glastornjet73

I am new to ls stuff i am building an iron block 5.7 with a 5.3 block and will be running on alky with n2o in a jet drag boat and advice on cam choice would be awsome will be turning around 6500 or soo and will primaraly be a race peice but i still want it to run decent off the n2o because i will be running it on the lake from time to time i was thinking about the thunder racing t-rex cam but there is a great deal on a texas speed ls7r cam on my local craigslist would that be a decent choice or not because the engine is soo small? Thanks

speedtigger

iTrader: (16)

Will this thing be running at high RPM for long periods of time? or just short spurts like automotive drag racing?

glastornjet73

18-20 sec probly at the most maybe a touch longer when playing on the lake but that would be without n2o im shooting to run 11's but there is a 175' approach to the course and i will probly have to leave about 6-7 sec before the race would actually "start" why?

speedtigger

iTrader: (16)

How much RPM will you be running?

glastornjet73

6500-6800 or soo

glastornjet73

On a 5.7 would ls3 heads make more power than 5.3 heads or would i be going backwards because of the small bore 5.7?

speedtigger

iTrader: (16)

The valves won't clear the bore on a 5.3. In my opinion, the most cost effective solution is CNC ported factory 5.3 heads. The smaller combustion chambers maintain the compression and they flow as much as a factory LS3 head. As for the cam, are you willing to flycut the pistons?

glastornjet73

Gotcha ok well im deff not gonna get the heads cnc ported but i will probly clean them up a little myself... And if i have to i will fly cut them

speedtigger

iTrader: (16)

What is your full RPM range? How quickly do you get up above 5500 RPM?

glastornjet73

Thats really not an issue with a jet boat they will turn full rpm without the boat even moving but there is a 175' between the holding rope and start beams and i will probly have to leave at about 7 seconds before the race starts so i would like to be to full rpm and and on the dope before it cross the start beam

speedtigger

iTrader: (16)

To optimize for what you are doing, the ideal cam for what you are doing probably won't look much like stuff most guys on this site use. And, since you are using nitrous and it sounds pretty much like you will be going straight to your target RPM range on launch, it does not sound like you will not be so concerned with midrange torque. I am thinking you will want a good amount of duration. How much nitrous do you push?

glastornjet73

I dont really know exactly how much nitrous i will need i dont think it will take much to get me to run my number 150 tops but i am not going to leave on the dope i am going to run a delay and use/adjust it to make the boat run the number add or remove delay weather it is running to fast or slow.... Rather than playing with nitrous jets constantly....