AND DON'T SAY 4* EITHER! What I'm asking is, what is the benefit of one over the other? Assuming 2 identical cams of 230/240* duration @ .050" and .500/.500" lift @ .050, does the 116 make more vacuum? Is the 112 a chopier idle? Does the 112 make more power? Is the power at a different RPM, given similar degrees when installed? Thanks.
Ummm Is it 3.999*?o No: Sorry, I had to... I'd say the reason is more/or less power. When the cam was dyno'ed, the manufacturer experimented with different cam positions, and recommend the position that made the most power...o No:
I know the basics, the closer the lobe center such as a lot of race cams at 107-108 L/C. the power curve is concentrated in a narrower range such as 4500-6500. So a wider lobe seperation spreads out your power band, that would explain why the wider the seperation the beter the cam is for tha street car. So it is a factor in cam choise when you are matching a cam to your cars combo. Also a closer L/C will idle rougher. Hope this helps,Kelly
completely off the subject (sorry Yards), Dan did you change your avatar? Isn't that Harvey's car? Or is there something going here?
I think Dan's 'Bittersweet Mist Dreamin' :bglasses: Yes, that is Harvey's car when Mike owned it :TU:
More overlap (i.e. the 112* cam) will allow more air to be drawn into the motor- during the overlap, there is a bit of extra vacuum created by the air being sucked out of the exhaust valve, and when the intake valve opens you suck a little more fresh mixture into the cylinder. The downside is that the overlap also reduces your gas mileage (since some unburned gas goes directly out the exhaust valve), and your emmissions get worse (more unburned gas in the exhaust stream, meaning higher hydrocarbons). -Bob Cunningham
Going from 112 lc to 116 lc is actually 8 degees difference. The intake center line of 112 is left or counterclockwise of "0" degrees( OR 112 degrees after top dead center-ATDC) and the exhaust centerline of 112 is clockwise of "0" degrees (OR 112 degrees before top dead center-BTDC). So when you move the center line of the lobes to 116 they move away from each other 4 degrees in opposite directions. GET IT? With moving the valve events away from each other you give up some of the good scavanging effects from the exhaust that helps bring air in AND ALSO you close the intake valve later which happens as the piston is going up on the compression stroke that reduces cylinder pressure which reduces your mid range power. With the wider lobe centers the valve stays open later which gives the cylinder a little more time to fill giving you a little more rpm. With the reduced overlap (wider lobe centers) ,at idle and very low rpms, you don't get reversion or pressure off the exhaust into the intake that kills vaccum. Hense the good idle characteristics and vaccum from wide LC. Does that help? And ,yes, the 112 will make more power on a "motor" combintion over a 116 across the board.
Is this always the case, or is there a point of dimishing returns? If you run a cam through desktop dyno, the ones with the very narrow angles, like 107 deg. lobe seperation never make the power of something that is around 112-114. Since everyone who uses the narrow lobe center cams in the real world always tells me they work in our 455's, I have assumed that this is a flaw of the modeling, or a quirk with our motors.
Hello, My motor is 9.7to1 comp pump gas street strip car and I have run 11.31 with a 105 lobe spread cam. Yes it idles rough but has great throttle responce and tons of low end power, maybe my heads are weak [home ported and never had them flowed] but MPH is not what I have hoped for. It is a old Poston 105A cam. Tom
That explains why my city mileage went down, and why my exhaust smells strange at idle. Mine is 112*:bglasses:
