I'm rebuilding the 350 TBI engine in my truck (89 Sierra), and I've been trying to decide on a cam. The stock cam is pretty lame, it's something like this:

194*/198* dur, .393/.398 lift, probably 112 lsa

The cam I want to put in is slightly bigger:
204*/214* .420/.442 112 lsa

Now will this cam work with the stock TBI unit, or will I have to mess with the computer or change injectors? If it won't work with the stock TBI, what would I have to do to make it work? Also I was thinking about getting some Crane 1.6 stamped rockers which would increase the lift to .460/.482 ish (too lazy to do the math), would this work or not? I know a lot about carbed motors, but I haven't done much with TBI and other fuel injected engines.

Thanks,

-Kyle

 

that one will work just fine with some fp adjustments and some extra timing. It wont make good high end power but it builds nice low-mid range torque and good mid range power. It seems to work nice with the high rear gearing and low stall stock tc that the truck will have. I say go for it. I have that one and it lacks power over 4000 or so but im too broke to afford a good tc and gears to replace my 1200 rpm stall + 2.73's to support a better cam.

 

Be careful with the 1.6 rockers. .482 could cause some valvetrain binding issues with stock valve train. I would recommend changing the valves springs too regardless of the rockers you use. The truck springs are as lame as the stock cam.

 

I'm getting new springs and retainers from CompCams. One question on the springs though, how do you find the max lift? Is it the seat load minus the open load or is it done by coil bind? I'm kind of confused with that. I'm getting new rockers anyways, so should I go with the 1.6's or go with 1.5's?

 

With a cam that size, an increase of lift without more duration is a two way street.

You'll get more lift and more air should help overcome the lack of duration. However, the small amount of time the valves are open because of the short duration won't allow the cylinder to take full advantage of the increased lift. I'd say it would help, but not at the expense of changing a lot of things to take advantage of it.

Another thing is that cam is a low RPM cam. It's designed more for torque "under the curve" as they call it. That basically means it uses more of the lift below the max lift to fill the cylinder. After all, a cam is at "half lift" twice as many times as it is "max lift."

Getting a good set of 1.5:1 roller tips like Comp Cams Magnums will help more than the 1.6:1 ratio will (although both together is better). You'll decrease frictional loss, AND the Magnums are more accurate and stable than stamped rockers.

Going with 1.6:1 is going to require elongating the pushrod holes, checking valve guide-to-retainer clearance and grinding them down if needed.

 

I should probably mention that the engine blew a head gasket and we're doing a budget and slightly better than stock rebuild (me and my dad). If everything were up to me, a lot of things would be different, but he wants to keep it close to stock with the exception of a few performance parts (I can't talk him into doing much extra to it). So unfortunately I can't go with anything bigger than that 204/214 cam (I tried to talk him into a nice XE268, but he didn't seem to like that idea much...). AJ_92RS you came up with some good points about the 1.6 rockers that I didn't even think of, so I'm probably going to go with the 1.5's now.
So all I should have to do is bump up the fuel pressure and advance the base timing some right?
Also, how do you figure the max lift for valvesprings?

Thanks.

 

You can look up that cam at www.summitracing.com

It's part # is SUM-1102

Click on the tab labeled "Installation" and it'll tell you what springs to use.

Here's a QUICK CLICK for ya.

 

I'm building a similar motor for my truck ('83 1/2 ton). I'm using the cam that's one step up from that, but basically the same. I wan't primarily pulling power and my 4 spd manual tranny has a 6.55:1 first gear so the upper RPM can only help.

Anyway, I punched in the numbers in DD2000 to show you what to expect. If you can talk your dad into headers that's the second set of lines. Keep in mind DD2000 gives exaggerate numbers so don't take the actual numbers as gospel, but it'll still give you an idea of what you'll get with and without headers.

 

I've tried many a time to talk my dad into headers, but he doesn't want it to be any louder, he likes quiet exhausts. I even tell him we can make it quiet, but he won't go for it unfortunately. Maybe if I show him the charts he'll change his mind. Thanks for the DD2k graphs AJ. I got my PAW catalog today and I found some cheap springs and retainers that I think I'm going to get. I'll probably also go with the magnum rockers too. Will I have to get an ajustable fuel pressure regulator for it or and inline pump or something to bump up the pressure, or what exactly?