Z-Rated

How bad would it be to have stage 3 heads on a 346? I understand that stage 3s are for bigger cube motors, but I found a really good deal on some. Im just wondering how much it would hurt my cars performance. I know that later I will go bigger cubes so I can get the full benifit of the heads. So for a temporary thing would this be alright to do? has anyone done it before? thanks

1999_SS_M6

well, my advice would be to buy 'em and shelf 'em. I mean, if you KNOW you are going big cubes down the line, and you've got a smokin deal goin, you don't have to pass them up.... however, you don't have to install them on your car when you know it's going to hurt performance either.

Stage 3's are going to kill your low end torque most likely. They are likely to have big valves, and more port volume than 346 cubes can support. Without starting some long dissertation about intake charge velocity and port stall and yada yada, just suffice it to say they were probably ported more aggressively than what could benefit your car.

I hate missing a good deal, but I would hate spending my cash, doing an extensive amount of work to my car, and then being rewarded by worse than stock performance even more..

2001CamaroGuy

iTrader: (6)

I have stage 3 heads with 2.08/1.60 valves on a stock short block with the TR 224 cam and love it.

It didn't kill the low end at all (at least I can't feel any loss) and the mid/high RPM SCREAMS!!!

I might would have had more low end power with stock sized valves, but the mid/high more than make up for any loss. Also, I'm now set to go SC, CI+, Nitrous, etc....what ever I want.

Chris

1999_SS_M6

This is why a thread like this is so tricky... it's not like the Industry Standards Organization has mandated a specific set of parameters to classify what is in fact a "stage 3" head.

I mean, who knows what the port volume is from one "stage 3" head to the next, or what valve size each porter feels is ideal, or whether the head was ported for mid-lift flow, or just peak valve lift #'s, along with about a million other variables specific to each porter's preference.

Making generalizations is generally a bad idea in my experience... however, MOST stage 3 setups are intended for big cube setups, or all out race, for the reasons I listed before.

Z-Rated

Thats cool, I guess I can shelve them or sell them. I almost positive that they are MTI heads..... so with that being said, it would probally do more harm then good correct? Hey Chris, who did your heads if you dont mind my asking.

DONAIMIAN

iTrader: (18)

As long as the combustion chamer isnt cut for a bigger bore I dont see a problem at all

JPR

IMHO, I would classify an S3 head to be..

Over 220 cc's of intake runner volume.
Over 2.02 valves.
Over .030 milling.
Double springs.
Enlarged combustion chambers.

I have 216 cc's of intake volume, 2.02 valves, .035 milled and flows well into the 312 cfm range in the cam lift area, but in my opinion, the daily driving has suffered under 3,000 rpm's, but shaggs azz over 3,500 rpm's though! so I guess it's just a matter of what your looking for?

Joe.

FrankSS

iTrader: (18)

i say throw those bad boys on there with a healthy cam.......

ChrisB

JPR pretty much went the the heart of the issue - it depends on what constitutes the "stage III". If you had a set of heads that were extensively ported, but were done so - properly - with a stock cubic inch motor in midn then probably only positive things. Conversley if you had a set of stage III heads for a 422 on your stock motor it probably would hurt low rpm VE.

Whether they are worth it or not depend on how much power you want to make.

Z-Rated

Well what about 400RWHP with a good size came? ie 224, .581 or something close? and thanks JPR that really cleared some things up. Thats what I was guessing but that cleared things up.

2001CamaroGuy

iTrader: (6)

I had my heads done local buy a guy that builds top fuel engines. I spent a good amount of time talking to him and his feeling was as follows:

"The LS1 intake is basically a long runner intake so it will keep things good down low (not perfect....but good...). The problem is that at high mid and high RPM, when the engine inhails fuel, the only place it has to pull from is right under the valve. It does not have time to pull fuel/air mixture down that long runner. So if you really open the area around the valve (ie larger valves for larger port volume), you will be able to more efficiently fead the engine at mid and high RPM."

I then asked him about low RPM daily driving. His answer:

"Don't worry about below 3000 RPM, people make too much out of that. You will have more hp than you need anyways for driving around (he is right....with 295s I smoke them off the light....). If your racing, you have NO BUSINESS being below your RPM band. For drag racing you launch at 4000 RPM anyways and for road racing (what I want to do....) you downshift to stay in the RPM band."

So after talking to him for a while and then talking to my father who has been doing hot rods since he was a kid in the 60s, I decided to go BIG on everything. It turned out to be one of the best decisions ever. The car has more power than I can use down low and it never seems to run out of RPM (7000 is a lot faster than I feel safe doing...).

I don't remember what my port volume is (I lost the flow card he gave me ) but the heads are:

2.08/1.60 valves
0.020" mill (glad I didn't go anymore.....with the big valves I could only fit a TR 224 without fly cutting)
duel springs
cc of the chamber came down to 60CCs I think (11.1:1 CR)

Chris

ChrisB

Z-Rated - with something like the TR 224 it should be cake to make 400rwhp - some people are getting pretty close/doing that with stock heads - if that is what you want to get out of your car then definitely save some money on the heads - most good quality "stage 1" heads should get you there with tuning and boltons easily.

2001CamaroGuy - I would pose the question from a different angle though - I agree that with large valves, etc. you can still have "plenty" of torque at low rpm (depending on your definition of plenty, etc) - but the question is are they really that beneficial for peak power, etc. - especially on a stock bore? I would submit that while they don't hurt they probably don't really help, at least on a stock bore.

Z-Rated

That wasnt what I meant. All I was wondering if it would hurt the power worse than stock heads. I was talking so some people and they mentioned that it would. But after reading what Chris said I think ill start saving up. I want to hopefully only buy heads once, so if I can get away with it ill use the S3. Thanks!

ChrisB

It definitely shouldn't be worse then stock heads - if it is, then something is wrong with the heads themselves.

Visceral

iTrader: (1)

I think the big elephant standing in the room is the combustion chamber size.

Are the heads going to fit a standard 3.90" bore? If not, will a standard head gasket even work? Take a set of micrometers and measure the diameter of the combustion chamber. Thats the only way you are going to know what you can do here.

If the chamber is still at 3.900, then ok, you'll have a little shrouding, you'll give up some port velocity in the midrange. MTI mostly works the exhaust port between stage 2 and 3. Worst comes to worst, you'll be down a few HP, but set if you ever go with a stroker or bigger motor.

If the chambers are larger than 3.9" diameter, consider either shelving them until you have the shortblock for them, or selling them and picking up some stage 2's.

chris

2001CamaroGuy

iTrader: (6)

"If" you go by what Rodger (the guy who did my work) said, then they help. The larger valve allowed him to port the bowl deeper/wider which increased flow capacity and gave the engine a larger "pot" from which it could pull from on intake. I'll admit they probably are not being used to their full potential due to the CI of the engine. The final thing to remember is, I'm planning on going to 383+ CIs some day so I wanted to do "everything" once and never have to play with the heads again.

The Dragon

iTrader: (6)

Ok, real world comparisons:

As everyone learns, tuning is EVERYTHING.

My buddy has an '02 WS6 with K&N FIPK, S3 TB, Hookers/Y, custom 3" exhaust with a MagnaFlow Bullet, a set of stage 3 LS6 heads from CNC, and the biggest cam in the country on a stock-cubed LS1.

He pulls me by 2 cars (he should get me by 4 or more when I complete his tune, get his MAF ends on, and open the FIPK plate thereby eliminating his 2 remaining chokes)

I pull a 440 rwhp '01 Viper GTS with full bolt-ons.

Neither of us have dyno'd as of now.

When I finish his car, I'll post dyno #'s for us; should be next weekend.

Bottom line: ported heads CAN'T hurt performance as long as you have a good, and extensive, tune.

ChrisB

I would disagree - ported heads *can* hurt performant - it all depends on how well the heads were ported.

Visceral brings up another good point (already too many Chris's on this thread though ) - if you had a set of heads that were worked for a 4.1 bore on a 3.9 bore, then yes, relative to a set of heads works as much - but for a 3.9 bore - you would probably loose a decent bit of power.

I would still be more inclined to have your heads worked over with the present combination in mind (even if not to a "stage III" spec, etc.) and then in the future when you do your motor have the heads freshened up, and you can have whatever additional porting you need done.

Z-Rated

Visceral, that was what I was looking for. A solid answer I can use when and if I get them.

The Dragon, are your heads for 3.9 or 4.1? this could important to know for what they are talking about.

ChrisB thanks for clearing some things up.

Robzilla

iTrader: (1)

I think you should just buy them and keep'em off the car until you get the bigger ci, it would just be alot easier