90hatchfox

I know this has been on other topics but just thought I would just see what other peoples opinions are.

Currently contemplating on selling my PRC 247 in favor of the TFS 245 mainly because im planning on running nitrous in the future, so the nitrous port seems like a better option but not sure if im pulling hairs. Just doing some reading and looking at flow numbers and such. Naturally Aspirated would i benefit from the swap?

Right now my setup is a 418 LS3 with a FAST 102 intake, 2" headers to 3" collector to 3" x-pipe dumped, PRC 247 heads on 93 octane making roughly 560 whp and 530tq with a 248/252 .621/.604 112lsa. 11.8:1 compression.

I am going to be going with a set of johnson link bar lifters and roller tip rockers and a cam motion cam spec'd:
Grind number XA248/400-XA262/390-113+4
.Lift with 1.7 intake .680" / exhaust .663"
.Duration at .050" intake 248 / exhaust 262
.Lobe separation 113 with 109 intake centerline.

If i have the heads off and everything i just want to make sure im going to get more out of my setup. Not worried so much about price.

PRC 247 Heads:
Features:

• 247cc Fully CNC Ported Intake Runners
• 84cc Fully CNC Ported Exhaust Runners
• TSP Dual Spring Kit w/ PAC Springs Rated To .660" Lift
• 68cc CNC Machined Chambers
• CHE Bronze Guides
• 2.120" Intake / 1.600" Stainless Valves

Flow Data: No Exhaust Pipe
LIFT INTAKE FLOW EXHAUST FLOW

.100" 66 CFM 57 CFM
.200" 147 CFM 117 CFM
.300" 228 CFM 170 CFM
.400" 282 CFM 206 CFM
.500" 321 CFM 227 CFM
.600" 343 CFM 235 CFM
.650" 355 CFM 241 CFM
.700" 360 CFM 245 CFM

TFS 245 Heads:
Combustion Chamber Volume:70cc CNC-profiled Standard
Intake Port Volume:245cc CNC Ported
Intake Valve Diameter:2.10
Exhaust Port Volume: 90cc CNC Ported Nitrous port
Exhaust Port Dimensions:1.700" x 1.550"
Exhaust Valve Diameter:1.600"
:Lift Intake Exhaust

0.100 69 55
0.200 146CFM 122CFM
0.300 237CFM 199CFM
0.400 294CFM 250CFM
0.500 336CFM 277CFM
0.550 348CFM 284CFM
0.600 353CFM 290CFM

These are all advertised #s from TSP and TEA By looking at the Flow #s the TFS for sure seems like a better option on paper but the fact that they test it with an exhaust pipe vs PRC doesnt use any exhaust pipe when bench flow testing means there could be alot less flow than in real terms with restriction. Also seeing that PRC uses a larger valve and also has a larger intake runner size means that port velocity could also be a big factor as im only going to run a FAST intake and not going to see much over 6800 rpm on motor.Mainly running N/A with some or limited use of Nitrous.

Any thoughts?

00pooterSS

iTrader: (40)

I think you're splitting some serious hairs and the money and effort you would put in the head swap would be better used on another area of the car.

00pooterSS

iTrader: (40)

I would post this in the gen 4 section. I see more conversations like this one in there than here.

G Atsma

Too much money for minimal payback. As said above, splitting hairs.

tech@WS6store

iTrader: (2)

The prc heads already have great valves the tfs will need to be upgraded to a manley severe duty if looking at boost over 20lbs or lots of nitrous. Ask me how i know.

I like both alot but lately PRC wins out on casting and built in features vs upgrades.

DietCoke

iTrader: (18)

Advertised flow numbers mean dick because you can't compare them to other advertised flow numbers.

Same bench, same day, third party is the closest to use you'll get out of flow numbers but that won't ever happen. If you already have the 247s, you're wasting your time eyeballing the other ones.

Public Enemy

I've ran both. You will waste your time selling the prc 247 and getting a tfs 245... Just send the prc to go a good head porter to get the n2o exhaust port.

Now, if you didn't have the PRC already then i would go for the TFS instead.. they perform almost the same and have almost the same features (I looked at them and they looked identical and performed almost the same) however the TFS was more consistent, better finishing and i just had better luck... PRC is still an awesome head.

90hatchfox

Thanks for the replies. I just figured the exhaust side flows a lot more would give me better results. I’ll just keep chugging away with what I have.

BlwnLs1GTO

iTrader: (12)

THIS, was the only real point that stood out for me. Even so, unless you have the coin and love doing this kind of stuff, I don't think it's worth it a bit to swap them out. I do like the N20 Ports on the TFS
but how much real difference will it make? And, will you need Kip or LJMS etc... take a look and spec a new cam to help pull as much power as possible? If so, add that in on top. Good Luck

big hammer

If you’re NA the engine doesn’t care about the exhaust port as much. If you’re boosted or nitrous it does

Darth_V8r

iTrader: (4)

I seen a article where Mamo, Darin Martin, and some other well reputed head porters all said the same thing. For NA main focus is the intake port. The piston will displace the exhaust gases.

G Atsma

Interesting! Maybe the reason LS3 heads stayed with smaller exhaust ports. I always thought porting them would release a decent amount of power. Maybe not!
Though I do understand the port size disparity is the reason engines with these or other rectangular port heads like cams with wider duration splits.

Che70velle

iTrader: (6)

My MMS 265’s have the “nitrous exhaust port” work done to them. I was shooting for max effort, and tony said it’s good for another 6-8 hp. Sounds meaningless but when you get north of 600 whp NA, 6-8 hp is hard to find, and crazy expensive.

Darth_V8r

iTrader: (4)

Not saying no benefit at all. Just that in that article they all said it's not super critical. Easier to cheat the exhaust flow with cam timing than the intake flow.

Mavn

iTrader: (3)

This is wayyy to true. for N/A .. ever 1 horse once you get close to maxing out the combo is ridiculously hard and MONEY.

Tuskyz28

If anything you want to change it may be the cam depending on how big of a shot you plan on spraying. A wider split/more exhaust duration would help the exhaust out the motor but it might hurt the motor naturally aspirated performance.

dr_whigham

iTrader: (49)

Good God isn't that the truth. The pictures I've seen lately with "out of the box" TFS 255's is straight CARNAGE. Even on as little as 12#'s

tech@WS6store

iTrader: (2)

We had 3 customers with straight up taco valves. They were like "to hell with tulip lets skip to taco Tuesday" Looked like some twisted form of edible arrangements meets man present.

And at $360-400+ extra they are no longer in the same price range. As far as heads go that would be a Bernie tax bracket setup.

The first thing out of tfs mouth was "well they must be running a ton of boost" Nowdays you aint sheet if you dont start at 20lbs

dr_whigham

iTrader: (49)

I like you. Can we be friends?

tech@WS6store

iTrader: (2)

I get in trouble for my snarky comments. Often lol