Turbo Cam

[38fury]

I've got a spare 3.8 long block and i'm looking to rebuild and turbo it over the summer. I've been looking into the intense turbo cams and i'm perplexed because they are a reverse split duration, (for those who don't know they favor the intake side) and i've always been told that you would want to favor the exhaust side more (esp with f/i) does anyone have one of these cams, or know more about it cause this proj can't move ahead until i pick a cam that will work.
here's the specs
CAM-901 - INTENSE™ Stage 1X Turbo Cam, duration @ .050": 211º/204º, lobe lifts: .323"/.320", valve lifts with 1.60:1 rocker arms: .516"/.513", lobe separation angle: 116º, intake centerline: 110º

[98Camaro3.8]

A turbo cam usually has a shorter duration on the exhaust side to keep the exhaust gases moving quickly so that the turbo will spin faster.

A blower cam is kind of the opposite, since there's no need to turn the turbo, you just want to get everything out of the cylinder.

[asdf1234]

I have an Intense Racing Stage 2 Turbo cam for sale if you're interested [img]smile.gif[/img]

[Turbo Kyle]

Im with Matt. That Turbo cam sounds like it will work well.

[38fury]

Ok, i wasn't sure the way i saw it it would kill efficiency, with the turbo pushing more air in then the engine can push out, but the way you said it makes sense. I didn't even think about the velocity. And i don't want to get into the valvetrain too much, sorry asdf1234, but i'm looking for the stage 1. Yeah i'm looking to do a simple t3/4 with about .58 a/r i've been looking at some forged alum pistons that'll drop my compression to about 8.0:1. I plan on running about 12 psi with that get hptuners and some alcohol injection and hopefuly run about 15 with all that.

[Turbo V6 Camaro]

what matt siad

plus with a turbo you have 2x the amount of back PSI , if you leave the exuast open to long the gas would push back into the chamber/intake and make things hell for the motor

[nocutt]

You can use a reverse split or a single pattern. Turbo cams especially for underdeveloped territory is a can of worms...the rule of thumb, is whatever cam you pick should have overlap closer to "0" (less overlap) as possible. And dependent on if you will be using turbo headers or log-style manifolds you can then take the single patterns or reverse splits into account...
my opinion is if you are going to be runnign less than 14psi especially with the xhaust scroll you are suggesting I won't even bother with a "turbo cam"... 0.5X A/R does NOT want to breathe, however it will be a torque monster coupled with a 58mm+ comp. wheel.
good luck...

[Turbo V6 Camaro]

i forget ho much overlap my cam has...it's not alot

[Turbo Kyle]

Whats the Overlap on the stock cam?

[nocutt]

Originally posted by Turbo Kyle:
Whats the Overlap on the stock cam?

I forget the stock cam specs but it is a lot...although since most ppl use looser scrolls = more power, few ever notice...

[98Camaro3.8]

Originally posted by Turbo Kyle:
Whats the Overlap on the stock cam?

If I calculated it right, there's -44° of overlap.

That's using duration at .05"...maybe I need to use actual duration?

[nocutt]

The stock cam 3800 cannot have a negative overlap...post the cams specs if you have it...

[98Camaro3.8]

http://engine.firebirdv6.com/cam.html

[Turbo V6 Camaro]

Duration I/E Lift I/E LS IC Rocker Ratio Valve Lift I/E
Stock GM 182 190 .258 .255 115 111 1.6 .413 .408

[nocutt]

98 camaro 3.8 YOU ARE absolutely right with those values cams specs are

Duration I/E Lift I/E LS IC Rocker Ratio Valve Lift I/E
Stock GM 182 190 .258 .255 115 111 1.6 .413 .408
giving theoretical valve timings of...

Ivo = -20 atdc
Ivc = -18 bbdc
Ecl = 119
Evc = -24 btdc
Evo = -14 abdc
Overlap = -44

I crunch the number with formulas so someone go over them with desktop dyno or something...

The cam specs I had were completely different from those posted...I apologise, now which is correct???? can anyone corraborate this specs...I find it odd that a OE will grind negative overlap into a stock cam with Sh!tty heads???
If the specs are correct at the advertized durations it will potentially mean that this stock cam is turbo favored...unfortunately more lift is definately needed...

[ April 22, 2005, 12:13 PM: Message edited by: nocutt ]