94 K1500 TBI / Vortec head swap - Cam question

[1project2many]

Howdy.

I've recommended that cam for towing applications before. I've got one in a 302 powered Suburban and another in a 350 powered bus. The 302 uses 1.6 rockers and the 350 uses 1.5 rockers. They work well but calibration work was required for both applications to idle smoothly. I wouldn't expect problems with the compression ratio unless you spend a bunch of time lugging the engine. The vortec heads work well with higher compression ratios. I think you have decent combination planned out.

[Fast355]

I have a 395' cam with 1.6:1 rockers in a Vortec 350 powered Express van. I only have 3.73s and run a 4L80E so the gearing is pretty tall. Pulls my 6,000 lbs travel trailer nicely. Mine idled well from the first start, but my previous cam I had dialed in was 215/220 @ .050.

[1project2many]

I only mentioned idle because several current descriptions of the cam include "idles smooth."

[Fast355]

I only mentioned idle because several current descriptions of the cam include "idles smooth."

Were you running the Black Box PCM or 0411 Silver PCM?

Reason I ask is I ran a Comp cam

258/264 @ .006,
203/210 @ .050,
.458/.458
(.489/.489 w/ 1.6s),
110* LSA, 106* ICL

On a Hypertech 93 octane tune in an 0411 for weeks without any driveability issues. I put the same tune in my buddies 1997 C1500 with the 0411 swap. He is running an Elgin cam.

210/215 @ .050,
.462/.470" lift,
110 * LSA, 106* ICL.

[Roadknee]

Have you done any tuning with the Vortec heads? If not, you're leaving a lot of performance on the table. I like your choice for a cam upgrade, and it should be good for 50 hp over what you're running. Either cam will need tuning though.

[dispoejoe95]

I haven't done any tuning since I put the heads on but I haven't driven it too much either because I didn't want to damage the engine. There is a small story behind this. I purchased a chip years ago from a company after a did some small upgrades (shorty headers, 3" catback, 3:73 gears). The chip didn't do much but as I have read more as of late, I realize that a flash without a datalog is pretty worthless. Anyhow, I contact this guy about a new tune and he tells me it would be free. I send him my datalog and he tells me the fuel table is really close and it won't take much. Now, I am ignorant to the PCM tuning world but I made some significant changes to let this motor breath (heads, intake, 2-1/4" ID Y-pipe with a 3" intermediate pipe (no convertor) to name a few things...I found it pretty hard to believe that my fuel table could be that close. Long story short, I didn't send him my chip and the truck has been sitting for about a month now. Honestly that is how I found this forum, searching the internet for answers. I figure the tuning needs done either way but the more I thought about it, for $300 more I should put a cam in and take full advantage of these vortec heads. I don't drive my truck in the winter if I don't have to so I have time to work on it. Northern Ohio roads suck in the winter with the salt, brine and cinders eating cars & trucks up.

Anyhow, thanks all for the input on my cam selection. I will investigate the Comp & Elgin cams before I purchase but I think I am leaning towards the GM cam.

Another question...I'm trying to determine if I will need a fuel pump. When checking fuel pressure, does it matter where in line you hook up the gauge? I put the fitting in line right behind filter (between the filter & the tank)...it was the easiest place to gain access. To my surprise it was 18psi at idle with the regulator adjusted all the up. To the best of my knowledge this is the stock pump. I'm the 2nd owner and I've had this truck since 2001.

[lionelhutz]

If it was TBI Chips then you're probably better off getting someone else or tuning it yourself.

The GM cam looks like a decent piece for a towing application.

Going to Vortec heads will require timing changes as well. You'll probably run out of fuel on the top end requiring more pressure or larger injectors. It may be just OK with the current cam but the new one will probably make run lean.

[Roadknee]

Another question...I'm trying to determine if I will need a fuel pump. When checking fuel pressure, does it matter where in line you hook up the gauge? I put the fitting in line right behind filter (between the filter & the tank)...it was the easiest place to gain access. To my surprise it was 18psi at idle with the regulator adjusted all the up. To the best of my knowledge this is the stock pump. I'm the 2nd owner and I've had this truck since 2001.

I prefer to check by the throttle body. But unless your filter is plugged you should be close. 18 psi with a stock spring makes me think the spring may be bottomed out. You'll need a stiffer spring for at least 22 psi with stock injectors for the vortec headed 350. I'd also recommend you upgrade to the EP377 fuel pump.

For tuning I'd recommend an emulator so you don't have to pull the ECM each time you burn a new tune to change chips. I use the Autoprom from www.moates.net. When I'm done tuning, I can burn a chip with the Autoprom, install the chip and remove the Autoprom from the truck.

[Fast355]

I only mentioned idle because several current descriptions of the cam include "idles smooth."

Here is how the 395 cam idles at 600 rpm with ~16° timing advance more timing made it idle even rougher. At 750 rpm it likes 22° of timing and pulls down to about 40 kpa.

http://www.youtube.com/watch?v=6Z3LLrZI7Qw

[1project2many]

That sounds pretty good. My Suburban has a black box but the minibus is running a 411.

Are you using ethanol blended fuel? That's about all I can get here.

[dispoejoe95]

That does sound good. Not too choppy just a nice rumble to it.