ayousef

I'm interested in a set of MAST ls3 bigbore heads to replace my stock ls3 heads with and some dyno results show gains of over 50rwhp in NA applications.

Wondering if there's any HP benefit to heads in general on a blown application say a 10psi 427.

What I'm trying to say is, I know there will be a boost drop since the motor is now more efficient, but assuming I DONT pulley down to get the boost back where it was, will there still be any power gains from tuning only by means of additional spark advance?

Bob@BruteSpeed

iTrader: (16)

Yes you should see a power gain, better heads on a forced induction engine generally make a huge difference in power. The only way I see where better heads wouldn't help is if the blower is on the small side and is working overtime, or the exhaust system is too small, etc. Bob

Jon@BruteSpeed

iTrader: (3)

I just received a set of Mast LS3 heads for a new build and they look nice. Buy them, if you don't use them you can sleep with them.

TermnEatr

iTrader: (24)

i will be getting the mast ls7 heads on my billy briggs 408 like stated above the mast heads are ****!!!!

I8UR4RD

iTrader: (16)

You can also check out PRC 227's or the 237's. They have a great quality, thick decklid, and are a little softer on the checkbook.






Boost is a measure of resistance/restriction. A motor that flows better and makes less boost, will make more power than one with more boost, and restrictive heads/exhaust setup.

Jon@BruteSpeed

iTrader: (3)

But seriously, they are a nice set of heads. I got the six bolt heads even though I won't be using the extra holes for awhile, at no extra cost. Recommend inconel exhaust valves in case you plan on turning it up down the road. Not to mention 3/4" deck. I just received T&D shaft rockers for them, if using factory rockers don't forget to order rocker stands. I received my heads within a week of ordering, outstanding service.

I8UR4RD

iTrader: (16)

yeah I was wishing I could use the extra holes in my PRC's too, but alas, the 1/2 head studs and ls9 gaskets will just have to do. haha. texas speed actually states that the deck is thicker than .750 in some areas. seemed strange to me. Mast,AFR,TFS,PRC are all going to be a great choice.

ayousef

thanks guys, I do love the MAST heads and wouldnt have thought twice if this was an NA build, I still dont get how they will make power ill give you an example:

10psi 427 with stock LS3 heads

add MAST LS3 heads and boost drops to say 8psi, but with no change in blower pulley size the blower is still pushing the SAME CFM through the engine at a lower boost/restriction level, which enabled you to run more timing, how much power are you going to get from timing alone?

I am turning up the boost however, but I doubt I will get back the boost lost from the heads since those heads flow SO well its un-real. Ive seen the engine dyno result where the mast ls3's made 65 bhp more, and ive heard of 50+ rwhp compared to stock LS3 heads.

KILLER-LS1

iTrader: (18)

imagine a straw and a paper towel roll. You can blow through both, the straw will have more PSI (harder to blow) but less CFM (less air coming out). When you blow through the paper towel roll, there is less psi, but more air. The air (cfm) is what makes power, not the psi.

Now Imagine pumping the air from your supercharger through both tubes, which will have more air coming through it?

also, the more psi, the more heat is generated which results in increased IAT's, which ultimately limits timing as well.

incon3037r

iTrader: (1)

Exactly what I was going to say. LOL!!

ayousef

Thanks I already know this, but:

Blower pulley is what determines how much flow in CFM the blower will make, REGARDLESS of boost.

so MAST LS3 heads or stock LS3 heads, the motor will flow the exact amount of air because thats the blower job. The boost PSI will be higher on the stock LS3 motor because it has to force more air into a less efficient head. On the MAST head, the ONLY way you can make more power is by running additional timing since you're at a lower boost psi.

The proper way to gain LOTS of power from heads is to pulley down to gain back the boost lost by the heads, but I clearly scratched this idea from the initial post for the sake of the conversation.

The Alchemist

iTrader: (19)

Not Mast heads, but basically the same, they are Performance Induction LXR heads prior to Mast and PI joining forces.




Think of it this way as well. The less boost, but the same cfm from the blower means less power needed to turn the blower. It might not sound like a lot, but you'd be surprised how much power is needed to spin the blower making higher boost pressures. Plus the less resistance means the blower runs more efficiently. The more efficiently it runs, the more power you make.

ayousef

Thanks, that was the kind of answer I was looking for, less boost means less power needed to spin the blower, less IAT rise, and the ability to run more timing.

I am pullying down for 2 more PSI however, so im hoping it works out nicely.

The Alchemist

iTrader: (19)

Also, the better flowing head means more air that is able to get into the combustion chamber when the intake valve is open. Sure, the boost pressure pushes it in, but ultimately, how well the air flows into the chamber determines how much power you make.

So if the head is choking the flow of air into the chamber, all you're doing is creating more boost and not getting more flow into the chambers.

ayousef

makes me wonder if its worth switching my lower intake from an LS3 style port to LS7 style and go with a MAST 305 LS7 Black Label which is supposedely better...

KILLER-LS1

iTrader: (18)

I disagree:

youre saying the blower puts out X amount of CFM regardless of the engine conditions, (which is true), however what the engine can actually ingest is a whole different story. The engine does not always use all of the available CFM. Its called volumetric efficiency.

By your logic, you can go ahead and throw away your long tubes and put stock manifolds on because regardless of restriction, the motor will still get the same CFM from the blower, and therefore still have roughly the same power, but that is incorrect.

read up on volumetric efficiency. it is the percentage of air that is physically ingested in to the cylinder compared to what would be measured mathematically.

stock engines can be anywhere between 75-95% volumetric efficiency. Add forced induction and your VE goes above 100%. the higher percentage, the more power the car will make. by increasing the flow of the cylinder heads, you are allowing the engine to ingest more air, therefore increasing your VE percentage.

Detoxx03

iTrader: (14)

I wouldn't worry about gaining boost back. The less restriction the better. If you car makes 700rwhp on 10lbs or 700 on 8lbs I'd rather be on 8lbs. More efficient and less strain on the blower and motor.

I had the stock procharger inlet on my car and it made 638rwhp but then I switched to the Dallas Performance 4" inlet and it picked up 38hp to put me 676rwhp. It didn't gain a pound or lose any. When I added headers it lost a pound. I'd love to get a set of heads or port my stock ones to lose more boost but also make more power.

dudeman

iTrader: (43)

mast ls3 large bore heads require a 4.125 bore. they wont work on a stock ls3.

they are very nice. i have a set sitting in my bedroom lol!

ayousef

well i happen to have a 427 with a 4.125 bore

427

iTrader: (3)

If you lower restriction with cent super the engine will pick up power as the super will move a higher volume of air. When the restriction is lowered the psi will go down but the power required to turn the super goes up as it is doing more work.

Kurt