Rocker Arm Ratio - Page 3

Phillip marvetz · 08-04-2012, 12:12 AM

I'm thinking roller cams will be legal next,lol. Good luck guy's.

Pedigo Perf · 08-04-2012, 08:06 AM

Quote:

Originally Posted by Phillip marvetz

I'm thinking roller cams will be legal next,lol. Good luck guy's.

Why not. Just lift check it and go. Wouldn't that be a lot easier on tech not to mention the engine!
What do you think the power gains if any would be from rollers for the old solid lifter cars vs. the cars that already have roller lifters? I am limited by piston valve relief as it is.

Kenny Wigington · 08-04-2012, 08:47 AM

Now Wesley has quit too ?? That's not good. Period.

Dick Butler · 08-08-2012, 08:56 AM

To Quote a famous un named Tech Man, " its all just dial in anyway"

Problem is the racer pays in money and frustration at lack of consistency

Ed Wright · 08-08-2012, 09:02 AM

Quote:

Originally Posted by Kenny Wigington

Now Wesley has quit too ?? That's not good. Period.

Yep!

Greg Reimer 7376 · 08-08-2012, 10:28 AM

I remember talking with a very successful builder of 283's years ago who mentioned going through a bucket of about 100 stock rockers before he found 16 that were right. OEM stamped parts can be all over the place as to their actual ratios.It is very possible to assemble a stocker motor with a set of them and have one or more over as well. If they check lift at the retainer, then lobe lift and even though net lift at the valve is OK, it can be and often is that the OEM rocker arm is over enough to render the combination illegal. On a SBC, rocker arm ratio is 1.5 to 1. That is a finite spec. Check the lobe lift at the lifter, multiply by 1.5, there is your maximum allowable valve lift. If lobe lift checks, rocker arm ratio is good, but valve lift is a little shy, try different length pushrods to see if it brings things up where they belong.That can be your variable to make this whole thing work. Remember, check EVERYTHING, leave nothing to chance, because they will if you don't, and nobody wants to be sent home early over something as simple to avoid as this.We had a very fun involved discussion on push rod length determination here in the last off season if you care to locate and review it.

Bill Diehl · 12-21-2013, 05:06 PM

So less rocker than the blueprint specs call for is ok? correct?

Dave Noll · 12-21-2013, 06:29 PM

Bill, from info I have absorbed off of here that would be yes. With the added caveat that lift comes in under spec.

Dyno · 12-21-2013, 10:07 PM

If a racer had a good stocker cam that used "stock" rocker arms that checked legal, then went to "stock" ratio roller rocker arms, more often than not, the lift would be over limit. Some had to go to a lower ratio rather than throwing away a good cam. As long as the lift is within the rules, it should be OK. Dyno

Adger Smith · 12-24-2013, 05:07 PM

Yes, Wesley is no longer working for NHRA.
He runs the Tech side of the Engine Masters Challenge.
RJ.Sledge, Sidney J. Bonnecarrere & I work for him.
He also does Tech work for a Mud racers association and a couple of other well known racing series.
A couple of years ago he and I had this discussion about rocker ratio. The paygrade above us at EMC was wanting us to limit Rocker Ratio.
According to him there is no real way to measure rocker ratio correctly.
Too many variables.
Example: In a Small Block Chevy you are dealing with three distinct intersecting angles. Pushrod, Rocker Stud, Valve angles. Yes, if extended far enough those angles will intersect. Where you locate the rocker on any of the various planes between those angles influences the effective ratio of the rocker.
Say you have a cam lift of .275 and you are looking for a 1.5 ratio to give you a net lift of .410. You set your valve length and pushrod length to get that .410 net lift. OK Presto we have 1.5 Rocker ratio. Does that make the rocker a 1.5 ratio rocker? Probably not. Now you drop the pushrod length by .100 and reposition the rocker and woops the valve lift is now .418.
OOPS, have we changesd the ratio of the rocker, what ratio was it and what is it now. Humm, lets see we lower the length of the valve tip and, oops again the measured valve lift goes to .412. Then if you want to get serious you can mill the stud bosses at an angle and tilt the stud back and the measured lift will change again, all with the same rocker. Wesley told me that measuring Rocker ratio on an engine is not a place you want to go.
Danny must know rocker ratio is a slippery slope. Wesley does.

08-04-2012, 12:12 AM	#21
Phillip marvetz Senior Member Join Date: Oct 2008 Location: Lynden ,WA Posts: 820 Likes: 0 Liked 3 Times in 3 Posts	Re: Rocker Arm Ratio I'm thinking roller cams will be legal next,lol. Good luck guy's. __________________ 2009 V/SA Record Holder

08-04-2012, 08:47 AM	#23
Kenny Wigington Senior Member Join Date: Sep 2004 Location: Cumming,Ga. USA Posts: 967 Likes: 36 Liked 60 Times in 12 Posts	Re: Rocker Arm Ratio Now Wesley has quit too ?? That's not good. Period. __________________ 2894 STK

08-08-2012, 08:56 AM	#24
Dick Butler VIP Member Join Date: Oct 2002 Location: Richmond Indiana Posts: 1,196 Likes: 5 Liked 32 Times in 19 Posts	Re: Rocker Arm Ratio To Quote a famous un named Tech Man, " its all just dial in anyway" Problem is the racer pays in money and frustration at lack of consistency

08-08-2012, 10:28 AM	#26
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,137 Likes: 172 Liked 717 Times in 220 Posts	Re: Rocker Arm Ratio I remember talking with a very successful builder of 283's years ago who mentioned going through a bucket of about 100 stock rockers before he found 16 that were right. OEM stamped parts can be all over the place as to their actual ratios.It is very possible to assemble a stocker motor with a set of them and have one or more over as well. If they check lift at the retainer, then lobe lift and even though net lift at the valve is OK, it can be and often is that the OEM rocker arm is over enough to render the combination illegal. On a SBC, rocker arm ratio is 1.5 to 1. That is a finite spec. Check the lobe lift at the lifter, multiply by 1.5, there is your maximum allowable valve lift. If lobe lift checks, rocker arm ratio is good, but valve lift is a little shy, try different length pushrods to see if it brings things up where they belong.That can be your variable to make this whole thing work. Remember, check EVERYTHING, leave nothing to chance, because they will if you don't, and nobody wants to be sent home early over something as simple to avoid as this.We had a very fun involved discussion on push rod length determination here in the last off season if you care to locate and review it.

12-21-2013, 05:06 PM	#27
Bill Diehl Member Join Date: Dec 2013 Posts: 311 Likes: 2 Liked 9 Times in 8 Posts	Re: Rocker Arm Ratio So less rocker than the blueprint specs call for is ok? correct?

12-21-2013, 06:29 PM	#28
Dave Noll Senior Member Join Date: Nov 2007 Location: Div. 6, Eastern, WA Posts: 710 Likes: 2,676 Liked 240 Times in 112 Posts	Re: Rocker Arm Ratio Bill, from info I have absorbed off of here that would be yes. With the added caveat that lift comes in under spec. __________________ Dave Noll, EF/S ,?/SA 6526

12-21-2013, 10:07 PM	#29
Dyno Senior Member Join Date: Dec 2002 Posts: 918 Likes: 1,140 Liked 693 Times in 205 Posts	Re: Rocker Arm Ratio If a racer had a good stocker cam that used "stock" rocker arms that checked legal, then went to "stock" ratio roller rocker arms, more often than not, the lift would be over limit. Some had to go to a lower ratio rather than throwing away a good cam. As long as the lift is within the rules, it should be OK. Dyno

12-24-2013, 05:07 PM	#30
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Rocker Arm Ratio Yes, Wesley is no longer working for NHRA. He runs the Tech side of the Engine Masters Challenge. RJ.Sledge, Sidney J. Bonnecarrere & I work for him. He also does Tech work for a Mud racers association and a couple of other well known racing series. A couple of years ago he and I had this discussion about rocker ratio. The paygrade above us at EMC was wanting us to limit Rocker Ratio. According to him there is no real way to measure rocker ratio correctly. Too many variables. Example: In a Small Block Chevy you are dealing with three distinct intersecting angles. Pushrod, Rocker Stud, Valve angles. Yes, if extended far enough those angles will intersect. Where you locate the rocker on any of the various planes between those angles influences the effective ratio of the rocker. Say you have a cam lift of .275 and you are looking for a 1.5 ratio to give you a net lift of .410. You set your valve length and pushrod length to get that .410 net lift. OK Presto we have 1.5 Rocker ratio. Does that make the rocker a 1.5 ratio rocker? Probably not. Now you drop the pushrod length by .100 and reposition the rocker and woops the valve lift is now .418. OOPS, have we changesd the ratio of the rocker, what ratio was it and what is it now. Humm, lets see we lower the length of the valve tip and, oops again the measured valve lift goes to .412. Then if you want to get serious you can mill the stud bosses at an angle and tilt the stud back and the measured lift will change again, all with the same rocker. Wesley told me that measuring Rocker ratio on an engine is not a place you want to go. Danny must know rocker ratio is a slippery slope. Wesley does. __________________ Adger Smith (Former SS)