Mopar Muscle Article on Stealth Heads

[67Satty]

I always thought the rule of thumb was 2.06 HP or so per CFM of head flow but after reading this article it seems like they got more like 1 HP per CFM of flow at best.

The they took a 440 and compared tested it with mildly ported 915s, OOTB Stealths and CNC-ported Stealths. The flowed each head and then put the engine on the dyno with each head.

Here's a summary of their results:

The 915s flowed 236 at .600 and made 467 hp.

The $995 OOTB Stealths flowed 268 at .600 and made 475 hp. (Spend another $995 for another 8 hp???)

The $2000 CNC Stealths flowed 323 at .600 and made 532 hp. (Spend another $2000 for another 65 hp????)

 

[rumblefish360]

It's because they never capitalized on the heads abilty. Your calc is correct largely on the head flow BUT only if you take advantage of it. This means an increase of compression and a bigger cam and headers and.........

 

[cdr]

what did the heads flow with the intake ??????the heads can flow great until you bolt on the intake manifold

 

[moparpoor]

With the stealth cnc heads,there are a couple of guys around here pushing well past the 600hp mark. It has been rumored some clicking over the 700hp mark.

 

[bigmanjbmopar]

I have a set of the gen 2 stealth's and they make great power ootb I can't wait to take them off and have them worked a bit sitting a 585 hp now with my 493 set up and could easily push 680 with worked stealth's. for $995 for two heads with comp cam springs and retainers, stainless steel valves already on them I think that is a hell of a deal eddy heads don't even come with springs for double that.

You also like said by others have to consider the build factor of other components, and also consider the weight taken off of the cast iron 915's Dyno a car not an engine for real world power, When you can feel 500+ hp under your feet you wont care about the $995 you just spent because the smile and heart rate will make it all worth it trust me lmao :headbang:

 

[IQ52]

It's because they never capitalized on the heads abilty. Your calc is correct largely on the head flow BUT only if you take advantage of it. This means an increase of compression and a bigger cam and headers and.........

Very true....as we will see further on in this reply, we have made 2.28 hp/cfm with the same design head.

what did the heads flow with the intake ??????the heads can flow great until you bolt on the intake manifold

Here is an answer, using a RPM head, various intakes and the same 850 Mighty Demon on each manifold.
#1 slight cleanup on a RPM and flowed with no intake manifold or carb,
#2 same head w/ stock 383 iron intake from '69 Road Runner,
#3 same head w/ Edelbrock Performer RPM intake,
#4 same head w/ Edelbrock Torker II intake,
#5 same head w/ Mopar M1 single plane intake,
#6 same head w/ Edelbrock 383 Victor intake.

Remember, each manifold test was with the SAME 850 Mighty Demon.

Lift..........#1..........#2.........#3.........#4..........#5...........#6

.100........72..........69..........71..........71.........72............72
.200.......150........131........145........148........148..........150
.300.......212........172........195........201........202..........202
.400.......254........187........228........242........234..........240
.500.......276........199........240........254........254..........261
.600.......290........203........251........264........266..........271
.700.......302........204........256........269........273..........280

With the stealth cnc heads,there are a couple of guys around here pushing well past the 600hp mark. It has been rumored some clicking over the 700hp mark.

We just shipped a pair of standard Stealth heads to Iowa for a pump gas 451 stroker. Those Stealth heads were:

Lift...............OOTB...............After porting

.................INT/EXH...............INT/EXH

.100............73/60..................80/67
.200..........151/122...............157/139
.300..........214/165...............220/190
.400..........245/196...............269/228
.500..........262/218...............306/255
.600..........276/220...............334/275
.700..........281/236...............345/287
.750.....................................345/293


Now with a pair of Edelbrock RPM heads that flowed,

.100............84 cfm
.200..........158
.300..........215
.400..........252
.500..........299
.600..........328
.700..........341
.750..........345

we made 723 HP in Mopar Muscle Magazine's engine challenge. Later, with nothing but a cam swap and a heavier load on the dyno, of 300 rpm/sec acceleration rate, the engine made 787 HP. The Stealth heads are capable of the same horsepower!

 

[rumblefish360]

67satty. Also note that the basic HP per CFM x's2 is a equation that works only in theroy if you take advantage of the heads flow abilty. The ported heads flow more but the cam never changed with its lift I. Order to have the valve lifted high enough to take advantage of the increased air flow. Also, hanging the valves open long allows more air and fuel into the cylinder. Of course, this is more power.

In an example with a small block, the stock X heads for a 340 flow a little better than 200 CFM. The math would suggest a little over 400 HP. But this flow level is at a high valve lift. If the cam doesn't open the valve up that far, breathing is not deep. If the cam does t hold the valve open longer, it is a short breath.

Small low lift cam equals short shallow breath.

Now that math also does not include the use of a very large cam. Connected with other overkill parts, it is possible to exceed the 2 HP per cube and go to 2.5 HP per cube. In order to do this in a lowly street engine, the combo becomes unbalanced. Starting RPM's of any power worth a mention would Begin at 5000+ rpm.

This is not street worthy unless you yourself are a bit cracked in the head. (Yes, I'm on the mend myself) race cars are built in this fashion since there more of a car dedicated to flat out speed and power in a narrow power band.

Use the CID X's 2cfm as a general rule of thumb for what is possible in a hit street car IF the full Monty is sought.

 

[67Satty]

Since the test motor in the magazine article had a cam with .567 lift and my cam is .534 lift and 238 @ .050 duration, then I should probably expect similar results - more like 1 CFM = 1 HP? So, I should expect maybe 40-50 additional CFM of flow and 40-50 more HP comparing my unported 452s to OOTB Stealths? Does that sound about right for a ballpark? So maybe I should consider a cam change to something closer to .600 lift and 250 @ .050 duration to take more advantage of a switch to Stealth or Edelbrock RPM heads?

 

[IQ52]

With the cam you have now, 30-45 cfm of flow difference, depending upon the characteristics of the head chosen.

Lift..........stock 452 iron............OOTB Stealth.............OOTB RPM

.100.............61..............................73...........................73 cfm
.200...........130.............................151.........................149
.300...........188.............................214.........................211
.400...........213.............................245.........................253
.500...........227.............................262.........................276
.600...........230.............................276.........................287
.700.............................................281.........................291


The bigger cam, your engine purpose and design will tolerate, the more power you will make.

 

[YY1]

IQ52, I like your chart and I like your "scientific method" comparison.

Your research seems to indicate to me...that the performer intake is not an "exact" replica of the factory part, as I've heard many times, and that the torker is not nearly as bad low end as I've heard lots of times as well.

Thanks for that comparison.

 

[Budnicks]

Since the test motor in the magazine article had a cam with .567 lift and my cam is .534 lift and 238 @ .050 duration, then I should probably expect similar results - more like 1 CFM = 1 HP? So, I should expect maybe 40-50 additional CFM of flow and 40-50 more HP comparing my unported 452s to OOTB Stealths? Does that sound about right for a ballpark? So maybe I should consider a cam change to something closer to .600 lift and 250 @ .050 duration to take more advantage of a switch to Stealth or Edelbrock RPM heads?

even with your current camshaft they will make a noticeable difference over a stock OOTB 452's... If you have enough valve to piston clearance, proper valve springs etc. & room on the valve guides to add some lift, you could also get some 1.6:1 rockers to boost your existing cam some, makes that 0.534" lift to a 0.569" gross lift, gain some flow... I personally like the Edelbrock RPM's better in 84cc combustion chambers, if you have the proper pistons, they can handle 0.600" gross valve lift OOTB, depending on your valve spring needs, I know they're more money too, have better parts in OOTB configurations, have better flow rates & better combustion chamber designs too, not to mention they are 100% made in the USA also, but also there's nothing wrong with the Stealth's mostly, www.440source.com assembled here in the USA, they have a straight plug & small 78cc combustion chamber, w/maybe better header choices/selection, than the angle plug design of the RPM's & look more close to stock, when they're painted, you will need to add some different &/or much better quality, springs, retainers, locks & seals on the std. no frills Stealth's, unless you step up & order them with the properly matched & much better parts to start with, they come with inferior parts in the std. configurations, adding some $$$$ cost to the lower price of the Stealth's, if you want to do them correctly... good luck & have fun

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IQ52, I like your chart and I like your "scientific method" comparison.

Your research seems to indicate to me...that the performer intake is not an "exact" replica of the factory part, as I've heard many times, and that the torker is not nearly as bad low end as I've heard lots of times as well.

Thanks for that comparison.

IQ52 He's a professional head porter & engine builder.... he knows his stuff

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IQ52/Jim hey buddy, I love your posts they're always so to the point & accurate

 

[IQ52]

The sad fact is that no matter how big of a cam you put in a 440 with stock 452 iron heads, the engine will make it's most horsepower around 4700 rpm as that is where the cylinder heads will be sucked dry. Just changing to the Stealth or RPM head will take the horsepower peak up somewhere around another 1000 rpm and that rpm increase will result in a real power difference. Just looking at an old 451 stroker dyno sheet shows that 570 lb-ft of torque @ 5000 rpm is 543 hp and that same 570 lb-ft of torque @ 7100 rpm is 771 hp.

 

[GrabberOrange69]

My take aways from the article was this: the Stealth's continued to see flow improvement to at least .600" lift, which means there is more left in them with more cam. If you are starting from scratch, the the Stealth heads are a great bargain. If you already have ported stockers, you might not get much bang for the buck.

I'll be putting stealths on my engine as I'm starting from scratch.

 

[67Satty]

even with your current camshaft they will make a noticeable difference over a stock OOTB 452's... If you have enough valve to piston clearance, proper valve springs etc. & room on the valve guides to add some lift, you could also get some 1.6:1 rockers to boost your existing cam some, makes that 0.534" lift to a 0.569" gross lift, gain some flow... I personally like the Edelbrock RPM's better in 84cc combustion chambers, if you have the proper pistons, they can handle 0.600" gross valve lift OOTB, depending on your valve spring needs, I know they're more money too, have better parts in OOTB configurations, have better flow rates & better combustion chamber designs too, not to mention they are 100% made in the USA also, but also there's nothing wrong with the Stealth's mostly, www.440source.com assembled here in the USA, they have a straight plug & small 78cc combustion chamber, w/maybe better header choices/selection, than the angle plug design of the RPM's & look more close to stock, when they're painted, you will need to add some different &/or much better quality, springs, retainers, locks & seals on the std. no frills Stealth's, unless you step up & order them with the properly matched & much better parts to start with, they come with inferior parts in the std. configurations, adding some $$$$ cost to the lower price of the Stealth's, if you want to do them correctly... good luck & have fun

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I started a similar thread on Moparts about this article and I'm pretty sure the guy from Modern Cylinder Head who does the CNC porting for 440Source has been chiming in with his take. He says that the current generation of Stealth heads now comes with decent hardware.

Hopefully he won't mind me quoting him here. He says:

"spring cups? same as edelbrock and comp, and everybody else on the planet

retainers? they are chrome moly steel,, nothing wrong with them,, at all,, they wont fail,, ever... the locks they used early on were stamped inconsisteltly and caused a few issues,, since they replaces them with locks from comp cams or same supplier as comp

guides??? brass just like everybody on the planet

seats?? they use a tungsten carbide seat of some form,, edelbrock uses ductiol iron,, the stealth seats are harder so they will last longer on same valve job

the valves in them are not severe duty type material,, but ALL stainless valves sold here in the us,, manley,, ferrea,, rev,, etc,, are made in argentina,, there are two large manufactures of valves,, they are adequate for what most people do with these heads,, if you were going solid roller and running it to 7500,, then id reccomend buying a 400 dollar set of manley valves ".

 

[IQ52]

I like the Stealth heads. Yet it depends upon your level of commitment to quality. The heads, as they come boxed, may work for 100,000 miles. Just turn a blind eye and bolt them on. I have disassembled many OOTB sets and had to file the gouges and proud metal caused by the current "improved" locks. I WILL NOT reassemble them without checking the guide clearance, seats, valve stems for nicks that I find constantly (I replace or repair 4-6 valves in each set) and replacing the "improved" locks, with better, as they are a lower quality stamping. Bolt 'em on and go, good luck. Most of you will have NO problem.

The stamped steel locks are about $7 for a set versus $23-$25 for the machined and hardened locks.

 

[Budnicks]

Thanks for clarification on the parts quality IQ52/Jim, you do a great job explaining stuff... It never hurts to take any cylinder head apart & do a thorough job of at-least cleaning & checking them out, no matter who you get them from... Opinions will always vary vastly... People get so attached to parts, they think what they buy is always the best & think your "personally insulting them", because you try to tell/educate them, something isn't of the same quality as someone else's, or bring up foreign made VS Made in the USA... They get really defensive, so emotional sometimes, personally I don't give a damn what heads someone wants to buy {I just prefer USA Made} as long as they do the proper thing to/with them, use the proper parts/quality for their applications... Like I said in an earlier post "there's nothing wrong with the Stealth's", for the most part, as long as if you, take the time to clean & check them out properly... Really depends on what performance levels you want & what your budget is... Maybe it's just me being **** retentive too...LOL... Cheaper isn't always better in the long haul....

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I started a similar thread on Moparts about this article and I'm pretty sure the guy from Modern Cylinder Head who does the CNC porting for 440Source has been chiming in with his take. He says that the current generation of Stealth heads now comes with decent hardware.

Hopefully he won't mind me quoting him here. He says:

"spring cups? same as edelbrock and comp, and everybody else on the planet

retainers? they are chrome moly steel,, nothing wrong with them,, at all,, they wont fail,, ever... the locks they used early on were stamped inconsisteltly and caused a few issues,, since they replaces them with locks from comp cams or same supplier as comp

guides??? brass just like everybody on the planet

seats?? they use a tungsten carbide seat of some form,, edelbrock uses ductiol iron,, the stealth seats are harder so they will last longer on same valve job

the valves in them are not severe duty type material,, but ALL stainless valves sold here in the us,, manley,, ferrea,, rev,, etc,, are made in argentina,, there are two large manufactures of valves,, they are adequate for what most people do with these heads,, if you were going solid roller and running it to 7500,, then id reccomend buying a 400 dollar set of manley valves ".

I got a feeling he maybe trying to sell some heads, especially if he's in that business, he has a stake in the games so to speak, it's to his benefit, to not say anything bad, or maybe that's what he really honestly believes, I have no idea, I don't know them... If they are CNC ported, then "maybe", the parts are changed out for better quality pieces also... I don't know anything about MCH, or the guy your quoting & I don't go on the Moparts forum, for a very long time now, don't plan to either... Opinions will vary vastly, those are mine... 67Satty hey good luck either way, I wish you the best no matter who's heads, that you ultimately end up choosing/using...

 

[67Satty]

Thanks Budnicks, I mentioned what the guy at MCH said because I'd been hearing online that the newer generation of Stealths came with Comp Cams hardware but then when you go on the 440Source website they still offer the Comp Cams hardware as an upgrade???

Either way it will be awhile before I tear apart the top end end of a perfectly good-running motor. I'll stick with my stock 452s until I just can't get anymore out of the combo from suspension tweaks, weight loss, and tuning, then at that point I will do a head and cam swap next. Right now I'm at 7.83 in the 1/8 mile (with a lot left on the table I think) and the cutoff for a roll bar is 7.50. I don't want to put a roll bar in my car due to wanting to continue hauling my kids around in the back seat so it might be awhile depending on how things go/how the car responds to things other than a head swap. If I can whittle it down from 7.80s to 7.50s without a head swap, I'll probably stay there awhile. If I can't get to 7.50s with the 452s, then I'll do the head swap sooner. As always I'm open to you guys' ideas!

 

[GrabberOrange69]

Bought my Stealths today at MATS from Viau Motorsports. I'll have my dad take them apart and do so minor port and bowl work (he owned his own machine shop for 30 years) and give them a "tune up". I'll report what we find, but they look fine at first glance.

 

[Moparmatt72]

Mine were good when I bought my set sitting on my motor I juat had them check out like you shoukd no matter who you buy from. Its always a good idea to have a machine shop look them over. My shop I go to said all in all a good head just a few guides needed to be fixed and I bought the upgrades and they set up the springs for me as well.

 

[robinsonwr]

I purchased Stealth heads for my 440/512 build with no regrets. They look to be a great performance upgrade for the budget builder. I chose them because the ability to run more compression with pump gas for one. Plus after sitting down and figuring out what it would take to refurbish my factory 915's the Stealths seem to make more sense. My engine should make around 575 horsepower. I will let everyone know once we go to the dyno.