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Just pulled the trigger on a 427 short block (4.125x4.00) I will be using GM LS3 heads because (I have a new set collecting dust) NOT interested in different heads.
I am trying to decide whether or not to have these heads ported. This is not a max effort build. I am not chasing time or a HP number, though I am shooting for 600-625. It is going in a 67 Camaro that is a weekend hotrod. I dont race it other than friendly pulls against buddies and maybe a few unsanctioned street duels.
My thought for porting is the possibility of getting more power with less cam...
I know that there are companies that claim bigger flow numbers but that usually comes with hogged out intake runners. I DONT want to give up velocity for a bigger number... My question is... what is the best size for a 427 that wont see anything over 7000-7200 RPMs? Ive been debating between stock, TSP, FED. for the port work on my heads. The FED flows the most.. but also has the biggest port.
Stock 260 cc
TSP 267 cc
FED 288 cc
67 Camaro 3200 lbs
427 (4.125 x 4.00) 11.2 static compression, .040 quench
Holley Terminator Throttle body/ Vic Jr single plane intake
Ball park cam specs: 23x/24x 63x/61x, 110-113 LSA (Cam not spec'd yet)
T56 Magnum/ 373 gears/ 26" tall tires
1 7/8 long tubs, X-pipe, 3" full exhaust
I have a similar build in my Chevelle, my heads are ported by advanced inductions with 280cc intake ports. I think you'll be fine either head but personally I'd go with the heads from fed. Here is the link to my engine dyno and specs.
I have a 408ci with stock port ls3 heads a bigger cam than you wirh a fast 102 and it dynoed 525 wheel through a 6l80e 4400 converter on a stingy dyno.
With more cubes I wouldn't be looking at the intake flow numbers . I would be looking at the exhaust numbers. Intake flows plenty even stock . The exhaust side is the choke
It really doesn't Matter who ports the heads as long as there Competent with a Proven track record they: will All be about the same HP.
Ls3 head test with Various porters showed that with all using a factory ls3 head.
Keep the port On the Smaller side..,..I think the ls3 head has a 3.1 CSA Standard which Is more than enough for a 427 to go to 7000+...
U Don't measure a head by a Damn CC number to know how much rpm a combination may have.
Also just porting the exhaust on a 427 is just Plain Dumb to the 6 people and there likes. Ported vs non ported @ $900+ in the Same Head test. The port needs to be cleaned up from being as cast = @ min the SSR, Bowls and a good valve job.
To add to the Discharge % of the Intake & Exhaust:
it's under Pressure it doesn't need much to get the exhaust out, besides that there's a reason for the bigger split in intake and exhaust duration....
Guys are sold on BS 7 days a wk 365 days a yr.
For the BS; I asked the same question with using a 1.55 exhaust valve. Was told what was Posted above by:
Darin Morgan, Cam Motion, Eric Roycroft, etc...
It's great to have higher Discharge numbers But, Not mandatory 👍
HP is gained on the front end being the intake stroke
We all know we can get a little HP on the back end with unCorking the thang. Also a person doesn't need the back side to be, too Large...Ride the wave out...
In and out like human breathing...the more ___ in the more output that can be applied - Work. In a Engine it's called Horse Power
Damn it Also seems like those Darin Videos are going to Waste. 😂🤣
As a general rule of thumb, you need about 1CFM of head flow per 2HP you want to make at the crank, this is with a healthy cam, intake, exhaust, all the rest. In practice, you will want a little more than that, maybe instead of 1/2 shoot for 3/5.
Darin himself ported his own heads for a Stock Cubic Inch ls3 Camaro...I know for a fact a 427 would love a little more CSA or a better said Ls1tech term of CC intake runner Volume..Ls3 head intake runner Needs: Bowls, Short Side radius with a good valve job....for a avg build.
Darin Morgan heads came in @ 264 cc vs stock @ 260.
Chad Speier is Like Darin's brother from another mother and has the CNC program....pictures provided from Chad
99 Black TA knows about Darin Morgan, others may have Watched or Read.
👆
👍
When going for HP use the math and money to clean up the port.
Trust me the cam and combination will like it with a Carb intake. A 427 may find as much as 15 to 25 HP at the crank....
Some of this stuff is 2nd nature...I've been done with the LS3 stuff 🤣😂
Btw isn't this who ported the heads in the 1st thread I posted with the 427 and Ls3 heads in WCCH? Remember the Ls3 head test and what WCCH heads did Vs others?
To add to the Discharge % of the Intake & Exhaust:
it's under Pressure it doesn't need much to get the exhaust out, besides that there's a reason for the bigger split in intake and exhaust duration....
Guys are sold on BS 7 days a wk 365 days a yr.
For the BS; I asked the same question with using a 1.55 exhaust valve. Was told what was Posted above by:
Darin Morgan, Cam Motion, Eric Roycroft, etc...
It's great to have higher Discharge numbers But, Not mandatory 👍
Just seeing this. I prolly shouldn’t post this info, but to aid in this technical discussion here, Corona is on point. Case in point, cam specs from a semi-current Cup engine…276/273 .722 lift both sides with 1.7 rockers (more dependent on lobe, less dependent on a mechanical device failing), ground on a 107 LC. I can’t tell you guys anything about the lobes (mind blown), what shop, Toyota, Chevy, or Ford. What I wanted to point out here is the reverse split camshaft. By the way, ex valve is 1.5”ish…Why do this in such a competitive sport that looks for every last hp? When the exhaust valve starts to open, the cylinder charge is already under great pressure. Picture opening a canned beverage here. When you pop it, a decent amount of compressed air comes out in a pssshhh sound. Same deal with exhaust valve opening. The cylinder is charging very rapidly at that time and the exhaust is exploded…literally…out the port and into the header, when the ex valve opens. Let the piston do the work for you on the exhaust side. Scavenging takes over from there. The exhaust systems are so well designed that the exhaust gases are pulled up and into the header from scavenging. Less exhaust duration means less energy being spent (pumping losses) trying to get exhaust out of engine, and less valve spring. Tiny things that add up to make big things.
Chevelle 👍....
🤔 I'll ask the Same question to different porter's and all Generally will give the same basic answer. We Know We're on the right path. Added I always ask different People to get a different view or a better one 👍
Once we get the Basic facts then we move on to another thought or question 😉 There isn't really that many parts to a engine..So there's Not to many questions once we have the basic knowledge or facts.
Chevelle 👍....
🤔 I'll ask the Same question to different porter's and all Generally will give the same basic answer. We Know We're on the right path. Added I always ask different People to get a different view or a better one 👍
Once we get the Basic facts then we move on to another thought or question 😉 There isn't really that many parts to a engine..So there's Not to many questions once we have the basic knowledge or facts.
I have sometimes found asking the same question to various people will give you different parts of the same answer. We get to compile the bits into (hopefully) the full solution.
G when it comes to a Engine specs or sizing of a part it's 99% Math...
🤔 Head Runner size for a combination is Math
Intake runner length and Plenum size is Math
Etc...reason when someone says oh this head is perfect and you or I go do the math we can tell a person basically there combination better than the guy who sold it to them
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Intake runner sizing for LS3 heads on 427 
