Checking lobe lift

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blackhand

blackhand

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Just got a new dial indicator and I'd like to use it to check lobe lift on my cam. I'm not so much concerned about finding the actual lift on each lobe as I am about making sure that they are all consistent and that none of them are excessively worn. The trouble is that I'm running hydraulic lifters and I really would like to avoid pulling the intake manifold if at all possible.

My concern is that differences in the amount of oil in each lifter will cause my measurements to show different amounts of lift on each lobe. Obviously taking my measurements with a solid lifter would be ideal, but again, I really don't want to have to change out my intake manifold gaskets right now.

So I was thinking that if I measure the lift after bleeding down all of the lifters I could get an accurate enough reading to make sure that none are overly worn. To do this I was thinking that I could turn the engine over with a breaker bar a few times with all of the valve gear installed. Valve spring pressure should bleed the oil out of the lifter when oil pressure is at zero, right? What do you think, will this allow me to measure each lobe for consistency??

Thanks fabo
 
I would rather measure them pumped up....but I don't believe either way will be accurate worth snot.
 
I guess, When in doubt...Change it out. I don't know how he did it but a Mechanic Named Ray knew my cam was bad just by listening to my engine for 5 seconds. Yes it had a miss or at least a rough idle. Sure enough one of the lobes was just about round when we got it out. That was on my first car(66 318 Dart-Green also) back in the '80's. I'm very interested to learn how to properly check a Cam Shaft and if it's at all possible without actually looking at it. My Brother in law always pulled the Valve covers off and looked at how far the valve springs moved up and down with it running. He adjusted them with it running too.
 
Pull the intake and measure the lobes directly. Summit carries a gage and magnetic stand set up to measure the lobes in the motor. I bought one a few years ago to do just that but never used it....
 
Thanks for the quick info. I guess the best way to go about this would be to obtain a used set of valve covers that I can cut a slot in to view the pushrods when the engine is running. Mark the pushrods with a sharpie and look for them to be spinning. If they're spinning the cam should be good, if not then it's worn
 
blackhand said:
Thanks for the quick info. I guess the best way would be to go about this would be to obtain a used set of valve covers that I can cut a slot in to view the pushrods when the engine is running. Mark the pushrods with a sharpie and look for them to be spinning. If they're spinning the cam should be good, if not then it's worn
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Or just bite the bullet and pull the manifold so I can measure the lobes directly. It would be nice to have the reassurance of having an accurate measurement of lobe lift. My simple valve spring project is snowballing in a hurry!
 
StrokerScamp said:
I would rather measure them pumped up....but I don't believe either way will be accurate worth snot.
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I'm leaning this way myself. If the stylus on your DI is long enough to reach the lifter cup, pull the rocker shafts and and pushrods and let it sit for a while. The DI wont put hardly any pressure on the lifters and they should stabilize enought to give you a close enough reading to see if a lobe is going flat or not. With that said, if you had a wiped lobe you'd be getting some racket out of it any way. Cam lobes generally don't just wear a little. When they start to go, they go.
 
OldmanRick said:
I'm leaning this way myself. If the stylus on your DI is long enough to reach the lifter cup, pull the rocker shafts and and pushrods and let it sit for a while. The DI wont put hardly any pressure on the lifters and they should stabilize enought to give you a close enough reading to see if a lobe is going flat or not. With that said, if you had a wiped lobe you'd be getting some racket out of it any way. Cam lobes generally don't just wear a little. When they start to go, they go.
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Thanks Rick. I had planned on measuring with the rocker shafts removed and pushrods in place. I was just going to put a socket or something next to the pushrod to stabilize it while while measuring and then set up the DI to take a measurement from the pushrod tip while I turn the crank over by hand. If I've wiped a lobe I thought it should be pretty apparent.

I have a 5,000 RPM misfire and occasional valve noise that I'm trying to sort out. I have a good feeling that the valve springs are shot so I'm going to replace them and thought I would check whatever else I could while I'm at it. As for the valve noise I suspect that the lifter preload may be off, or maybe the lifters are just bad. I Just measured the pushrods and they range from 8.549"-8.556". I'm going to measure the preload next to see if any of them may be too short for whatever lifters are in there.

Once I have all these measurements I should have a much better idea of what's going on.
 
You could always try to set the dial up on the very edge of the lifter. I've done it, but depending on how the lifters are made, it may not allow the indicator to rest on the lifter edge with any stability.
 
StrokerScamp said:
You could always try to set the dial up on the very edge of the lifter. I've done it, but depending on how the lifters are made, it may not allow the indicator to rest on the lifter edge with any stability.
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That's a great idea, I will definitely take a look to see if that'll work. Thanks Stroker. BTW, where in Georgia are you? I'm applying to grad school at Georgia Tech and may be moving to Atlanta next summer...
 
Why not start the engine and let it run for a minute to get the lifters pressurized, turn it off and yank the covers and rockers and then measure off the push rods? The dial indicator doesn't have enough spring pressure to compress the lifters so they should stay where they are when you check them. Even if they are not pumped up all the way it shouldn't make any difference. It would still start at zero on the base circle and give you an accurate max lift.:cheers:
 
blackhand said:
That's a great idea, I will definitely take a look to see if that'll work. Thanks Stroker. BTW, where in Georgia are you? I'm applying to grad school at Georgia Tech and may be moving to Atlanta next summer...
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I'm in Jones County about 70 miles south of Atlanta.
 
mopar340dave said:
Why not start the engine and let it run for a minute to get the lifters pressurized, turn it off and yank the covers and rockers and then measure off the push rods? The dial indicator doesn't have enough spring pressure to compress the lifters so they should stay where they are when you check them. Even if they are not pumped up all the way it shouldn't make any difference. It would still start at zero on the base circle and give you an accurate max lift.:cheers:
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Unless of course the lifters are malfunctioning and leaking oil, which is possible since I'm getting occasional valve noise. Wish I had the funds to just install a new cam, lifters, pushrods, valve springs and be done with it!


StrokerScamp said:
I'm in Jones County about 70 miles south of Atlanta.
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Nice. My fiancee and I visited Atlanta a few weeks ago and loved it. Great school, job opportunities, cost of living, etc... Plus better weather than Seattle and less tree-hugging hippies means I'll probably have more of a chance to enjoy my hobby and meet people that share my interests :burnout:
 
If you pull the intake you will be able to see the cam lobes. If they are wiped you would be able to tell pretty easily without measuring them. I don't know about you but I would sure rather pull an intake than take the rockers off and then have to reset it all back up again.
 
stumper said:
If you pull the intake you will be able to see the cam lobes. If they are wiped you would be able to tell pretty easily without measuring them. I don't know about you but I would sure rather pull an intake than take the rockers off and then have to reset it all back up again.
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I just might do that in the end. I've already got the valve covers off and rockers disassembeled in order to change out the valve springs. Was hoping to kill two birds with one stone and check the cam while I have the valve train torn down. I'm just being cheap and lazy and not wanting to buy new intake gaskets, clean the rtv off of the block from the valley pan, retorque everything, etc... Oh well, it's not really that difficult or expensive in the end and it would be nice to have precise measurements of lobe lift for future reference. I guess there's not really any room for cheap and lazy in this hobby!
 
Well good luck with the crime rate. It's the Chicago of the South.

blackhand said:
Unless of course the lifters are malfunctioning and leaking oil, which is possible since I'm getting occasional valve noise. Wish I had the funds to just install a new cam, lifters, pushrods, valve springs and be done with it!




Nice. My fiancee and I visited Atlanta a few weeks ago and loved it. Great school, job opportunities, cost of living, etc... Plus better weather than Seattle and less tree-hugging hippies means I'll probably have more of a chance to enjoy my hobby and meet people that share my interests :burnout:
Click to expand...
 
Just one more suggestion. Maybe remove distributor and prime oil pump. Keep priming while checking Lobe lift.
 
OwdKasd said:
Just one more suggestion. Maybe remove distributor and prime oil pump. Keep priming while checking Lobe lift.
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I have an oil pump priming shaft so that could be possible... how much of a mess am I looking at making? Seems like I'd have oil shooting out of the rocker shaft pedastals onto my nice, clean engine compartment?

*edit: nevermind, if I did it that way I suppose the valve train would be assembled and I could take the measurements from the pushrod side of the rocker arm
 
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