Mark Campbell

FWIW, using the Crane spring seat locator #144460-16 causes the installed height on most LS1's to be 1.760" (it is .040" thick) and results in 126# of seat pressure.

mrr23

iTrader: (3)

using a bigger cam, just moves the entire valvetrain(lifter,pushrod, rocker, and valve) faster. using a smaller cam with higher ratio rockers only moves the valve faster. that way, the valve spring only needs to control the valve speed. and like mark campbell said, using less seat pressure to boot. less pounding on the valve seats is another benefit of that as well. the motor doesn't care what happens at the cam. it only cares about what happens at the valve. the cam is just one way of moving the valve.

why run a bigger cam, when a smaller cam with the right parts will do better??? here's a prime example. comp cams 220/224 .581/.581 115 LSA with the vinci/crane 1.7 accelerated lift rockers vs the vinci 055 216/224 .551/.551 (1.7) 113 LSA with vinci/crane 1.8 accelerated lift rockers (bringing lift to .589/.589)

mrr23

iTrader: (3)

the bad thing is most people don't take the seat locator into consideration when measuring spring height either. they measure from the spring pocket to the bottom of the retainer. then tehy go hmmm, i need .030" shim. then, they throw the shim AND the locator on and leave it at that. then wonder why the spring failure. they needed .030" and they put it at .070".

mrr23

iTrader: (3)

here's my dyno of swapping from the stock rockers to the vinci/crane 1.8 accelerated lift rockers and dual springs. and this on stock tune as well.

dyno 9 before
dyno 11 500 miles later
dyno 14 10 months later

mrr23

iTrader: (3)

http://stealthram.com/reddogplan.htm here's the CHP article on the 5.3L truck they did the vinci/crane 1.8 accelerated lift rockers and springs on as well. now the article only pointed out the peak differences of 20 rwhp and 9.6 rwtq. but look at 3300 rpms in the torque tables. right there was a 23.4 lbs-ft of torque gain. and this was on a 5.3L motor with stock cam and heads to boot.

mrr23

iTrader: (3)

some more nifty reading right off vinci's site on the tech and tuning page. http://www.vincihighperformance.com/...20PAGE%20.HTML talks about how the rockers work. titled, More On Why Our Unique New “Quick-Liftä” Rocker Arm Geometry Makes More HP!

XTrooper

And this is usually only necessary with the '97 and '98 cars with perimeter bolts. The Crane 1.80s fit under the valve covers of my 2000 with no modifications whatsoever.