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Old 05-06-2005, 03:25 PM   #1 (permalink)
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Lost Motion Assemblies Explained

Well for the few of us that are all motor in here it seems as though lost motion assemblies have come up in conversation as of late. i wanted to fully explain these things to you guys so you can make an informed judgement as to what you need to do about them.

First off an explanation
lost motion assemblies have a very simple job to do. they basically provide constant pressure to the rocker arm that the vtec lobe travels on. as for the reasons to why this is necessary i have no deffinitive answer but its fairly obvious. when you are not in vtec and the rockers are not bridged together with the locking pins the rocker arm that the vtec lobe rides on basically just sits there. without the lost motion assembly the rocker would just sink or most likely fling itself around from vibration. so this item, the lost motion assembly sits underneath of the vtec rocker arm and keeps it held up so the vtec lobe on the cam can ride on it. i would also assume that without this device in there and the rocker arm being either sunk or flinging around it would be alot harder for the pins to slide and bridge the rockers for vtec operation. i would also assume from just looking at the design that by keeping the rocker suspended and allowing the lobe to ride on it would help balance centrifical stress.

these are the two versions of prelude lost motion assemblies.the spring style lma on the left IS IN FACT the newer style from the 99-01 h22a4 according to the helms. i had previously thought the cylinder style (on right) was the newer style but after getting off my ass and actually looking in the helms and talking to some people I WAS WRONG. sorry, get over it!


this is a picture of the b16a lma (left) and the type r (b18c5) lma (right)



now if you will look at the tips of the lma you will see what the difference is. the actual head of this thing is where the problem arises. its obvious by looking at the type r lma that the head has a much greater surface area. this is why the type r lma's are able to support much higher lift cams in b series motors. i will show exactly why later. see its not actually a straight up and down movement that is going on here. remember the rockers are moving in an angular movement. so the actual top to bottom compression isnt what is looked at.

now if you go back and look at the actual h22 lma's and compare them you will see the newer style has a slightly larger diameter head on it. this is why these are better for higher lift cams

next is a series of pictures borrowed from ek hatch on h-t. these pictures demonstrate the movement of the rocker arm and how it actually rides on the lma

this is a picture of the rocker arm depressed on the lost motion assembly with what would be the lift of a normal cam


this is a picture of the rocker arm depressed on the lost motion assembly with what would be the lift of a bigger cam that exceeds the amount the lma can actually handle



after seeing those pictures i hope you can now understand the whole lost motion assembly thing thats been floating around. so its quite obvious that the actual surface area of the head of the lma is what is important.

as of now b series builder that use prelude lma's need to shim the installed hieght .040 to work in thier motors. if one were to use type r lost motion assemblies they would need to shave that amount off of them for them to function correctly and sit at the correct height. if these things to do not sit at the right height you are asking for problems so do not take my word as law and do what you are supposed to do when you assemble a motor and measure everything, check clearences and rotate everything before actually using it to check for binding.
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Old 05-06-2005, 03:31 PM   #2 (permalink)
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Excellent write-up, You sir are indeed a master.
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Old 05-06-2005, 03:45 PM   #3 (permalink)
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Great info! My hat's off to you sir.
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Old 05-06-2005, 04:14 PM   #4 (permalink)
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Old 05-06-2005, 04:18 PM   #5 (permalink)
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dood you rock.

so were you saying in one of the other threads (either mine or prelude drivers) that itr owners usually go to h22 lma's b/c they're cheaper, or vice versa?

and would it be beneficial for all-motor people to switch to that spring looking ones or keep the cylinder looking ones?
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Old 05-06-2005, 09:15 PM   #6 (permalink)
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Quote:
Originally Posted by crdcz03
dood you rock.

so were you saying in one of the other threads (either mine or prelude drivers) that itr owners usually go to h22 lma's b/c they're cheaper, or vice versa?

and would it be beneficial for all-motor people to switch to that spring looking ones or keep the cylinder looking ones?

prelude lma's are cheaper, A LOT cheaper. which is why more and more b series guys are using them.


spring or cylinder style really depends on the application. hopefully if i can ever get the time to pull my head and do my repair i can also do some write ups and do a little guess work while i am in there and figure out just how big of a cam you can run with these lma's. although b series and h series rocker ratios are both 1.55 so i would assume the largest cam you can run in a b series on prelude lma's would be the largest size cam you could run in an h series equally. but all assumptions right now
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Old 05-09-2005, 12:31 AM   #7 (permalink)
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I've already put my new rockers in on my all motor sh. I do however need to replace the LMA's I'll almost bet money on it. Depending on my mood and when I break down and put even more cash into the car I might do a write up on how to take the rockers out and remove and install the LMA's. I want to wait and get a new fitv when I order the LMA's so it might be another two weeks or so. I basically don't even care about my lude anymore. It just sits and sits because I've exhausted every extra penny and then some on this car. Pretty bad when you can't afford 60 dollars worth of LMA's huh! Guess that goes along with owning your own home!
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Old 04-27-2006, 09:30 AM   #8 (permalink)
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can worn lma's hamper performance? i did a valve adjustment yesterday, but I am still hearing a lot of rattle(sounds like if you have a loose washer) coming from a the valve assembly. I want to run the car this weekend. I tried it after the adjustment and it pulled to 8gs without a problem 1st through 3rd.
oh The noise would quite down after driving the car.
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Old 04-30-2006, 08:49 AM   #9 (permalink)
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So are the H22 and B16 LMA's the same size, no shimming required? And u said it is better to use the newer spring styled ones than the cylinder ones right? I HAVE to get rid of this sound on my engine, it's killing me. How much for a full set of H22 LMA's is it? IF the spring style ones are better for the application I will go with those, I jsut need to know which ones to get and what I will need to do. AS of now I am running a CTR cam, I am planning on moving to a Buddy Club 3 cam in the next year. HELP ME OUT PLEASE!
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Old 10-14-2006, 12:55 AM   #10 (permalink)
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I am currently experiencing this problem right now (ticking LMA) does anyoe know the average price of the set and does anyone know if there is a way to test them so they do not all have to be replaced. Or is it better to replace them all? Thanx
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