you gotta look close but theres slightly better flow differences between the PRC 862's and PRC 243's (243's being the higher numbers). is it enough to justify more money? I'm not sure.
I'm planning to purchase the PRC 2.5 243's

 

I ended up getting PRC 2.5 5.3 heads with 62cc chambers
I talked with Aaron from TSP and he could of up sold me on the LS6 heads but he actually talked me out of it
Compression should be right around 10.6
Can't say enough about Aaron's help, great guy to deal with and answer questions.
I ordered them this afternoon and will receive them on Thursday

 

my first shipment of parts arrived from TSP today
.40 cometic head gaskets, pushrods, LS7 lifters and trays.
Heads and head bolts will be hear Thursday. gonna clean bolt holes and get it all ready to hopefully put together thursday

 

got the heads today and got most of it back together, just have to check pushrod length.
I have never done it before, basically pick a length that I think it will be around, mark the valve, torque it down and turn it over enough times to leave a mark on the valve to see where the rocker is sitting and get it as close to the middle as I can and then measure the checker?

 

is that the method to using that tool?
I forget the "technical" name but I thought it was find the zero lash without preload while tightening down the rocker and add 0.50" for lifter preload?

 

I found this on Corvette Forum + a very similar write up on LS1tech
I just dont like "counting turns" though especially when shipping to Canada is so expensive




1. Open the adjustable pushrod to the same length as your stock pushrods
2. Close it down two turns
3. Put your rocker rail on the head
4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
8. You can try and adjust the pushrod in place but my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
11. Tighten the pushrod until it is fully closed counting the turns as you go.

To figure out your pushrod length you do the following. Let’s assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".

Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:

6.800 +10.5 X 0.050 = 7.325"

This is the length you measured to zero lash without any lifter preload. Now let’s say you want to have 0.100" lifter preload, you add that to the measured number and you end up with 7.425" pushrods.

 

how do you like the heads?
what method did you end up using to measure the push rod?

 

sorry to thread hog but i'm getting ready to order some heads as well and I was stuck between some
and the numbers are SOOO close I spent some time on google and hey....I found and answer instead of making a new thread so I'm gonna share what I found
this was found on a corvette forum asking the difference between the PRC stage 1 and 2.5 ls6 heads
trevor from TSP answered this


"The only difference between our PRC stage 1.0 and stage 2.5 LS6 cylinder heads is valve size. The stage 1.0 heads will use the stock 2.00"/1.55" valves, and the stage 2.5 will use larger 2.02"/1.57" stainless steel valves. The stage 1.0 LS6 heads can accomodate a larger cam because they have smaller valves, so it allows more room for piston-to-valve clearance. There is not a difference in deck thickness between the two heads; they use identical GM head castings. The actual horsepower difference between the stage 1.0 and stage 2.5 LS6 heads is 5-7 HP. The stage 2.5 is also a better way to go if you plan on forced induction or nitrous. The stainless steel valves will handle more heat than the stock valves will.

With respect to camshaft, your biggest limiting factor will be CA emissions. We have had quite a few customers in CA use our 224R 114 LSA cam and pass emissions. Anything with more duration is going to really push it. Our 228R makes an additional 8 flywheel HP over our 224R, so you're not giving up a huge amount of power. With a six-speed manual, you can expect our PRC stage 1.0 LS6 heads and 224R cam to make right around 420 RWHP. It does vary some from car to car, though. This is also assuming you're running long tube headers, good induction, and the normal bolt-ons that will help your new heads/cam package breathe. Additional compression is a great way to gain some additional power, and I consider it free HP and TQ! We don't charge to mill your cylinder heads because every set of PRC cylinder heads will be milled. If we are looking to retain maximum p-to-v clearance, the heads will typically get a .003" clean-up mill. The LS6's 64cc chamber size will net right at 10.5:1 CR, and if they are milled an additional .030" it will put you right at 11:1 CR. With a 224R cam, you won't have any clearance issues with the stage 1.0 or stage 2.5 cylinder heads milled .030". The cam is small enough that you will not have any issues.

What we can offer every customer is proven performance. We have an in-house Superflow 902 engine dyno, as well as a Dynojet chassis dyno. EVERY cylinder head and camshaft package is developed and tested on our engine dyno before it is installed on a vehicle and strapped down on the chassis dyno. We don't pick some lobes off of a chart and hope for the best. Some of our cams do use standard lobe profiles, but we will literally dyno the same duration cam changing nothing more than LSA and ICL. We want to see what works best with the combination. All of our cylinder heads are CNC'ed on one of our three 5-axis CNC machines, as well as valve jobbed on one of our Newen single-point cutter CNC valve job machines. We spend a LOT of time and money making sure our products are not only correct but also the best available. When you consider other cylinder heads like ones mentioned in this thread, keep in mind that higher price does NOT mean higher power. Some cylinder heads you will pay quite a bit more for just because they are an aftermarket casting. These will cost more money because they cost quite a bit more to manufacture vs. buying GM cores. We speak from personal experience on this because we have our PRC 215cc, 227cc, 237cc, and soon-to-be-released 245cc cathedral-port aftermarket casting cylinder heads, and we are getting ready to release the PRC LS3/L92 and LS7 aftermarket cylinder heads that we have developed from the ground up. All of our aftermarket castings do offer thicker deck surfaces, better piston-to-valve clearance, smaller chamber sizes for better compression without reducing p-to-v clearance, and our LS3/L92 cylinder heads will also offer smaller runner sizes for better port velocity vs. stock as-cast heads! I could go on and on. It's not just because I'm biased; it's also because I KNOW how much time, money, and effort have been spent to make our products some of the best on the market
"

 

The heads work amazing!!! it was a very very noticeable hp increase. well worth the money.
I bought a push rod length checker
when I ordered the heads I talked to TSP and I was pretty set on 2.5 243/799 heads and they actually talked me out of it and told me to go with the 2.5 5.3 heads. wasn't worth the extra money for little flow gain for my truck.

 

Right on I'm.glad to hear they worked well!
How did you find using the comp cam length checker? The instructions sound pretty straight forward but I hate counting turns haha