As I'm getting closer to buying my C5z I'm looking more into build plans. I have below what I'm seeing from Texas Speed, although I'm open to other options.

tsp by LSX StreetCars, on Flickr

1.) Stg 2.5 LS6 heads versus 225cc heads/cam packages - Am I wrong to think that for $100 the 225 cc would be a better set? I would have the chambers at 62cc, which I believe would be the largest I can go with a stock bore 5.7 being it should me 3.90" bore size. Because of this bore size, should I go with the Stg 2.5 instead?

2.) Looking at headers, I'm going to be shooting for about 430-450 wheel horse, but I'll take more if that head/cam package will give more. Should I be looking at 1 7/8 headers? I think the difference is minimal and the 1 3/4 keep some more low end torque.

3.) Underdrive pulley.. I get the point, but is there any real benefit to running this on a sub-500 horse build?

Any input is appreciated.

 

I have a few thoughts that I will share:

-In my opinion, arguably the two best places in the nation for 243 head porting are TEA and Advanced Induction. If it were me, I would send the stock 243 heads to one of them. And...since the C5Z's already have 243 heads I would opt for having them ported before going with an aftermarket casting. There are some aftermarket castings out there that are better than the 243's no doubt, but you will be able to achieve your rwhp goals with a simple $1,000 job from TEA or AI.

-That's a pretty big cam you picked out, 235/240 duration is a lot for a 346 motor. I don't know what all of your goals are so it may be perfect for what you are looking for but just something to be aware of.

-Save yourself the $990 by using the factory Ti axleback instead of buying the Stainless Works axleback. The factory Ti's sound great with headers and flow very well too. If you decide that you don't like the sound with the Ti's then I would invest in another axleback but at least try it first IMO.

-1-3/4 headers will be fine.

-Do some research on those TSP headers before you buy them. When I was looking for long tubes I researched all the brands and decided to stay away from those in particular. Good price though.

-The underdrive pulley is worth a couple/few hp. When doing a cam swap, that is the time to swap the pulley if you are going to but I don't see them as a necessary mod. The money may be better spent elsewhere but if you want the most you can possibly get from your combo then perhaps it's worth doing. Don't forget you will need new belts as well.

-You may also want to include the rocker trunion upgrade in your list of parts.

-I'm not sure if the ported LS6 pump on your list is absolutely necessary over the stock LS6 pump but it certainly wouldn't hurt.

Hope that helps some!

 

Thanks for the heads up!

I will definitely look into getting the heads ported as opposed to going with aftermarket casings. On top of that I'll go through the valves and springs and such while they're out.

For the cam - I saw some really good numbers out of that cam. I like the idle, but I'm not buying a cam for the sound. I just liked the output that I saw on the dyno sheets, but I see that it is a little hard on the springs. I would like power with the idle, do you know of a cam that will provide similar power with a similar idle?

That works for me, I'll gladly save that $990 I think I'd probably look into different mufflers, but that might be difficult being Titanium. Something to look into further for sure.

I've heard mixed on TSP, but wasn't sure what else is out there around that price range. I'll definitely look around further.

I'll defintiely check out getting the rocker trunion upgrade as well!

As for the underdrive pully and LS6 pump, I figured while I'm down there with the timing cover off and all, I might as well just do it all, it's only another $400 I think in total.

 

I can answer on the TSP headers from my experience...
Got my set 2+ years ago (maybe they've improved since then), they took some work. The flanges were warped far beyond use. Being in Canada I chose to rework them instead of sending back and getting another set (and dealing with MAJOR border issues/fees which are guaranteed).
Thankfully I work at a fab/machine shop, so got a good deal on milling them flat/usable. After that all worked OK, but they definitely hang a bit low on one side (I am not lowered, so no bottoming yet).
I'd opt for the latest gen of XS Power if trying to save, but more so keep an eye here for some used "better" brand headers. There were some ARH on sale here recently for $500 IIRC! Might still be there...

 

With your 430-450rwhp goal, you can actually hit the higher end of that goal pretty easily with top notch ported 243's and a 22x intake duration cam which will exhibit better drivability, come on the power sooner and have more under the curve than that 235/240 cam. You can also have a smaller cam than the 235/240 sound the same or similar because the chop we all love is due to the amount of overlap in the cam. Something with a healthy amount of overlap will give you that chop. Whoever/whatever heads you decide to go with I would work with that vendor for the cam selection, depending on who they are they should be able to design a custom grind or point you in the direction or an appropriate choice.

Something you may not know about the 243 heads on the Z is that they have awesome hollow/sodium filled valves. A lot of 243 port programs will reuse these lightweight valves which is great.

Regarding the headers, the Kooks and ARH's and LG's etc. of the world are considered the best. I've gone cheap on headers before and have learned that you get what you pay for. Like stated above, the XSPower headers (latest gen) are probably the best of the cheaper $$$ headers. A sponsor on here sells them. Could always try and find some used headers in the classifieds, I see them all the time.

And don't forget a shifter. The stock shifter is terrible and I highly recommend an upgrade.


EDIT: You may want to budget for a clutch too, I don't see the stocker lasting long with heads/cam.

 

I am at 429 rwhp with the PRC stage 1 heads (just basic 243s that were cnc’d) and the 228R cam. XSPower headers, LS6 intake and Corsa cat back.

I used a power bond pulley just as a replacement for the stocker that was starting to wobble. I installed a number of XSPower headers on C5s and really like them. 1 ¾ systems. (Rocker trunion upgrade, LS2 chain, Melling oil pump,FAST injectors, PAC springs and stock GM head gaskets and bolts)

I consider this a mild build. The cam isn’t big enough to need double springs that need to be replaced to often, at 116LSA it has a great sound and lopey idle.
Stock clutch works fine. Good drivability.