Big Cam for TBI

[kyotey1693]

Hey guys,

One of the members of GMT400 recommended your sight. I have already read some pretty interesting things in the short time I have been snooping through the threads. I realize you guys cater more to tuning. I eventually will need a new chip for my truck but right now I am trying to iron out a parts list.

I have an 89 c1500, rcsb, 5.7 tbi (with all the tbi mods), 5spd, long tubes, full exhaust, crane cams ignition and coil, 1.6 roller rockers, open element air cleaner, etc. The usual stuff.

I have a bad lifter and would like to swap cams and would like to throw some better heads on at the same time. The truck is a street truck. It's a daily driver. It is a work truck for me but it's pretty light duty work. I run a pool cleaning business, so, no heavy loads, trailers, etc.

I haven't decided on which cam for sure, I want more performance obviously but I want a lopey idle as well. I plan to stay flat tappet because I doubt my block is tapped for the spider and I don't plan on converting it this time around. I also figured I would go with a regular sbc intake and a tb adapter. So, I have questions...

I am thinking about going with these heads. I have never seen or heard of aluminum vortec castings. Any info or opinions on these? They are 2.02/1.60's. That shouldn't be an issue, should it? One of the other reasons I like them is for the weight savings. I would like to drop some nose weight off the truck. I plan to add one of the Weiand superchargers later down the road. I also want to retain my 1.6 RR's, will they cause and ptv clearance issues with this head combo?

What cam recommendations do you guys have that can increase performance and give me some lope? (I know that is hard to do on one of these engines but I'm willing to sacrifice some of the lower end performance for a little sound) What injectors and fuel pump should I go with?

I realize some of what I have planned may not be the most cost effective in but that's ok. I like where this project is going and I intend to have fun with it. I'm not trying to make a street monster, I just want to make what I have better and more fun. I know many will say to do an ls swap but that is out of the question for the time being. If I had the time, resources, and location, it would have already been done.

[Hog]

The GMPP Fastburn heads have a 210cc intake runner volume and are used on the limitd production ZZ430hp/350cib crate engine and the 425hp ZZ383 crate engines.TRhere is the ETC Edelbrock 180 and 200 cc heads as well.All these heads are Vortec compatible.Oh there is an AFR head that is designed for L31 Vortec 350 use that even has it emisions exemption they are 190cc. peace Hog

[1project2many]

I think you're not going to be happy with the 200cc port as I think a close to stock truck should go a bit smaller. If you ever get around to installing that supercharger you'll have more than enough power to make up for smaller ports.

Vortec Bowtie heads are relatively new but they seem to be a very good performer although they aren't aluminum.

[EagleMark]

There's loads of good cam choices, but the lope is hard to do, EFI hates fluctuating and low MAP. Can do it with Open Loop Idle but it still a hard transition to CL. I think it's the TBI wet intake that makes the varible if idling for one minute the tune wants one thing and if two minutes it want another? I got it to work once but never liked it.

[kyotey1693]

Thanks for the replies. I hear a lot of people say that I will give up a lot of low end torque with the bigger cams. Will I actually be losing it or is it more of just shifting the power band a little higher?

[1project2many]

It's the same meaning. You'll move the powerband higher and give up torque at the bottom. Of course if the cam is too big you'll give up torque all over your rpm range.

[jim_in_dorris]

You will also need to consider a different stall converter for your tranny if you move the powerband up. Also consider the fact that TBI runs out of air above 5000 rpm. Changing the heads will help a lot, but the tbi manifold will be a big restriction also.

[EagleMark]

There are bigger then stock cam choices that won't hurt the low end torque as bad as needing a higher stall converter. But none are going to be big enough to cause the lope you wanted. Cams that big would need a high stall converter along with some serious tuning. It's still a bad choice for a daily driver. Now if this is a go fast toy then OK, just keep spending money!

If not then vortec/aftermarket/aluminum heads along with intake, some TBI mods and your headers and a good cam choice will make the world of difference you may be looking for?

[kyotey1693]

There are bigger then stock cam choices that won't hurt the low end torque as bad as needing a higher stall converter. But none are going to be big enough to cause the lope you wanted. Cams that big would need a high stall converter along with some serious tuning. It's still a bad choice for a daily driver. Now if this is a go fast toy then OK, just keep spending money!

If not then vortec/aftermarket/aluminum heads along with intake, some TBI mods and your headers and a good cam choice will make the world of difference you may be looking for?

I hear ya. Now you know this one is a 5 speed manual? Does that make a difference from what you were saying about needing a big torque converter. Or do I still not have enough compression to pull one off? I'm down for whatever tuning is required. I'll gladly pay for that. It's not a go fast toy, it is a dd, it does have to be reliable but it does get treated and driven more like a car/street rod than anything. Definitely not driven or used like a work truck.

I guess if the lopey cam is going to be too big to retain reliability and somewhat manageable street manners then I can live with a biggest small one I can get. Any particular recommendations?

[EagleMark]

Ooops! Manual trans is more forgiving on the cam... the problem with an auto and stock converter is they lock up before the engine RPM has reached wheat the cam is designed for and you get a big blah/bog/dissapointment.

Have some fun looking at cams and post a link to the specs. and we will let you know with your head choice. There's guys here that are better engine builders then me, i can tune whatever. Hints for specs are .224 duration @.050, lobe seperation of 112 or better, look at RPM range, you don't want anything that starts at 2000 RPM up, with a manual 1200 up is OK.

[Hog]

The 1996 production LT4 roller cam works excellently on a TBI 350, up top and down low. 203º/210º 0.456"/0.450" on a 115ºlsa WITH 1.5:1 ratio rockers, stock LT4 roller rockers are 1.6:1 and will raise lift to 0.476"/0.480" with teis camshaftpeaceHog

[kyotey1693]

I like this xe268. It's a 110 lsa. Can I get by with that?

Specifications			Intake	Exhaust
RPM Range: 1600 to 5800		Valve Lash:	Hyd.	Hyd.
Valve Timing:0.006		Duration:	268	280
Lobe Separation:110°		Duration @ .050" Lift:	224	230
Intake Centerline:106°		Valve Lift:	0.477	0.48
		Lobe Lift:	0.318	0.32
Valve Timing @ 0.006 Lift:

A lesser choice is the xe256 still a 110 lsa thought :(

Specifications			Intake	Exhaust
RPM Range:1000 to 5200		Valve Lash:	Hyd.	Hyd.
Valve Timing:0.006		Duration:	256	268
Lobe Separation:110°		Duration @ .050" Lift:	212	218
Intake Centerline:106°		Valve Lift:	0.447	0.454
		Lobe Lift:	0.299	0.304
Valve Timing @ 0.006 Lift:

I'm gonna show my ignorance with this question.. These trucks are speed density right? Do they need a map signal reading? Is it a pre calculated formula is the computer? Feel free to educate me on that one. You wont hurt my feelers. :)

[EagleMark]

First cam choice is to big, you won't like it in a street truck.

Second one is much better although I think there is a bigger split duration available with .224 on exhaust.

Yes Speed/Density and the MAP sensor is key to how the ECM responds.

[kyotey1693]

Ok, I picked a few more...

Lunati

Hydraulic, lopey idle. Good street cam for 350 cubic inch motors, popular in 383-406 cubic inch applications. Will work with power brakes.

• Advertised Duration (Int/Exh): 276/286
• Duration @ .050 (Int/Exh): 221/230
• Gross Valve Lift (Int/Exh): .454/.454
• LSA/ICL: 112/106
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 1000-5800
• Includes: Cam Only

Part Number: 10120318



Hydraulic, good idle. Good mid-range torque and horsepower. For high performance street vehicles.

• Advertised Duration (Int/Exh): 270/280
• Duration @ .050 (Int/Exh): 220/230
• Gross Valve Lift (Int/Exh): .465/.490
• LSA/ICL: 112/108
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 2000-5500
• Includes: Cam Only

Part Number: 10120639


Hydraulic. The most awesome 268 cam ever produced! Out-powers all others! This High Performance street cam likes 2400 RPM stall, 700 cfm carb, dual plane intake and headers. Makes un-equaled power to 6200 RPM with proper valve springs. If you're looking for a Very Strong cam with great street manners then this cam is it.

• Advertised Duration (Int/Exh): 268/276
• Duration @ .050 (Int/Exh): 227/233
• Gross Valve Lift (Int/Exh): .489/.504
• LSA/ICL: 110/106
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 1800-6200
• Includes: Cam Only

Part Number: 10120703

And I think this is the comp cam you may have been talking about earlier?

Specifications			Intake	Exhaust
RPM Range:1300 to 5600		Valve Lash:	Hyd.	Hyd.
Valve Timing:0.006		Duration:	262	270
Lobe Separation:110°		Duration @ .050" Lift:	218	224
Intake Centerline:106°		Valve Lift:	0.462	0.469
		Lobe Lift:	0.308	0.313
Valve Timing @ 0.006 Lift:

[1project2many]

I plan to stay flat tappet because I doubt my block is tapped for the spider and I don't plan on converting it this time around.

What's the rear axle ratio? Does this truck have to work as in hauling or towing large loads? Manual trans... light duty 5 speed or converted to NVG4500?? What size tires? Are you in hilly country or living in the flatlands? Are you willing and able to make other changes to the truck to match your cam or are you trying to fit the best cam into the budget you can?