Odd Solid Roller Valve Lash Observation While Adjusting
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Melting Slicks
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From: Bogart GA
Odd Solid Roller Valve Lash Observation While Adjusting
I am running solid roller cam with a fairly aggressive cam. I am using the EO/IC method to adjust. This states that when the exhaust valve begins to open, the intake lifter is on the base circle. I set the cold lash on the intake rocker just as the exhaust valve on cylinder 8 started to close to 0.015. I then moved on to cylinder 4 to adjust the intake rocker there just as the exhaust started to open. This is where it gets weird, at this point the exhaust valve for cylinder #8 was almost all the way open so I thought I would recheck the lash assuming it should still be 0.015 but was shocked to see it was 0.020! It increased by .005". I did the same thing on cylinder 4 and it did not change from one position to the other. This is a new engine. Not even broken yet fully other than some engine dyno runs. What would cause this? I will check the others as I go.
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From: Corsicana, Tx
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You want to follow the EO/IC method. That means you set the intake as the exhaust starts to OPEN( E))....and the exhaust when the Intake is CLOSING..about halfway through it's closing cycle (IC).
Run through them again...you've got the concept..just fudged it a little.
JIM
Run through them again...you've got the concept..just fudged it a little.
JIM
Last edited by 427Hotrod; Dec 14, 2015 at 09:20 PM.
Thread Starter
Melting Slicks
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From: Bogart GA
Thanks for the quick reply guys, OK, as far as I know, the base circle should be the lowest point on the cam, the point closest to the cam axial center line. My concern is that if I follow the method and measure my intake lash just when the exhaust valve starts to open, it actually increases to a maximum value when the exhaust valve is fully open. If I set it 0.015 initially, it opens to 0.20 at full exhaust. It only does this for cylinder #8. I have a couple of others that increase 0.001.
Last edited by KJL; Dec 14, 2015 at 10:15 PM.
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From: Corsicana, Tx
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You need to ck for something binding. A pushrod dragging the side of the head, a rocker bottoming on a stud or something like that. Or a goofy cam grinding job. I've had pushrods lightly drag head on one cylinder and it would feel tighter than it was when adjusting.
I've run some pretty nasty cams and this system always works whether it's mild or wild. Since it only happens on one cylinder..something is happening there.
JIM
I've run some pretty nasty cams and this system always works whether it's mild or wild. Since it only happens on one cylinder..something is happening there.
JIM
Last edited by 427Hotrod; Dec 14, 2015 at 10:26 PM.
Thread Starter
Melting Slicks
Joined: Nov 2000
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From: Bogart GA
You need to ck for something binding. A pushrod dragging the side of the head, a rocker bottoming on a stud or something like that. Or a goofy cam grinding job. I've had pushrods lightly drag head on one cylinder and it would feel tighter than it was when adjusting.
I've run some pretty nasty cams and this system always works whether it's mild or wild. Since it only happens on one cylinder..something is happening there.
JIM
I've run some pretty nasty cams and this system always works whether it's mild or wild. Since it only happens on one cylinder..something is happening there.
JIM
Team Owner
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From: Reno Nevada
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They are shaft mount rockers. Nothing rubbing or binding as far as I can see. The only thing it could be is an issue with the cam grind. The only other thing I can think of is excessive cam bearing clearance. The cam is moving in the bore. But if that were the case I would think I would notice this elsewhere.
many years ago cams were way wide lash like .030 and they chewed up push rod tips modern SR cams are .008-.012 lash You only loose a little lift being loose or tight you loose some noise
Le Mans Master
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They are shaft mount rockers. Nothing rubbing or binding as far as I can see. The only thing it could be is an issue with the cam grind. The only other thing I can think of is excessive cam bearing clearance. The cam is moving in the bore. But if that were the case I would think I would notice this elsewhere.
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Melting Slicks
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From: Great Plains Iowa
I am running solid roller cam with a fairly aggressive cam. I am using the EO/IC method to adjust. This states that when the exhaust valve begins to open, the intake lifter is on the base circle. I set the cold lash on the intake rocker just as the exhaust valve on cylinder 8 started to close to 0.015. I then moved on to cylinder 4 to adjust the intake rocker there just as the exhaust started to open. This is where it gets weird, at this point the exhaust valve for cylinder #8 was almost all the way open so I thought I would recheck the lash assuming it should still be 0.015 but was shocked to see it was 0.020! It increased by .005". I did the same thing on cylinder 4 and it did not change from one position to the other. This is a new engine. Not even broken yet fully other than some engine dyno runs. What would cause this? I will check the others as I go.
I have always set them at TDC @ .003" less than specs call for to compensate for the ramp. As the lash isn't a critical adjustment its plenty close. Its very common for drag racers to adjust theirs several thousands tighter or looser to move the torque band.
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Melting Slicks
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From: Bogart GA
Yes, the exhaust is at max lift the the intake sees max lash.
Team Owner
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From: Reno Nevada
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Is your cam made out of spring steel so it can withstand 1000's of flexing per minute? A cam is supported every few inches and is generally a steel shaft @.900 inch minimum diameter.
From an engineering stand point do you really believe that big of steel rod cam shaft would flex before some little hollow tube push rod?
prove it to me! support a cam shaft on some steel blocks at each cam bearing on a press and apply 600 pounds to a lobe and let me see how much a dial indicator reads?
Last edited by gkull; Dec 15, 2015 at 06:46 AM.
Thread Starter
Melting Slicks
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From: Bogart GA
Is your cam made out of spring steel so it can withstand 1000's of flexing per minute? A cam is supported every few inches and is generally a steel shaft @.900 inch minimum diameter.
From an engineering stand point do you really believe that big of steel rod cam shaft would flex before some little hollow tube push rod?
prove it to me! support a cam shaft on some steel blocks at each cam bearing on a press and apply 600 pounds to a lobe and let me see how much a dial indicator reads?
From an engineering stand point do you really believe that big of steel rod cam shaft would flex before some little hollow tube push rod?
prove it to me! support a cam shaft on some steel blocks at each cam bearing on a press and apply 600 pounds to a lobe and let me see how much a dial indicator reads?
Team Owner
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From: Reno Nevada
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I just had another thought. Years ago I was using cheaper solid rollers and I had put quite a few miles on the vette. like 5000 to 10,000 a year. Well as luck would have it I blew a head gasket and the motor started misfiring. It was a blessing in disguise. When I took the manifold off I pulled all the roller lifters and several of them were starting to have bad wheel barrings and one was really bad. The wheel had slop in the bearings.
If the wheel could move as it rolls around the cam maybe it could account for a lash change during rotation.
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From: Reno Nevada
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I'd have to see it change in lash to understand better what is going on
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Melting Slicks
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From: Bogart GA
I would not expect problems with new lifter. I think it was Crower SR lifters that failed on me. To adjust I just draw out 8 circles per side and X them off after adjusting because you can do more than one valve before breaker bar cranking the motor. i just learned how to do it fast between heat races. I only have the stud girdle setup, so I have not really messed with the shaft rocker adjustments.
I'd have to see it change in lash to understand better what is going on
I'd have to see it change in lash to understand better what is going on
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From: Reno Nevada
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Basically, I check the lash for the intake just as the exhaust valve begins to open. If I continue to measure at multiple points in the opening cycle, it will gradually increase to maximum lash at 100% open. So if I set the lash at just open to 0.015", by the time I get to 100% open, the lash will be 0.02". This is only for cyl 8. Cyl 7 increases about 0.003". All the others are more or less the same. Interesting that both cylinders in question are directly across from one another... which is why I thought the cam bearings.
I really don't believe that the cam shaft can bend during it's rotation. The push rod is tiny in comparison and it would bend.
You think about the V-8 design. The lifters are coming in at a V at any give place in rotation you might have 0 to lets say 600 pounds on all the different lobes and it is only 90 degrees to the shaft at max lift. On the side of the ramp it would be causing twist
This is an old picture of my .680/.714 billet steel SBC I think it is a .960 base circle for rod clearance
This one on the right is another of my own custom design from the lobe profile catalog. Replacing the XE off the shelf on the left
Last edited by gkull; Dec 15, 2015 at 01:53 PM.
Le Mans Master
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Is your cam made out of spring steel so it can withstand 1000's of flexing per minute? A cam is supported every few inches and is generally a steel shaft @.900 inch minimum diameter.
From an engineering stand point do you really believe that big of steel rod cam shaft would flex before some little hollow tube push rod?
prove it to me! support a cam shaft on some steel blocks at each cam bearing on a press and apply 600 pounds to a lobe and let me see how much a dial indicator reads?
From an engineering stand point do you really believe that big of steel rod cam shaft would flex before some little hollow tube push rod?
prove it to me! support a cam shaft on some steel blocks at each cam bearing on a press and apply 600 pounds to a lobe and let me see how much a dial indicator reads?
Le Mans Master
Joined: Apr 2015
Posts: 9,428
Likes: 124
I really don't believe that the cam shaft can bend during it's rotation. The push rod is tiny in comparison and it would bend.
You think about the V-8 design. The lifters are coming in at a V at any give place in rotation you might have 0 to lets say 600 pounds on all the different lobes and it is only 90 degrees to the shaft at max lift. On the side of the ramp it would be causing twist
This is an old picture of my .680/.714 billet steel SBC I think it is a .960 base circle for rod clearance
This one on the right is another of my own custom design from the lobe profile catalog. Replacing the XE off the shelf on the left
You think about the V-8 design. The lifters are coming in at a V at any give place in rotation you might have 0 to lets say 600 pounds on all the different lobes and it is only 90 degrees to the shaft at max lift. On the side of the ramp it would be causing twist
This is an old picture of my .680/.714 billet steel SBC I think it is a .960 base circle for rod clearance
This one on the right is another of my own custom design from the lobe profile catalog. Replacing the XE off the shelf on the left
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
What are you running that requires 1200 pounds open pressure? That is a little far removed from a small block with 5/16th push rods and maybe 600 pounds open. I use the CC high tech .105 wall
I've just never experienced a lash change after setting and then rotating the motor
I've just never experienced a lash change after setting and then rotating the motor