Cam selection. What ramp rate
01-26-2005, 08:31 PM
#1
Cam selection. What ramp rate O.k. This is the cam I am going to try for my setup.
STS GT-67 with FMIC
LQ9 truck heads flowing 306cfm @ .600
346 c.i.
LS2 intake
1.75 roller rockers
Crane Dual springs
Stock sized Thunder chromoly push rods
230/222 .595/.595 on a 116lsa
question is what kind of ramp rate should be used???
I will also be using some N20 as a kick in the pants. 50 shot to begin with.
It will be a track car with a 4.30 gear 28" tall tire and will spin to 6800 rpm with a projected race weight of 3200lbs.
I tried to include all details.
STS GT-67 with FMIC
LQ9 truck heads flowing 306cfm @ .600
346 c.i.
LS2 intake
1.75 roller rockers
Crane Dual springs
Stock sized Thunder chromoly push rods
230/222 .595/.595 on a 116lsa
question is what kind of ramp rate should be used???
I will also be using some N20 as a kick in the pants. 50 shot to begin with.
It will be a track car with a 4.30 gear 28" tall tire and will spin to 6800 rpm with a projected race weight of 3200lbs.
I tried to include all details.
01-27-2005, 10:06 AM
#4
I woudlnt go with a super aggressive exhaust lobe. Something pretty slow/controllable on/off the seat, and I wouldnt run it real hard over the nose, but healthy in the middle. You dont want to have to open it real early either as it will cut into the power stroke more then on a high comp NA car.
Something around 0 overlap and close exhaust open intake around TDC is what most seem to prefer in a street car. Also intake lobe I wouldnt be too concerned about running a real aggresive over the nose lobe, it may get you another 10 hp, but boost can easily offset that, and if it comes at the expense of valvetrain control its not worth it
Something around 0 overlap and close exhaust open intake around TDC is what most seem to prefer in a street car. Also intake lobe I wouldnt be too concerned about running a real aggresive over the nose lobe, it may get you another 10 hp, but boost can easily offset that, and if it comes at the expense of valvetrain control its not worth it
01-27-2005, 10:33 AM
#5
LS1Tech Co-Founder
iTrader: (34)
Your best off contacting a sponsor with a lot of cam experience like:
Jim @ LS1Speed
or
Kurt @ Wheel to Wheel
When you go with aggressive lobes you need more spring pressure and better rockers, you might want to look at what valve springs you can fit as well.
I say go middle of the road.
Jim @ LS1Speed
or
Kurt @ Wheel to Wheel
When you go with aggressive lobes you need more spring pressure and better rockers, you might want to look at what valve springs you can fit as well.
I say go middle of the road.
01-27-2005, 07:50 PM
#7
Well I have the Comp Cams Pro Magnum 1.75's with the Crane Dual spring. I understand them to be good to .650 lift. I was reading some stuff on Turbo Cams and some articles spoke about wanting the total lift being 10% higher then what the head flows at .600. I am trying to understand all of this F/I stuff as I was a N20 guy before.
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01-27-2005, 10:15 PM
#8
generally you want alittle more lift then where the head stops flowing an appreciable amount of air. if the head goes turbulent at some point though, you would want it under that.
Dont really have to worry about it as critically with a froced induction motor. Are your cranes shimmed and if so to what pressure closed? they are a litle soft on the seat at factory height. This compounded with the pressure exerted on the intake and exhaust valves under boost and healthy backpressure in the exhaust will make it a little more likely to float the valves
Dont really have to worry about it as critically with a froced induction motor. Are your cranes shimmed and if so to what pressure closed? they are a litle soft on the seat at factory height. This compounded with the pressure exerted on the intake and exhaust valves under boost and healthy backpressure in the exhaust will make it a little more likely to float the valves
