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measuring lift at the valve #1664418 08/27/14 06:04 PM 08/27/14 06:04 PM
Joined: Oct 2003 Posts: 7,506 Az Crizila OP master
Crizila OP master Joined: Oct 2003 Posts: 7,506 Az	Decided to take some lift measurements at the valve ( see pic ). On the average, I am coming up about .040" short per valve as compared with the cam specs lift. Is this normal for a 59* stock small block? Solid lifter cam that visually looks good, as do the lifters. Couple of years running on the cam. All the valve train is in good shape. Running very light spring loads ( 110 - 315 ) so I don't see deflection as an issue. All measurements on all valves are within .010", so I don't have one way out of wack. . I accounted for valve clearance. Thoughts? 8253247-valveliftmeasure.jpg (149 downloads) Fastest 300

Re: measuring lift at the valve [Re: Crizila] #1664419 08/27/14 06:17 PM 08/27/14 06:17 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	What you are measuring is correct. The problem is that the lifter is not pushing straight on the pushrod. This was first brought to my attention a few years ago when Rob McC was designing LA rockers for Erson, and was wondering if he should make the true ratio of their 1.6 rockers something like 1.65, in order to get the valve to open exactly 1.6 times the lobe lift. He posted the question in a Moparts forum. I remember trying to figure out why that would be and finally came up with the idea that the actual lift at the top end of the pushrod is the lobe lift times the cosine of the angle between the lifter axis and the pushrod. R.

Re: measuring lift at the valve [Re: Crizila] #1664420 08/27/14 06:25 PM 08/27/14 06:25 PM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Pretty normal... are you sure your rocker ratio is correct.. I get a little less than .040

Re: measuring lift at the valve [Re: MR_P_BODY] #1664421 08/27/14 06:31 PM 08/27/14 06:31 PM
Joined: Oct 2007 Posts: 156 Southern California B BIG DRAG member
BIG DRAG member B Joined: Oct 2007 Posts: 156 Southern California	That is the way it is for a 59* small block.

Re: measuring lift at the valve [Re: dogdays] #1664422 08/27/14 07:00 PM 08/27/14 07:00 PM
Joined: Jan 2003 Posts: 9,826 las vegas 70AARcuda master
70AARcuda master Joined: Jan 2003 Posts: 9,826 las vegas	Quote: What you are measuring is correct. The problem is that the lifter is not pushing straight on the pushrod. This was first brought to my attention a few years ago when Rob McC was designing LA rockers for Erson, and was wondering if he should make the true ratio of their 1.6 rockers something like 1.65, in order to get the valve to open exactly 1.6 times the lobe lift. He posted the question in a Moparts forum. I remember trying to figure out why that would be and finally came up with the idea that the actual lift at the top end of the pushrod is the lobe lift times the cosine of the angle between the lifter axis and the pushrod. R. basically cosign of 11 degrees times the gross lift...minus the lash... then you have the true rocker ratio...which is ??? Tony 70 AARCuda Vitamin C 71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield) 71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas) 71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)

Re: measuring lift at the valve [Re: 70AARcuda] #1664423 08/27/14 11:51 PM 08/27/14 11:51 PM
Joined: Oct 2003 Posts: 7,506 Az Crizila OP master
Crizila OP master Joined: Oct 2003 Posts: 7,506 Az	Quote: Quote: What you are measuring is correct. The problem is that the lifter is not pushing straight on the pushrod. This was first brought to my attention a few years ago when Rob McC was designing LA rockers for Erson, and was wondering if he should make the true ratio of their 1.6 rockers something like 1.65, in order to get the valve to open exactly 1.6 times the lobe lift. He posted the question in a Moparts forum. I remember trying to figure out why that would be and finally came up with the idea that the actual lift at the top end of the pushrod is the lobe lift times the cosine of the angle between the lifter axis and the pushrod. R. basically cosign of 11 degrees times the gross lift...minus the lash... then you have the true rocker ratio...which is ??? - 1.59. Actual rocker ratio = 1.6. Lost .007" lobe lift through the 11* angle. Fastest 300

Re: measuring lift at the valve [Re: MR_P_BODY] #1664424 08/28/14 12:07 AM 08/28/14 12:07 AM
Joined: Jul 2008 Posts: 361 Canada onig enthusiast
onig enthusiast Joined: Jul 2008 Posts: 361 Canada	Quote: Pretty normal... are you sure your rocker ratio is correct.. I get a little less than .040 Agreed with above statement. If rocker geometry is off it will affect lift numbers, as well if your pushrod lengths are not correct. 69 Dart

Re: measuring lift at the valve [Re: Crizila] #1664425 08/28/14 12:47 AM 08/28/14 12:47 AM
Joined: Aug 2003 Posts: 43,129 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,129 Bend,OR USA	Have you checked all the rockers at the valves yet? If not do that and let us know what you find for the variences on yours I've seen .030 difference at the valves on the same brand of rockers, the losss of lift followed the rocker when I swapped them around I have checked a bunch of stock type Ductile iron Hemi, wedges and LA rockers, Harland Sharps, Crane iron and extruded aluminum roller tip rockers, T&D single shafts and so on I've yet to see a perfect set that all the rockers lifted the same at the valves I do have a new set of Jesel paired shaft rockers that I haven't checked or tried to use yet I'm hoping that they are as good as all the high buck racers say they are Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: measuring lift at the valve [Re: Cab_Burge] #1664426 08/28/14 01:37 PM 08/28/14 01:37 PM
Joined: Oct 2003 Posts: 7,506 Az Crizila OP master
Crizila OP master Joined: Oct 2003 Posts: 7,506 Az	Quote: Have you checked all the rockers at the valves yet? If not do that and let us know what you find for the variences on yours I've seen .030 difference at the valves on the same brand of rockers, the losss of lift followed the rocker when I swapped them around I have checked a bunch of stock type Ductile iron Hemi, wedges and LA rockers, Harland Sharps, Crane iron and extruded aluminum roller tip rockers, T&D single shafts and so on I've yet to see a perfect set that all the rockers lifted the same at the valves I do have a new set of Jesel paired shaft rockers that I haven't checked or tried to use yet I'm hoping that they are as good as all the high buck racers say they are Haven't checked the rockers yet, but I have less than .011" difference from lift readings on all 16 valves, and that is including any cam wear, etc, so they can't be too far off from one another. I'll check a few. Not even sure who's rockers they are as I bought them from Hughes as a package deal. RR350A 1.6 stamped on the tops. Fastest 300

Re: measuring lift at the valve [Re: Crizila] #1664427 08/28/14 01:45 PM 08/28/14 01:45 PM
Joined: Jan 2007 Posts: 8,031 Mt Morris Michigan mopar dave master
mopar dave master Joined: Jan 2007 Posts: 8,031 Mt Morris Michigan	I loose about .025-.030" using t&d 1.6 rockers. http://www.youtube.com/watch?v=aIxaesJ190U http://youtu.be/lCZAaN7fFLg

Re: measuring lift at the valve [Re: mopar dave] #1664428 08/29/14 02:17 PM 08/29/14 02:17 PM
Joined: Jan 2003 Posts: 3,504 DFW M mr_340 master
mr_340 master M Joined: Jan 2003 Posts: 3,504 DFW	I ended up with ~.475" lift with the .528" MP cam using 273 rockers. The .028"/.032" lash accounted for most of the loss, the rest probably in the 273 rocker ratio being less than 1.5.

Re: measuring lift at the valve [Re: mr_340] #1664429 08/29/14 02:28 PM 08/29/14 02:28 PM
Joined: Feb 2003 Posts: 12,675 Columbia, CT M moper I Live Here
moper I Live Here M Joined: Feb 2003 Posts: 12,675 Columbia, CT	... and it's worse with hydraulic roller lifters - shorter pushrod = more angle. It's fairly subjective but in my experience it's .018-.022" less with 1.5s in most circumstances. Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.

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