We finally got snowed on and MN-Dot started salt-coating the roads so my LT1 has officially gone into hibernation. (BTW: LT1 + RE730s + polished ice = a very entertaining trip across town to the storage garage. Years off my life.)

I was planning a bottom end teardown over winter, but after some reconsideration, I've decided to build a 2nd motor. While snooping around for hardware, I came across these:

http://www.araoengineering.com/Chevy/chevysmb.htm

At roughly $3500 they ain't exactly giving them away, but beyond that, my GTO-tweaker buddy and I cant' see a down side, although he doubts he'd put 'em on his '69 perfecto resto. Has anybody here ever heard of these? If anybody's running them, I GOTS to hear about it...

 

This is :cool: ... wondered how anybody could ever do it without a belt or chain driven cams... like it was done back in the 60's. Whats really neat is stock intakes will bolt up! Downer is custom headers only...or at least the Hooker large tube style which I'm not sure they make for our C4's :( Flow characteristics on these heads are phenominal... along with a hp/torque curve that is to die for. Alot of money... but one could make a real nice sleeper with a set of these heads :yesnod: :crazy: :yesnod:





[Modified by billreid1@home.com, 11:14 AM 12/27/2001]


[Modified by billreid1@home.com, 11:15 AM 12/27/2001]

 

There were a few posts on these heads in the "Engine Mods" section not to long ago, you might want to go check them out. Also I don't think these heads will work on an LT-1/LT-4 engine.

 

L98 sleeper that is... :D


[Modified by billreid1@home.com, 11:17 AM 12/27/2001]

 

Bill,
I like the way you think :D

 

I've read detailed tests on this head. It was developed in the middle '90's when everyone thought this 4 valver conversion was "the answer". Panic gripped Chevyville as they read about the new '96 DOHC 32V Cobra and the aftermarket came to the rescue with this "wallet emptying" piece of conversion hardware for 32v wannabes. Reality set in when everyone realized this is head is a total joke. The valvetrain is a huge, overweight mass of rockers, levers and related componentry. It does not provide the inherent benefits of a DOHC or even a SOHC head (no pushrods). Also, compromises were made to the head's ports to allow the crazy valvetrain geometry. Basically, it is the head for those of us who must have something different. This head is overpriced, complicated and does not offer the performance of $700 conventional heads.


[Modified by Rick93Z07, 1:55 PM 12/27/2001]

 

Rick, have you read the comparisons (claims) on their website? I would agree that the valvetrain is complicated... has to be when your pushing 32 valves open with 16 pushrods. According to their numbers, though, it seems they overcame the problem. If anything durability of this setup could be questioned. I didn't see any comparisons with SOHC or DOHC heads so it doesn't look like they are trying to say they are better than OHC designs. One would think if the small block Chevy could have had an efficiant SOHC or DOHC setup bolted to it that perhaps GM wouldn't have gone to all the trouble of designing the ZR-1 motor. If you say that these heads don't match up to a set of $700 convential heads I'd like to see a side by side comparison of the heads your thinking of and these heads. Their dyno results seem impressive. I'm not doubting you... and if I ever had $3500 to spend on heads I'd make sure the claims were backed up by solid proof... I'd even go so far as to contact some of their customers if they would allow it and see how they liked them. :cheers:

 

Amen, Bill

Because all I have to go on is the manufacturer's propaganda, some real-world feedback is exactly what I'm looking for. They look so good on paper, I figure there must be a catch. Thanks, Rick for the heads up (pun intended) on the 'snake oil' angle.

 

Rick,
I think the heads you were thinking about were the Dominion heads. I think these are the same heads but I think Dominion was bought out by this company and they did some improvements to them. I would like to see some real world feedback on them too.

 

I don't have any first hand knowledge, but I've seen reference to someone on the F-body digest who tried to get these heads to work. The story I heard was they weren't worth the time/money to make work, they aren't bolt-on like a set of AFR heads. Maybe you can search f-body digest archives and see if there's any posts.

Eric

 

These comparison data on these heads look interesting but I am not sure they are going to be very good street heads. One problem is that they use the stock intake which means they cannot control the timing of air through each set of valves like the ZR1 did so the airflow gets divided up between the two halves. I wonder what this does to air velocity. Notice the torque curve below 3500 rpm either merges or is not plotted below that rpm. The horsepower curve looks like it drops off much faster as you go below 3500 rpm. The flow data does look really good on the heads. These would probably be great heads for a 3500 - 7500 rpm powerband motor.

The second issue is whether they will fit on an LT1. I have wondered if non LT1 heads could be modified to fit LT1s. I haven't looked at the water ports etc to make a comparison but it might be possible to convert a set by machining additional water ports in the heads to match up with the front water ports on the LT1 block and drill the holes for the air bleed passages on the back. The waterports on the intake side of the heads would also have to be blocked if the LT1 intake doesn't cover then completely.

 

Yes, theses heads can be had in the proper reverse cooling configuration for the LT1/4.

I had previously contacted the company when it was still Dominion, before Arao. As far as I can tell, these are one of those phantom products that seem to offer terrific potential - but the phantom part is that you can search far and wide and never find anyone who is actually running these heads. The $3,500 price tag doesn't scare me, heck, I've spent multiples of that on engines - what does bother me is that after more than four years on the market I still have yet to run across them on a car at the drags or any of the numerous shows and events that I attend.

I would be thrilled to see even one successful application of these heads...yes sir, I could dig a smooth idling 600 hp naturally aspirated smallblock!

Thomas

 

So, you've got a 9000 rpm set of heads that makes 474 hp. Big deal :rolleyes: . If you are going to run 9000 rpm, you should be making a lot more than that. NASCAR engines turn 9000, and make close to 800 hp. With 16 valves. And a carbuerator.

Rick is right. Until you loose the pushrods, there is no real advantage to 32 valves, especially for a street motor.

 

Bill,

I agree they post big numbers on the site. In a lab environment, big numbers can be generated with almost any head to produce warped advertizing propaganda. How many valve trains failed during the 2 minute test?? I dunno. Many of us saw the struggles that companies went thru like Summit TFS, AFR, AR and others when their "simple" heads became "mainstream". Suddenly, weaknesses pop up like flow efficiency & driveability at lower RPM's, cooling passage shortcomings that result in pre-ignition, cracking, valve train problems, guide problems, durability, porosity etc, etc. It took thousands of owners and several years for the word to get out that the TFS valve guides lasted ~10K miles (and years more for TFS to recommend a lame resolution). These heads look like a nightmare to me & I would not want to be a $3500 guinea pig for this company. IMHO, these heads belong on a waxer Show Rod or perhaps a trailered drag car experiment that sees 500 miles/year, until a bunch of owners post results. It is also clear these heads will never be legal on the street (and could not be passed off as such, as many do with 16V aftermarket heads). Just a few things to consider.


[Modified by Rick93Z07, 10:11 AM 12/28/2001]

 

Thanks all,

I cut my teeth on Detroit muscle but after decades of tinkering with various high-strung small-displacement Ger-***-Ital-Brit sports cars, I've become acutely aware of a few things that probably apply here;

1. It's universally understood that on four-valve and rotary engines without variable-volume induction, the bottom absolutely drops out below 3000rpm. I bought the Corvette because and I knew those screechers I was messing with were lacking one critical element; great hairy gobs of torque. No way on earth I'd do anything to jeopardize that now.

2. Fewer valvetrain components are better. Anyone experienced with Jaguar E-type's million-moving-parts school of design knows what I'm talking about. The pushrod-actuated valves of the good ol' American V8 still seem clunky to me, refined but unchanged in principle since the freakin' 1800s, but short of an LT5, there ain't much I can do about it, is there? Punch it and smile, I guess...

Have a Happy New Year!

 

I have heard these should be an improvement on the Dominion heads (essentially the same people;different name now though) - but the Dominion heads had horrible casting quality. Craig@GTP worked with a few, and suffice to say when you spend 3500 on a set of heads you don't expect to be welding them up in spots to fix leaks you found when you pressure tested the bare castings.

The other problem is mixture motion. The heads do put out excellent numbers on a flow bench. The problem is getting those numbers to translate to power. The 4v configuration inherently has very poor mixture motion (swirl or tumble, etc.) and also is not very well suited for large bores (it works much better in a smaller bore/more cylinder configuration).

The heads are available in a reverse cool casting, though how well this adresses the problems that reverse cooling inherently has with hot spotting I don't know.

When you get down to it though, if we are talking SBC/L98 here is how it looks to me

dominion - require custom intake/custom headers. 3500. Good flow numbers, poor mixture motion

say 18 degree pro action heads. require custom intake/headers/valvetrain. Excellent flow, excellent motion.

The 18 degree PA heads are going to romp all over the dominion heads in just about every category. Sure the dominions already come with their exotic valvetrain, but look at those rockers and tell me how comfortable you would be at 8000rpm with a high spring pressure solid? I would much rather have a nice jesel shaft mount setup for less.

Without the benefits of a DOHC valvetrain I don't think 4v has much of a future/potential.


Chris

 

Chris, well said - I can only add that in mechanical engineering that size plays a significant role in design selection, i.e., suitability for intended purpose. What is lost on a lot of the enthusiast public is that there are many desireable characteristics found in pushrod two valve engines of moderate to large displacement. As a general statement two valve heads tend to experience "swirl" on the intake charge (at least the good designs do), whereas four valve heads tend to flow in a "tumble" fashion (the intake charge tumbles down into the cylinder. All things held equal, swirl is better than tumble as it promotes a more homogenous mixture - but nothing is ever really held equal, like rpms and cylinder bore diameter vs available valve diameter. Also in the two valves favor is that a head can be designed with a good quench area . To get a good quench area in a four valve head requires pop up dome pistons, which have their own issues (whole books are written on this subject). yada, yada, yada...

Now if you want to get into something really interesting in valvetrain technology, look into rotary valves - hard to describe to the uninitiated.

Something for everyone to think about: cylinder head port shape and airflow is still more art than science.

 

I've seen a rotary valved V8... back in 86 or 87 at a dragstrip near Sacramento. Kinda looks like a DOHC from the outside at first with 2 belt driven "cams" per head. The one I saw was a top fuel rail, I think, from Australia. Man did that motor sound different... can't describe it. It blew up as soon as he cracked the throttle at green light. The explosion was violent enough that it sent parts into the spectator stands... nobody being injured. I did see the rail in the pits prior to it self destructing with the "valve covers" off. The valvetrain was awesome looking. Unconventinal doesn't even begin to describe it :yesnod: I've never seen a rotary valved motor since :nonod:

 

Bill, I understand that more recently some high tech ceramics have come to the aid of making rotary valves a viable technology (the main engineering obstacle to rotary valves has always been how to keep them sealed).

Because of the current and future realities of emissions and economy I actually expect that the next big production technology sea of change will involve electric solenoid operated valves (just imagine programming the car's computer to have variable valve events).

Bill, I am glad that at least one forum member has seen, and been as impressed with, rotary valves as I have. Now here's a piston engine technological marvel that probably no one here knows anything about: sinosuidal "crank" and piston layout

 

Actually, Arao Engineering owns the patents on the 32V heads. They designed them and sold the rights to market them to Dominion, (who as you said had very poor casting quality) and they took back the marketing rights and are now selling them direct. The build quality has gone way up (according to some of their customers).

I've seen this concept (if not actually the Dominion heads) on a BBC in one of the car rags quite a few years back - somewhere around 1990. The right-up was very positive, and I think it was in a Chevelle. The magazine did a very detailed comparison between an after-market BBC head and the 32V version. It was actually along the same lines as what Arao has on their web site. They tuned the motor with the 16v heads, took everything apart and installed the 32v heads, set timing back to where it was with the old heads and cranked out gobs of additional horsepower (in excess of 100 more). They then changed the cam to take advantage of the additional airflow, re-jetted the carb and gained substantial horsepower over the original set-up.

Also, the 32V heads do not require any custom intakes or headers. They accept any standard Chevrolet intake. For headers you only need the Hooker or Stahl 7-bolt flanges welded to a set of Lingenfelter, Hooker or TPIS headers to complete the assembly.

I've done a fair bit of research on these heads. I'm planning on using them on my 427 SBC motor. I'll use a Hogans intake on it though just to get the airflow. The SuperRam or Mini-Ram don't come anywhere near the required 400 CFM flow needed by those babies. I admit I like being on the bleeding edge, and I'll bleed a little money before this is over. I've talked to actual owners of these heads, and was told no horror stories about them (and I did ask). One guy had a set of heads exactly like I was going to use (CNC'd Brodix Track 1's) and he gained 175HP with the Arao's after he was finished tweaking.

:confused: :confused: :confused: I'm confused here Chris. If 4-valve configurations are so bad, why did the ZR1 do so well? Why does Audi, VW and quite a few other foreign manufacturers use 4 & 5-valve designs on their motors? The smaller 2 intake/exhaust valves actually flow faster than a larger valve does, thus keeping the fuel mixture in suspension longer than a larger valve setup.

Oh....and the price is actually $5,100 for the B2 heads.... :eek: :eek: