When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Just revisiting this... (heads are at Katech now...)
Golan and SDPC don't publish (I cannot find it...) intake runner sizes. As mentioned above, I am not interested in some hog'd out 225+ intake runner option. These are going on a 346 (for street use...), and of the 6 head\cam cars I have wrenched on, 3 had huge intake runners and were mushy, soft low rpm performance (cam of course matters...)... until they were twisted to plus 4000rpm. I simply don't live at 4000+ rpms. I drive the car daily, in traffic, in parking lots. The Katechs got their flow numbers with only a 215cc intake runner, which is only 5 CC larger than the factory 243s. In short every modification is a compromise, I am shooting for some balance.
Just revisiting this... (heads are at Katech now...)
Golan and SDPC don't publish (I cannot find it...) intake runner sizes. As mentioned above, I am not interested in some hog'd out 225+ intake runner option. These are going on a 346 (for street use...), and of the 6 head\cam cars I have wrenched on, 3 had huge intake runners and were mushy, soft low rpm performance (cam of course matters...)... until they were twisted to plus 4000rpm. I simply don't live at 4000+ rpms. I drive the car daily, in traffic, in parking lots. The Katechs got their flow numbers with only a 215cc intake runner, which is only 5 CC larger than the factory 243s. In short every modification is a compromise, I am shooting for some balance.
Hopefully 2 weeks will tell...
I use my car the same way. Local city driving and occasional short rips to 4K—5k.
I've had Katech do a couple sets of LS9 heads and they do great work. My bill was always around $1500-1800.... obviously hoping for less. They replaced valve guides, exhaust valves, CnC, deck, clean, disassemble, reassemble etc. I supplied the dual BTR springs.
TSP definitely has its detractors. They've never wronged me, but I know people they have
I ran Lingenfelter 243s for years on my C5, 100's of passes at the strip, had them freshened up once in 15 years... great heads ... just sayin...
I had all the flow sheets and dynos, but can't seem to find them ... sold that C5 in '19 and bought a Grand Sport...
I would be interested in your results as well, base on my similar camshaft specs. Do you have dyno results of you current combo before sending the heads off to Katech?
I would be interested in your results as well, base on my similar camshaft specs. Do you have dyno results of you current combo before sending the heads off to Katech?
Nope... but completely factory 2002 - 2004 ZO6s dyno between 355 and 365 (rwhp) all day long.
There are some low ***** and some HP freaks... but those are the middle numbers.
... on a side not I am ditching the LGs and getting a set of American Racing headers. I am also getting the rear diff rebuilt with 3:90s.
Last edited by Pipedream; May 29, 2025 at 07:42 PM.
I believe the accepted power train loss on a manual C5 is15%. In that case 405 hp would make 344 at the rear wheel.
Who knows for sure…but I have found this to be the case with my two C5’s…
The multitude of people who've dyno'd know for sure, unless dynojets are unrealistically optimistic. Those (DJ) tend to be the numbers that I see quoted the most and they tend to land in the 355-365 range. Stock manifolds, free flowing catless exhaust, and a dyno tune should have an LS6 at 380whp all day. Just ask the Spec Corvette guys.
Subbed for OP's feedback on these heads. I've long kicked around the idea of them. I have a similarly sized cam waiting to go into mine as well.
Below is the image from Katech's website which seems to agree with what TonyM was saying nearly 20 years ago. I would think that Katech's 215cc intake port would help any combo breather better at top end vs stock 243/799 castings - while also helping to minimize any torque lost below 4000 RPM due to lower intake charge velocities, which dyno testing has confirmed with the larger CNC 225-228cc intake ports on say a 5.7 to 6.0L LS engine.
Basically it comes down to where you want / need the power to be in the RPM range. Personally (due to the -2cc valve relief in my forged pistons) I would also want Katech to mill the heads slightly to get back closer to the 64.5cc chamber size to maintain the stock LS6 CR target and / or at least run a set of Cometic 0.040" compressed MLS head gaskets for the same reason.
For most of our street driven miles, I would also think mid range punch from improved torque is more important than top end dyno bragging rights, but as always YMMV.
That’s precisely why I had my cam configured with .587 lift (I told CamMotion .590 max and they decided on .587 …). I’m no expert for certain, lol, but my “research” indicated stock 243 heads potential is around .590 lift. So with CNC and headers, I hope to break out of that flat spot (shown in the Katech graph) in the .450 to .600 range. I strictly street drive so a strong midrange rip to about 5,200-ish is the most it’s going to see before speed, even in second gear, becomes the performance limiter.
Like others have said, the dyno is a tuning tool, so not too hung up on numbers, as long as the butt-o-meter approves.
I was told they would be done this week... then shipping time.
... that being said... the TSP's are large intake runners... 225+cc, from what they (TSP) told me. Great at WOT, 4000rpm+ again, simply not where I drive the car.
I was told they would be done this week... then shipping time.
... that being said... the TSP's are large intake runners... 225+cc, from what they (TSP) told me. Great at WOT, 4000rpm+ again, simply not where I drive the car.
