Brodix -12 heads with 264 - 305 cc intake ports are 1/2 the cost of of other high flowing heads. @ $2400 complete.

You can get the choices of 2.15, 2.17, or 2.20 intake valves with 347 -374 cfm of intake flow.

The 18 degree heads use smaller intake ports and have higher flow for twice the price.

I've been sitting and looking at my recently rebuilt 427 small block and nearly .700 lift 4-7 swap cam. I decided that it's not ideal to run my small Dart 227 cc heads on them. They are only 306 cfm.

I have 20 cc dished pistons and these -12 heads can be ordered with sub 60 cc to get my compression into the mid 11's for being very pump gas friendly with a 248/250 @ .050 cam with 110 lsa

My question is: Has anybody known of anybody using such huge ports on their street machines?

It's been the special spread port headers and intake system that kept me away from special valve angle heads before.

I've kind of quit worrying about being street friendly and it will become a dedicated race machine that will be street legal

 

Take a look at the ports on the LS series engines... much bigger
than conventional 23's and, of course, the LS motors have altered
valve angle heads...
I think your concern is valid... perhaps Brodix can answer this
question... or call Chapman Racing and inquire. Chapman has Winston
Cup experience... and CNC's alot of the delivered "rough" altered
angle heads. What size ports does the LS7 have??

http://www.chapmanracingheads.com/p_home.asp


altered angle heads require matching pistons, normally

 

The race shop that put my 427 short block back together machined my pistons to clear my 2.08 valves with an anticipated up to .780 lift with 23 degree heads. I ask about using 15 or 18 degree with up to 2.20 valve size and he told me that the decrease in angle aids clearance. They are also 20 cc dish wiseco pistons

 

Ok... just checking on the pistons, ... if it helps any.. some of the
smaller Big Block ports, I believe, are 265cc... you are running Big Block cubic inches.. and flowing near Big Block cfm...

Performance Big Blocks are 310cc to 350cc ports

 

That is not a valid comparison. The greater length of the ports in the big block heads would make the BB ports bigger in volume, even with equal cross sectional area ports.

RACE ON!!!

 

BBC and small block are not on the same playing field as far as port CC comparison. big block heads have a greater casting distance from the manifold to the intake valve. So a 305 cc small block has a dimensionally larger port than a big block 340 cc.

That is why so many of the car rag big block vs small block just plain suck. They need to run simular CFM heads to really compare apples and apples.

If i didn't have this 427 small block right now I would be purchasing the LS7 Warhawk and get into the modern erea of race motors. One of the C-3 forum guys has bought one for his next project.

http://www.worldcastings.com/ls7x_story.htm

 

The one mistaken on port legths effects is you CFI EFI... a little
strange since you own a crossfire..... crossram.. Port length effects
torque sweet spot...not the heads efficiency in ingesting air.



Here is a pic of the 30 inch long Sonoramic Commando crossrams I
own.... they place the torque sweet spot at 2800 rpm's....
These came out in 1960.... by the time the Max Wedge 413's and
426's came out...the length of the ports had shrunk to 15 inches..
this placed peak torque at 3500 or 3600 rpm... which is almost
exactly in the middle of 1500 rpm's and 5500 rpm's... the most likely
operating range.

A more complete explanation of the Sonoramic Commandos
and port length effects is available here:

http://www.allpar.com/mopar/sonoramic.html

It was definately not a scientific evaluation I made in the Big Block comparison... it was
an off the cuff comment.... I

 

Kyle, I've seen a few of those original cross ram cars over the years and often wondered if they really worked that well. I've also had a few different Hilborn injected motors and played with different stack lengths.

I even have considered this setup.

http://www.hilborninjection.com/prod...Id=52&CatId=37

 

Do you have a comprehension problem? YOU made a comparison between SBC and BB port VOLUMES. You said:
I merely countered that port volumes between the SBC and the BB don't compare because of the difference in the lengths of the ports.
Now, apparently because I mentioned that the lengths of the ports are the reason the ccs of the ports can't be compared between the two families, you answer with a tuning via port length discussion. Also, you say:By that are you saying I am wrong and the BB ports are NOT longer than SBC ports?


What does my Crossfire and the Power Ram Induction Manifold of a 45 year old Chrysler intake have to do with the volumes of the SBC vs the BBC??? You stated "you are running Big Block cubic inches.. and flowing near Big Block cfm". I made a correction to that statement by pointing out that the volumes don't compare, and you go off on a tangent, off subject. Are you having trouble following a train of thought and sticking to a single subject?

RACE ON!!!

 

I'm going to have to throw in on this. I have built a lot of engines using the -12's, ranging from 358 inches up to 434 inches. I have not built any low compression motors using the -12, as none of my street engine customers ever wanted to spend that kind of money on a SBC street car, but I do have a set laying around for that "project to be later determined" for myself some day.
IMO the -12 is one of the best racing cyl heads ever desgined. As far as 18 degree heads offering better flow, that is not really all that true. Head porters will and always have gotten more out of a set of -12's, but the fact that NASCAR utlized 18 degree for so long helped them close the -12's gap in a hurry. With the "cookie cutter" CNC head porters out there selling off 10 yrs ago's junky old port desgines they look alot more even on paper than they really are. You can see this yourself on Weld Techs web site. But look at the mid and low lift numbers the -12 is up on even the best 18 degree stuff at those lifts, and anything 18 degree wise that has max numbers exceeding the -12's (Broxix 18 degree AP266's) are woefully ineaduquate at lower lifts. Of course we are talking about the best of the best offered here and if you look at the lower flow -12's compared to the lower flow 18 degree they are pretty even with the -12 offering a bit bigger port volume which of course favors bigger engines and more carburation. I'm only trying to show that even for even port desgin wise (both put to the max the -12 offers engine builders an edge). In your application IMO you couldn't go wrong using either really.

http://www.weldtech.com/productsframe.html

Now as far as -12 engine combinations. I have a 421inch (3.875 stroke) SBC drag engine that has a set of hand ported -12's flowing 410CFM @.700 lift with a lower end flow curve to match. Now that engine runs 4.50's flat out in a 2000lb Rear Engine Dragster. It makes peak power at 7600RPMs with a 270-280ish @.050, .730 lift 108L/S cam. 800+hp with 2 C&S Aersol Billet Dominators on gas and a sheet metal tunnel ram.
All the oval track -12 motors I have built made way over 680hp and most in the 730-750hp range with a cast intake and one Dominator. I like a 260-270ish@.050, 680-700lift(depending on RPM range and engine size) and 106-110L/S (depending on stroke to rod ratio and RPM range). Most tracks I like to get my big motors to peak in the 72-7500 RPM range and little motors to peak in the 8000-8500RPM range.
As far as your combo is concerned. IMO the ramps on your cam are a bit mild at only 240/250@.050 with .700 lift for a 427 inch engine. I would use something in the 25X-26X range with .660-.680 lift. No matter how soft you make the ramp .700 lift is going to be hard on valve springs IMO you should at least make the most of it. The L/S at 110 is fine IMO. HVH has a good head port profile for your engine in the 305-12RVR. I think even at 10-10.5 to 1 with something in the range of my above mentioned cam specs you could make 650hp or better and a stupidly strong power band from 4000rpm to well in the 7000 rpm range depending on carb.
I wish you luck in you endeavor, you definatly do not see many people (althou some are getting brave as prices go down on this tech) taking the rolled deck leap for a street car. You will definatly have something very powerful, pretty streetable (dependant on your defination) and definatly unique.
Will

 

Gkull, what are the flow numbers across the board for your 18 vs 15 degree heads?

 

I took the leap and got a set of 363 castings off ebay with matching intake, thay are readily available.

My builder said the same thing about it being basically ten year old Cup technology. They are 54.5 cc chambers and appear to be in the 250cc range for runner. The flow numbers: (int exh)

.200 147 127
.300 223 178
.400 277 215
.500 310 241
.600 342 254
.700 337 264

The cam is in the mid 250's at .050 with around .630 lift. It willl be surrounded by 434cid. Compression should come in around 11.25:1 which I am running now with no detonation issues to speak of.

I am hoping to have a well mannered yet extremely powerful streetable combination.

 

The rolled valve angle makes the port volume's not directly comparable. The flatter valve angles will lengthen the intake port. Should try comparing cross sections.

 

Champion is a great resource.
I purchased my Dart 320's from them, and the quality, workmanship and customer service was
pretty dam good. I will use them again for the next motor.

Joe