Joined: Mar 2006
Posts: 9,815
MI, usa
Quote:

Quote:

FWIW this cam 320 / 320, 288 / 288 @ .050 .691 when installed 4 degrees retarded (@ 112) from the recommended 108 picked up 2 tenths. We were just looking for a little more top end and it worked but what was that telling us?





......could be one of four thing....or maybe two of four things........heck it could be all of the four differing valve events.

just messing , would'nt like to speculate. ........would take a bet idle was lumpy.



I retarded my cam years ago with -1 heads. it picked up as well. my heads were unported. Not enough intake flow for the combo? That was my bet.
Doug

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