na svt
10-01-2011, 09:05 PM
The lobe centers at which the cams are installed will make or break the powerband of an engine, especially on these heavy, auto trans cars. Also, the stock lobe centers and the lobe centers of all aftermarket 4v cams are terrible for Marauders (both FI and n/a).
This is to warn those that may be paying for someone to install cams at non-stock lobe centers or lobe centers different than what is on the cam card.
I had a discussion with a well very known shop the other day about the lobe centers (LCs) I recommended to a member here. The LCs I recommended were 106/110 and the shop didn't know if they had to advance or retard the cams to get there, unbelieveable! First, if you're paying someone to install and degree cams they better know how the advancing or retarding of the intake and exhaust cams affects the lobe centers...especially when they are charging darn near $100 an hour for labor. Anyway, I told them the as-ground lobe centers for teh cams they were installing and also told them how much to retard the exhaust cams and also how far to advance the intake cams. They would have know this had they looked at the cam card which was in their possession. However, the cams never fall into the LCs on the cam card, so...
The problem with aftermarket cams is that the LCs are rarely where they should be and the only way to find where they are is to check them with a degree wheel. You cannot advance or retard the cams without first knowing the starting lobe centers.
My point of this thread is this, I believe that most shops just advancing or retarding the cams without knowing where they are to begin with. For example, if the cam card says 112/116 and you want them at 108/114, they're just installing the cams with the adjustable gears in the position to retard the exhaust cams 2 degrees and the advancing the intake cams 4 degrees and calling it a day. The problem with this is that retarding the exhaust cams 2 degrees also retards the intake cams 2 degrees to 114. So now the intake cams have to be advanced 6 degrees. To make the problem worse is that the LSA on the pass side is tighter due to the orientation of the secondary tensioner but that takes a lot more detailed explanation.
So, to all of you having cams installed and degreed, make sure the shop knows what the hell they're doing before throwing any cash at them.
This is to warn those that may be paying for someone to install cams at non-stock lobe centers or lobe centers different than what is on the cam card.
I had a discussion with a well very known shop the other day about the lobe centers (LCs) I recommended to a member here. The LCs I recommended were 106/110 and the shop didn't know if they had to advance or retard the cams to get there, unbelieveable! First, if you're paying someone to install and degree cams they better know how the advancing or retarding of the intake and exhaust cams affects the lobe centers...especially when they are charging darn near $100 an hour for labor. Anyway, I told them the as-ground lobe centers for teh cams they were installing and also told them how much to retard the exhaust cams and also how far to advance the intake cams. They would have know this had they looked at the cam card which was in their possession. However, the cams never fall into the LCs on the cam card, so...
The problem with aftermarket cams is that the LCs are rarely where they should be and the only way to find where they are is to check them with a degree wheel. You cannot advance or retard the cams without first knowing the starting lobe centers.
My point of this thread is this, I believe that most shops just advancing or retarding the cams without knowing where they are to begin with. For example, if the cam card says 112/116 and you want them at 108/114, they're just installing the cams with the adjustable gears in the position to retard the exhaust cams 2 degrees and the advancing the intake cams 4 degrees and calling it a day. The problem with this is that retarding the exhaust cams 2 degrees also retards the intake cams 2 degrees to 114. So now the intake cams have to be advanced 6 degrees. To make the problem worse is that the LSA on the pass side is tighter due to the orientation of the secondary tensioner but that takes a lot more detailed explanation.
So, to all of you having cams installed and degreed, make sure the shop knows what the hell they're doing before throwing any cash at them.