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changing rocker ratios #490116 10/06/09 08:53 PM 10/06/09 08:53 PM
Joined: Sep 2006 Posts: 2,587 missouri, USA moparmojo OP master
moparmojo OP master Joined: Sep 2006 Posts: 2,587 missouri, USA	Ok, changing rocker ratios has always kind of confused me and I was hoping someone more knowledgable can educate me on the pro's and con's of this or why it is done. Can it be done on a relatively stock motor to increase performace or is that a no no?

Re: changing rocker ratios [Re: moparmojo] #490117 10/06/09 09:27 PM 10/06/09 09:27 PM
Joined: Feb 2006 Posts: 1,949 land of 10,000______'s B BDS871Cuda top fuel
BDS871Cuda top fuel B Joined: Feb 2006 Posts: 1,949 land of 10,000______'s	Quote: Ok, changing rocker ratios has always kind of confused me and I was hoping someone more knowledgable can educate me on the pro's and con's of this or why it is done. Can it be done on a relatively stock motor to increase performace or is that a no no? On anything but a race motor, it is a waste of money. On a stock motor with a mild or even a big cam, your better off with the stock rocker ratio. Use your money on better things. Snap your neck, mega G-force launch, is all I want!

Re: changing rocker ratios [Re: BDS871Cuda] #490118 10/06/09 10:47 PM 10/06/09 10:47 PM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	My take... increased rocker ratios with a valvetrain and cam and head designed for them can improve breathing and performance. The stock muscle MOPAR head and valvetrain, however, was designed for 1.5. Unless you do a lot of checking, adjusting and perhaps grinding it won't work so well with higher ratios. For near stock or "stock style" valvetrain and heads its much better to stick with 1.5 ratio and pick the cam accordingly.

Re: changing rocker ratios [Re: ahy] #490119 10/06/09 10:57 PM 10/06/09 10:57 PM
Joined: Aug 2007 Posts: 6,095 Valencia, España NachoRT74 master
NachoRT74 master Joined: Aug 2007 Posts: 6,095 Valencia, España	ok, but for example... has been told since I have memories here and several Mopar boards that old MP Cam grinds are right OLD DESIGN because the low lift profile and long duration times. Nowdays performance is just right the opposite. so if you have an HP Resto cam you can increase performance keeping low duration and 115 centerline, so LOT OF DRIVEABILITY... or not ? yes I know you can pick another cam, but still. With a Charger born in Chrysler assembly plant in Valencia, Venezuela

Re: changing rocker ratios [Re: NachoRT74] #490120 10/06/09 11:31 PM 10/06/09 11:31 PM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	no problem if you check & adjust rocker tip to valve contact pattern and pushrod to head clearance. If you want to avoid these "adjustments" 1.5 is a better bet. No avoiding the checking though.

Re: changing rocker ratios [Re: ahy] #490121 10/06/09 11:39 PM 10/06/09 11:39 PM
Joined: Aug 2007 Posts: 6,095 Valencia, España NachoRT74 master
NachoRT74 master Joined: Aug 2007 Posts: 6,095 Valencia, España	do you think jump 450 stock cam lift to 480 lift really needs clearence check? if so, then nobody could install a modern grind cam , or even a stock MP 509 camshaft then if changing also the camshaft to a modern cam grind DEFINITELLY will need to be checked anyway is true, check everything is a good advice, but some cases I don't think DEMANDS a check With a Charger born in Chrysler assembly plant in Valencia, Venezuela

Re: changing rocker ratios [Re: NachoRT74] #490122 10/06/09 11:50 PM 10/06/09 11:50 PM
Joined: Jan 2004 Posts: 27,347 Today? Who Knows? 1_WILD_RT Management Trainee
1_WILD_RT Management Trainee Joined: Jan 2004 Posts: 27,347 Today? Who Knows?	Quote: do you think jump 450 stock cam lift to 480 lift really needs clearence check? if so, then nobody could install a modern grind cam , or even a stock MP 509 camshaft then if changing also the camshaft to a modern cam grind DEFINITELLY will need to be checked anyway is true, check everything is a good advice, but some cases I don't think DEMANDS a check It isn't valve to piston clearance thats an issue... It is pushrod to cylinder head & block that can be a problem... To change the ratio the effective leverage (ratio) is changed.. Your not changing the distance of the valve stem to the center of the rocker fulcrum so therefore you must be changing the distance from the center of the rocker fulcrum to the pushrod.. To increase the valve lift you need to shorten the distance from the center of the rocker fulcrum to the pushrod... So that potentially brings the pushrod into contact with the block or head...

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