PAC 1518 springs with MAST VVT SS cam
08-03-2013, 03:21 AM
#1
PAC 1518 springs with MAST VVT SS cam I upgraded my rockers to 1.8 YT and I am going to run them with the MAST VVT SS cam it has a .588/.607 lift w/1.7 rockers. With the 1.8 rockers the lift is .623/.643. The PAC 1518 springs are good up to .650 lift. I am damn close to maxnig out on the exhaust, will that be a problem? I will also be running about 8-10 psi of boost.
08-03-2013, 03:30 AM
#2
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I was looking at doing similar already have 1.8 YT's from my original LS2 cam and was thinking of fitting them to my current Comp 212/218 LSA115 ,557/.563 and have patriot gold duals good for .650.
But everybody bar 1 person have all said that although the overall new lift height is ok the actual lobe lift is too aggresive (Like most modern LS cams) to run 1.8's and could cause harmful lifter/cam harmonics.
But everybody bar 1 person have all said that although the overall new lift height is ok the actual lobe lift is too aggresive (Like most modern LS cams) to run 1.8's and could cause harmful lifter/cam harmonics.
08-03-2013, 04:02 PM
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Unless you've already bought the 1518's you might look at the 1519's... a bit more pressure and therefore perhaps a bit more leeway on install height. I note the PAC site lists both as .625 max lift but the bind on the 1519's is .040 lower. Probably best to contact PAC and see what they recommend.
08-03-2013, 05:29 PM
#4
I dont have any PAC springs yet, I have a brand new set of COMP 918s and a brand new set of COMP 921s both sets with Ti retainers. I dont think I can run the dual springs because of the VVT. I know that COMP had their problems, but are supposed to be straightened out. HOWEVER! why chance it over 200.00? What ever springs I dont use will just get sold.
08-07-2013, 06:37 PM
#6
I would contact Mast on the ramp rates of their cams, the higher ratio rockers aren't helping out valvetrain stability and neither is boost. The problem is the limiting factor of spring pressure based on the VVT lifters, as I'm sure you know a single valve spring failing is not pretty.
08-08-2013, 05:10 AM
#7
I talked with MAST yesterday about the springs. The tech I talked to told me that in previous testing that a double spring was too much for the VVT phaser to handle, and it stops the VVT from proper operation. The beehive spring was the best and only spring for this VVT application. That they currently have several setups out there running strong with a 1.8 rocker, VVT and their cam with no problems. The PSI and PAC springs are the only way to go, and that the failure rates of the Comp springs are not worth the risk. I will be using a PSI beehive spring on this motor. I will of course post the results of any testing that happens.
