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Ho-made cam for Chevy 350

 
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ranman
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Joined: 24 Feb 2004
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PostPosted: Wed Feb 25, 2004 1:22 am    Post subject: Ho-made cam for Chevy 350 Reply with quote

Quite a while back, I made up a cam on DD2000. ( yes.... I know Laughing )
I was looking for something with a little more zip than my Performer 2101.... nothing radical, but with a bit more HP and torque, yet still friendly with my stock or possibly RV converter presently on a TH350. I wouldn't mind more MPG also............ and this is part of my question.

The cam I made up is kind of weird. The longer I let the exhaust duration get, the better the VE percentage readout got on the DD2000.
The HP and torque was nearly identical to the XE262, Crain H-260-2,
and Crain Compucam 2030...... amongst others. It had about 10# less torque at 2000 RPM which I thought might mean I could still use regular unleaded fuel.

I know DD2000 is not considered super accurate, but thought it would make a decent comparison using the same engine data for each.

I like the cam that I made up, and wonder if any number crunching cam gurus could explain why my cam design wouldn't work.

Here's the cam specs
.440 .454 lift
260 288 duration
46 degrees overlap
114 lobe center
intake valve open BTDC 23
intake valve closed ABDC 57
exhaust valve open BBDC 85
exhaust valve closed BTDC 23
ICA 107
ECA 121

I will give as much engine data as I can if there are any takers on helping with my setup. Thanks.

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cobblemaster
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PostPosted: Wed Feb 25, 2004 5:57 pm    Post subject: Reply with quote

Call the tech line at Comp or another good company.

They will be frank with you.
A machinist and stock car engine builder I know called them with a cam he came up with like you did, but pretty radical. The tech guy said "If you want my honest opinion, that cam wouldn't pull a string outa yer ass".
He went on to say that you never know until it hits the dyno or the track, and even then you might get 2 differing opinions.

Call them. It can't hurt.

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1979 Chevrolet Camaro

PostPosted: Wed Feb 25, 2004 6:21 pm    Post subject: Reply with quote

I agree with cobblemaster, call the cam companies. A lot of dynamics are going on with the cam.

On the flip side you can have them grind one up to your spec and you can try it out.
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ranman
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PostPosted: Wed Feb 25, 2004 9:06 pm    Post subject: Reply with quote

cobblemaster wrote:
Call the tech line at Comp or another good company.

They will be frank with you.
A machinist and stock car engine builder I know called them with a cam he came up with like you did, but pretty radical. The tech guy said "If you want my honest opinion, that cam wouldn't pull a string outa yer ass".
He went on to say that you never know until it hits the dyno or the track, and even then you might get 2 differing opinions.

Call them. It can't hurt.

Sounds like good advice, but I was fearing they would just say something off the cuff without actually running any numbers......... but then again, I don't have any flow numbers for my heads, or anyone near by to flow test them.......... so it's a catch 22.
I was just wondering if anyone here uses a higher tech program than DD2000.
I mentioned in my original question that "my" cam, was nealy identical to a few off the shelf cams, both in HP and TQ, maxing out only about 500 RPM's higher or lower depending on the cam.
My biggest question I guess, is about the volumetric efficiency of "my" cam. The Crain 2030 had 78.5% and 80.5% VE at max tq and hp
Mine had 89.1% and 89.7% VE at max tq and hp.
Not sure what this difference means, but it seems like a lot.

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SMOKEmUP
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Joined: 30 May 2002
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1979 Chevrolet Camaro

PostPosted: Wed Feb 25, 2004 11:34 pm    Post subject: Reply with quote

Improving the VE is how you make power. The cam timing has a large effect on the intake and exhaust pulse tuning and therefore affects VE. DD2000 is a good program to determine where the torque and HP peaks are. IMO the peak numbers are close but I don't believe the down low numbers.

Working backwards from my chassis dyno to what DD2000 predicted the number was 0.756. What I mean is take DD2000 predicted HP number and multiply it by 0.756 and that was the rear wheel HP my car made. DD2000 predicted 380 HP and my car my 288 RWHP.
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cobblemaster
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PostPosted: Sat Feb 28, 2004 8:11 pm    Post subject: Reply with quote

The whole idea of pulses seems to escape many when they theorize about combinations/tuning/building. Glad to see it mentioned. These engines might inhale and exhale air, but I hesitate to treat them as simple air pumps when it comes to porting and valvetrain.
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1979 Chevrolet Camaro

PostPosted: Sun Feb 29, 2004 1:23 am    Post subject: Reply with quote

cobblemaster wrote:
The whole idea of pulses seems to escape many when they theorize about combinations/tuning/building. Glad to see it mentioned. These engines might inhale and exhale air, but I hesitate to treat them as simple air pumps when it comes to porting and valvetrain.


The laws of physics always apply. The hard part is to model it correctly. I don't think any engine is simple. I've been working on my own version of dyno simulation program and it's anything but simple and I'm sure I only scratched the surface.
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