Total valve lift has nothing to do with possible PtV clearance issues. Stage2 cam uses an X-303 intake lobe so clearance on the intake side shouldn't be a problem even with stock heads based on what I have experienced. Exhaust clearance needs to be checked. Checking for PtV and correcting if required, is a procedure that needs to be done anytime you upgrade the camshaft anyway. LUK
Total valve lift has nothing to do with possible PtV clearance issues. Stage2 cam uses an X-303 intake lobe so clearance on the intake side shouldn't be a problem even with stock heads based on what I have experienced. Exhaust clearance needs to be checked. Checking for PtV and correcting if required, is a procedure that needs to be done anytime you upgrade the camshaft anyway. LUK
ok well we just installed a trickflow stage 2 cam with 1.6rr in the car and had no problems but with the 1.7rr i am not sure if we can do that with no ptv clearance problems. i am not sure of the formula that you can use to check it and not sure what difference the 1.7 vs the 1.6
Total valve lift has nothing to do with possible PtV clearance issues. Stage2 cam uses an X-303 intake lobe so clearance on the intake side shouldn't be a problem even with stock heads based on what I have experienced. Exhaust clearance needs to be checked. Checking for PtV and correcting if required, is a procedure that needs to be done anytime you upgrade the camshaft anyway. LUK
Joel, can you explain that to me? I do not understand how lift has nothing to do with clearance... I understand the overlap period is the crucial point for clearance issues but how does a .600" lift cam not come closer than a .300" lift cam?
The only reason I didn't buy the TFS Stage 2 cam is I thought it was too much lift for my flat tops, I would still like to get one myself, if you don't have to flycut the pistons.
ok well we just installed a trickflow stage 2 cam with 1.6rr in the car and had no problems but with the 1.7rr i am not sure if we can do that with no ptv clearance problems. i am not sure of the formula that you can use to check it and not sure what difference the 1.7 vs the 1.6
There is no formula. You need to measure the "partial" valve lift of both valves during the 20° BTDC - 20° ATDC exhaust-to-intake cycle changeover phase, and the gap between them and the piston within that window.
The following graph shows the difference between 1.6 and 1.72 rockers and the X-303 camshaft degreed + the configuration of that setup (piston deck, HG thickness, valve position height in the chamber, angles, etc) ONLY for comparison purposes....... not to be inferred as the case for all the possibilities out there.
As you can see, valve lift is below .080" on the intake valve when the piston and intake valve get very close.
Joel, can you explain that to me? I do not understand how lift has nothing to do with clearance... I understand the overlap period is the crucial point for clearance issues but how does a .600" lift cam not come closer than a .300" lift cam?
The only reason I didn't buy the TFS Stage 2 cam is I thought it was too much lift for my flat tops, I would still like to get one myself, if you don't have to flycut the pistons.
Check the graph posted above, if you have a .600" lift cam with the intake valve open event @.050" tappet lift happening at 5° BTDC (.080" valve lift with 1.6 rocker and .086" valve lift with 1.72 rocker) will have the same lift with a .300" lift cam that opens the valve @.050" tappet lift at 5° BTDC.
You also have to keep in mind that the opening rate of a lobe is not 100% linear. The opening rate may increase past the duration @.100" tappet lift.