Thread: Just trying to learn a little more

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From my understanding intake and exhaust runner size has a huge effects on torque especially with heads for a primarily street engine (big block) . Correct?

Question is how much and what is a considered to be too large for intake runner cc. Were talking a pump gas big block?

Then next question is they efficiency of an oval port versus and rectagular port head for a street motor. Have always read to go with oval port for street use seeking torque . I have trouble with this concept cause most of GM's crate big block motors sport rectangular ports. In fact if I remember correctly all of GM's current crate motors with the exception of 1 use rectangular ports.

So any eduacation I can get from others to understand this will be much appretiated.

Thanks for sharing your know how gentlemen.

bigger is NOT always better. it depends on several different things such as desired rpm range, camshaft selection, intake, exhaust system, among other things. if you run into too big of a port it will end up being "lazy" i would rather have a high velocity port which all depends on the application.
as far as which is better the oval or square i really can't answer most of my learnings have came from the blue oval.

It's very confusing. I have driven both on the street, and I doubt that your "pants seat dyno" will tell the difference. Some of the older GM rect. port heads were about 327cc runner size, and that is considered my most hot rodders as a little big for the street, and lower rpms. I will really flow at 5K and up, but that's where they work best. An average size for oval port intake runners is 260/270cc, quite a difference. Now, the confusing part...you're right, many aftermarket heads and crate engines use rect. ports, and they run strong, even on the street. I have a friend that owns a garage and drag races, and he's a huge rect. port fan...he swears you'll never tell the difference on the street. I dont know if I can make a fair comparison, cause the rect. port engine and oval port that I drove had different cams, pistons, etc....not really the same. But I can tell you that both were animals. If it's strictly a street engine, and 454 or under in cubes, I would probably lean towards the oval ports. If it's bigger inches, go with the rect. ports. From a physics standpoint, the air will move more quickly thru the smaller port, packing more volume in the cylinder. Lots of things will depend on your build. If you're using a stock or near stock stall speed converter, or a standard tranny, the lower rpms will inhibit low end a little, cause you'll spend more time in that rpm range. If you have a bigger stall, maybe 3200 like mine, or more, every time you hit the throttle, you'll pass thru the lower rpms pretty quickly, and the bigger ports will be less noticeable. There are a couple really good books on big block chevy's...look in your bookstore and read up as much as you can on them. It's valuable info, and will help you make the right choice. Do you know yet what you're trying to build?

JOHN is rigth i will mark you down to day with a gold star. ok i have had both oval and rect small engine and torque o port .hi hp rect what do you want to build??

Thanks for the input gentlemen.

John you know hwat I am building and Im just trying to comprehend what those Canfield heads will run like compared to lets say Brodix RaceRite oval port aluminum heads with the 270cc oval ports VS. Canfields 310cc rect port

to refrsh for any appretiated additional comments here is the build to this point:

454 .030 over
Cast iron crank (10/10)
Stock rods with ARP harware
TRW forged small dome pistons (L2349F; LS6 repo piston)
Howards cam: 304/314 adv dur; 234/240@.050;
.540/.540
110 LSA
Some type of dual plane intake (rpm air gap)
750-800 cfm, vac secondary holley type carb

going into a 66 chevelle
Th400 Trans with 2500-3000 stall
3.73:1 rear gears approx
(NOT a daily driver. 95% street driving, occasional strip; like most trying to get the most fun out of what I got)

I love the price and value of Canfields heads...but once you buy them with the CNC upgrade to be sure equal comb chamber size they cost just a few hundred less than some quality oval post aluminums with smaller intake runner sizes. Like I said just trying to educate myself best as possible before making a purchase.

Thanks again for sharing your smarts gentlemen.

the c r ??? . canffields are good heads the 310 cc will work you can try 119 cnc but i would o deck the block to get the cr up run the fel-pro head gasket f1027 and howards cam 595/609 286/292 250/250 LS 110 this cam will work but I like the 639/645 302/310/ 268/278 108 if this will fit i would run this try to get the cr up run the direct lube soild lifters and the intake team g 3500 stall to 3800 the rear gear is fine

Im sorry. I forgot the C.R..

Should be in the neighborhood of 10:1.

Bump. Any other input from you wizards out there would be appretiated.

Bump Bump

Damn no other opinions of info from any of the expecrts on here. No more comments JohhnyO, Pat Mc, Tech?

what can i say. the canfields are very good heads but to build it with the 310 runner i would try to get more cr i see that they have a cnc 113 ?? head .run this head and hand fit the pistons by cut out the chambers 'not to much' for the dome and then cc the head you this will cr get it up there and run the the cam i said i like .but check for piston to valve on all piston

Ok Pat. I appretiate the time you take to respond to my posts.

The motor I am building is for a street car that will see occasional track use, just for fun. reason I say this is that I will have 10:1 already, which will be ok with pump gas. Question I have is why raise the compressiona ratio. Other question I have is cam cause the one you mentioned brings my RPM range up a lot higher. Do you think the suggestion you made of higher compression and a larger cam is wise for a car that will be run primarily on the street?

Again thanks for taking the time to reply!

bigger heads cc runner more rpm .bigger cam is need for rpm CR is needed for the cam to work rigth to make hp .or build aO port heads and smaller cam i have runned cams this big and bigger i do not know what you want ?? if you spend big money on heads dont you want it to make power??

Thnaks for your input Pat.

Back to my orifinal question was me needing help in deciding rect or oval ports. You responce has me now leaning towards the Brodix RaceRite heads with 280 CC runners and oval port. Thanks again for the input

Originally posted by 30-A Rider
Thanks for the input gentlemen.

John you know hwat I am building and Im just trying to comprehend what those Canfield heads will run like compared to lets say Brodix RaceRite oval port aluminum heads with the 270cc oval ports VS. Canfields 310cc rect port

to refrsh for any appretiated additional comments here is the build to this point:

454 .030 over
Cast iron crank (10/10)
Stock rods with ARP harware
TRW forged small dome pistons (L2349F; LS6 repo piston)
Howards cam: 304/314 adv dur; 234/240@.050;
.540/.540
110 LSA
Some type of dual plane intake (rpm air gap)
750-800 cfm, vac secondary holley type carb

going into a 66 chevelle
Th400 Trans with 2500-3000 stall
3.73:1 rear gears approx
(NOT a daily driver. 95% street driving, occasional strip; like most trying to get the most fun out of what I got)

I love the price and value of Canfields heads...but once you buy them with the CNC upgrade to be sure equal comb chamber size they cost just a few hundred less than some quality oval post aluminums with smaller intake runner sizes. Like I said just trying to educate myself best as possible before making a purchase.

Thanks again for sharing your smarts gentlemen.

Well it sounds like your gonna have a screamer to begin with, im not too good on the particulars with runner cc's but i know oval ports are really good for for low rpm torque, or street use, once you start getting into large runners your looking to get alot of upper rpm torque, looking at your build sheet it looks to me like you built you motor for mid rpm 2500-6500 rpm maybe 7000 rpm's
power, Personally i think if i was going to build a motor like yours, naturally aspirated, i would go with a good set of rect. port heads
but you need to keep in mind your running a cast crank and stock rods also, you may want to take into consideration horsepower, if you break a rod in a bigblock at upper rpm's usually the only thing salvageable is like the intake and the headers.. Just a suggestion. Canfield heads are really really good heads for the money. brodix makes really good stuff also but they cost alotta$$$ Anyway good luck with your project, i love to hear about people building some real big block horsepower, be it chevy, or or even.....moper oops i meant mopar lol only kidding let us know how it works out for ya later,Joe

Thanks for the input Joe.

From my reading and watching guys at the track there are lots of people running stock cranks. I personally (not that I am so experienced) have never seen a cast iron crank in a big block let go. I would expect a main cap or bearing to be a weaker point than the crank. From my understanding a cast crank is a little more forgiving because it flexes a little which is optimum for a car that will be primarily street with a few trips down the track a year. Now yes the rods are from my understanding to be the weakest link; but they have had the beams ground down to reduce potential stress cracks, they have been shot peened and balanced with Pioneer
180, 000 psi bolts. GM has quite a few motors from the factory with stock rods producing 500-600 hp/ TQ figures so I think Im probably safe.

I appretiate your input. I like the Canfield heads, and was basically asking the benefit of oval vs. Rectangular ports for a car that is primarily street with the stats I mentioned in my first few posts. Of course when I talked to the guys at Canfiled they say their heads woud be excellent for my build but of course they are gonna say that. I just want optimum. If Im gonna spend 1400 for Can field heads, and another 200-300 for the CNC'd version...the difference in price for the Brodix RaceRite oval ports are a couple hundred more....If Im gonna spend the $$$$ I want the ones best suited for my build.

Any other opinions are very welcomed! I really do appretiate experience you guys share with your posts...it really helps prevent mistakes and make educated decisions.

Scott

the cast crank is ok the bottom end of a stock big block is the best. they can take one hell of a beating you do not have to do much . but i do not like pioneer bolts they are ok for stock stuff .i like the arps.but if the rods are done use them i would go with canfied head s i have talk to him and seen his work it is very good for the money