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pushrod measurement
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SNJ
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PostPosted: Tue May 20, 2008 8:55 pm    Post subject: pushrod measurement Reply with quote

First time doing this. Please advise/correct me as required.

The engine is a 350 mounted on a stand. I have Crane cam and hyd lifters, 278 adv duration, .467 lift. RHS vortec style heads. Proform aluminum roller rockers. The deck is uncut.

I made a solid lifter from an old hydraulic lifter. This made up solid lifter has the same pushrod cup height as the Crane hydraulic lifters I will eventually use.

I'm using an adjustable pushrod and have a dial indicator mounted on top of valve spring retainer.

I place some machinist's blue on intake valve tip.

I rotate the crank until the exhaust valve begins to open. I then set the intake valve of that same cyl to zero lash.

I then rotate the crank through a couple of revolutions.

I take note of valve lift indicated on the dial indicator at max lift and also at 75* ATDC. I read about this someplace but not sure of it's significance.

Then I disassemble and look at the pattern left on the valve tip.

Is the valve tip pattern the deciding factor as to whether the pushrod length is correct or not?

Should I be concerned about the dial indicator readings? How do I use that information in deciding pushrod length.
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clay
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PostPosted: Tue May 20, 2008 11:58 pm    Post subject: Reply with quote

Sounds like the first time I degreed a cam, I had a bunch of numbers written down but not a clue what any of them meant. You have everything right as far as procedure goes. The indicator on the valve measuring lift is to assist you in determining where half lift is. At this point, the roller should be centered on the valve. I'm assuming this occurs roughly 75* after top dead center - sounds about right anyway. I don't really mess with finding half lift. I just mark the valve tip with something, magic marker, dykem, even a light grease film and run the assembled valvetrain through a cyle and look at the pattern. Adjust pushrod length accordingly to center this pattern on the valve. Longer moves the pattern toward the exhaust side of the head, shorter of course does the opposite. If you run into anything else, feel free to ask. Clay
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SNJ
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PostPosted: Wed May 21, 2008 1:08 pm    Post subject: Reply with quote

Thanks Clay.

Any opinion or experience with the Manley plastic type pushrod checker. I think I could use the actual hydraulic lifter I'd be running when measuring the pushrod.
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bosshoss
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PostPosted: Wed May 21, 2008 2:15 pm    Post subject: Reply with quote

Might want to take into consideration you are checking with a soild lifter. Won`t make a whole lot of difference but when you go to the hydraulic lifter you willl be sinking the lifter into it`s bore some. (I think one turn is about .050) So if you go 1/2 turn your pushrod measurement is .025 off.
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bill jones
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PostPosted: Wed May 21, 2008 3:43 pm    Post subject: Reply with quote

-Depending on how serious you want to get about the project here is how I go about it all.

1-the modified lifter needs to have adjustability to the pushrod cup height.

2-you need a way to measure the hydraulic lifter to the pushrod cup---so you can determine the overall length of the hydraulic tappet in a preloaded condition.

-I use a 5/16" ball bearing in the pushrod cup and the top of the bearing (will usually) protrudes above the top of the lifter body so that you can measure it with a dial caliper.
---------------------------------------------------------
3-measuring the pushrod length----after you decide on a pushrod length---maybe you'll actually need two different lengths for the intake and the exhaust----then the problem is getting coordinated with the vendor you choose to buy the pushrods from.

-you also need to consider the length tolerance you can live within in case can't get exactly the right length.

-typically the easiest way to measure the pushrod length is to lay the pushrod on a tape measure starting at 10" and see where the other end is.

-this allows you to look straight down at the 10" mark and eyeball that end of the pushrod perfectly to the 10" line.

-then peering at the other end it should be something close to 7.9" to 8" away from the 10" mark.

-you need to convert the tape measurements to decimals---which is pretty easy-----say you are at 7-31/32" and want to know what 31/32 is.

-just divide 31 by 32 and you get .96875---add that to 7 " and you get a number rounded off to 7.969".

-so you'd probably have a choice of 7.950" or 8.000" to choose from.
---------------------------------------------------------------
4-roller rocker rollout across the valve tip.

-this is a big controversial subject about when and where the roller should sit and traverse across the valve tips but here is what I do.

-first off is to eyeball the position of the roller wheel on top of the intake (and also check the exhaust) valve tips---check it at rest and at max lift just to get an idea of what length pushrods you need to get reasonably close to the center of the valve tip.

-the roller wheel typically rolls outward across the top of the valve as the valve is opened by the roller rocker----then just before max lift you should see it slow down and actually come back a little.
--------------------------------------
-I have found that however far it rolls outward--say it rolls out .122"---that the geometry on stud mounted roller rockers is OK if the roller comes back in about 10% or say .012".

-This example is from a typical .640" net lift application that ran excellent with NO valve train issues.
-----------------------------------
-I'd suspect that having only .467" net lift that the roll out might be something like .060" to maybe .080" or so----and the roll back in would then be about .009".
---------------------------------------------------------------------------------
5-to measure roll out I use a set of dial calipers out to the side of and parallel to the spring retainer with the caliper stem touching the crown of the roller wheel----then check at .002" lift--call whatever that caliper number is zero-----then measure and calculate back to that zero point in .050" or .100" valve lift increments.

-the roller will always move the most in the first .100" lift something like .030"---then the next .100" it slows down to about .020"----next .100" I'd expect to see something like .008"-----next .100" lift maybe .000"---- then roll back in maybe .008' or so at max lift.

-This means the roller is ratio is the highest in the last .167" and has the least amount of roll happening when the valve spring pressure is the highest.
---------------------------------------
-I do NOT believe in the Manley checker tool-----I have used various tools like that but rockers are NOT all the same---so those tools are just to give a very general idea---but there's a possibility you'd end up with the same answer compared to this doing this roll out and roll back idea.


Last edited by bill jones on Wed May 21, 2008 8:45 pm; edited 1 time in total
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SNJ
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PostPosted: Wed May 21, 2008 4:44 pm    Post subject: Reply with quote

thanks bosshoss, once I determine the pushrod length I figured to add .015 (head gasket compressed thickness) and .032 (what I measured the hydraulic lifter pushrod cup depresses with 1/2 turn after 0 lash).

bill, I need to re-read and think about your post a while. Lot's of information.
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af2
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PostPosted: Wed May 21, 2008 7:48 pm    Post subject: Reply with quote

SNJ wrote:
thanks bosshoss, once I determine the pushrod length I figured to add .015 (head gasket compressed thickness) and .032 (what I measured the hydraulic lifter pushrod cup depresses with 1/2 turn after 0 lash).

bill, I need to re-read and think about your post a while. Lot's of information.
Read Bill's post I am glad to have his infortamive post's!!!!! True to the form!
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clay
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PostPosted: Thu May 22, 2008 12:00 am    Post subject: Reply with quote

Thanks for explaining what you are doing on your website Bill. I looked at it and my guess was you were going for the least travel with pushrod length and that you could put the pattern in the center by moving the rocker stands. I see now you are looking for a certain relationship in the rollout / roll in and it makes sense now - just never knew or thought about it in that much detail. I know my method is sort of general, thanks for taking it to another level. Clay
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SNJ
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PostPosted: Thu May 22, 2008 8:15 am    Post subject: Reply with quote

bill, I've read your post several times and looked at your website - very cool.

I understand most of what you're saying. Can't say I understand your method of measuring roll out but I'll keep thinking about it as I'd like to give it a try.

Thanks everyone for your help.
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bill jones
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PostPosted: Thu May 22, 2008 11:01 am    Post subject: Reply with quote

-if you were looking at the story about the big chief heads--that is an entirely different deal---because it deals with shaft mounted rockers.

-shaft mounts and stud mounted are significantly different and you can't really compare the roll out results because the rocker bodies are built quite differently.
---------------------------------------------
-but the idea of looking at roll out is still important.

-that big chief deal is a mess----is supposed to require 3 different pushrod lengths if everything is right----but I have seen where I needed 6 different lengths because of side to side variations of the heads to the block deck height---and differences in valve depths thru the heads etc.

-but when you are dealing with 400# seat pressure and well over 1000# open pressure and an inch or more of race ready valve lift and $40,000 toys----bad stuff can happen in a hurry when the details are not right.
--------------------------------------------
-measuring the roll out on the stud mounted deal----I mount a dial indicator on top of the retainer and in front of the roller wheel and just far enough away from the wheel that the wheel doesn't touch the indicator stem as the wheel rolls outward.

-then I position the engine on the engine stand so that the top of the retainer is virtually parallel or level in relation to the floor.

-I take a set of dial calipers and use the stem of the dial indicator as a starting point to measure over to the roller wheel.

-just light touch the dial caliper body against the indicator stem----open the calipers to touch back in to and touch the crown of the roller wheel---write that number down and call it a zero for your reference points.

-example is the the dial indicator stem will be out away from the roller wheel something like say .300" when the valve lash is gone and the valve is preloaded to .002" lift.

-so you need to use this .300" as your zero point and measure all the roll outs or roll back ins from that .300" number.

-if you had digital calipers you could just zero the calipers at the .300" point and eliminate the math.
-----------------------------------------------------------------
-the main thing is you just have to get in there and look at it--spend some time trying to figure out how to chart the roll out and roll back in----in relation to various valve lift points.

-after you get it figured out it's easy---especially if you keep some notes--maybe take some photos----and make a reference for yourself for the next time in case you forget.

-then by time you've grown old and done a couple hundred of these it's pretty simple practice to include in any roller rocker engine.
---------------------------------------------------------------
-stud mounted rockers also have issues with loose trunnion bores in relation to the OD of the stud threads----the trunnions actually bearing against the stud threads rather than the stud shanks.

-so if you start to thinking that longer pushrods are better for a tricker geometry pattern then you end up with the trunnions way up onto the threads which have only about 1/10th the actual bearing surface against the inside of the trunnion compared to having the full surface of a proper length shank in there.

-when you get to measuring the trunnion ID's and the stud shank and stud thread OD's of every piece you are using----it gets to be a wonderment as to how does this stuff survive at all.
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SNJ
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PostPosted: Thu May 22, 2008 9:36 pm    Post subject: Reply with quote

bill, first, thanks, great stuff

Your measuring method is much clearer now and I will start experimenting tomorrow. If I understand correctly, I will be looking for a rollback-in of 10% of the rollout measurement. If I get that, then my pushrod length is ok.

I can see this keeping me busy for a while.
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bill jones
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PostPosted: Thu May 22, 2008 11:41 pm    Post subject: Reply with quote

-after all this I look thru my references and find that I have only one reference that is close to what you have.

-seems like I was always using 1.6 or 1.65 rockers on the intake and 1.5's on the exhaust--and most everything I ever checked had over .600" raceready valve lift.
---------------------------------------------------------------------------------
-I have just one hydraulic lifter SBC example that had .477" valve lift with a 8.050" pushrod that had rollout as follows:

.002 lift = .000"
.100-------.020 roll out
.200-------.030 total roll out (.010" more than at .100"
.300-------.031 total roll out (maximum roll outwards)
.400-------.024 meaning it rolled back in .007" from the .031
.475-------.010 meaning it rolled back in a total of .021.

-I personally didn't like having that long of a pushrod in there and having that much roll back in.

-the pushrod was at least .050" too long for my liking---but when I checked it I gave the customer two choices of pushrods---8.000" and the 8.050's.

-I had measured the valve lift timing points at each of the lift increments and had figured out the duration at each point-----and the 8.050's showed a small but positive gain in duration at the higher lifts----so the guy wanted to try'm and see what happened.

-He ran the 8.050's for a year---never had any valve guide issues or any other problem----then one day he got the bug to install the 8" pushrods.

-His comment was "those shorter pushrods just castrated the power---took the engine from being a stud to being a gelding"---meaning it made a noticable difference in power---from really good to just mediocre.

-so he put the long pushrods back in and was happy.

-the rockers that were used were the Comp Cams pivot ball rockers that look very similar to stock but had the roller tips.
---------------------------------------------------------------
-here's another example but using 1.75 BBC rockers on an old Studebaker that I did a fairly costly conversion on---but I got to install the rocker studs of my choice and at the height of my choice--and I had 100% control of ALL the details including the exact position the roller wheel sat above the valve tips.

.002" = .000"
.100-----.016 roll out
.200-----.029 total roll outwards
.300-----.035 was maximum roll outwards
.400-----.030 (rolled back in .005")
.500-----.023 total roll back in

-this deal was set up more like a shaft mount would be--and I had made some trick thinwall crush sleeves that slid onto the rocker studs so that the trunnions were preloaded and locked into place from the bottom---sort of like what is called a pedestal mount rocker.
-------------------------------------------------
-so this will give you a couple of examples that will probably have less total roll that you will be able to get with your Proform rockers.
-------------------------------------------------
-haven't yet figured out why you were told to check at 75 degrees.

-and I would install a used headgasket or even just snug down the head on a new gasket just to eliminate that chance for an error --and I'd use the real valve spring rather than some soft checking spring.
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SNJ
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PostPosted: Fri May 23, 2008 1:35 pm    Post subject: Reply with quote

bill, you lost me a bit there. I'm going to have to think about your latest post. I'm doing some experimenting now.

So you used 8.000 or 8.050 pushrods with a similar setup to mine.
Hmm, I get 7.650 when using the method I originally mentioned - like Clay uses, looking for pattern centered on valve tip. Makes me think I'm way off.

In your experience can you give a push rod length range where you would expect my pushrod length to fall?

http://www.thedirtforum.com/pushrodlengths.htm

here's where I read about 75*
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bill jones
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PostPosted: Fri May 23, 2008 2:13 pm    Post subject: Reply with quote

-if you were to try 10 different brands of rockers on the same valve and same cam you will find they will NOT be wanting the same pushrod length.

-so whatever I test has no exact relevance to what you are doing.

-The whole idea here is to get your big eyeballs on and get in there and look at what you have to work with----listen to and read all the information you can get----then use your own brain to choose what you want to try.

-I can say that typically I'd expect a need for a somewhat longer pushrod when going stock old style rockers to about ANY roller rocker arm.

-this entire deal is rocket science----you can only deviate maybe plus or minus .050" before you'll be out of the ball park.

-it's one thing to be wanting something that is trouble free and something else when you are trying to squeeze out another 5hp on some chassis dyno---and that 5hp might have to come at the expense of accelerated valve guide and valve stem wear etc.
-------------------------------------
-the 75 degree range is all about knowing where the valve is in relation to when the piston is moving it's fastest---meaning when the piston speed supposedly has the greatest affect on airflow.
-----------------------------------------------
-if you totally disregard everything I've said and figure out what you think you need by yourself----just buy it and try it----chances are it will work fine.
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SNJ
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PostPosted: Fri May 23, 2008 8:32 pm    Post subject: Reply with quote

bill, please stay with me a little longer

Here's what I got.

First I set my pushrod to 8.00 and just eyeballed it. Was way towards exhaust side - too long. Don't think I could have even rotated the engine without it rolling off.

Next I set it to 7.60 and tried to follow your procedure. Did it 3 times.

002 lift = .000"
.100-------.039 roll out
.200-------.077 total roll out (.038" more than at .100"
.300-------.100 total roll out
.400-------.116 total roll out
.439-------.119 total roll out (this was max lift, fyi, got .405 at 75*, the cam is supposed to be max lift .467)

So, there was no roll back and I never reached full lift. So dumb me says this pushrod length is no good. Time to lengthen the pushrod and go again. Yes?

I hope these numbers sound reasonable to you.
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