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Tbi Vortec Head Cam Suggestions

K

KMAYK5

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So here's a rundown of what I have so far. I bought a complete wiring harness and throttle body off 87 454 with a Manual transmission. I am going to be installing it on my a vortec headed 350 with about a 9 to 1 compression using the GMPP vortec tbi intake.

First question is what kind of cam would you guys recommend for this setup? It will be a street driven truck and would like the motor to be built more for torque so I can try to get some reasonable mpg numbers when highway cruising. The cam needs to be hydraulic flat tappet because at this point I can't afford the retrofit roller lifters. So what cams have you guys run and what kind of power were you making with these heads.

My second question is what bin file should I start with for this setup? I will be purchasing an Ostritch 2 and using tunerPro Rt to get the tuning right before I have it burned to the chip.

Eventually the truck will be running a nv4500, 4.56 gears and 37s.

Any help will be greatly appreciated.
 
I asked the same ?? some years back, here's that thread


http://coloradok5.com/forums/showthread.php?t=265844

still haven't done the swap...been broke since obummer took over...:dunno::whistle:

edit: my bad...just saw you need flat tappet...

be aware, the Vortec head is only good for about .470 lift stock...

Comp Cams has a bee hive spring & retainer kit that raises it above .500 iirc...here's an article...clicky
 
The lift problem has already been addressed. Had the machine shop grind them down and pin the studs also when I had them rebuilt. I will take a look at that thread and see if I can get some insight.

I wish I would have gone with a roller block but when I originally put this motor together a few years ago I didn't know any better. Lol
 
Cam selection is really based on your own desired outcome. Just go with something mild. Anything over about 4000RPM is probably going to be near useless for you, and while the power might start falling off at that RPM, if you are having fun and exceed it a bit, it's not like the engine is going to just stop running if you do.

Worrying about MPG is really, really, really about the last criteria you should be basing your decision on. I've spent THOUSANDS of dollars on my truck, at least partially geared towards improving MPG, and except one "trick" I've not yet implemented, my mileage after thousands of dollars, is the same it was with a worn out stock 305 AND 350. I'm talking a $500 TPI setup, $300 in new injectors, a $500 intake to run TPI on Vortec heads, a $100 EGR kit, an $800 retrofit roller cam/lifter setup, $300 steel full roller rockers, $125 fuel tank, $75 electric fuel pump, $300 headers, $600 vortec heads (including new springs and ARP studs), and probably a myriad of other things I'm not thinking of, all to get exactly the same MPG I did with a carb. I turn about 2200RPM on the freeway, so it's not like RPM is killing me. (BTW, the "trick" is called highway mode, you can google it to learn what it is, basically, you run the motor leaner than normal at cruise)

These trucks just can't get good mileage with a gas motor. If you want economy, don't waste money on gas, go with the 6.2L diesel. I somewhat regret not doing so, because economy and range are important to me. Some here get 25MPG out of those trucks, and on a 31 gallon tank, that gives you MASSIVE range. Even leaving some in the tank for safety, that's ~700 miles/tank.

What trans are you going to be running before you convert to the 4500? Generally speaking, auto trans, start with an appropriate auto trans bin, if manual, appropriate manual trans bin. Normally the newer the bin, the better it is.
 
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The truck will be running an sm465 for the time being and eventually will put in a nv4500. Until that time if could really care less about mpg.

The bit about mpg was more wishful thinking than anything. My main goal is a reliable motor that will get me from point a to point b. If it gets 10 mpg I will be ecstatic. I was just hoping to be a least double digits when cruising the highway in od.

My end goal is to build a pretty capable overland rig.

There is also the option to go with stock swirl port heads if that is deamed neccesary but was hoping to make a little more usable power with vortecs.
 
We had a discussion awhile back about Vortecs vs. swirl ports. If you look at a 1995 TBI motor HP numbers (available here on the tech pages I think), and a 1996 (which is Vortec, "port" injection, etc) the power difference can pretty much be accounted for SOLELY based on the head difference, even though the Vortec peak HP number is achieved at a higher RPM than the TBI motor. Vortecs are pretty regularly said to be worth 40HP even on a stock motor, but the Vortec motors had roller cams too...so the swirl port heads don't really seem to give up as much to Vortecs as you'd expect. I dunno, I'm not sure I've seen a dyno test back to back of stock swirl ports vs. stock vortecs, with no other changes.

I tend to think the swirls can't possibly be as good overall as Vortecs, since the swirls are prior to the valves, and the Vortec chamber is a vast improvement over all the earlier chambers, so I'd think both combustion efficiency and flow characteristics would be better on Vortecs across the board. Is it worth the expense of a new intake, springs, etc. for a "low end power" motor? I know I can't answer that authoritatively.

What are your RPM's at freeway speeds? Along those lines, how are you calculating MPG? If by the stock gauges, your speedometer has to be correct for the MPG calculations to be correct.

With my setup, ~2200RPM on the freeway, 16 is the norm if I keep it @ or below 65MPH.
 
All of this is hypothetical at this point. The truck hasn't been tested for milage as it's inoperable at the moment. Once the Drivetrain is finished I will redoing the dash and going with a bolt on Vss unit to make the odometer and speedometer work properly. Until that time I will be relying on my gps to give speed.

Guessing that my 37s will actually be closer to 36, the rpm calculator shows 2213 rpm at 65.

My reasoning for going with the vortecs was like you said to gain a little more power to the top end to make it easier for the motor to cruise down the highway. I will be looking into the lean cruise mode to are if I can squeeze some decent mpg numbers out of it but not till everything is set to how it will love the rear of its life.

If a stock cam is what's best for my goals then that's what I will run. I was just hoping for a little bump in hp like mentioned above. When I first bought the truck I had 4.10s, 38s and an sm465 and was content with the power(stock 84 motor sans ccc Qjet). Just looking for a little upgrade going with a new motor, little bit bigger cam and and tbi to help keep it from bogging out off road.
 
It will be interesting to see what your mileage ends up being. Obviously big tires and weight are two negatives, but I also believe that certain factors are less than others. In the case of our trucks, assuming no bad driving habits, I think aerodynamics is the #1 problem for highway MPG, far more than tire size, how much air gets under the truck, etc.

Displacement is a factor as well, IMO it's pretty well been determined that a 305 and 350 get the same mileage in the same rig (I've done it, so that's what I believe) while a 454 will quickly drop you into the 11-12MPG on the freeway. But since you are 350, not really going to matter. Aerodynamics is something we can't change.

You don't need the Vortecs to cruise down the highway...the figures I have somewhere that purportedly came from GM state that it takes less than 40HP to go 60MPH in these trucks....it's accelerating, hills, towing, and passing that you need and notice power.

What kind of exhaust will you be running? Looking at the engine as a package is really whats needed before picking components...what cam works with manifolds might not be the best choice with headers. What cam works with swirl ports might not work best with Vortecs, and so on. The Vortec cam was by all accounts tiny.

As almost all dyno testing starts around 2000RPM, low end grunt to get a heavy truck moving, is pretty hard to figure out. With the Vortecs apparently pulling harder on the upper end, but giving up some on the low end (I'd have to google data on the swirl ports and Vortecs) I'd think a good tradeoff would be a cam designed around low end. If the cam was a bit more towards the upper end, then coupled with the Vortecs which are also better on the upper end, low end would be a bit less than with swirl ports.

Efficiency-wise, it may be better to go with a small cam and swirl ports as both will make good low end power. Everything is a compromise, it gets a bit easier when you have to build power for a very narrow RPM range. In this case, it would be idle to roughly 2500RPM.

If there is any dyno software out there that shows power numbers below 2000RPM, it might be very useful for you. Even discounting the actual numbers that it spits out, the changes based on cam profile, head flow, etc., is usually quite enlightening. And it's fun to play around with too. :)
 
I've read that an LT1 cam is a good cam with the Vortecs...get em used on evilbay for about 50$. power bump without getting crazy

being roller cams they shouldn't be hurt at all
 
He doesn't have a roller block. I assumed that to mean it's not an '86 or later where a retrofit of stock roller lifter hardware would be easy?
 
Correct. I don't have a roller block so I would have to buy a retrofit kit.

I have a friend with DD2K but I don't know when it starts it's estimation program but I will see what it comes up with.

I'm mainly looking for tips on what to look for in a tbi cam that will make it easier to tune in the end and not freak the computer out with the initial start up.
 
Maybe EagleMark will chime in on the cam/tuning. If doing your own, I don't think there is a real problem with most cams that any of us would be interested in running on the street...I know people have made MAP injection work with rough cams, so I doubt that will be a concern in your case. I really have no experience with anything but cams that are considered "computer friendly", hopefully someone else has some insight on that.

I think DD2K starts at 2000 as well, but if you get the parameters right, you can see where the HP and TQ curve "start" and approximate what it's doing before 2000RPM...you'd not want it dropping like a rock at the start, or peaking way out past 4000RPM, but if it's already somewhat at a plateau @ 2000RPM, and stays flat for awhile, it's probably a good indication that the cam has some low end, and the power band to be somewhat broad, which obviously will help acceleration AND felt power as the engine starts to spin up.
 
Opps, sorry missed that... I'm not a engine builder, but I can tune any cam. Yeah some are easier? But they all need a new chip!

Problem is I can't change what it does. I can make it idle... but if it has no power under 2000 RPM then it's still a bog... till it hits there.

With a manual it's a little easier. With an auto if you get a cam designed to come on at 1500-2000 RPM it usually recommends a high stall converter too! None of this helps fuel milage but it's cool to drive in the HP department.

Personally I have not liked driving any cams in autos that were 1500 RPM up, without a high stall converter. For a daily driver this is a bad plan...
 
Got that same cam in my k20. Has 305 gasket matched heads and intake. Stock valve springs. Seems to pull good to about 4200 or so, lots of torque down low as. Don't look at my tach to much while wheelin. And it's not like them "416" heads would be good for much more rpm w/o work.

As far as mileage goes, seems to be in the 11-13mpg range depending what I'm doing. Not really a concern for me. Truck specs are in my sig.
 
That's the kind of info I'm looking for. What's kinda frustrating is I just pulled the cam above this out of my truck and sold it because I didn't thing it would be tune able.

Looks like I will be ordering the cam I listed pretty soon here. Now just to come up with the money for that overpriced tbi intake. Lol

Thanks for the help guys.
 
Yes it is. I was just hoping for a cleaner looking engine with out an adapter.

That being said I just got my tbi setup and it has the factor adapter since it came from a 454. I will look into just picking up another intake now.
 
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