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Hey Jason, im trying to decide between the 255cc and 260cc heads. Theyre going on a stock LS3 block. It will stay a 376ci for as long as the bottom end survives but after that I'll probably go to a 418ci stroker. Is there a big difference between both heads on a stock LS3? I know the velocity might slow down a tad with the 260 runner but I cant see by much. Also would you recommend 1 3/4 or 1 7/8 headers? I currently have TSP 1 3/4 headers and a 231/236 114lsa cam. I plan on milling the heads to 64-65cc for 11.35-11.4:1cr.
Jason I was actually just on your website earlier. I am retrofitting an LS2 into my 92 camaro and had my goal set of 500whp. I am looking for a set that will get me there, and since I know the ls3 head swap is popular, do you believe these heads would get me there?
I am seriously interested and have the money to spend, I just need to have the proper research and guidance. A complete kit would be ideal for me (fully assembled heads/cam/gaskets/bolts etc) as once I get back from vacation there is no telling how long I have before I leave for the air force, so I want to complete this project as easily and reliably as possible.
Those asking for dyno data, I'm sure if you get into contact with Aaron@Texas Speed he can provide you guys with any information and dyno graphs needed.
Just FWIW we have a customer that had a 12.8:1 SCR 416 c.i. stroker motor. We used these 260cc LS3 heads from PRC in conjunction with a GMPP single plane intake manifold and a 1050cfm carb along with a 251/259 .624"/.624" 111+2 hydraulic camshaft and 2" headers.
On the chassis dyno through a Power glide(unlocked stall converter obviously), a 12 bolt rear end, spool and 3.73's it made 566rwhp/456rwtq on motor with 32* timing and 12.5-12.7 AFR on C16. This is a nitrous motor that was raced in our local real street 275 class(same class as LSX real street just no slicks, progressives, boost controllers or billet wheel 76mm turbo's allowed) it had a best E.T. and mph of 5.38@130mph weighing in at 3250lbs. The lack of torque on motor isn't that big of an issue as it is a nitrous engine and we all know nitrous engines make big torque. The car made 842rwhp/680rwtq with that .082N jet which is rated at 225-250hp of jet, but the car picked up around 275rwhp with that jet.
Square port heads love nitrous and they love boost. When you've got all that port volume available.......that is a nitrous engines/boosted engines world right there. Density needs port volume. Large N/A motors also need port volume as do big bore engines that like to breathe deep to make their power. High RPM engines will also need a larger amount of cross sectional area to operate efficiently in their intended RPM range. I would not consider this combo high rpm by any means, but just look how flat the torque curve is from 5800-7000rpm. Obviously, this is a by-product of the cam design, but without the heads it wouldn't of made anywhere near this kind of power.
Hope this helps those looking at these heads, and if anyone would like a combination similar to the one I'm posting about, we can set it up with these heads and a custom camshaft to do the same thing!
Last edited by Sales@Tick; 04-17-2013 at 07:31 AM.
I'm going to bump this for more info. I'll be in the market for heads and a few friends are also with boosted applications like myself. Looking at the 260's on 376-416ci setups. First option is Mast heads but if these are legit they could get purchased.
I've made great power with these heads and the new TFS LS3 heads, but I have never been impressed with the Mast stuff and Corey I know I've told you that before.
I only have one customer who I've been impressed by his Mast heads, and I have good reason to be impressed by those. He has been very fast at the track with his.
I Like I like.... 566rwhp I really like the cam you did for me, now that cam is nice but not Solid(looks kind of close to mine but it lacks lift) thanks again Martin
Had to get up to check on my lamb shanks ...been cooking for 6 hrs at 250deg. Heres my ? to Jason or anyone at TSP what bore size did you use for the 255's or the 260's I thought I seen 4.125 to.155.
I've made great power with these heads and the new TFS LS3 heads, but I have never been impressed with the Mast stuff and Corey I know I've told you that before.
I only have one customer who I've been impressed by his Mast heads, and I have good reason to be impressed by those. He has been very fast at the track with his.
You may have told me that but I'm very forgetful. So the question is the TFS 255's or the PRC 260's?
Originally Posted by Camper
ill be on the dyno adding PRC 260s and roughly 4psi of boost next week detoxx.
Looking forward to what they do on all of that boost haha
I have my own ideas.......about this ...1st What size bore do they use to get these #'s.
I understand that the PRC heads are great and by they way at a good price too...They will be right on par with TFS head but cheaper..There TSP as cast version of the 255's for 1600.oo is down right good.But I want to know about what bore they used to get the #'s...We all know that these heads are a bargain & better than ported L92's. I'm N/a with small bore engine 4.030 with over .700 lift and this to me is what I need to know before I go buy TFS bare heads again 975. each vs 1600 TSP bare heads.I understand it's not about #'s but to me 380 cfms @ .700 with a 4.125 or 4.155 bore if that's correct I will be buying TFS heads again 382 cfms@ .700 with 4.065 bore. I'm willing to spend the extra 400. If Jason to were show me that they used a bore of no more than 4.070 I would gladly pick up a set and still have change to do other things.
They Do Make A Great Product.
Are there any other PRC LS3 head owners out there that have bothered to check swipe on these heads with stock LS3 rockers???
I don't know why I even bothered, as the geometry is pretty much set in stone, but I had to know, and I'm a little concerned.
To me, the optimal swipe pattern would start somewhere toward the intake side and rock toward the center of the valve stem at full lift, so that the load on the valve stem is centered at max spring pressure.
Well, that's not the case on my heads. For one, the valve stems on the intake are about .020-.025" taller than the exhaust stems. Is this normal?
Also, my rockers start at the center of the valve stem, maybe even biased slightly toward the exhaust side, at ZERO lift. Then, as they approach max lift(~.630") they rock toward the exhaust side of the stem even more. In other words, at max lift they are nowhere near centered on the valve stem.
Should I be concerned? I see this resulting in more lift, but also way more lateral load on the valve guides, given the 465+ pounds of spring pressure at max lift.
I'm REALLY hoping the guys at Texas Speed know something I don't and that there's nothing wrong with my heads...
Thought I was having installed spring height issues, but my dad was too gentle with the spring locks. Spring heights are 1.795-1.797. Not quite the 1.810 that the springs are spec'd for, but no worries since I'm switching to btr 660s. 15 thou shims will be perfect.
Gotta give a shout out to the guys at Texas speed for helping me out with these heads. Mine is a long story, but the short one is that the FIRST set of heads I ordered I'm sure were exactly what I ordered, but they were promptly stolen from my porch before I got home. Took 2.5 weeks, but Texas speed got their(or ups') insurance to cover it and promptly shipped out a new set. Unfortunately, the chamber size wasn't what I ordered. Again Texas speed paid for return shipping to get them cut to my spec. Got them back, and in the middle of changing out springs, found out that I didn't get the hollow stem valves I paid for. Guys at Texas speed apologized and next day aired my valves. In talking on the phone with Dominic he really wanted to make sure I was made whole for the inconveniences I've had with these heads. I told him I was concerned about the high spring pressures of the eht 480lb springs and was wanting to run something different. He offered to exchange them out for what I want at no additional charge and promptly shipped them out. I got the heads back together and installed this week and couldn't be happier with the overall quality and level of customer service!
Finished my PRC255 heads/cam install a couple weeks ago. Other than a crappy fel-pro valve cover seal failure and a slight oil pan leak(it was there before I started the build - guess I didn't fix it), it went flawless! Basic specs of the build are in my signature.
First fire up, hoping for no BANG and good oil pressure, check!
But they definitely contributed to the horsepower gain! It pulled 512RWHP/446RWTQ, on a MUSTANG dyno, no less. Cunningham motorsports guys, who have done a TON of high HP builds/tunes, said that this was the highest HP stock bottom end, heads/cam only build they have had so far. Mind you, I am on the stock intake manifold, and 1-3/4 to 1-7/8 Kooks stepped headers with 2.5" exhaust. I was also on break-in oil for the pull(knew I didn't need it, but it's cheaper than LS30), which may have impacted peak performance. If all I cared about was peak numbers, I'm sure a different intake, 2" headers, and 3" exhaust would have got me to 525 or so, but I wanted to keep the torque down lower in the RPM band for streetability.
Guys we're proud to announce we have finalized the PRC 255 & 260cc LS3 aftermarket casting cylinder heads. These new runners are smaller than stock runners for improved velocity & move unmatched amounts of air! The 260cc runner moves right at 380cfm & the 255cc moves 370cfm!
255cc Heads Features:
260cc Heads Features:
Initial testing has shown the 255cc head to be capable of producing 600 flywheel horsepower through a stock intake LS3 engine on the TSP Superflow 902 engine dyno!
look for dyno data from strokers using the 260cc version very soon as we have several builds going together with them right now!
04-16-2013, 01:00 AM
