 What rocker arm ratios do people see? |
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| stugray |
 Dec 17 2012, 10:26 PM
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Advanced Member  Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None  |
I am adjusting the valve geometry while putting in a Raby 9700 cam and I am seeing .38 on the exhaust cam lift and .496 at the valve (an exh rocker ratio of 1.3) and I have a .39 on the intake with a .546 at the valve ( an int rocker ratio of 1.4) is this what everyone else gets for rocker ratios:
Intake rocker ratio = 1.4 Exhaust rocker ratio = 1.3 These are the 1.7 (1.8?) rockers that accept the 911 swivel feet. I am using the swivel feet, have modified the rocker faces, adjustable push rod, and zero lash to do the meaurements. Do those rocker ratios look like stock? I want to take 50 thousandths off the Combustion chambers to increase the CR, but my measurements say I wont have enough clearance on the Intake valve once I shave off 50 thousandths. I only have ~0.075 clearance now from the piston to the Int valve as it is with a deck of 0.030 and everything else (crank & rods) stock - flat top 96mm pistons. That Intake valve travel of ~0.55 looks huge to me. Anyone else care to comment? Stu |
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| stugray |
Feb 11 2013, 07:51 AM
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Advanced Member Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
Chris,
That's right. I need to remeasure the cam lift now that I have full spring tension on the lifters. I'll do that today. Stu |
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| worn |
Feb 11 2013, 10:30 AM
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Winner of the Utah Twisted Joint Award Group: Members Posts: 3,489 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest 
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QUOTE(stugray @ Feb 11 2013, 05:51 AM)  Chris, That's right. I need to remeasure the cam lift now that I have full spring tension on the lifters. I'll do that today. Stu I have followed this with interest, for a while now. It seems like you can safely draw a few conclusions. 1. The rockers are what they are. 2. The valve lift is the goal, and apparently for you, it is too high. 3. The cam causes the valve lift. So, with all of that in mind, I respectfully submit that the cam you have may not be able to produce the goals you have set. Your diagram about changing the height of the rocker pedestals isn't going to cure this. For one thing, while you showed the arm length changing on the push rod side, you didn't take into account the change in moment arm on the valve side, so the impact on ratio is not as big as you think. It may be that the cam is designed for people who want a great deal more lift than you or most people want to run. Good luck - My next project is (IMG:style_emoticons/default/w00t.gif) cutting push rods to length . |
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Posts in this topic
stugray What rocker arm ratios do people see? Dec 17 2012, 10:26 PM
Dave_Darling The stock ratios range from 1.3 to 1.4, so you... Dec 17 2012, 11:29 PM edwin Call European machine works?
They've helped in... Dec 17 2012, 11:38 PM stugray Dave - So is it possible to find an intake rocker ... Dec 18 2012, 12:08 PM
Dave_Darling
Dave - So is it possible to find an intake rocker... Dec 18 2012, 06:02 PM monkeyboy I believe WebCam actually makes them, but they are... Dec 18 2012, 12:32 PM brant I too believe they are built to order...
custom o... Dec 18 2012, 12:41 PM Mark Henry
I too believe they are built to order...
custom ... Dec 18 2012, 12:45 PM bobhasissues When you say "at the valve" are you actu... Dec 18 2012, 06:23 PM stugray bob -
Yes - and simultaneously at the pushrod t... Dec 18 2012, 07:22 PM bobhasissues Stu,
Nobody will try to help you if you continue ... Dec 18 2012, 09:40 PM stugray
Stu,
Nobody will try to help you if you continue... Feb 10 2013, 11:07 PM bobhasissues Bob, now that we have established that these rocke... Feb 11 2013, 08:15 PM stugray bob-
I see nowhere in the previous post that co... Dec 18 2012, 11:01 PM Racer Chris I'll gladly trade you a set of 1.3 ratio, 1.7L... Dec 18 2012, 11:44 PM Mark Henry Dude the reason I don't help you is simple....... Dec 18 2012, 11:50 PM stugray
That's funny because it says Type IV store r... Dec 19 2012, 08:27 AM Racer Chris
I am also reading on Jakes cam instructions that ... Dec 19 2012, 10:10 AM Jeff Hail
I am also reading on Jakes cam instructions that... Feb 4 2015, 11:39 PM Mark Henry
[quote name='Racer Chris' post='1786713' date='De... Feb 5 2015, 06:27 AM r_towle post a picture of the cam card.
It will possibly g... Dec 19 2012, 09:13 AM stugray rich,
Thanks. I will scan the card & post it ... Dec 19 2012, 09:33 AM stugray
I will take pictures tonight.
I measure .388 Cam... Dec 19 2012, 11:42 AM nathansnathan "Valve lift" is taking the ratio of the ... Dec 19 2012, 11:50 AM stugray I will get pics of the test rig after dinner, but ... Dec 19 2012, 07:04 PM Todd Enlund
And BTW - I fully profiled the cam myself, and th... Dec 27 2012, 02:22 AM Racer Chris
And BTW - I fully profiled the cam myself, and t... Dec 27 2012, 05:55 AM r_towle I am confused.
You have not milled out your heads ... Dec 19 2012, 07:41 PM stugray
Not exactly - I am measuring how much clearance ... Dec 19 2012, 08:43 PM stugray Some pics:
Pics of setup to measure deck height:
... Dec 19 2012, 09:02 PM nathansnathan My experience with it was that it was easy to get ... Dec 19 2012, 11:42 PM stugray
I have taken ~.060 off the rocker faces and coun... Dec 20 2012, 12:02 AM nathansnathan
I have taken ~.060 off the rocker faces and cou... Dec 20 2012, 08:36 AM Racer Chris Stu,
Is it possible the ratio was altered by remac... Dec 20 2012, 10:02 AM stugray Racer Chris,
I measured all 4 of them, Valve lift... Dec 22 2012, 04:09 PM stugray Ok, so after some measurements, I get the whole ... Dec 23 2012, 06:29 PM stugray Two more questions:
1 - When some of you have had... Dec 24 2012, 04:51 PM nathansnathan
And nathansnathan
How is that possible? Regard... Dec 30 2012, 06:02 PM wndsrfr
2 - Who has a good selection of rocker shims?
... Dec 30 2012, 07:26 PM stugray Quick bump so racer chris doesnt forget about me ;... Dec 26 2012, 05:17 PM Racer Chris
Quick bump so racer chris doesnt forget about me ... Dec 26 2012, 07:10 PM tscrihfield stu,
if i could lend some advice. I would not adv... Dec 26 2012, 07:17 PM nathansnathan I've given it more thought their and edited ab... Dec 30 2012, 10:02 PM stugray So I had the engine case "decked", the r... Feb 10 2013, 05:11 PM nathansnathan It sounds to me like you are doing something wrong... Feb 10 2013, 06:44 PM stugray :confused: Feb 10 2013, 10:54 PM Racer Chris It is not possible that you are the first to disco... Feb 10 2013, 11:05 PM stugray
Chris - I had three reputable machine heads sit ... Feb 10 2013, 11:13 PM barefoot
Chris - I had three reputable machine heads sit... Dec 7 2015, 04:34 PM stugray
Chris - I had three reputable machine heads si... Dec 7 2015, 07:31 PM barefoot
[quote name='stugray' post='1818427... Dec 7 2015, 08:50 PM Racer Chris The cam card says the valve lift is .368".
Yo... Feb 11 2013, 12:03 AM stugray I just spoke with one of the Type-IV experts at Fa... Feb 11 2013, 02:11 PM stugray Bob I " will build a grenade, that's why ... Feb 12 2013, 02:40 PM stugray Ok, so I decided to go with a webcam 86b instead o... Mar 26 2013, 08:25 PM worn
Ok, so I decided to go with a webcam 86b instead ... Mar 27 2013, 09:38 AM nathansnathan
So apparently Webcam knows that these rockers are... Mar 27 2013, 11:09 AM stugray My plan is to set the intake right at the "ad... Mar 27 2013, 12:13 PM worn
My plan is to set the intake right at the "a... Mar 27 2013, 02:09 PM stugray I have found (after testing 8 sets of rockers) tha... Mar 27 2013, 03:29 PM stugray So I put in the new webcam 86b.
Advertised lift i... Mar 31 2013, 03:14 PM stugray Just finished the "Clay on the Piston" t... Mar 31 2013, 03:26 PM stugray One observation that I made:
When measuring the w... Apr 1 2013, 09:55 AM stugray Important lesson learned!
I cut the pushrods ... Apr 3 2013, 12:20 PM worn
Important lesson learned!
I cut the pushrods... Apr 3 2013, 03:22 PM Jake Raby
So much for us just repackaging things and selli... Apr 3 2013, 06:43 PM worn
Not even Web Cam knows what we do to camshafts... Apr 4 2013, 10:35 AM stugray Jake
I have promoted your hardware often, even a... Apr 3 2013, 09:39 PM Jake Raby
Jake
I have promoted your hardware often, even ... Apr 4 2013, 05:45 PM stugray Jake, the above quote was merely an exact comment ... Apr 4 2013, 09:21 PM stugray After going through all of this measuring and havi... Apr 29 2013, 01:31 PM stugray Bump the above question for rdauenhauer.
Jake? Ty... Feb 4 2015, 02:21 PM rdauenhauer I missed this. Good read. Feb 4 2015, 03:19 PM Dave_Darling The ratio of all of the stock rockers "should... Dec 7 2015, 05:30 PM Steve Pratel :rotfl: Really? come on guys let it go already. Dec 7 2015, 08:54 PM stugray
:rotfl: Really? come on guys let it go already.
... Dec 7 2015, 09:43 PM Superhawk996
:rotfl: Really? come on guys let it go already.
... Jan 9 2022, 08:18 AM 930cabman What is the consensus from this dramatic post? can... Jan 8 2022, 06:14 PM iankarr I used Jake's method as the basis for my video... Jan 9 2022, 09:52 AM 930cabman
I used Jake's method as the basis for my vide... Jan 9 2022, 10:34 AM iankarr Please don’t do THAT lol. Jake’s method, yesâ€... Jan 9 2022, 10:43 AM Mark Henry There's always going to be variants of small d... Jan 9 2022, 11:50 AM 930cabman Exactly, overthinking can be problematic. Part of ... Jan 9 2022, 04:01 PM |
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