Glen-L.com

What is good way to check cam lobe lift on a hyd lifter engine.
I have a GM 3.0L and suspect a 2,5L cam was installed prior to my ownership. I have found a difference in cam specs of .020" between the two engines. I thought a simple dial indicater on a rocker arm would quickly tell the tale. However, when I get to max lift I am far short of spec lift and th dial ind falls off slowly, as if the lifter was bleeding down. I thought I could repeat this process until the lifter was flat, but I find that the 'zero' on the heel remains steady.
"If the lifter was in fact bleeding down then my zero would also change, wouldnt it?"

This engine has been run many hours since rebuild, and I am turning the crank thru a window in bellhousing. Can anyone tell me how to verify the lobe lift with dial indicator without tearing down the motor?

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God Bless our Troops; especially our Snipers

Rocker arms may not have a 1:1 ratio?

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As Conan the Barbarian says, " It's not how hard you can hit, it's how hard you can get hit and remain standing".

No, I'm reading on the pushrod side, that should read lobe lift.

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God Bless our Troops; especially our Snipers

Put a solid lifter in it and use that to check the lift. Of course this would require a partial tear down. I'm not 100% sure you can get a proper reading with the hydraulic lifter in there. I'm sure Paul will be along to give some input.

BTW remember that lobe lift is different than valve lift. Most, if not all, rocker arms are NOT 1:1 ratio. SBC is 1.5:1 while BBC is 1:7:1 so if the specs you have is valve lift you will need to mulitply the lobe lift your getting by the ratio of your rocker arms to get the correct lift.

I agree with Duane. You can take lifter preload out of the equation by taking your readings at zero lash. How short of spec lobe lift are you ??

'fess up Kens ... what are you really up to ??

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Paul Kane Chelsea, PQ

Building the Glen-L Hot Rod : http://www.boats.chelseacoachworks.com

I am suspect that a 2.5L cam is in my 3.0L engine. The two cams have .020 difference in lobe lift according to the specs. I am only trying to verify at this point. I am reading a dial indicator on the pushrod side of rocker arm; and I am getting erroneous readings.
How can I get a accurate reading?.............without a engine teardown

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God Bless our Troops; especially our Snipers

As the motor currently sits I do not believe there is any way to be more accurate then you have been thus far. However, they do make really light springs for doing this type of work when you're first assembling a motor. You would have to pull the valve springs on 1 cylinder and replace them with the lighter springs. They should be weak enough that they will not cause leak-down of your hydraulic tappets. Removing valve springs on an assembled motor can be tough if you don't have access to a air compressor and an spark plug adaptor (so you can attach an airline from your compressor to your motor to keep the valves closed when the springs are removed) This should give you the results your looking for with minimal disassembly of the motor.

http://www.cranecams.com/product/cart.p ... il&p=25286

http://www.lislecorp.com/divisions/prod ... category=6

I was just going to suggest those springs. Another thing I have done on race engines is to use a lifter puller and removed the lifter and pushrod and read directly from the camshaft via a long extension on my dial indicator. That and multiply by the rocker ratio and you're good to go. The rockers on most smaller engines are around 1:1.45 to 1:1.6 ratio and on larger engines 1:1.6 up to about 1:1.85 all depending on make, brand of rocker, type of engine etc...

BTW, my ratios are to be read as cam:valve ratio which is exactly opposite how most rockers are advertised, but makes sense to most engine builders

George

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I Peter 2:17

I have a dozen or so extensions, but here's a link to a 6" for $8, you can stack multiple extensions if needed to reach way down in a hole
http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=5802373&PMAKA=325-1418


George

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I Peter 2:17

I don't know if it would work but one site said to use a oil priming tool like (KD Tools 3446 GM Oil Pump Primer) and run up the oil pressure while you do your measurements.

Rich

if your going to pull a lifter would you not need the intake off? If thats the case you shouldnt need a very long extension on your dial indicator as you should be able to sit the indicator the your lifter valley.

You know, if you could prime it up to operating oil pressure, and keep it there while you checked valve lift, I would think this would likely work. However I suspect it might be messy as your valve cover would be off while checking valve lift and it might send oil all over the place depending on your oil pressure.

Why couldnt I just remove one rocker arm, this would take valve springs out of the test. Then would the tappet plunger have enough ooomph to lift the dial indicater? Perhaps use a dummy pushrod for the indicatr to rest upon.
I could care less about rocker ratio at this time, i'm trying to read the lobe.

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God Bless our Troops; especially our Snipers

True, you would need the intake off on a V-8, however some of the inline engines you can remove a lifter fairly easy through the head and the 3.0 is an inline although I'm not certain if the lifters can come out with the head in place or not as I've not worked on one of those in many years and my memory isn't that great Anyway, that's why I suggested the extension as I thought it might be possible seeing as it's an inline 4cyl

The other option would be to leave the lifter in, remove the pushrod and put the indicator on the rim of the lifter instead of the plunger. This would take the plunger travel out of the equation although you'd still need a long extension

Just tossing out ideas, take them or not. Somtimes I get engines confused after having worked on so many of them so it never hurts to double check my ideas

George

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I Peter 2:17

opps...I dont know why but I was thinking V6...my bad