Im building a 454 poked and stroked to 489. Looking for around 650HP all motor.

Im already using these parts. The rotating assembly is already purchased, the rest will be soon.

Eagle 18021 esp 4.25 stroke crank
Comp 11-242-3 Extreme energy hydraulic flat tappet cam
Edelbrock 7561 RPM air gap oval port
Keith Black Pistons
Holley 850 DP

Should I use:

Dart 19000111 oval prt 275cc

OR

AFR 305 w 315cc chamer CNCd Rectangular ports (dont they make oval?)

My builder says I should go with the Dart heads because they produce power in the lower RPM ranges and the AFR make power in the higher ranges. But I have several people who actually are using AFR who say they flow better all around. What do you all think of this combo?

TIA

Are either raised ports? If so you will need custom built headers, by somebody like Lemmons, and those items are around 1000 bucks a pair.

I never used either, but the AFR's BBCs have a good rep for being streetable and making good power.

The intake you listed is oval, but the AFR's are rectangle? I had a friend do that kind of combo-rect intake with oval heads, worked okay but still.....


I remember reading a few years ago that it was actually an individual that developed those heads and went to AFR with the data and they went into production......

AFR used to only be into small block stuff until then.

If I go with AFR and they are rectangle I will get the RPM with rectangle ports. I was told oval would flow better for what I want to do and even confirmed that online. But Im being told if I go with AFR they will be rectangular.

I would go with ovals too-you just might want to make sure these aren't raised port heads unless you are willing to pony up 1000 plus for custom headers....

BTW-the edelbrock performer RPM oval head works great. Stock port locations and is even approved by the NHRA for use in BBC's running in Super Stock and I think stock too.

I have a similar build 489 Eagle rotating assm, Air Gap etc, but I went with the Brodix Race-Rite Oval ports with the 270CC runner. Still putting the engine together.

They are raised ports but I didn't have to buy special headers, Hooker Comps fit fine.

Might be another head to consider:
http://www.brodix.com/heads/raceritebb.html

I really thought that there were, (AT ONE TIME), some 290 cc Merlin cast-iron, large ovals, but I'm probably all wet?????

Seem's like they were listed as VR Marine grade or some such heads??????

pdq67

[quote=Eleanor's Nemesis;884063]I would go with ovals too-you just might want to make sure these aren't raised port heads unless you are willing to pony up 1000 plus for custom headers....

I have the larger Darts on my 540. The exhaust ports are raised .300. My Hooker Comps fit fine. Damn tight, but fine. No modifications needed, no denting, bending, or anything else. You won't need the Super Comps at 650hp.

Between the two Id pick the AFR. Lots of guys make excellent numbers right out of the box. And even if the dart moved air just as well.....there are still some inherent advantages with aluminum VS iron. Id rather have a proven aluminum head VS a proven iron head.

but to add another option...for this build the race rite 270cc ovals by brodix would be my choice.


But to add another option......truthfully if you intend to keep the cam that mild Ive have a hard time looking at aftermarket heads in the first place. That is VERY mild cam specs for 496 inches. Stock big block chevy heads can go a LOOOONG way in terms of the power they are capable of. So...if your gonna product an aftermarket head that people will buy...it had better be better than a stock head right? And these aftermarkets are better than stock. The aftermarkets sit better on top of something thats a good bit more serious. In comparison to a stock head, most of the aftermarkets wont even begin to show what they are worth with anything less than a middle 240's at .050 cam with at least .600 valve lift and preferably .650 or more lift. THIS is the territory where the good aftermarekt heads begin to show their value.

Another thing you have to keep in mind is the valvetrain. If you buy any of these heads "as is".....they are intended for your harder hitting stuff. The standard issue valve springs on most of em will not like a hydraulic flat tappet. Actually its the other way around.....the hydraulic wont like the standard issue valve springs cause these heads are assembled with stuff that lends itself to a serious camshaft. The spring pressures would "have their way" with a hydraulic lobe in a bad way. So, youd have to go to the effort of making sure you get a lesser spring on these heads. Just for example....the wimpiest spring the race rite is offered with "standard" issue is a hydraulic roller spring thats 140 on the seat, 400 open. 400 open or anything much over 330 lbs over the nose will not agree with a hydro flat tappet. You most definitely can get different springs than the factory equipment if you ask....but I dont know how that will effect cost factor.

Unless you know you will in the future add a fair amount more camshaft with intentions of going at LEAST low 11's....if not tens....it would be hard for me to justify the cost. A set of stock cast 781's or 049's will take this engine as is anywhere it needs to go for much less money.

If you still do want to go aftermarket just in case future plans change and you wanna go faster....Id seriously suggest the race rite ovals. It will take a LONG time to outgrown those heads(easy low 10's in a camaro with pump gas). And they are the best fit for the engine right now.

Good greif is that the right cam? Also the Dart heads are aluminum. I would be buying the complete setup from the respective manufacturer. Im not trying to cheap out.

The cam I want to use would be something like this

Comp street roller. 260/266 110 lobe sep w/ .677/.687 lift.


Thanks for the tip on the brodix heads btw.

AFR all the way.....you will never be disappointed going that route.

The Brodix have stock locations on the ports. Here is a line from their website:
"The most important improvement is that the exhaust ports are in the stock location eliminating header or manifold interference."

I considered Dart vs AFR for my 540. Ended up going with AFR and never looked back. In addition to geat air flow and hp, the AFR's have a thicker deck (.75") and will not warp with nitrous or blower applications like I've been told the thinner Dart's will. Also I liked the way the intake gasket surface is supported all the way across, where the Darts have some unsupported areas. So, I'd recommend the AFR's. Their 305cc heads are as cast, while their 315cc heads are CNC'd. And yes, they are both rectangular ports.

Is your crank forged? Pistons? If not, you may want to consider going that way for durability/reliability.

Here are your cam specs:

Xtreme Energy XE268H Hydraulic Flat Tappet Camshaft Only
Lift: .515''/.520''
Duration: 268°/280°
RPM Range: 1600-5800

249-11-242-3 *Note: In order to use these camshafts in 1965-66 396/427ci blocks, it is necessary to machine a 3/16'' wide x 7/64'' deep groove in the rear main journal of the cam to allow oil flow to the top of the engine. Good for street machines, slightly rough idle, stock converter. Operating Range:1600-5800 RPMDuration Advertised:268° Intake / 280° ExhaustDuration @ .050'' Lift:224° Intake / 230° ExhaustValve Lift w/1.7 Rockers:.515'' Intake / .520'' ExhaustLobe Separation Angle:110°


That cam puts you at about the top of the ordinary street range, or the very bottom of the street/strip range. So, I'd suggest you consider stepping up to a solid roller cam, even if only a modest one, and using an Edelbrock Victor Jr single plane intake. These upgrades can support the power level you are looking for, where the parts you have now, may be hard pressed to do that. Something to think about before you go any further. Either way, it'll be a lot of fun, good luck. Let us know how it comes out :thumbsup:

Ah ok dart aluminums. Somehwere I thought I saw "iron eagles". So naturally....those would be iron heads and I figured we were talkin dart irons vs the AFR.

Either one would be nice in aluminum form...but Id still prefer AFR for a head to be run right out of the box.

Now were talkin with the 260/266 comp roller(make SURE to order it on a billet core)! Unless things have changed....their street rollers are done on cast cores.....and no roller cam with these kinda specs have business being ground on a cast core. If you "spring" it enough to really take care of the valves...the cast core will show wear quicker than you would like. Matter of fact, try this and you may get a similar result. Call comp and ask about that very cam as is(assuming they still grind it on a cast core). Ask about what springs to use/spring pressure. Call back, dont let em know you just called and ask about the very same cam. Tell em you want it on billet. THEN ask for the spring reccomendation. They often give a different...heavier duty spring if its done on billet. Reason being. Those lobes truly do need a fair amount of spring. Its much better to over spring a roller than under spring a roller. But...the cast core wont work in perfect harmony with "enough spring". So they recommend a softer spring that still works for the cast core....but your limited in how hard you can turn the thing(be very careful of float).

That earlier number you provided is for the XE 268 hydraulic flat tappet....so thats what my post was geared towards. I thought you were putting the little wee flat tappet in a big 496. So disreguard all that. I love a good aftermarket head now after seeing your actual ideas. And if you got the coin.....seriously consider the full CNC AFR 315 heads. They are a dead wringer for this build. 305's will be great too.

The Brodix have stock locations on the ports. Here is a line from their website:
"The most important improvement is that the exhaust ports are in the stock location eliminating header or manifold interference."

I have compared the exhaust ports to a stock head, they are definitely raised, might not be enough to require custom headers, but they are enough to require grinding on the header flange to keep the head bolts from hitting them :thumbsup:

Looking just at the numbers, the AFR 315 should be a winner for your engine. Exhaust flow is far higher than Brodix RR and this is an area that can choke a BBC. AFR uses longer valves so make sure you include new pushrods in budget too. Believe the exhaust ports are raised 3/8 of an inch - not sure how this impacts header clearance.

Don't worry about whether the head is oval or square port. Way too much discussion about nothing. The anti-rectangular port argument is a throw back from the days when GM heads were the only choice and the rectangle port iron heads were too big for most normal street/strip combos.

What you really want is the right port cross-section for your engine and intended RPM band. At 489" with your 650 HP goal I like the AFR 305.

Hate to say it but I don't like that cam. 224* is way too small at 489" to make 650 HP. It will make a tow truck motor. If you insist on a hydraulic flat tappet and want the Comp XE series flat tappet I'd look at the 11-254-4 (294* advertised and 250* @ .050). That will still make a ton of grunt but should pull pretty good to 6000 RPM.

Hope that helps.

Might be slightly off subject of BBC stuff. I recently upgraded AFR heads. At the same time I upgraded roller cams, went from a cast roller (due to wear) to one of Ud Harolds billet grinds. He did stress the point on spring pressures on a hyd roller. Where I was running a 1.55 spring with 140# closed pressure, he said it was inadequate.
Harold recommended a 155# seat pressure on his cam. He also mentioned that any of his cam designs have a differant closing ramp on the lobes, that eases the valve closed , no slammng the valve closed like other cams do.
So when I ordered my new heads from Mike Lewis Racing, he agreed to the higher seat pressure. He made comments as to many people just did not put the right amount of seat pressure on a hyd roller. This topic will lead you into the rev kit discussion and I am not using one. Mike ordered a beehive type spring with titanium retainers with more pressure, smaller id(less mass) and this alone will lighten up the spring mass to aid in better valve control.

I do agree with the topic of using some of the iron heads but it all depends on how fast your want to go and how deep your pockets are.

Also consider that CNC heads are close to a porting job as you will get without paying big bucks. You can also run several points higher compression with alloy heads too when comparing to cast iron.
Your call.

".....He made comments as to many people just did not put the right amount of seat pressure on a hyd roller.....Mike ordered a beehive type spring with titanium retainers with more pressure, smaller id(less mass) and this alone will lighten up the spring mass to aid in better valve control....."

This is an old thread but anyway...I set up the UDHarold designed Hyd roller in our 496" BBC
with 170-175 Lbs seat pressure with around 440 Lbs open.
No problems reving it to the 6400 rpm chip.

And those beehive springs just wouldn`t feel comfortable for me, break one and it`s a good possibility a valve could drop...no thanks, I`d prefer a dual spring with no damper when using Titanium ret`s

My builder talked me out of building a 650 ho motor. We lowered the compression and went with a mild street cam. It should make about 500hp. I also went with the Dart heads once I saw the price for the AFR heads.

My builder talked me out of building a 650 ho motor. We lowered the compression and went with a mild street cam. It should make about 500hp. I also went with the Dart heads once I saw the price for the AFR heads.


your builder needs to talk to my buddy!
i have a 18 yr. old friend with some money he earned burning a hole in his pocket
he wanted me to build a 383 .....turned into a 454...into a 496.
i don't want blood on my hands

anyways, the brodix race rite heads are great for the aforementioned application
mike lewis could probably get you a set for a good deal

the afr's would be slightly better, but at a higher cost

i have no first hand experience with darts

you don't need custom headers for raised port heads (as long as you don't have power steering). Hookers 2" comp headers on my 69, with .600 raised port canfield. Had to grind the steering box, and put a very shallow dent on one tube.

If it were me, I'd go with the AFR 305, but get them with the CNC combustion chambers (the CNC machine actually Cleans the bowl area of the heads as well) for the extra 400 bucks. That is the BEST bang for the buck (even Tony from AFR says so) if you aren't looking for the very last drop of hp. They will come with 121cc but you can have them cut back to 118 or whatever you'd like (max to 114cc).

with the 260@050 roller cam and 305 cnc chamber, with 10 to 10-5 cr, a good carb and single plane, I'd say 675. I had a book with a 496 and 315's with around 260@050 and they got it to 713hp at 6800rpms

just buy AFR...I wish I could have at the time...it's on my list of upgrades though :)

This is an old thread but anyway...I set up the UDHarold designed Hyd roller in our 496" BBC
with 170-175 Lbs seat pressure with around 440 Lbs open.
No problems reving it to the 6400 rpm chip.

And those beehive springs just wouldn`t feel comfortable for me, break one and it`s a good possibility a valve could drop...no thanks, I`d prefer a dual spring with no damper when using Titanium ret`s

Don't get me started again on worrying about this single spring issue, thats why I was using the dual spring or even triple.. One of my biggest pet peeves about single. Something else I will need to check into on the next teardown.

Good greif is that the right cam? Also the Dart heads are aluminum. I would be buying the complete setup from the respective manufacturer. Im not trying to cheap out.

The cam I want to use would be something like this

Comp street roller. 260/266 110 lobe sep w/ .677/.687 lift.


Thanks for the tip on the brodix heads btw.

Oh if thats the case by all means get the AFR 315's they will blow the Darts out of the water ( at ALL LIFTS ) throughout the entire RPM range. I was with Greg till you specified a Street Roller.

you don't need custom headers for raised port heads (as long as you don't have power steering). Hookers 2" comp headers on my 69, with .600 raised port canfield. Had to grind the steering box, and put a very shallow dent on one tube.

If it were me, I'd go with the AFR 305, but get them with the CNC combustion chambers (the CNC machine actually Cleans the bowl area of the heads as well) for the extra 400 bucks. That is the BEST bang for the buck (even Tony from AFR says so) if you aren't looking for the very last drop of hp. They will come with 121cc but you can have them cut back to 118 or whatever you'd like (max to 114cc).

with the 260@050 roller cam and 305 cnc chamber, with 10 to 10-5 cr, a good carb and single plane, I'd say 675. I had a book with a 496 and 315's with around 260@050 and they got it to 713hp at 6800rpms

just buy AFR...I wish I could have at the time...it's on my list of upgrades though :)


I 2nd this. Im using 2" basic headers ( freebees) with AFR 325s AND a tall deck block and had some trouble with the steering box clearance but everything else is fine.

My build cost with machining and parts was 7k and growing and I had to scale it back or risk not having enough cash to complete the restification of the car. I went with a non roller cam, KB hyper pistons and a Edelbrock RPM Airgap. The Dart heads are very nice but not CNCed. Reality check was that this is 99% a street car and I was low on funds at the time.

Part Number11-246-3 Engine1965-1996 Chevrolet
396ci-454ci
8cyl. Grind Number CB XE274H-10 Description IntakeExhaustValve Adjustment0 0 Gross Valve Lift0.552 0.555 Duration At 0.006 Tappet Lift274 286 Valve Timing At 0.006 OpenCloseIntake31 63 Exhaust77 29 These Specs Are For The Cam Installed At 106 Intake CL IntakeExhaustDuration At 0.05 230 236 Lobe Lift0.325 0.327 Lobe Separation110 Recommended Valve Springs924-16