Any videos of how to set up indicators to check a Hemi cam. I understand a non Hemi is checked off pushrods. They say a Hemi is checked off the retainers but i don't understand exactly where to put the indicator. Are there any videos showing this. I think ARC shows how to do a non hemi.
Hemi duration check
- Thread starter bullerman
- Start date
DynoDon
Moderator
Checking off the retainers will not give you an accurate reading of the cam. It needs to be done at the pushrod. Stuff a paper towel around the area you are going to remove the c clip from the pin that holds the rocker on the shaft. This is so if you loose it, it won’t go in the engine. I Use a pencil magnet and keep it attached to it during removal and replacement. Line up the pushrod as close as possible to the other one in reference to the position it should be in when running after you get your dial indicator set on it. If you aren’t in alignment as it runs you will not get a correct reading
I bought a bracket for the Hemi off ebay. When you bolt it to the head with the two top bolt valve cover bolts in indicators are on the rocker arm itself. I had read the hemi measurement is taken off the retainer. A video on you tube by arc shows it taken off the push rods. I don't think he said if it was a hemi or non hemi.
The bracket i bought is a little fiberglass bracket that hold two indicators. Any body explain or have a picture.
The bracket i bought is a little fiberglass bracket that hold two indicators. Any body explain or have a picture.
Just watched the arc video again. He is checking center line on a non hemi. He shows the rocker arm for it. He says he does his checking off the push rod. I believe he's says on a hemi you check it off the retainer but i am not positive. He says you don't get movement of the rocker like a non hemi.
DynoDon
Moderator
The reason people check at the retainer on the hemi is because removing the rocker arm is problematic. If you don’t know what you’re doing. The ideal way to check, your cam is off the push rod. If you’re going to check it off the retainer make sure you have all the rocker arm lash removed. It cannot have any lash or you won’t get an accurate reading.
I made a mount and used my indicator with the base. I pulled the rocker arm off and used the push rod. I got the center lone on the intake valve off as 1 degree. Could be me though.
One question. The cam says use .003 thousandths of lash. Are the opening and closing of the valves on the cam card sheet figured with three thousandths lash. That's what it looked like. Going to check the exhaust valve center line and opening and closing tomorrow.
One question. The cam says use .003 thousandths of lash. Are the opening and closing of the valves on the cam card sheet figured with three thousandths lash. That's what it looked like. Going to check the exhaust valve center line and opening and closing tomorrow.
The center line will not change because of lash.
Lash is set at zero at room temperatures because that will open up to .003 or more as the engine warms up.
Because the aluminum block and head expand much more than the steel pushrod. Lash could be even tighter, but engine start problems occur when cold.
If you wish to move centerline, you must change the relationship between the crank and the cam.
Read that to mean move the gear on the crank.
Lash is set at zero at room temperatures because that will open up to .003 or more as the engine warms up.
Because the aluminum block and head expand much more than the steel pushrod. Lash could be even tighter, but engine start problems occur when cold.
If you wish to move centerline, you must change the relationship between the crank and the cam.
Read that to mean move the gear on the crank.
Ideally, to check cam centerlines, the dial indicator should extend to reach the pushrod cup in the lifter. The indicator rod should run exactly the same path of motion as the lifter.
Centerline should be read as a set distance from max lift. Industry standard I believe to be .050 inch.
The reason this is important is because cam lobes can be (most likely are) asymmetrical. So any deviation from this number can skew the centerline slightly.
If you then measure from the pushrod at the original angle, you can then see the phenomena of cosine error.
The only way lash can affect centerline is if your reading is based off zero lift (valves closed) at the retainer.
Which is just an indicator of the combined errors of the system including the asymmetric cam lobe.
If you measure from the retainer at .050 cam lift, the numbers will be exactly the same. If the rockers have any ratio to them, this will skew the numbers from not being the same position on the asymmetric cam lobe.
Of course, for tech, you must use the same method as the tech man.
Centerline should be read as a set distance from max lift. Industry standard I believe to be .050 inch.
The reason this is important is because cam lobes can be (most likely are) asymmetrical. So any deviation from this number can skew the centerline slightly.
If you then measure from the pushrod at the original angle, you can then see the phenomena of cosine error.
The only way lash can affect centerline is if your reading is based off zero lift (valves closed) at the retainer.
Which is just an indicator of the combined errors of the system including the asymmetric cam lobe.
If you measure from the retainer at .050 cam lift, the numbers will be exactly the same. If the rockers have any ratio to them, this will skew the numbers from not being the same position on the asymmetric cam lobe.
Of course, for tech, you must use the same method as the tech man.
Is that one of the things motor builders do. I assume you will get the best performance if you get the numbers the cam card says. Get the centerline and opening and closing of the valves perfect? I am not a motor builder by any means. I used to build my own flatheads. I always tried to get the opening as close as I could and as I remember the closing fell where it fell.
Depends on how your engine theory uses the timing of valve events. And the track you are running.
A stop and go track will like more bottom end, so advance the cam slightly.
Momentum tracks favor top end, so retard cam slightly.
If that fits the rest of your setup.
Never heard of Rix Tools. They have some nice stuff.
I just made a make shift tool to check lift on the cam. It worked ok but kind of hard to set up. Thanks for the information.
Been watching the ARC video on cam timing. It says you try and get the numbers that are on the cam card to get the best possible performance. Center lines and duration to get the best performance. He says that's why the stock motors cost so much because of the time it takes to do this.
I'm not a motor builder but I do my motors. My question is if the centerlines are perfect on the intake and exhaust will the duration numbers be right?
I don't have a way of changing centerline numbers or anything.
Just wondering if I put my new cam in and get the centerline and duration numbers and send it to Dyno cams.
Can they grind a cam to the right numbers to fit my motor with the right center line and duration numbers. I probably wouldn't ever do it but I am just asking. I need to buy me a indicator bracket for this non hemi. The way I do it works but would be better with a bracket.
I'm not a motor builder but I do my motors. My question is if the centerlines are perfect on the intake and exhaust will the duration numbers be right?
I don't have a way of changing centerline numbers or anything.
Just wondering if I put my new cam in and get the centerline and duration numbers and send it to Dyno cams.
Can they grind a cam to the right numbers to fit my motor with the right center line and duration numbers. I probably wouldn't ever do it but I am just asking. I need to buy me a indicator bracket for this non hemi. The way I do it works but would be better with a bracket.