Marc '99T/A

iTrader: (22)

I ordered the 2.5's Friday but now i'm wondering if I should've got the 1.5's instead. It is for a 224/228 on LSK lobes and a FAST 90. I'm going to be running a .040 Cometic for a DCR of 8.76 and SCR of 11.33.

Ryne @ CMS

iTrader: (10)

neither 224 nor 228 are lsk lobes, 223-227 are both lsk lobes

Marc '99T/A

iTrader: (22)

They are both available with either 2.02" or 2.04" intake valves, but the 1.5's have 1.55" exhaust valves and the 2.5's have 1.75". I went with the 2.02" intake. Is 1.75" too big for the exhaust?

oange ss

iTrader: (50)

1.578 exhaust valve

NHRAFORMULA00

iTrader: (2)

the 2.5 heads come with stainless valves intake and exhaust, the 1.5 heads have stainless intake valves only and STOCK 1.55 exhaust valves,IMO get the 2.5 heads,i would not want stock size valves in a ported head.

MARKSZ71

iTrader: (3)

2.5 are hard to beat

PREDATOR-Z

FWI those heads still have stock seats.
Stock seats are 2.02 so putting a bigger valve on them (2.04) will not yield the full potential a 2.04 should deliver. Also the 2.04 valve on a 2.02 seat is never fully properly seated. Any honest head porter will vouch for that.
IMO more than a 2.02 valve on those is a waste.

00T\A

I think you made a good choice.

TVWilkes

The valve job that TSP cuts for a 2.04 vavle is opened up for a 2.04 valve. They don't jam a 2.04 valve in place of a 2.02,that would be stupid. So yes,you do get the potential of the 2.04 valve. The 2.04 valve will work properly in the factory valve seat. This has been performed thousands of times will zero problems. Just because you can fit a 2.04 valve in the stock seat doesn't make you dishonest. TSP's work is quality and spot on. BTW,they don't offer the 2.04 valve anymore.

Jason 98 TA

iTrader: (4)

The 2.5 cylinder head is definately the best way to go. The bigger exhaust valve is well worth the extra little bit of money.

The 2.04 valve has been used by just about every LS cylinder head company around. With our cnc valve job machine we can create valve job configurations that most machine shops could only dream of attempting.
That being said, the 2.04 valve option is no longer available @ TSP. Our port design & 2.02 valve configuration just work better together.
Just because a 2.04 valve is bigger doesn't mean it will work better in every application. There's tons of aspects of a valve that determine how it works & flows. The PRC 2.5 cylinder head was designed with a 2.02 valve, as a results that configuration works best for us. I personally prefer the 2.02 valve in both of our cylinder head configurations because it moves better low lift flow, better p/v clearance, and works best with our chamber designs....

Marc 85Z28

iTrader: (8)

You still equip the heads with the 2.04 valve according to your website. If what you say is true, you may want to change your site. Additionally, I just bought a set of your 2.5 5.3L heads very recently... do I have 2.02 valves? I was told 2.04 over the phone!

Marc '99T/A

iTrader: (22)

Thanks for the input guys.

PREDATOR-Z

Please do no put words in my mouth. I NEVER said TSP is dishonest.
I said that "any honest head porter will tell you that 2.04 on stock 2.02 valve seat will not yield the full potential of what the 2.04 can achieve".
Please let us get that straight.
An aftermarket seat that can properly seat a 2.04 valve will yield better flow results.
That is plain and simple.

Just because it was or is common practice, it doesn't mean it is the BEST option.

There is the proof of what I said.

TSP is a good sponsor and has been known to make quality products. What I like about them is they R&D their products and if some need upgrade, they are not afraid of divulging their findings.
When we work in the HI-PO area, we learn from our live results and TSP is always on top of their game to seek unchartered territories for more power.

BTW I used run a 5.3L with 2.04 valves and TSP ground cam, so I know first hand about the items I used.

9ball

iTrader: (6)

Sorry to bring up an old thread, and somewhat off topic, sorta ... but better than crowding up the forums with a new thread.

Will the PRC Stage 2.5 heads work with an LS2 with G5X3 cam (as far as PTV clearance goes) with the 2.02 valves? Doesn't say that the heads are milled on their site and I know of many other vendors who have heads with this sized valve and people running them with cams just as large if not larger on LS2. Just being safe before I drop the loot on these heads.

THANKS!

PREDATOR-Z

No, not enough PTV clearance. You'll need LS2/LS6 stage 1 (stock valved) CNC ported with dual springs.