Intake Runner volumes
 

I know alot of you probably have seen this article from AFR's website, but maybe some havent. Either way, I find the results kind of interesting. I see alot of guys suggest that if you go outside the norm, say too big on intake runner size, the engine combo will be a "Turd, lazy, pig, wont get out of its way, or simply a piece of crap".

In this test, they had a 496ci, with a solid roller camshaft as the test mule. The power band they measured, was 3500-6500rpm. Kind of relevant to a high performance offshore boat power band. I find it interesting, that a huge 360cc runner head, like the trick flow, or 355 edelbrock, smokes the 325cc stock head, in average torque. and about the same or better than the avg torque of the smaller dart 308cc runner. Maybe these numbers are lies , as we know magazine articles may not always be 100% truthful, or accurate. I know that if someone here, recommonded a 335cc port on a 496ci, they'd be kicked right in the ball bag thru the keyboard, let alone a 360cc runner head, and pretty much told the engine probably won't even get the boat on plane do to the lack of torque . Any thoughts on this article and the results?


GM rectangle ports
Peak Power- 630 @ 6,600 rpm
Peak Torque- 577 lb-ft @ 5,300 rpm
Avg HP (3,500-6,500)-532.4
Avg TQ (3,500-6,500)- 560.5 lb-
TQ @ 4,000 RPM - 562.7lb-ft

Summit/Dart 308 Iron Eagle
Peak Power- 688 hp @ 6,600 rpm
Peak Torque- 607 lb-ft @ 5,400 rpm
Ave HP (3,500-6,500)-555.5
Ave TQ (3,500-6,500)-582.1
TQ @ 4,000 RPM-563.3 lb-ft

Pro Comp 360cc
Peak Power- 690 hp @ 6,300 rpm
Peak Torque- 600 lb-ft @ 5,500 rpm
Ave HP (3,500-6,500)-554.2 hp
Ave TQ (3,500-6,500)- 581 lb-ft
Tq @ 4,000 RPM-568.3 lb-ft

Trick Flow 360cc
Peak Power- 691 hp @ 6,400 rpm
Peak Torque- 603 lb-ft @ 5,400 rpm
Ave HP (3,500-6,500)-555.3
Ave TQ (3,500-6,500)- 581.9 lb-ft
TQ @ 4,000 RPM-562.3 lb-ft

Brodix 332 CNC ovals
Peak Power- 705 hp @ 6,400 rpm
Peak Torque- 624 lb-ft @ 5,200 rpm
Ave HP (3,500-6,500)-574.6
Ave TQ (3,500-6,500)- 602.7 lb-ft
TQ @ 4,000 RPM-585.7 lb-ft

Dart 335 CNC
Peak Power- 717 hp @ 6,500 rpm
Peak Torque- 619 lb-ft @ 5,600 rpm
Ave HP (3,500-6,500)-568.0
Ave TQ (3,500-6,500)-594.3 lb-ft
TQ @ 4,000 RPM-572.5 lb-ft

Edelbrock CNC 355cc
Peak Power- 723 hp @ 6,500 rpm
Peak Torque- 627 lb-ft @ 5,600 rpm
Ave HP (3,500-6,500)-573.5 hp
Ave TQ (3,500-6,500)- 599.9 lb-ft
TQ @ 4,000 RPM-574.0 lb-ft

AFR CNC 300cc
Peak Power- 729 hp @ 6,500 rpm
Peak Torque- 639 lb-ft @ 5,400 rpm
Avg HP (3,500-6,500)-584.1
Avg TQ (3,500-6,500)-611.4 lb-ft
TQ @ 4,000 rpm-587.0 lb-ft

http://www.superchevy.com/how-to/pro...ut-the-o-vs-r/

Interesting data

but the smallest head made the most power and the gm head did the worst.

I believe the afr had a 110cc chamber, and the dart a 121cc chamber, so it had a little help from some extra compression, to make that extra 12hp and 20ft lbs.

If one was to put say, the dart 335, afr 300, brodix 332, or 355 edelbrock (all the cnc ported heads), headed setups in a boat, how much mph difference would we see ?

Or, we might say the 308 dart would be a better fit for a 496 because of the runner size. Obviosuly though, the 335 dart, flows a bunch better, and is making a fair amount more HP, and torque. On this dyno test, looks like the 335 would be a better choice (disregarding cost obviously).

I'm glad you posted this. I've always stayed on the small side with any of the boat engines I've built. Personally I don't see any need for more than 265-280 oval port on a 454-468, 310 max on a 496-509, 315-330 on 540-565
And so on. At least for the marine apps running under 6k

I will give up a little top end for throttle response any day.

Say What!? More compression = More Power? You don't say
What's the first thing you learn in any introductory statistics class?...
Another apples to oranges comparison from a magazine.

Also does this seems like a very happy dyno?
Comp Cams 300BR-14 offered 0.652 lift, a 255/262 duration split and 114-degree LSA (not that aggressive of a cam)
630HP on Stock GM rectangular port heads @ 10:1

I've been looking around lately myself. Going with 320 pro filers and have valako work his magic with them. He said when he's done they'll be a little under 330 and that for my 565's. Not sure if he's gonna wedge them or not. Regardless I've always been a dart guy however the cnc 315 afr' pull some awesome flow numbers out of the box.

Personally I was thinking 335 runners for my 565's but Jim talked me out of them. Buying the pro filers through him.

I'd love to make some hefty bets with the majority of these if not all who are advertising x for their hp, torque, etc. I see sales/ads for 496's making over 700 hp on pump gas. Wtf. Really. Guess I have to go back to school.

Did I miss somewhere if these were out of the box or completely tricked out heads. 100 hp bolt on head. Don't think so. I've spent a lot of time in the dyno room and there is no way.

She told me port size doesn't matter...its all about the flow.....

imo,a head&cam upgrade is usually good for 100 hp,even more with a little compression bump.

Everyone want more top speed, till there` s a head thread, then everyone wants a small head for down low tq. :confused:
I don`t get this automotive off idle acceleration mindset.
This guy need lots of TQ down low that I can understand.

http://www.mastercraft.com/teamtalk/...6&d=1239124489






None of those heads give up anything worth talking about to consider a small head over a future proof larger one

Here's something ya'll might find interesting reading....some stuff I have witnessed myself----I know of 3 different BBC engines with the exact same Cubic Inches (500+cid) dyno tested on the same dyno over the past year all destined for offshore applications.....a Roots 14-71, an M4 Pro-Charger and a Whipple 8.3L/510. All 3 engines were built with solid roller cams and inter coolers.

I do not have the liberty to give detailed specifics because these engines belong to customers of my builder.

The Roots 14-71 engine was destined for an offshore racing application and had the largest cam of the 3 engines, but the heads are some older aluminum designs with porting and the same size as the M4 Pro-Charger heads. The M4 Pro-Charger engine's cam was about 3* duration larger on a 112* LSA compared to the Whipple engine's 114* LSA "tight lash" cam.----therefore, the Whipple engine has the smaller/milder cam design.

All 3 engines made peak HP and TQ within about 10hp. The Intake runners of the heads of the M4 Pro-Charger engine were about 20cc larger than the Whipple's engine's heads. Both heads were a late design cnc ported head design of the same manufacturer---with the same exhaust port size/design and same size valves. The Roots engine heads were the same size as the M4 Pro-Charger's heads, but different manufacturer/design.

The M4 Pro-Charger engine was very impressive...it had the lowest Intake Air Temps between the 3 engines. However, it took 9 lbs of boost to make the same peak HP as the Whipple engine.....The Whipple engine only took 7.5 lbs of boost to make the same HP....and the Whipple did it at a 300rpm lower rpm rate compared to the M4 Pro-Charger engine. Both engines were timed at 32*. The Roots 14-71 engine made peak power with about 11.5-12 lbs of boost with the same peak RPM as the M4 Pro-Charger. I don't remember what the timing was for the Roots engine, but being that it was built as a racing engine destined for offshore racing with the heads that the customer had at the time, then I am sure the timing was set a little higher.

This is just my own observation/opinion...but I thought it is/was a very interesting comparison and from some of what I have heard in the past about the Pro-Chargers, I thought the M4 Pro-Charger would have kicked a little more arss in the HP per RPM per pound of boost, etc, department....and I am sure it would have kept going, but at the sacrifice of higher RPM.

Even though the Intake Air Temps of the M4 Pro-Charger were cooler than the Whipple, and the Whipple cooler than the Roots---the Whipple after a long pull on the dyno with a hard pull at the end, you could lay your bare hands on the surface of the blower case of the Whipple and it would be COLD to the touch....unlike a Roots. I thought that was very impressive.

I understand every engine is different and you can argue the finer details if you want, but the smaller intake runner CC sized heads of the Whipple engine beat the larger 20cc sized heads of the M4 Pro-Charger plus with the slightly larger 3* cam and tighter LSA...at least in this reference.

I absolutely can't stand head tests that have very varied combustion chamber sizes. Difference between a 9:1-10:1 BBC can be huge !
Seems every BBC head test in the mags does this.

More than a few 30-33ft twin engine boats out there running over 90mph with 496's and AFR 315-325's.

Raising a port lengthens it. This makes for a larger measured CC runner. So, this is not always a good indicator of performance.

100 rpm?

Absolutely but example I would bet anything if you took my 496 with 10.5:1, 244/248-647/637 on a 111 and dart intake with pro one 310's and dynoed with stock gm heads I'm not gonna drop 100 hp. That's all I'm trying to say. Especially with that cam. Like rookie said its not that Big of a cam. Gm heads are taking a nap anything over .600 lift.

Knowing how my little 265 AFR's preformed, which is certainly a small port, high velocity design. I was so happy with those that I’m going with the new AFR 300 oval for my current engines. As for runner size- I'm really confused as why someone would want to use a large runner head when a small runner will perform the same or even outperform its bigger brother. If you can get high velocity AND high flow why would you not pick the head that does both?

Below is a flow chart of the different heads in this comparison. Even compared to the Dart 335 CNC or the big Trick Flow 360, the AFR 300 is the better flowing head.

Lift AFR 300........DART 335...........Trick Flow 360
.20 165..................121........................15 1
.30 240..................203........................22 7
.40 296..................276........................28 3
.50 340..................322........................32 5
.60 378..................365........................36 2
.70 388..................395........................38 2

Yes- the numbers above came from different shops, so yes this is not exactly apples to apples. What these numbers do show, is that the old thought of bigger is better is not true. The numbers above show this as well as the dyno results. 35cc is a lot bigger and in this case flows LESS until .70, and none of us on here are running a cam big enough to take advantage of any increase at that lift. And why anyone would ever want to put a 335 cc head on a 496 is beyond me, let alone a 360 cc, especially given the choices we now have with some of the new AFR designs. Another very important difference is that the mid-flow numbers on the smaller head are substantially better, resulting in better filling of the cylinder.

Now a comment that KAAMA made, that I also experienced on my AFR 265 engine. Again not apples to apples, but that engine would pull so much air thought the carb I would get serious condensation on the carb. While my current 454’s are running GM heads and HP500 carbs vs Holley HP 950 on the afr engine, I’ve never seen a drop of condensation on the current carbs and they are never cold to the touch after a hard run. I’m not saying that runner size is what caused this, but both engines are running similar cams, and similarly sized carbs, so the heads are the one big difference between the two.

This is an interesting comparison that super chevy did, and IMO proves that fact that there is more to making power than slapping a large head on an engine.

That would be on a snowmobile here in nw mi today. Snowing again.

As long as your hittin the side walls it's all good dude. Ha

I've seen my carbs iced over many times after hard runs.

I did a cam swap and head change and I netted 8-9 mph. I don't think you could go wrong with any of the top 4 heads in this test. Flow bench and dyno racing at it's best! The true dyno is the boats performance or the track.

The rpm's dictate what cams we use so with that said most on average aren't more than .575-.700. Larger runners are for higher rpm and higher lift cams. But even then if they don't have the felicity they aren't worth road kill in in the road. Back in the 80's several great engine builders failed with marine performance engines until they finally took off their tight jeans but realized bigger wasn't always better.

That was a happy day. Realistic 120 hp plus gain. That's why I take my jet pack with me on the lake. It's not unusual to pick up a couple in just jetting or lose if you don't.

I agree Dan. At least for the average offshore boat. The majority of guys, including myself, got our basic engine knowledge from being into cars before boats. The average cam tech guy is used to camming a car, and so on. Lets take a look at an average Chevelle big block build for a guy looking to go cruising. He maybe has some 3.08 rear gears, an automatic, wants to take the kids for ice cream on weekends, and blow the tires off at a stop light. Having a large, poor low rpm airspeed style of cylinder head, especially when couple to a cam that closes the intake valve very late in a quest for upper rpm power, will be dissapointed in his performance off idle. The engine will be sluggish down low, until it can build up enough piston speed, then it will come on like a monster, not the best for a street car, or even a strip car looking for good ET's.

This small port high velocity head thing is nothing new. Its been going for 50 years plus. The infamous little peanut port truck heads, were a perfect fit for what they were intended to be used on. Your typical 70s/80s' 454 truck engine with peanuts, made peak torque in the 1600RPM range, close to 400ft lbs. 400FT lbs of torque at 1600rpm, was impressive for a low compression smog gas engine. It worked great for pulling a trailer.

My opinion is though, is that intake port runner volume, is just one area of concern when choosing a cylinder head, and not the end all be all. The stock GM head mercury used on most of their engines, had a runner volume of around 325ish CC. When put up against those 360cc Trick flows, 355 Edelbrocks, 369cc Pro Comps, or 335 Darts, the GM head lost EVERYWHERE, including torque output. Just because it had a smaller runner, does't automatically mean its filling the cylinder better at lower rpms. And just because a runner is smaller, doesn't automatically mean it has better airspeed.

Of course when one doesn't have cylinder heads, and needs to purchase some, there's a good reason to choose a cylinder head that is best suited to the size engine/rpm/power level. But, more often than not, guys here ALREADY have cylinder heads. I've seen guys throw away/give away, some really nice cylinder heads, because someone told them their port volume was too big for the cubic inch/rpm band, etc that they will be using.

A good example is the old 454 magnums, 454 420's, 454 440's. They all had a runner volume of 325CC, and sub 9:1 compression, as low as 8.6:1, and never turned more than 5200rpm. The 454 Magnum, has probably pulled more tubers and water skiers, than any other engine out there. The 400hp, 420hp, were great old offshore engines. Were they power houses, heck no, not by todays standards. Were they good running engines, hell yes. Now, if you took that same 454, 420HP Merc, and bolted on a set of Dart 325's, everyone would call you an idiot, and tell you how bad the engine would suck. Ignoring the fact, that while the Dart 325 has the same runner volume of the stock heads, it flows a hell of a lot better, and will show a nice increase in power.

Am I suggesting bigger is better, absolutely not. But I believe if you are cammed correctly, with the right induction setup, being a little too big (within reason), isn't going to make the engine a failure, or unuseable.

Didn't you end up getting Jim's marine head? I wanted to look at a those as well, but I heard they are no longer available.

I agree, the afr 290/300 is a great cylinder head.

Not everyone is buying new heads from scratch though. I mean, certainly if you are buying new heads, by all means, go with the proper runner sized head for the application. We all , well most of us, understand bigger isn't always better. The question I bring up here, is at what point, and at what level, are the results dramatic enough, to make one switch out a set of heads, for smaller ones.

Icdedppl had some 540ci roots blower engines someone else had put together. They had 345 Iron eagles. Textbook would say, that head is a bit too large for a 6000RPM 540. I knew that, he knew that, Mike Tkach knew that, the guy who built the engines knew that. But, they were there, and they got used. They ended up making 900HP on a 7.5:1 540, on pump gas, and pushed a heavy old tank Cigarette very well. Would he have been better off with maybe some 320cc heads, very possibly, but where, how much better, and what would the cost have been. Nobody has those answers, unless, they've done a back to back heads up cylinder head swap, with no other changes made. Most of us, don't have the time or money to do that on the dyno.

my buddys 454's that make 450hp had ice on his holley 750's one day while I was out there helping him tune the boat. Those engines are nothing fancy. Stock heads, cam and intake upgrade and 750 holley. Boat runs 63mph.

Like rookie said the real deal is how the particular head works on the water. Plain in simple. I don't agree with the so called hp and tq numbers achieved at 6,500 so why believe what else the article claims. BTW I personally would only look at flow numbers as reference. The day I throw on an out of the box ready to go set of heads I'm done. There is a lot of power to be made their and would never ever bolt and go. There are some really good heads out there. Some castings are designed for porting in areas others aren't so it all depends on wheat your wanting to achieve at the end of the day.

I bet valakos NA 565 has no more than 310/320 max intake runner and he's well over 900 hp on pump gas. That certainly wasn't achieved with just out of the box anything. He prefers darts cause there's enough casting to port where necessary so he can achieve flow numbers like non others.

You been to jv's lately. Just wondered if you seen him flow those pro filers? I was shocked when he said to purchase them. I've read a little about them but no first hand knowledge of or experience with other than jim advised to get those for my 565's. I thought about just using my pro 310's for the builds and spend the time and money snuffing those up.

Why was it merc ever got away from the old 049 castings anyway. I'd choose those on a 454 any day over the rec ports. Wonder if it was only cause of the lift of the cams to make the extra hp. But even then your not talking much difference. The 049 castings were done at .550 lift max and probably closer to .525. Did they ever use the 049's on a 454/365 mag? I don't remember. I didn't think they did depending on what year the mag was introduced. Wasn't that mid 80's?

The only heads I knew of Merc to use, was the peanut ports on the 330's, and the Rectangles, on the 365+ engines.

You think this is top secret? Just share the numbers lol

Merc has (had) to use what GM supplied. Blue motors a little different scenario.

If GM continued with the 049's, they would still have the small valves.

Also, as a Manufacturer, you never wanna come out with power that will be hard for them to beat every 5yrs or so.

Say, when they introduced the 502, if they did the HP500 first and as a black motor, they would have kind of boned themselves.

Heres another interesting topic. it came up on facebook a while back. Somehow, the talk of advancing, vs retarding cams came up. Typically, advancing a cam, makes more low end, retarding makes more upper power.

in this guys case, retarding his custom specd cam, 4 degrees from its intended install centerline, resulted in more power, from 2500RPM, all the way to peak HP rpm. He lost nothing, anywhere in the power band, by retarding the cam 4 degrees. My assumption, the cam was too small to start with. Was it a huge gain, not really. But hey, 16hp gain at peak, as well as a gain of 5lbs of peak torque, with no losses anywhere, seemed like a good move when dyno tuning. Of course, we don't know what happened between idle and 2500rpm, if any torque was lost, but are we going from idle, to sticks to the dash full throttle starts with offshore boats? Usually, everything is a trade off, but sometimes, you have nothing to lose, and only to gain.

good information.while a 16 hp gain is a good thing what will it do for him when installed in his boat?my guess is 1 mph or less.

Always a fair point, however it seems someone always says this no matter what performance part thread.

Tuning - fuel / ignition
Exhaust - we here this all the time
Cam / Head / Intake etc
Oil Level

Well, who would want a 560-hp engine if it could make 600 ?

That's for the owner to decide.

And yes, some boats will respond to smaller hp additions than others....so that is a factor.

so did all the heads listed in this test have 26° valve angles?because what we learned way back in the motorcycle days of the late 80's/90's was valve angle was the biggest gainer in flow.then make the ports bigger and straighter to get even more air in.
all about making the short side radius better.
all I know is aftermarket heads are better than stock,except in the case of merlin heads,they just plain suck.they need alot of work to make them right.

Especially when its a free mod. I've seen guys spend thousands on hyd roller conversions, to gain 1-2mph in their boats, and thousands on prop work to gain 1-2mph.

What is interesting in that article, is 730ish hp from a 496ci engine at 6500rpm, with around 10:1 static compression and a 650 lift cam.

Absolutely.

chevy heads would have done way better if they had 2.300" valves like the rest of them and a quick fluff and buff.:)

i guess to see the 16 hp gain you would actuially need to do back to back dyno pulls with the cam straight up and then retarted.i know that sounds simple enough but even with a cloyes 2 peice timing chain cover and a cloyes hex a just timing set it still requires some work.all the rocker arms need to be backed off before making the cam adjustment and even if you think you moved the cam 4 deg without checking with a deg wheel you really don,t know exactly where the cam timing is at.imo the hex a just is great for helping the builder degree the cam but i would not trust the marks on it without redegreeing the cam after the move.