Does anyone know about this truck?

[04silveradomykk]

aROpyi6xgGs

What kind of 4.3L cam gives a idle lope like that but can still be computer controled?

Somehow this dude got a cam to work in his 4.3L LU3 GMT800 fullsize.

Does it sound like one of those cams that you have to do head work to accomodate the lift?

I'm thinking of throwing a bumpstick in my 4.3L, now that I have HP Tuners to write the tune.

I've been looking at the Crane Cams 1439811. Grind # HR-204/286-2S-12. It doesn't look like the vortec heads & valvetrain need any work to accomodate this cam, but it sure won't have the idle from the vid. I'm open to any input, what cam are you running in your Balance Shaft Vortec 4.3L?

Duration at 050 inch Lift:204 int./214 exh.
Valve Lift with Factory Rocker Arm Ratio:0.429 int./0.430 exh.
liftLobe Separation (degrees):112

http://store.summitracing.com/partdetail.asp?part=CRN%2D1439811&autoview=sku (http://store.summitracing.com/partdetail.asp?part=CRN%2D1439811&autoview=sku)

Cheers ~Mykk

[01blzxtreme]

that truck sounds badass....

[fastSdime]

It sounds bad ass.

[turbine guy]

The thing with 4.3's, especially in a full size GMT-800 chassis, is they don't have torque. Simple physics, you only have 262 cubic inches to work with, i.e., you have roughly 262 ft/lbs of torque. Now all a cam does is shift that peak torque either up or down the rpm scale, not actually change the amount. For street driving, you are using the engines torque to haul your truck around, and the lower in rpm it occurs, and the higher it is, the happier the driver. Your stock cam will give you that situation, especially if degreed in to optimum specs. Obviously, occasionally we are in situations where peak horsepwer comes into play. Passing, and sometimes actually going down the 1320' with your foot planted. In those rare occasions, yes, a bit more top end hp is welcome. So......put in a bad ass cam, without supporting mods such as exhaust, looser converter, lower rear gears, ect., the truck will fall flat on it's face on the street. Sure that lopey idle sounds good, but, if that Geo Metro has a better 60', it can be embarassing. That said, in my opinion, the best advise I can give, is call Crane, or Comp Cams' tech lines, and ask their recommendations. The guys are really knowledgeable, and will recommend a cam that is right for you, and your driving habits.
Any lift over .480" requires guide work on the newer Vortecs. Crane and CC will custom grind any of their shafts to accomodate this, if you really don't want to yank the heads, for only a few dollars over the list price of their off-the-shelf cams. For my bone stock GMT. I put in the GM '92-'95 "X" cam (208/208 degrees.) With HP Tuners, I changed my timing, VE and MAF tables to optimise for this shaft. It worked out to a 35 horsepower boost at the flywheel. Max horsepower @ 5150 rpm. Yes, even with this mild cam, I did lose a tiny bit on the bottom end, as reflected by my VE table, which had to be dialed back a bit in the idle to 1600 rpm range. Off the line, my buddies GMT (Which is identical to mine, same engine, weight, rear gears, ect.) with stock cam, is slightly faster in the 60'. I pull by him at the 330' mark.

Of course, this ALL goes out the window when boosted............

turbine guy

[04silveradomykk]

As always, thank you for your input Turbine Guy... I check the HPT repository everyday looking for your tune. I still haven't seen it.

I am familiar with camshaft pros & cons, just not on computer controled & balance shaft motors.

[turbine guy]

04silveradomykk: Yeah, don't know what's up with the HPT site. They must be swamped, and a 4.3 tune would be low on the priority list. Let me know an e-mail address I can send the tune directly to. I have a new tune available finally, with my long term fuel trims dialed in. (VE, MAF and timing tables, with just a hint of knock at high loads/low rpm.)

Regarding camshafts, I tend to get on a rant. You having HP Tuners, you can practically run any 'shaft you want, and tune for it accordingly.

I'm still a fan of the old Rhoads variable duration lifters. They bleed off a portion of the lift/duration at idle and low rpms, and pump up to give full cam specs at about 2500 rpm and higher. (This is variable somewhat with oil viscosity, and temp.) They now make lifters for roller cams, and I think they could potentially be a good investment for the fellow who would like a good mid range/top end rush, say the equivalent to a 216-220 degree intake profile (@ .050" lift.) and still idle and pull off the line like a 204-206 cam. Have your cake and eat it too! They are a bit noisy at idle, but the tradeoff may be well worth it. A option to think over a bit.

turbine guy.

[turbine guy]

Dogs: I should send you my latest tune. The one posted on HPT has a terrible VE table. I posted it just for the timing tables, but if you want, I can send you my latest tune, with much better VE and MAF tables. let me know an e-mail addy, and I'll send it along.

turbine guy

"Carry on as if normal" Ron Chopiak.