Max Valve Lift Specification???
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Max Valve Lift Specification???
Help me understand what the "max valve lift" specification means.
I though "max valve lift" was calculated by taking the max cam lift and then multiply it by the rocker ratio; for example, a cam with a lobe lift of 0.600 x 1.7 = 1.02 of valve lift.
But looking at valve spring charts, I see "max valve lift" numbers range of 0.500 to 0.850.
What is it I am not understanding?
Sure appreciate some help.
I though "max valve lift" was calculated by taking the max cam lift and then multiply it by the rocker ratio; for example, a cam with a lobe lift of 0.600 x 1.7 = 1.02 of valve lift.
But looking at valve spring charts, I see "max valve lift" numbers range of 0.500 to 0.850.
What is it I am not understanding?
Sure appreciate some help.
Tech Contributor
Joined: Jan 2007
Posts: 19,465
Likes: 1,167
From: Dyer, IN
Help me understand what the "max valve lift" specification means.
I though "max valve lift" was calculated by taking the max cam lift and then multiply it by the rocker ratio; for example, a cam with a lobe lift of 0.600 x 1.7 = 1.02 of valve lift.
But looking at valve spring charts, I see "max valve lift" numbers range of 0.500 to 0.850.
What is it I am not understanding?
Sure appreciate some help.
I though "max valve lift" was calculated by taking the max cam lift and then multiply it by the rocker ratio; for example, a cam with a lobe lift of 0.600 x 1.7 = 1.02 of valve lift.
But looking at valve spring charts, I see "max valve lift" numbers range of 0.500 to 0.850.
What is it I am not understanding?
Sure appreciate some help.
https://www.corvetteforum.com/forums...-question.html
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Well....sort of.
In my first post, my question was what is the suggested margin between lobe lift and valve lift numbers be.
In doing more research, I am now confused as to just what exactly the valve lift number means on spring specifications.....hence the second post.
In my first post, my question was what is the suggested margin between lobe lift and valve lift numbers be.
In doing more research, I am now confused as to just what exactly the valve lift number means on spring specifications.....hence the second post.
Advanced
Joined: Apr 2009
Posts: 51
Likes: 14
From: AR
@LannyL81 I'm going to go out on a limb and say you have confused valve lift and lobe lift. In your example above you used .600 as lobe lift, in your other thread you stated the cam you have has a lift of .600, we have to assume this is valve lift. So, your cam with .600 valve lift is going to have a lobe lift somewhere around .353. .353 x 1.7 = .6001.
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
@LannyL81 I'm going to go out on a limb and say you have confused valve lift and lobe lift. In your example above you used .600 as lobe lift, in your other thread you stated the cam you have has a lift of .600, we have to assume this is valve lift. So, your cam with .600 valve lift is going to have a lobe lift somewhere around .353. .353 x 1.7 = .6001.
I will go back and check my postings to ensure I did not confuse the two terms.....which is a possibility.
Race Director
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Le Mans Master
Joined: Jul 2010
Posts: 6,013
Likes: 726
There's as much chance your cam has .600" lobe lift as there is me winning the lotto, and I dont play it!! I'd bet my Corvette on that. A .600" lobe lift cam probably wouldn't even be able to be inserted into the block. .600÷1.7 rocker ratio, as stated above, equals approximately. 353" lobe lift. .353"×1.7=.600" valve lift. It is all really that simple......
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
BINGO!!!!
I had read some incorrect information in that a diagram was showing a cam lobe with the height of the cam lobe labeled with the valve lift number. That is what began my confusion.
When I read your second response the ole light bulb went off and showed me through my confusion. I had been all through cam and valve specs a good 20+ yrs ago and just this week was trying to remember what I have forgotten.
Thank you for the replies......
But how is a valve spring's max valve lift determined?
I thought it was installed height - coil bind height - (0.050 to 0.100), but this is not real close to the stated numbers of various valve spring charts.
What have I forgotten here?
I had read some incorrect information in that a diagram was showing a cam lobe with the height of the cam lobe labeled with the valve lift number. That is what began my confusion.
When I read your second response the ole light bulb went off and showed me through my confusion. I had been all through cam and valve specs a good 20+ yrs ago and just this week was trying to remember what I have forgotten.
Thank you for the replies......
But how is a valve spring's max valve lift determined?
I thought it was installed height - coil bind height - (0.050 to 0.100), but this is not real close to the stated numbers of various valve spring charts.
What have I forgotten here?
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Le Mans Master
Joined: Jul 2010
Posts: 6,013
Likes: 726
BINGO!!!!
I had read some incorrect information in that a diagram was showing a cam lobe with the height of the cam lobe labeled with the valve lift number. That is what began my confusion.
When I read your second response the ole light bulb went off and showed me through my confusion. I had been all through cam and valve specs a good 20+ yrs ago and just this week was trying to remember what I have forgotten.
Thank you for the replies......
But how is a valve spring's max valve lift determined?
I thought it was installed height - coil bind height - (0.050 to 0.100), but this is not real close to the stated numbers of various valve spring charts.
What have I forgotten here?
I had read some incorrect information in that a diagram was showing a cam lobe with the height of the cam lobe labeled with the valve lift number. That is what began my confusion.
When I read your second response the ole light bulb went off and showed me through my confusion. I had been all through cam and valve specs a good 20+ yrs ago and just this week was trying to remember what I have forgotten.
Thank you for the replies......
But how is a valve spring's max valve lift determined?
I thought it was installed height - coil bind height - (0.050 to 0.100), but this is not real close to the stated numbers of various valve spring charts.
What have I forgotten here?
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Trying to determine what valve springs I have is what I have been doing.
The information on the springs is rather limited: OD, max valve lift, dual, lock style.
I wanted to know what PAC springs they are, looked-up PAC springs to see which springs matched the specs I have and nothing matched 100%, so I was trying to calculate max valve lift to see if the specs I was given had an error.
Could not get the max valve lift numbers listed in the specs using installed height, coil bind height and then the (0.50 to 0.100) margin.
Got close but not exact.
I have assumed that the springs on the heads were made by PAC for AFR only: a modified PAC 1904 with reduced max valve lift, or a modified PAC 1914 wound tighter.
I think I would have been find using the cam I had received with 0.600 valve lift with these springs (max valve lift 0.600) due to my driving style, but went on the safe side and exchanged for a 0.550 lift cam.
Thanks once again for helping me get the confusion cleared-up.
The information on the springs is rather limited: OD, max valve lift, dual, lock style.
I wanted to know what PAC springs they are, looked-up PAC springs to see which springs matched the specs I have and nothing matched 100%, so I was trying to calculate max valve lift to see if the specs I was given had an error.
Could not get the max valve lift numbers listed in the specs using installed height, coil bind height and then the (0.50 to 0.100) margin.
Got close but not exact.
I have assumed that the springs on the heads were made by PAC for AFR only: a modified PAC 1904 with reduced max valve lift, or a modified PAC 1914 wound tighter.
I think I would have been find using the cam I had received with 0.600 valve lift with these springs (max valve lift 0.600) due to my driving style, but went on the safe side and exchanged for a 0.550 lift cam.
Thanks once again for helping me get the confusion cleared-up.
Le Mans Master
Joined: Jul 2010
Posts: 6,013
Likes: 726
Trying to determine what valve springs I have is what I have been doing.
The information on the springs is rather limited: OD, max valve lift, dual, lock style.
I wanted to know what PAC springs they are, looked-up PAC springs to see which springs matched the specs I have and nothing matched 100%, so I was trying to calculate max valve lift to see if the specs I was given had an error.
Could not get the max valve lift numbers listed in the specs using installed height, coil bind height and then the (0.50 to 0.100) margin.
Got close but not exact.
I have assumed that the springs on the heads were made by PAC for AFR only: a modified PAC 1904 with reduced max valve lift, or a modified PAC 1914 wound tighter.
I think I would have been find using the cam I had received with 0.600 valve lift with these springs (max valve lift 0.600) due to my driving style, but went on the safe side and exchanged for a 0.550 lift cam.
Thanks once again for helping me get the confusion cleared-up.
The information on the springs is rather limited: OD, max valve lift, dual, lock style.
I wanted to know what PAC springs they are, looked-up PAC springs to see which springs matched the specs I have and nothing matched 100%, so I was trying to calculate max valve lift to see if the specs I was given had an error.
Could not get the max valve lift numbers listed in the specs using installed height, coil bind height and then the (0.50 to 0.100) margin.
Got close but not exact.
I have assumed that the springs on the heads were made by PAC for AFR only: a modified PAC 1904 with reduced max valve lift, or a modified PAC 1914 wound tighter.
I think I would have been find using the cam I had received with 0.600 valve lift with these springs (max valve lift 0.600) due to my driving style, but went on the safe side and exchanged for a 0.550 lift cam.
Thanks once again for helping me get the confusion cleared-up.