Getting ready to build the 4.3 in my 2002 ZR2. Need input on aftermarket cams and machining required for use in the 4.3. I have already procured a marine intake and plan on using stock exhaust manifolds and 2-1/2 single exhaust. Looking to gain around 50HP. Please post your cam specs (manufacturer and part numbers if available) and what mods/machining were required to run your cam. Did you have to change the valve train to adjustable? Choppy Idle? What RPM range does it pull best at? If you had it to do it over, what would you do that was different? I know this is a lot to ask for but I have been researching this for about 9 months and have been getting conflicting information and the cam manufacturers aren't much help at all.

Here is what I have learned this far, please correct me if wrong.
Current engine has hydraulic roller lifters.
Most aftermarket cams use a different base circle (requires adjustable valve train).
500 lift and above requires machining (but what machining are they talking about)
May require deeper valve relief in pistons (don't want to go there)
May require taller valve covers depending on rocker studs (don't really want to go there either)
Will require a professional tune. (got that covered)

Not looking to build a straight line car, will be my daily driver. Just need a little more punch for getting around in rush hour traffic and the occasional bass boat pull.
Thanks in advance for your informative input. Oh and last but not least.......because I don't want a V-8.

 

I am full stock option yet With a transmission rebuild in progress. Cannot share own experience with tuning - by no means I am an expert here - but a bit of knowledge I have.
First of all, adding extra HP means less MPG.
This is a simple physics: fuel combustion creates energy. The more fuel You combust within a time, the more energy You got. The more hp You have, the MPG becomes worse, making it eventually less a daily driver. According to that, the more combustion cycles per time unit, the more energy You produce. That implies, the higher the RPMs are, the more power You get. This is one of the main factors of tuning: You have to tell what RPM range You want to use. As, for example, for high RPMs You want to use:

• a wide and short intakes (like Edelbrock Victor)
• hydraulic tappets become inefficient at high RPM, so You may want to change them for mechanical
• at a high RPM, when You get really high power requires forged connecting rods of "I" type
• and use aggressive cam shafts to allow high fuel volume to pass through the engine block

If You're aiming the range of 1500-6500RPMs as a daily driver You may want to use another type of intake, that has the coolant channel underneath the bores that heats up the fuel prior it gets into a combustion chamber (like Edelbrock RPM Performance) That improves engine operation at this range. Making same feature in Victor makes no sense, the fuel flow is way too fast. You may stay hydraulic poppets. And You may use "H" type forged connecting rods.

Another story are the heads and camshafts. A compression ratio makes all the power. The more compression ratio You have, the more power You'll get out of it. In this aspect, the connecting rod length, valve length, and the head is important. I know some freaks who aim to have a diesel compression ratio in a gas engines. In a naturally aspirated engine, what comes into the cylinder has no pressure, and then it is compressed while the piston moves up. So, as a matter of fact, if You pre-compress the fuel-air mixture, You gain the profit. You may "pre-compress" by using a turbocharger or a supercharger. Turbocharger is exhaust powered turbine, while the supercharger is usually a serpentine belt driven device. The supercharger runs even at a low RPM area in contrary to a turbine, that gives a kick when You cross - let's say - 4k rpms. As a sidenote, the supercharger may be a nice feature for You to get this extra 50HP You want. As far as I remember, someone said, that You may pre-compress the mixture up to 10PSI on a stock engine without any modifications. You already have the right intake.

Last but not least - fuel supply system. As far as I know, marine intake has a separate injector for each cylinder, unlike the spider assembly. With another options You may want to use a carburetors. They have insane flow abilities, are used in aspirated engines, but engine devours the fuel twice a normal rate (my expectations)

...and a last but not least: the knock combustion. You have to pay lots of attention not to destroy the engine. In other words - ask an experienced shop to tune all the setup You build. I haven't been giving a recipe, rather a general overview on how to think of the build. There are lots of option and all the fun is to chase the sweet spot. You have a marine intake - then You may want to add a supercharger. I'd rather stay with naturally aspirated engine, use the RPM performance intake with a carburetor. Once we build, then we could compare and (maybe?) draw the conclusions.
Cheers, Mike

P.S. You have another option for a public traffic: https://www.sonnax.com/parts/3734-2-...ut-carrier-kit

 

Shooting for 2000 to 4500 RPM range. Daily drive is 14 miles total, dont much care if I lose MPG's. Put a Vortec supercharger on my 99 with marine intake, once I got the meth injection, cooler, electronics and tune I was almost $6000. Wasn't impressed and made my truck overheat in the summer at speed.

 

Unfortunately with how cheap.you could find a 5.3 or 4.8 would prove better performance and mileage at the same time.

 

Better performance and mileage yes, the problem with the LSX conversion is not only the cost of the motor and probably rebuilding it, but the cost of a complete wiring harness ($750), all new brackets for AC, Alt, Ps, etc ($500 minimum) new AC compressor and components since it has to be moved from its original position ($1000), Complete new cooling system with electric fans and those have to be moved forward into the hood latch area to make room for the new engine ($500 minimum).

A 5.7L vortec would be more cost effective and easier to transplant, but like he said, he does not want to do the V8 conversion.

 

Yeah it definately starts to add up lol I am in the process of acquiring parts as well.

 

I am also at that decision point of going with a rebuilt 5.7 Vortec, only because I can use the front brackets and AC system with a small amount of money needed for the proper wiring and tune. We can use our 4.3 flywheel, starter, alt, etc, maybe even the radiator if its moved forward enough without having to do to much fabrication, otherwise the cooling system and exhaust would be my biggest expense.

Keep me updated on what you plan on doing, would be interested to know.

 

Considering a regrind from Schneider Cams ($160). They claim to be able to increase lift and duration without losing enough base circle to have to change to adjustable valve train and retain stock (new) lifters. This would be a substantial savings in my build. Once they have my cam they can tell me what type of specs I can get out of it. I have googled this process and don't quit understand how they increase lift by removing material from the cam, maybe somebody here can shed more light on this process.

 

They grind down the base circle of the lobe. Taking material off the low side and leaving the high side of the lobe alone increases lift. Then they can play some with the shape of the lobe to slightly adjust the duration.

 

So if you remove .030 from the bottom of the lobe it's like adding on the top side? The lifters (hydraulic rollers) will make up for the changes?