Difference between lobe lift and pushrod lift

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Has anyone measured the loss of lift on the small Mopar because of the lifter and pushrod not being in plain with each other? I have...and I come up with aprox. .009-.010. Lobe lift on my comp XE275HL is .350 actual lift on push rod end is .340. Most racers do this wrong by multiplying lobe lift by rocker ratio and NOT including this offset loss of lift. Cam card says .525 lift (hyd.) divide by design ration 1.5 and you get .350 lobe lift. True, I measured it. subtract .010 for offset loss, and I now show .340 on pushrod end, true, as measured. Multiply by 1.6 (Crane 1.6), and I should have a TRUE .544 at valve as installed. And I have exactly .544 at the valve. You can use a solid lifter to measure this or make a solid out of a hyd. lifter by removing spring and turning bucket over.( this works better with hyd. cams because lifter is same length.) Using the standard practice ... .525 and plug in 1.6 rackers it will show .560 lift... Nothing wrong with getting it right. Just wanted to throw this out there..I'm sure it has been tossed around before. TLB.
 
Well you bring up a good topic, but you have to take into account that the lifter will vary as to oil pressure also since it's hyd., then you have to also take into account the stock rockers are only 1.43-1.46 in actual ratio. Then for that matter the aftermarket rockers aren't really true either. Unless you buy a true ratio rocker from one of the few manufactures that offer them. But you don't buy them for $200.00-$300.00 either.
I believe that the manufactures of camshafts grind the cams to a given spec. and then heat treat them and this is where the loss of lift comes in, as the cams are heated and then cooled the cams will have a tendency to shrink as the material that the cam is made out of tends to get tighter as to make it (the surface) stronger and more duriable.



BJR Racing
 
I havent actually EVER seen that come up before, on this or other boards..lol. You are right, the small mopars have one of the worst designed valvetrains when you look at angles. High lift rollers really make things interesting. But, it terms of effects on the package, the rockers being off due to production tolerances is a bigger problem then pushrod angles. I think the cam companies are aware of this, but I'm sure they dont need to make the choosing process that much harder for someone..lol.
 
BJR. Shrinking cams(?) possibly so. That's why it should always be checked(measured) also rocker ratio isn't always true. What I am saying is... we loose lift from what the actual lobe lift measures, and what the pushrod measures or "see's" from the lifter. The rocker ratio has NO effect on the loss of "motion" transfered from lifter to pushrod. regardless of lift or "shrunk" cams. I measure ALL of my cams as installed and I can tell you that whatever the lobe lift measures...less .010...X rocker ratio, is what you will see at the valve (hyd.) or less lash (mech). If the rocker measures 1.46...then use 1.46 x lobe lift less .010 and that is what you will see at the valve as installed. The fact remains..small mopars do loose lift(motion) from the cam(lobe) because of design...lifter is not in plain with pushrod..now introduce off set rockers (W2, W5 ect.) and the loss is compounded. Does anyone remember what DLI. did to remedy this? Terry.
 
I am simple bringing this out so it can be taken into acount when choosing camshfts. A racer friend bought an expensive roller grind for his W2 small mopar. The heads flowed 307 @.640. so he ordered .640 lift cam. I degreed it in for him and as installed with 1.5 Harlin Sharpe. He only had .598 at the valve with lash. Heads flowed 287 @.600 . He was not using all of his heads. Using the Superflow formula, he was loosing aprx. 41 H.P. with wrong cam. Car went best of 10.37 @128. but 10.40's most of the time. I ordered him a grind that would give .645 at the valve as installed with lash. No other changes the car went 10.11 @131 off trailer without tuning. Just a word to the wise will suffice.Terry.
 
headsbikesmopars said:
BJR. Shrinking cams(?) possibly so. That's why it should always be checked(measured) also rocker ratio isn't always true. What I am saying is... we loose lift from what the actual lobe lift measures, and what the pushrod measures or "see's" from the lifter. The rocker ratio has NO effect on the loss of "motion" transfered from lifter to pushrod. regardless of lift or "shrunk" cams. I measure ALL of my cams as installed and I can tell you that whatever the lobe lift measures...less .010...X rocker ratio, is what you will see at the valve (hyd.) or less lash (mech). If the rocker measures 1.46...then use 1.46 x lobe lift less .010 and that is what you will see at the valve as installed. The fact remains..small mopars do loose lift(motion) from the cam(lobe) because of design...lifter is not in plain with pushrod..now introduce off set rockers (W2, W5 ect.) and the loss is compounded. Does anyone remember what DLI. did to remedy this? Terry.
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Well then I have to ask what are you trying to accomplish here? As I recall you asked if anyone has ever seen this before? Now your going else where with this. I tried to tell you why, with what you stated, and a reasonable answer, without going into all kinds of stuff that most people won't understand. If you are looking for the perfect cam then I have to say spend the money and have a cam ground for your needs. Most racers use custom grinds and not off the shelf, so I'm asking where are we going with this?
I'm not hitting you for this but would like to know where you'er going so we can help you with this. I guess I'm not following you?

BJR Racing
 
The only place you will get true lift is on the end of a solid lifter.Your statement is true in theory,and when measured.A hydralic lifter can never give true lift 100% of the time due to oil viscosity change and grade.Only the solid lifter gives you the excact amount of the cam lobe.A push rod in any motor does not sit true to the geometry of the lifter and thus can not give you the full lift as the lifter due to the angle that it intersects with the rocker arm and side to side movement and the bending of the push rod for high tension springs.Only with solid lifters can you come some what closer to this zero lose or by running a over head cam and rocker set up can you acheive this,as you no longer have the components running at the wrong angles and reatings lose of lift.How you should state your questions is this:How much difference is there between static lift and dynamic lift?When I worked for Ray Barton racing engines we would go throught this daily,and the conversation between me and comp cams,crane,and others where,lets say,interesting.Mrmopartech
 
Just an attempt to enlighten. A very IMPORTANT factor in why we choose the wrong components. MrMopartech is close though. Take this info and use it as if you wish. TLB.
 
MrMoparTech, I tried to IM you. I will try to call you today . Trying to finish outside work (painting) on house and shop this week before weather changes. Getting ready to get real busy in shop. (Cylinder head shop). Thanks for e-mail. MoparTech, some subjects are just too deep for some. Again, thanks. TLB.
 
In most situations,peple pick the parts for their motors in the wrong order.Some times a deal comes about and they buy item B then find item F,still not knowing if they will work with the main component,(THE HEADS).If every one was to spend money right the first time,it would be on the heads you need on your build,and for the purpose of your applacation.You would then buy comonets around what you need,and only buy your cam to match the specs of your heads and and in a +.050 lift to the final lift figure to have the max lift to match the heads specs.This is done due to the fact that a hydraulic cam valve train will come up short every time as compared to a solid cam valve train,and that still has some loss of lift due to about 40 different problems that occour.So in the end,get the heads done to the best of what you can afford and to the level of power you need.Most street applacation do not need alley heads and the expense,when a iron head can be alot cheaper and most cost effective when done right the first time.If you where to do your self a favour,pick a super stock drag class that your car and motor come close to.And learn about that class of motor and how they approach the times they run,iron heads,stock rods and cranks,blocks,original design pistons but light weight,and read the class rules,and watch them pull off unreal numbers with half the parts that 85% of the street cars run,then ask why,Mrmopartech
 
MrM:
Strictly from a layman's point of view, I think you've aptly summed up where most people make their biggest mistake when building a street / mild strip engine. It has always been my contention that torque is produced by the engine, while the final horsepower figure is ultimately determined by the heads. As you stated, once the heads have been configured for the power level of the engine, it's then time to pick the other components to complement the heads, with special consideration going toward camshaft selection.

Terry:
You gave a very good example of matching the cam to the particular heads in a race engine. Most of us street-and-sometime-strip warriors never do get to this level of tuning, mostly due to lack of expertise on the subject of head/camshaft matching, and partly due to the fact we have to draw the $$$ line somewhere. Most of us either do our own head work, or trust our machine shop to the job for us, and seldom do we have the luxury of flow testing the heads then trying different cams until we find one that gives us the maximum bang for our buck.

BRJ:
I was with you at first - what's he trying to say, and how the heck does this apply to my street 360 with the "J" Heads and MP cam. It was beginning to hurt my head - no pun intended - until Terry gave the track example, and then it all became clear. If you're after the last 1/10 in the quarter, then I guess it all makes sense when trying to make your final determination in camshaft selection.

O.K. I'm getting off the soapbox now. :)
 
Ok,lok at it this way.My motor is a 440max wedge motor.I run 426 max wedge heads on my motor with a air flow rating of [email protected] cam is a .562 lift,but I do not get that at the valve,I lose through clearances and bending and geometry.my lobe lift is .375x1.5 for rocker ratio? if the rocker is truly 1.5,comes to .562.my valve clearance is .022&.024.I am down to .538.If any type of clearance or bending is in effect happening,I can lose .010 easly.I am down to.538.Now for my combo I also need to run a mixed set of max wedge rockers,of .485 offset intake,left and right,and a set of striaght rockers,and all of these are 1.6 ratio.If you apply the same situation as above,my lift now is .600 minus the .034 of lost lift,equals=.566 lift at the valve.A little rule of thumb,to get a true lift at the valve,and .050 lift to the cam.Mrmopartech
 
headsbikesmopars, I heard that you liked the heads that cheapstreet has on his car, well he didn't tell you but I'm the guy that built them into T/A heads. (from mopartech) I also built the heads for Mrmopartech as he will tell you. I won't get into ANY head disscussions as this is where a site can get vary heated, I have been into it with Curtis, Ryan, Dwayne and others and have helped people from California to Canada, but if you think that I don't understand this will be your misconseption as my list of credentials is long and very good, with Chrysler, Ford Motorsports.
As for doing heads and race engines I have been doing this for more than 25 yrs. and with Chrysler and Ford for more than 10 yrs., I was working with Loren Zydeek (Zeeker Racing componets) 15 yrs. ago when he was doing the W-5 and W-7 small block project with Chrysler as he was a engineer with them. He also was the first or one of the first to make a aluminum max wedge head for big blocks until another company bought a set and then copied them and called it there's. One of the heads that was copied from me was the twisted wedge from TFS as I owned the rights in 1991.
Most people start in the wrong place as mrmopartech and others have said, and every engine per the application needs to have different things done to the heads to get the most out of the engine. Some don't need as much and others need more but this depends on the engine and what is going to be done with it.
I'm done venting, and don't mean to offend anyone sorry if I did.


BJR Racing
 
BJR, The small block mopar camshaft does not transfer all of it's motion to the pushrod end of the rocker. I am not speaking of pushrod deflection, rocker arm flection, hyd. lifters (plungers), solid camshafts (lash), inaccurate rocker ratio's or cams ground incorrectly. We all know as you have correctly stated, these things contribute to a loss of lift on thier own. That's a given. Because of the poor valve train geometry in the small block mopar, mainly due to the lifter body and the pushrod not being in plain with each other...there is a loss of lift (motion), from the camshaft to the pushrod end of rocker arm. As correctly stated by MRMoparTech, "one of the reasons we choose the wrong components". As for the 'ranting'..it's ok..no need to apologize...I do it too. Terry.
 
BJR, one more thing...two thumbs up on those heads. excellent work. I told Jim that was good work. No,.. didn't know that was your stuff. Well done. Terry.
 
Thanks Terry! Theres alot of things that I do that DON'T ever come out. Sorry for having the big head,but it'snice to have the inside of things. Chrysler and Ford have been very good to me with knowledge that they have shared. I've seen things clear to 2010 and thoughts beyond, I must say it's going to be very interesting.


BJR Racing
 
BJR Racing said:
I won't get into ANY head disscussions as this is where a site can get vary heated, I have been into it with Curtis, Ryan, Dwayne and others ...
BJR Racing
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Gee, I cant understand your apprehension...lol
Luckily, I'm just a dumb hick :)
 
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