Intake Port Volume

[LowDeck451]

A couple questions for the engine builders here. Do you think the theory of taking intake CFM flow, times 2, will give you the potential horsepower an engine 'could' make (with the proper combo of carb, intake, cam etc.)? If so, wouldn't you want to reach that CFM with the smallest port possible, to keep the port velocity high, which would help low speed torque? (street/strip engine) In other words, easy to get 300 CFM with a large or 'hogged out' port, tougher and more specialized porting needed to get there on a closer to 'stock' sized port. Or am I splitting hairs? (I realize the CFM goal should be achieved at cam lift) Hope I made sense! Thanx.

[Challenger340]

The 2 hp per cfm number is just a "ballpark" many builders use when doing quick assessment of potential, but a myriad of other factors also modify things in efforts where quite obviously everything in an engine..... affects everything else ? It can also be exceeded substantially.

Getting the highest Flow possible, with the smallest Port possible, IMO, has also always been a "rule of thumb" anyways, if for no other reason than to try and prevent dead spots, where Flow is fine at one lift, but avalanches at the next as the turbulence past the problem area becomes a factor.

Any idiot can make dig a big hole, but that doesn't mean it will Flow "well" from a whole host of criterion including quality of the Air/Fuel charge ?

I just went through with a guy running 340 CC BB Chev Rectangulars.(ported elsewhere)
Dummy has been whooping on his junk with an .800" Lift Cam for quite a while, shows up here with them for freshening.
I always do a "before & after" test Flow to prove my work.... nonetheless, goober's Heads went in the toilet at .600" Lift as delivered, and actually LOST air by .650" to .700" !
I had to phone and inform him asap  before I was touching them.
So in his case....
WTF was the point in beating his V/Train with an .800" Cam just to lose power ?

This entire Head Porting/Flowing subject could get extremely involved, and suffice to say..... waaay too involved for discussion here, and I typically shy away from discussing Flow over the internet.

Flow Benchs are not, never were, and never will be a Dynomometer.
That said,
after 40 years of doing this, they are still one of the primary tools necessary for Engine development and making power on the Dyno.

I just moved up to a newer SuperFlow SF750 Bench if for no other reason than the simulation power in Software, Port Mapping and data-logging it provides.
Heads are still where a guy makes his power...... THAT, will never change !

[LowDeck451]

Thanx, good info. Just trying to plan and sift through all the information out there and choose a head that will meet my 550ish HP goal, and not buy a head that is 'larger' than I need, even if that head may be 'affordable'. (DUH...Right?) Thanx                                                                                                                                                                                                                                                                                                                     

[c00nhunterjoe]

An out of the box stealth or edelbrock head is capable of that on a 440, let alone a stroker.

[garner7555]

You may already be aware of theses heads but just in case your not check out these Sidewinder heads.  Todd has a good reputation and can do any custom work or machining before he ships the heads out to you.   

http://www.mopartsracing.com/parts/Sidewinder.html

[LowDeck451]

Thanx guys. I will look into the Sidewinders also.

[firefighter3931]

For the typical street/strip 440/451 you want a small, efficient port to maintain velocity and maximize torque & throttle response. A 300cc port can flow poorly while a 230cc port can be outstanding. Size isn't as important as shape. 

I like the stock sized port for smaller displacement builds. You can make excellent power without having to go to a max wedge port....and it will be a blast to drive. 


Ron

[LowDeck451]

That's what I was thinking. I like the idea of a CNC'd head, like the Stealth, but at 255cc, way bigger than I need. Wish someone offered a lower level CNC port job. Thanx for the input.

[BSB67]

Your thought process is good.  If you are clear on what you want from the engine and the car, I would recommend that you now call a few reputable head porters.  There are levels in between doing nothing to an aluminum head, to a full-on CNC port job.  When you call a couple of guys that do hand porting, you will also find that not all aluminum heads are created equal, particularly when it comes to  how they respond to light to moderate hand porting.

Finally, depending on the goals for your motor and the car, OOTB or checked and prepped aluminum heads could be just what is needed.  But, in my opinion, the new Trick Flow PowerPort 240 is a bit of a game changer and should be considered by anyone looking at aftermarket heads.  With the TF 240, it is hard to think of a circumstance where you would rather have some other head CNC ported.  The TF is simply a smarter head.  Arguably, it might be more than you need, based on what you are looking for.

[Challenger340]

That's what I was thinking. I like the idea of a CNC'd head, like the Stealth, but at 255cc, way bigger than I need. Wish someone offered a lower level CNC port job. Thanx for the input.

Have you checked any Performance Shops in your geographical area ?

We are too far away in Canada,
but we periodically(as time permits) do a Stealth Head Port & "Prep for Service" Pkg.(3 sets at a time), that yields ~300 cfm by .550" to .600" @ 28" H2O for $1,000. a pair(which would be about $700. U.S.)  
Takes 1 guy pretty much a full week to do 3 sets, nowhere near as fast as a CNC LOL ! so either pre-sold or maybe 1 set for stock.
just say'in....
gotta be somebody closer to you offers the same thing ? Phone around ?

[LowDeck451]

Thanx '67. My goal for the car is a low/ mid 11sec. (rollbar rule) '72 A body, full interior, steel wheels, drag radials, headers, sub-frame connectors etc. (60' important), guessing 3600 lbs. w/ driver. I live about an hour from two tracks here in Northern Calif. so street manners are a big consideration. The TF 240's are interesting and to be fair, Challenger 340 mentioned those in a PM the other day, duly noted. I've always been most impressed with the cars that run quicker than they 'look' (like yours, well done!), I also know there is a lot of 'whittling away' at E/T needed, which separates the 'faster than it looks' cars from the 'OK' cars so, trying to educate myself during the planning stage. Anyway, thanks for everyone's input, appreciated!

[LowDeck451]

Challenger 340, yeah, there must be someone here in CA. who offers, has experience with these. I saw a post by Eric Jones somewhere saying he had a porting package for Stealths, called him, he said it was an old post (it was) and he now mainly does Stock Elim./Super Stock stuff now. So, no big deal, I'll call/ask around, I'm sure I'll find somebody. Thanx for the info.

[heyoldguy]

We're in Central Idaho, have experience with, and have a preparation and hand porting service for the Stealth heads.

[LowDeck451]

Thanx 'hey', good to know, I'll be talking to you in the near future.

[c00nhunterjoe]

Ported stealths on a 440 a body will have DEEP 11s with no problem on tire.

[Challenger340]

We're in Central Idaho, have experience with, and have a preparation and hand porting service for the Stealth heads.

You will not find any better skillset's or experience with the Stealth Heads than this Guy(Jim/heyoldguy) ! 

[LowDeck451]

Great. Yeah, an experienced recommendation to an experienced shop is a whole lot more reassuring to me than 'cold calling' a local speed shop who might just "Gladly!" port/prep my heads. Thanx Again!

[LowDeck451]

c00nhunter, or anyone else for that matter, I came across a guy on YouTube a few weeks ago with a 440 Duster (a bit 'hotter' than I am planning) but, pretty impressive I thought. Search 'Doosterfy' if interested.

[Challenger340]

c00nhunter, or anyone else for that matter, I came across a guy on YouTube a few weeks ago with a 440 Duster (a bit 'hotter' than I am planning) but, pretty impressive I thought. Search 'Doosterfy' if interested.

I went over and watched " Doosterfy"  on youtube.

How is that "hotter" than you are planning ?  Ported Stealth's on a .030" over 440 W/10.5:1, something 240' ish @ .050 Cam in an A-Body can easily run that fast or faster.

But then again,....  I never did see an E.T. ?
What's he running ?
High 11' s ?

[LowDeck451]

Challenger340, he has a handful of vids., one is titled 'Best run to date - 11.12 @ 121'. Lists specs in the comments - CNC Stealths, 292 solid street roller, A518 O/D tranny, 4.57 gears (uses O/D as 4th gear at the track).

[c00nhunterjoe]

Unless he is running a 24" tire, he shouldnt be in od in the 1/4. For that matter, you should NEVER be in od at the track. I have 4.88s in mine and dont have a problem.

I saw an 11.27 @ 120 on his latest video. No reason your car wont do the same.

[LowDeck451]

It's one of his 'in-car' videos, O/D switch on the dash. Tires 'look' like 275/60's to me. Anyways, I just thought it was cool and different.

[c00nhunterjoe]

Damned if he didnt, i just watched it. It was in od for quite a while. Watched if several times to count the shifts. Something isnt adding up. 4.57s shouldnt have a 1:1 gear wound out that far in the 1/4 at 121 mph to need od at the 1/8 mile marker.

The run in question. https://youtu.be/BZFNbRsd-b8

I wonder if the switch is for a converter clutch? But it sure does sound like a 3-4 shift.

Edit- def a 3-4 shift. He has more videos, 1 with a shift light. He has to be shifting at 4000 or so.ething ridiculously low, its in od beforr the 1/8 mile box.

[LowDeck451]

I believe a manual switch like he has gives you O/D and conv. lockup at the same time, plus there's a delay before it actually changes gear. Sounds like he's only in O/D for a slow 'one Mississippi' count before the finish line. Edit: Well, maybe a slow 'two mississippi' count!

[c00nhunterjoe]

If you count the reflector boxes in the center of the track, he engages overdive before passing the 1/8 mile box, which means he either has 7.00 gears in it, 18" tall tires, or is shifting at 3800 rpm.

[BSB67]

If you count the reflector boxes in the center of the track, he engages overdive before passing the 1/8 mile box, which means he either has 7.00 gears in it, 18" tall tires, or is shifting at 3800 rpm.

At the 1/8 mile, he will be at 97 or 98 mph, and with a 27" tire will be about 5900 rpm in third gear.

With out the overdrive he would be trapping at 7300 rpm.

[LowDeck451]

Yeah, the 'outside the car' video of that run shows the tires are definitely not 'short', (275/60 drag radials maybe), and although he hits the switch at the 1/8th, it doesn't actually shift into O/D until just before the thou' marker (looks to me). Not tryin' to beat a dead horse though (I hope!) Thanx

[c00nhunterjoe]

No, not at all, it is an interesting racing theory to watch. Youtube sound especially via cell phone is hard to judge what rpm it is turning. The od use is definatly hurting him. That car could be easily into the 10s setup a little differently. Not enough informatio on his videos about the car.