2FNQUIK

iTrader: (17)

Alright, trying to put together a head and cam package, I want to go with ported 243's on a stock bore LS6 block, milled for compression, but want to run larger valves on the intake and exhaust sides, my question is, what is the largest valve that ou can safely run on a stock bore without it being overkill, after the heads are assembled and flowed I will then get a cam designed to match the heads as well as a free flowing tb/manifold setup with larger injectors and upgraded fuel system, trying to get good, reliable hp/tq for a dd that I can depend on and dive for a while with no problems, I am doing roller rockers(yt ot hs) with all of the necessary valvetrain upgrades at the same time...Trying to build it the right way

Old SStroker

IMO, you are going about this the wrong way. Bigger valves don't mean bigger power especially on a 347 (3.900 bore). Obviously you have a budget (everyone does, but some are much bigger than others), so to get the most bang for the buck, you need to look for setups that drive like you want and make the torque (and power) curve you need. It can be done with stock size valves. The porting and valve job are the most critical thing to get right on the heads. Not every supplier gets that right.

As for rockers, you might rethink the rollers, but go wilth the necessary valvetrain upgrades specified by you chosen valvetrain designer.

2FNQUIK

iTrader: (17)

Thanks for the reply...what are the drawbacks of rollers..I was reading the post on here that said that the stock rockers are only good .550 lift and the h/c/i package that i am trying to put together is going to be over that, I was under the impression that after you have decided what your goals are for the car to get the best possible heads that your budget will allow and meet your specific needs and get your cam designed to complement the heads. In researching other companies and their offerings I noticed that most aftermarket heads offer larger both intake and exhaust valves..if there was no benefit in doing this and optimal results could be achieved with smaller valves then why do it??? I know that valve size is not what necessarily produces power( bigger is better theory) but I do know that with the right porting and valve job combined with (possibly) larger valves can yield surprising results..please correct me if I am wrong..I have been researching various aftermarket heads as well as ported offerings of stock castings from sponsors and trying to put together my own little combo ( I know that there are already proven combos out), especially with some of the new developments being made in camshaft and head technology

jimmyblue

iTrader: (11)

I think you are not valve limited but runner limited,
the stockish heads don't respond to lifts over .550
until ported. If you were valve limited they would
respond to lift. Big valves don't help if they put you
closer to the cylinder wall (shrouding). Duration is
where it's at.

Old SStroker

Here are some results from a recent head/cam/intake install on an LS1 Camaro.

The stock engine with bolt-ons including 1-3/4 long tubes, SLP cat'ed Y pipe, stock 4L60E automatic with Yank 3600 TC, center mount exhaust and stock 32.3 gears made 345 lb-ft and 330 hp on a fairly stingy Dynojet.

The same bolt-ons were used for the H/C/I package. The heads were very high-end CNC ported 243's (with stock diameter valves), the intake was a FAST 92/92 and the HR cam was done to compliment the entire package.

This H/C/I package, on the same dyno, raised max torque to 405 lb-ft (up 60) and max hp to 448 (up 118). The H/C/I had 375 lb-ft or more from 3500 to 6500. That's about 92% of max torque from stall rpm to shift rpm. It was at least 40 lb-ft better from 3000 up and it was up 122 lb-ft @ 6300. That's up 146 hp (@6300) if you do the math.

The 3600 stall might now be a little much. That 92% of max torque available from 3500-6300 should make it fun on the street.

Now this is probably the very high end of what you can expect from an H/C/I package, and is is not cheap. Hell, it's quite expensive in $, but somewhat reasonable in $/hp or $/average torque and hp throughout the driving range. The heads are most definitely not a DIY project and they were not from a sponsor, so names and charts are also not included here.

This shows you what can be done with 243 heads. If you don't use the same sources and parts, your results may vary.

As far as the roller rockers, I had my say on another thread:

https://ls1tech.com/forums/generatio...ockers-no.html

SStrokerAce

iTrader: (2)

While part of what you said there is correct being that big valves don't help (sometimes) a lot of the other assumptions are very off.

1. Almost every LS head is valve throat limited in terms of area, which is the way it should be. The port is only limiting in getting the air to the throat cleanly.

2. Stock heads DO work well over .550" due to the valve throat being the limit and the stability of valvetrain dynamics and limited lift applications.

3. You should do some research on 25% Lift to Diameter ratios and what that means in terms of AREA the cylinder sees.

4. Duration IS NOT where it is at.


As Old SStroker mentioned the stock size valves can do a hell of a lot more than most people think. Especially on AUTOMATIC cars where they can make more than M6 cars with similar modifications done incorrectly.

Bret

2FNQUIK

iTrader: (17)

Alright..sticking wih the stock valves offered by the porter which are new LS2 intake and exhaust valves, what , if any, would be the advantage of using either hollow valves or the stock LS6 sodium filled valves( being that you want your valvetrain as light as possible correct??) and are the LS6 (Z06) rockers any different from the rockers on my stock 01 Camaro(241 heads)....pushrod length and spring choice would be chosen at the time the cam is built correct??

SStrokerAce

iTrader: (2)

Why stick with the stockers? There is strength and flow in a set of aftermarket valves.

The LS6 stock valves are some of the lightest steel valves I have ever seen, and yes that is a very GOOD thing!

All cathedral port rockers are the same.

Bret

2FNQUIK

iTrader: (17)

Currently the porter said they offer either manley stock diameter valves and stock ls2 valves..I am willing to purchase the ls6 lightweights and have them install those

SStrokerAce

iTrader: (2)

Last time I bought or sold a set of the Hollow Stem stockers they are $400.... Ferrea 6000 series are $275 retail roughly.

deuce_454

if i were you i would not worry so much about the valve diameter... it isnt what makes or breaks an engine build.. send your 243´s to TEA and get a good CNC port, hand finished chamber and exhaust and a good valvejob.. (i have a set of TEA ls6 stg 2´s and have never seen that level of craftmanship on a head before)

as for rockers, i vote for the stock ones... many a 500+ rwhp engine is running stock rockers, and aluminium will break eventually its just a question of loadcycles and load... (same reason you don´t run aluminium rods on the street) you mentioned reliability... so why discard a great OEM engineered product that will last forever in favour of somnthing that has been known to break (do a search...)


ps. the bit about aluminium breaking.. im not just taking out of my azz, i hold a degree in mechanical engineering and its a property of the material that there is no threashold load below wich fatigue doesnt occur (as there is for steel) the curve is a straight line... so its just a matter of time...... and with stiffer springs.. less time

nastychevelle

iTrader: (7)

you could always send your rockers to someone to get reworked...

2FNQUIK

iTrader: (17)

Well are there better stock gm rockers (LS3,2,7,6) that I could run instead of the ones that came with my 241's????...I just want to build it right the first time and not really worry about anything failing..I am keeping my stock shortblock and really don't plan on changing that unless something drastic happens, but my topend will be completely worked over from injectors and fuel rails to heads, cam and supporting valvetrain....trying to build as much power as I can but still maintain a few more years of troublefree operation...

02*C5

iTrader: (1)

All I can say is that as we speak my porter who is a legend (hit me up if you want his info) on LS heads is doing my heads. He is doing my stock 241's and a costume ground cam. He suggested because the cam I am getting to go with the over sized valves 2.02/1.60 also to go with double springs (also a big thing in choosing rockers/rod and lifters.) I am getting my heads milled along with port and polishing . I am sure that if this guy did not know what he was doing he would not be telling me to go with the over size valves. Oh and I am running a stock bottom end. I say this. If you trust the guy who is doing your work, go with his advice, if you don't then you need to get your heads back, do more research and then take them to some one who you trust. Oh and the guy has great prices for the budget racer like us. Like I said you want info hit me up and I'll be more than glad to share.

Old SStroker

The highlighted phrases above throw up a number of red flags, IMO. All of them added together go against what works very well on LS engines especially if you are on a budget...or even if you are not.

It would be nice to post some results of his head/cam packages here or in the dyno results and comparisons section.

I did say all this before, but it bears repeating, IMO.

turbo'd stang

You talking about the guys at CFE...Carl?

2FNQUIK

iTrader: (17)

The chosen porter has produced some proven results while not breaking the bank, budget is of the utmost concern but not at the cost of quality. Just trying to pt together a solid combination that will not only prove powerful but reliable as well without hurting the pockets too bad. I know that there are many proven combos out there already but none of them seem to really satisfy everything I am looking for. I realize that if you want performance sacrifices have to be made and that reliability and drivability have to take a back seat..to a limit! I'm not going out here slapping a huge cam in with a guy who has limited experience in porting heads( NO PUN INTENDED) and other items and have a car that not only runs like crap but doesn't last. The LS engines have proven themselves over the years and the r/d that gm put in to them seems to produce results( seeing the results that people come up with by modifying some of gm's designs) but as I said before after it's built I want it to last..Thanks for the offer about the porter and for all those who responded , I am waiting to hear back from the porter in regards to changing my rockers....he also recommends the stockers but I was wondering should I get new stock rockers or is there an upgrade stock rocker that gm produces(LS6,7,3..etc..) that will work??

turbo'd stang

If you're working with Carl, I'd go with his word. He's done alot with heads.

SStrokerAce

iTrader: (2)

If he is giving Carl 241 castings to work on it better be for Super Stock racing... otherwise he's not in the ball park of the right budget.

Umm, you might notice people on here who don't do quality work and use quality parts have that tradeoff of performance and durabiliy, but it is by FAR not the case when the setup is handled professionally. Your goals are EASILY achiveable but the knowledge to do so seems rare for some reason.

Bret

2FNQUIK

iTrader: (17)

Umm, you might notice people on here who don't do quality work and use quality parts have that tradeoff of performance and durabiliy, but it is by FAR not the case when the setup is handled professionally. Your goals are EASILY achiveable but the knowledge to do so seems rare for some reason.

Bret[/QUOTE]

My point exactly..I take everything off of the forum with a grain of salt( so to speak) but I do know that there are alot of knowldgeable people on here and that you just have to kind of filter through them and the other places on the internet and come to your own conclusions about who to trust when building a setup.Thats why I posted in this section, to try and get some info from more "knowledgeable" "advanced" people who have seen what works and what doesn't over the years...I am not a fan of off the shelf combo's and really like going the different route(which I know isn't always better). I know the 243 catsings are proven when used with the right combo of parts and tuning as well as non-cookie cutter port job(you guys know what I mean, there are certain areas of "ported" heads that some people don't show much attention to when they make a difference) Any body have any info on the rocker situaton as I asked..still waiting to hear from the porter.