Thinking about Doing Up Iron Heads

[67Satty]

I know most people probably don't bother with them these days but I'm thinking of having some 906s done up to replace my bone stock 452s (what would you guys say they flow 210? 220?).

I've been considering the Stealths for a long time but here's why I don't think I want them:

$1000 purchase price + having to replace springs, locks, retainers to be able to work with my cam + plus shipping gets the price closer to $1250. I'm already at $1250 without even having them checked out by a machinest or given a good valve job. Then, I will have to either clearance for my 3/8" pushrods or buy another set of 5/16 pushrods. More time and/or aggravation or $$$.

I called 440Source today about the pushrod clearance issue and they said something about it was necessary because their runners are bigger than stock heads and different blocks have different amounts of core shift. I called Edelbrock's tech line and they said there is no issue with 3/8" pushrods with their RPMs. So something doesn't smell right to me. If Edelbrock can do it, they should be able to.

So I've been talking to a local SoCal head porter who is known for his work with 906s. For under the price of the $1000 Stealths, he will do a set of 906s that:

flow 270 cfm (with a flow sheet)
Springs matched to my cam
10 degree locks and retainers
New 2.14/1.81 valves
New Seals
Bronze guides
Surfaced

He asked lots of questions about my car and where I raced. He wanted to know stall, gears, intake, carb, CR, weight of car, cam lift, where I want to shift - leads me to believe he will taylor his porting work towards my cam and car.

Stealths prepped the same would cost about $1750 total. So about an $800 difference but the Stealths would flow more than 270 cfm after the porting, save 50 pounds, and have quench.

Or, I could go for the RPMs for about $1600. I called their tech line and it sounds like the springs would work for my cam. The tech guy says they test/QC each head to make sure all the valves are sealing good and they are ready to bolt on. It would still be about $650 more than the prepped 906s but they would flow about 20 cfm more, be 50 pounds lighter, and have quench.

Of course, with the irons, I'd have to worry about cracking them someday but they'd be far from maxed out porting wise, compression and power wouldn't be that high so maybe it wouldn't be much of a worry?

What do you guys think? Goals are to get the car from high 7s in the 1/8 to mid to low 7s in the 1/8 or to get into the high 11s in the quarter. Thanks!

 

[mopar12372]

nothing wrong with that but the 452 heads flow better and the quench area is better than the 906 , iron is better with heat in the combustion chamber anyway . the only thing that is different is the weight between the 2 heads . you really dont need big ports/runners with low compression you need the velocity . with aluminum you have to run a higher compression 2 points i believe . thats a great price .

 

[Budnicks]

Budget seems to drive this subject way too often... your goal is only like an 7.50 1/8 {or 11.70 car in the 1/4}, a good set of ported iron heads on a well built 383-440 can do that, pretty easily & especially if you spend the money well & in the proper places... {to get a set of OEM cast iron heads to the level of just the OOTB RPM's {100% Made in the USA, unlike others} you'll spend easily $1000, most all on just port work & the heads are pretty topped out/done at that level, just a short side radius & good valve job will only get 260-275cfm max, if done right, but they can be taken out to 330cfm but you better have a great cylinder-head guy, that knows what the hell they're doing & it won't be a cheap port job either} All this is well documented many times over, I hope IQ52 will chime in here.... IMHO you'll spend $1000 on a set of old iron heads, when all's said & done, if it's done right, to put the right size valves {906 castings still only have 2.08" int.}, have the valve guides machined down for camshafts of anything over over about 0.520" gross lift & springs {added expenses} & port job, performance valve job, set up could be maybe a little less $$$, depends on who does the porting & machine work, or how good they are at porting & machine work... But you still have a heavy set {near 70lbs more} of 40 old iron heads, with smaller intake valves & more limited port potential, with cracking potential & limited on future improvements... To me I think like it like this, why spend the money several time do it ?? when you can do it once right & save a little longer for the more pricey parts, then have a better part... IMHFO with a set of reasonably mid ranged priced Eddy RPM's you will have bigger valves {2.14" int.} much better port design out of the box a realistic 291cfm @ 0.600" gross lift, better designed combustion chamber, especially with the 84cc closed chambers, near 70lbs of weight saving off the front of the car, than most any economical iron head, valve & port job will get you, for $500 more, if ported way better head... the Stealths are a cheaper alternative, but still need more work, {like 260cfm OOTB & if you use 1.6:1 rockers &/or 3/8" push rods you will need to grind on them, just to clear the push-rod} spend more money & time, just to even match the RPM's OOTB potential, but they are a good replacement head if done correctly, they look more like a factory iron head too {especially if painted}, but only it the $$$ money spent in the right places, not just a bolt on OOTB deal... Also anything you buy or build should be gone thru & match your springs retainers locks seals etc. to your build, proper installed heights & pressures, so that's a wash either way, no matter what heads you go with... IMHFO the weight saving is a great thing alone, somewhat free ET improvement, even if the heads were identical, in flow & port configuration... You also have better/quicker cooling & a slight compression bump & better quench area, with closed chambers... You really need to weigh what the best for you, it's not always just what you spend right now but what is the potential for improvement with out spending a bunch more again if you stay with the iron factory style heads, just because of a $500-$750 price difference vs any aftermarket aluminum head... I've seen good iron heads make really good power, like 720hp but they were on the edge too, personally I'd rather have something that I can take to the next level, 800hp if need be, with just more trick port work or a larger valve size change etc., than an old factory style ported iron heads, just because of a few hundred $$$... it's your decision, you can put what ever spin on it you want to justify your reasoning but that's how I see it & how I would recommend to build an engine to do what your trying to do... Good luck either way you decide I will try to help you, but I will say I told you so too, when your not satisfied latter, & want to go faster, but can't because of head limitations or because of not spending a little more now, for a better outcome in the future.... There are other heads out there too, but in the level you talking about the 3 types we discussed are the norm... even if it's $1000 more on the cylinder heads it's money well spent, heads are the biggest choke point on a BB MoPar wedge engine, they are the biggest in potential improvement too... Have fun

 

[lewtot184]

nothing wrong with that but the 452 heads flow better and the quench area is better than the 906 , iron is better with heat in the combustion chamber anyway . the only thing that is different is the weight between the 2 heads . you really dont need big ports/runners with low compression you need the velocity . with aluminum you have to run a higher compression 2 points i believe . thats a great price .

there's no difference in quench area between the two. 452's will have about 2cc's more volume. aluminum heads don't require more static compression.

- - - Updated - - -

the OOTB flow numbers for stealths is pretty dismal compared to the advertised numbers. i don't see anything wrong with doing a set of iron heads. the down side is if you don't use a quench dome piston with the open chamber heads. i've used a set of mopar stage 5's for years, and yes i have some $$$ in them, but they flow at least as good as OOTB edelbrocks. made more power than what i needed.

 

[67Satty]

I always read that stock vs. stock the 906s outflowed the 452s (something like 235 cfm vs. 220 cfm) but that the 452s were easier to port and that after porting it was a wash. And I thought the quench area or lack of it was the same between all the open chamber iron heads?

The guy I've been talking to seems to hate the 452s because of the short turn or lack of one.

Budnicks, I think you are probably right about me being pennywise and pound foolish. I've already been bitten many times by that with this car.

But...these sub-$1000 906s might do the job for my current goals. The way I figure, I'm at 425 hp with these bone stock 452s (based on my car's weight, the DA, and my ETs). Going from 220 cfm to 270 cfm should get me to 500 hp which should be enough to get me into the 7.30-7.50s range in the 1/8.

Any faster, any more power and things start to snowball with safety equipment and getting it to hook up at the track.

That said, who knows what the future holds? I know I don't want a 6 point bar in the car now but maybe in the future I will want to go down that road. Some RPMs with porting could support a lot more than 500 hp, something I might want to try for in the future with a cam swap. And it's possible since my shortblock is pretty much the same as IQ52s in the Pop's 440 on the Dyno thread.

Something to ponder, that why I'm bouncing it off of you guys. Thanks!

One thing I have made my mind up on is if I have to choose between the Stealths and the RPMs, I will pick the RPMs, if for no other reason it seems a lot easier to ding a couple off my header tubes with a hammer for angled plug clearance than grind for hours on cylinder heads for pushrod clearance.
I'd also be alot less nervous about dinging my used $150 headers than grinding on $1000 cylinder heads.

 

[Budnicks]

67Satty, that why I threw it out there, you could bolt on a set of RPMs for a few hundred more & be able to bump up or expand the ports latter & still have a better/lighter head... It's win, win situation, for $500 more for the RPM's vs Iron or OOTB Stealths 270cfm x 2.06hp per/cfm = 556hp potential if everything is tuned properly etc. & then the OOTB RPM's 291cfm x 2.06hp per/cfm = 599hp, 43hp more for $500 = $11.62 Per/HP, I call that money very well spent & still have the weight saving, for quicker et's & less wear & tear too

 

[Herr_Poopschitz]

iron is better with heat in the combustion chamber anyway . the only thing that is different is the weight between the 2 heads . you really dont need big ports/runners with low compression you need the velocity . with aluminum you have to run a higher compression 2 points i believe

Please explain all of your contentions, please.

In what way is Fe better than Al 'w/ heat'?

If velocity is so important, why not fill in the ports to reduce x-section even more?

You HAVE to run 2 pts higher compression? Why?

Anyway, Satty, if you were my customer I would recommend the Edelbrocks. Check the springs...just bc they will 'work' doesn't mean they are ideal. Also, if the VJ is anything like my Vics, again, will 'work', but less than ideal. On the other hand, you could check the springs and vj yourself and if acceptable, put 'em on and run 'em...maybe upgrade later...

They will be more detonation resistant, lighter, repairable, and upgradable. The iron heads are great for cheap thrills, but are not, imo, heads to use in a performance application. While you 'can' go somewhat quick w/ them, it's much more difficult and usually requires compromises to do so.

Cam, compression (which chamber are you looking to get?), converter, gear, and race weight?

Was 440Source referring to their super stealths with respect to pushrod clearancing possibly?

That said, if you don't already have them, I have a set of assembled 906s w/ big valves, bowl work per the MP templates, and hardened seats I'll have for sale soon...

 

[YY1]

I thought the physics were such that heat dissipation was better with AL, and that you could run higher compression, which equates to a more efficient engine.

 

[Cranky]

Awhile back I checked a set of OOTB Eddys against a set of max ported 906's that I ran on a Super Street car. It would run a 10.50 if I tuned it to do that but it wasn't consistent so I slowed it down a bit to make it that way. Anyhow, the Eddy's flowed the same! Thing is, we're not racing flow benches and when looking at the Eddy vs stock based heads, the Eddy is the better head just because of the better port configuration, better combustion chamber design and the angled plugs AND you won't have to buy reverse dome pistons to get a good quench distance. There's no way I would spend that kind of money on an iron head unless I'm porting it myself and even then, I'd have to think about that one. Cast iron dust flying around isn't something I care to do much of anymore. Not sure what you're running now but if your iron heads haven't had any port work done to them, do a pocket port job and run em. The factory back cut sucks big time and just doing that will wake them up a lot.

 

[GTX MATT]

906s will slightly outflow the 452s stock for stock. I myself would prefer a killer set of stock heads, just so that I can claim I'm making X power with stock heads. However, when facing the same question myself, I went with the Stealths for the compression bump and the quench factor.

What are you planning to run for a cam? The Stealth heads come with comp locks and retainers now, and the springs are good for something like the 509 Mopar cam or something similar with moderate ramp speeds.

What do you want to run for a cam? If you want to run something like the 509 I think you can grab a high 11 second slip with OOTB Stealths, 509, and a solid short block. Just disassemble the heads yourself clean them, lap in the valves and make sure the pattern is decent, and make sure the valve guides aren't excessively tight.

As far as pushrods, you may need a set no matter what heads you go with, and probably will if you're changing cams. You can get a strong set of 5/16 pushrods from Smith Brothers for around 160.

 

[Cranky]

nothing wrong with that but the 452 heads flow better and the quench area is better than the 906 , iron is better with heat in the combustion chamber anyway . the only thing that is different is the weight between the 2 heads . you really dont need big ports/runners with low compression you need the velocity . with aluminum you have to run a higher compression 2 points i believe . thats a great price .

I've checked a lot of open chamber heads over the years and they all come out to be right around 90 cc in stock form.....and, a ported head can work with a low compression engine. Done it many times.

 

[mopar12372]

there's no difference in quench area between the two. 452's will have about 2cc's more volume. aluminum heads don't require more static compression.

- - - Updated - - -

the OOTB flow numbers for stealths is pretty dismal compared to the advertised numbers. i don't see anything wrong with doing a set of iron heads. the down side is if you don't use a quench dome piston with the open chamber heads. i've used a set of mopar stage 5's for years, and yes i have some $$$ in them, but they flow at least as good as OOTB edelbrocks. made more power than what i needed.

you are wrong , even the mopar performance book and any head book for chevy or ford will say that you NEED more compression for aluminum heads .castiron is the best way to go , its just heavy. stage 2 stage 3 heads mopar still old tech the way togo . for his build a mild port on a set of 452 0r 906 head with the valve back cut will be good to go . just say in

 

[67Satty]

To answer some questions, when I spoke to 440 Source today, they told me I would need better springs, locks, and retainers than what comes on their Stealths to work with my cam which is a .534 lift. They said my 3/8" pushrods would make it so I would have to grind on the Stealth for clearance. I could buy some Smith Brothers 5/16" push rods but now my $1000 Stealth heads have become $1400 Stealth heads after adding in springs, retainers, locks, and pushrods. The Edelbrock tech guy said he's never heard of anyone having to clearance RPMs for 3/8" pushrods and I've searched the forums and never heard of that problem with them either. Someone was asking about my converter, it's a 9.5" Dynamic that's supposed to have a 4200 stall, but I've never really tested that. Gears are 3.91s, car weighs 3600, I was looking at the 84cc RPMs. Thanks for all the input!

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[IQ52]

you are wrong , even the mopar performance book and any head book for chevy or ford will say that you NEED more compression for aluminum heads .castiron is the best way to go , its just heavy. stage 2 stage 3 heads mopar still old tech the way togo . for his build a mild port on a set of 452 0r 906 head with the valve back cut will be good to go . just say in

Argue with this.

http://www.chevyhiperformance.com/techarticles/83858_iron_vs_alloy_engine_heads/#13922568757961&1,tss

http://www.carcraft.com/techarticles/ccrp_0602_iron_versus_aluminum_cylinder_heads_test/viewall.html#13922568380621&1,tss

 

[Herr_Poopschitz]

you are wrong , even the mopar performance book and any head book for chevy or ford will say that you NEED more compression for aluminum heads .castiron is the best way to go

Explain it or stop spreading misinformation, please.

 

[BeastlyBirdie]

Don't forget different head bolts in your cost.

 

[747mopar]

I built a set of 452's (from my research they are really close in flow to the 906's) for my 456" that sound identical to what you are proposing "valves and all". I had them cc'd at 88cc and did the porting myself (total ammeter) with good results 260 @ .550 Int and 198 @ .550 Ext. I didn't go crazy at all with the porting knowing I didn't need allot of flow for my setup and not wanting to screw it up so there's allot to be gained if needed in that area. Doing the porting myself I still had $900.00 in them because they needed everything, bronze guides, valve job, valves, springs retainers etc. For me the Chinese heads were never an option so $900.00 versus $1,600 (Eddies) for a head that was more than I needed was the deciding factor although if I had money I would have bought the Eddies.

 

[67Satty]

Another question I have on the subject of how much work needs to be done to the "bolt on" aluminum heads before you can bolt them on, I was reading about a guy on another forum who flowed all the different intake ports on his new RPMs and found one that was at 257 cfm vs. the 290 or so cfm on all the others. So then he had to straighten that out. IQ52, maybe you can answer this, how common is that kind of problem on the RPMs?

I starting to seem like the price difference between these fully checked out 906s I can get done and fully checked out aluminum heads might be more like $750-$1000.

I've heard of people buying Indy EZs all done up and gone over by an Indy dealer/head porter for just a few hundred more than the $1600 RPMs. If that's the case, then maybe the EZs are the best bang for the buck with the most potential for future upgrades?

Just a little leery of the 75cc chamber giving me too high a compression for pump gas and that they might be overkill and/or have poor low lift flow for my cam.

 

[cdr]

440 Source
3 hours ago
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[BIG-A]

440 Source
3 hours ago
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