JRoy91RS

Ok, I came across a letter to the editor in either GMHTP or Hot Rod magazine about a company called dominion performance that made a 32-valve head for the SBC. They were supposedly 5500 bucks a pair, but oh my *** did they outflow any other aftermarket head by almost twofold at least. Does anyone know what happened to this project, and if any of the heads are available? I can't imagine trying adjust valve lash on a 32V valvetrain, but I plan on winning the lotto and having lots of spare time . Anyone else heard of this mythical company and their mysterious heads??!!??

soulbounder

Somebody posted something about this a while back. It may not have been on this board but they refered to the magazine article. It may be worth a shot searching for it.

ronterry

If those are over head cam, then you'll do away with push rods & rockers. The cam just pushes the lifters which pushes the valves.

I know the LT-5 form a Vette ZR-1 has a DOHC cam 32 valve setup. (That's four cams in total, no push rods & no rockers)

4 valves per cylinder allows you to get more air in the cylinders, and get rid of more exhaust. It breaks the 2.02/1.60 barrier, or what ever the max is in a .30 over 350. Plus allows you to wine them up quicker(less drag). I almost said more RPM's but you'll still need a bullet proof buttom end to take 8000rpm's.


Ron

rezinn

Overhead cam engines do have rocker arms. Do a search and you will find a link to the website for the 32 valve head place. IIRC they use small valves(1.64/1.35)ish x2 and they do outflow the largest valves available for a small block.

jcb999

http://www.araoengineering.com/

I kind of doubt that a 350 with the stock iron head was 275hp. That seems a little low.

89Irocz23

what about that cadaliac motor that has the 350 with 32 vavles?

D_Amlee

These Dominion heads have been around for many years. I think I first heard of them nearly five or six years back. At first glance it would sound like a wonderful system, with massive flow numbers at both low and high lift regions, which ought to be able to generate a nice flat torque curve. I have also heard that one of the biggest problems with this design is the lack of adequate quench area above the piston. The quench area is one of the critical design features of any cylinder head / piston face combination, and is responsible for more power generation than many people realize. The quench area in a 2-valve head is huge compared to the quench area in a 4-valve head.

Flow isn't everything. Power is everything. It won't do you any good to have heads which flow like the Hoover dam if you can't make power when the valves slam shut. The comments I have read say that the actual performance of the dominion heads were pretty lackadaisical. People would bolt these on and expect huge power increases only to be disappointed with what they saw on the dyno and at the track. Simple investment in better flowing 2-valve heads with an eye towards optimizing the camshaft timing sequence generally gained better final performance than this massively expensive set of magical heads.

It's a tradeoff: air flow vs quench area. The 4-valve heads have better flow numbers, which get more air into the cylinder, but lower power generation because of the lack of adequate quench area. At very high rpms the power gained from the increased air flow may offset the power lost due to inadequate quench. Or, maybe it won't offset and the net effect will be a loss of power.

Based on the fact that these heads have been around for many years and are still very rare and almost unheard of I suspect that the jury has spoken, and that these dominion heads are solidly in the category of "all show, no go".

Grim Reaper

Well said.

V8Astro Captain

iTrader: (1)

They do, but they call them "followers". Or better, hydraulic roller followers

AJ_92RS

I know you didn't way this, but you can't say that ALL overhead cams have rocker arms, 'cause they don't.

Some have the cam lobe right over the lifter, and push it straight down.

Just an FYI, no flame intended,

AJ

Guest

There isnt one. I think you are thinking about the Northstar, which is not a 350, its a 4.6 (281)

ronterry

Thanks 'AJ_92RS' for backing me up a little.

As my post stated, If it's a <<< over head cam >>>, meaning the cam is on top of the heads why praytell would you need rockers ?

Breaking the 2.02/1.60 barrier I thought I made that clear, I guess I have to remember to be more detailed. The total size of both intake, and both exhaust on a four valve system is greater than the max you could ever get with two valves.

Ron

Guest

Some overhead cam engines do have followers, some dont. Some have lifters, some dont. Some have both. Depends on the engine. Why would you need rockers? Single cam, canted valves. Now the cam cant reach both valves anymore. This is quite common too.

AJ_92RS

Yea, I just recently did a head swap on a 89 Ford Probe GT w/Turbo. It had the rockers. They just kinda ride along the lobe of the cam. IIRC, they were 1.75:1 ratio. They're canted valves like madmax said. 2 intake valves and 1 exhaust valve/cyl. Kinda weird looking to me cause I'm so used to pushrods.

They ride on the lobe kinda like a solid lifter. In other words, they have a lash. Like .035" maybe. I don't remember cause we just swapped the old cam onto the new head. (Not my car, not my choice so no flames man! ) But there is no way to set lash on them. The only thing that dictates the lash is the cam wear.

I also had a 85 Yamaha 700cc Maxim X. Inline 4 with 5 valves/cyl. The lobes on that cam rode above the tappets. Yes is had tappets. Basically just metal plugs. The way to set the lash on them was to remove the cam and insert washers between the tappets and the valve tips. It was kind of a two piece tappet.

Anyway, those are the kind I've seen and worked on. And I'm sure there are many more.

AJ

Ions91Z28

Just though everyone should be reminded that they also run over 4 grand.

I think a good set of AFRs would be just fine.

ronterry

Ok, so well meet halfway.

I know the LT-5 doesn't have rockers, or the 2.3 Litre Quad 4.

I keep forgetting how it works: reply - defend - reply - compromise.

Ron

Guest

I dont think its any different than the 2 valve head, but there should either be an adjustment at the end of the rocker where the valve is (threaded shaft with a slot, and a hex nut), or theres this miniature lifter in the end of the rocker that has some preload. The lifters are expensive little suckers, and they started using those in 87 on the 2 valve heads.

8Mike9

Ya, I had adjustable rockers on a B2000, and on a Volvo I had, the lifters were shimmed. Volvo was a bear though, IIRC the head had to be removed to add/take away shims...also needed to be removed in order to replace stem seals..PIA.

AJ_92RS

That could be adjustable, although I don't think so. I do know it had no hex nut. So judging on that alone, I'd say 'no it wasn't adjustable'.

It did have a bleeder through which the oil flowed over the valves and springs. And I believe it was feed through the roker arms by the shafts on which the rockers tilted.

I dunno. If there is a way to set it, then I totally missed it.

I wish now that I would have looked more, 'cause that sucker is ticking lick a room full of Grandfather clocks!!!!!

Oh well. The car is in Ohio now. And I'm in (near) the Chicago Land area.

Thanks anyway though madmax.

AJ

steve8586iroc

Just to add to the original topic, the dominion heads are of the pushrod type. They were made to set on a stock sb chevy short block. you probably hade to have special length pushrods but that would be a small inconvienance compared to the cost of the heads themselves.

Guest

Sounds like its the lifter setup. The lifters are about 1/4" in diameter (or smaller) and maybe 1/2" long, fits inside the rocker arm. Easy to miss. I think they could take up about .015 of space and beyond that you get tick city. They also like to go bad due to a lack of oil. Mazda has a TSB on that engine, they recommend increasing the size of the oil hole from the block to the head but I forget by how much. Little late now eh?

Grim Reaper

Max, you have to quick hanging around us Canadians, eh?

Guest

Sorry aboot that slipup there, living up that way it sorta rubbed off on me and never left ya know eh?

Vader

Max,

Go ahead, hang around dem Canucks. You might learn a couple of things.

BTW - How DO you spell that place? C, eh - N, eh - D, eh...

(Just pullin' yer chain a little Glenn - you know what I think of Canadiens.)


Back to the topic at hand, if you want to compare apples to apples, look at the aforementioned LT5, produced by Kiekhefer-Mercury Marine for Chevrolet. It displaced 348 cubic inches, had four valves per cylinder, four overhead camshafts, and about a quarter-mile of silent chain. It made a then-impressive 375HP and 370 ft/lb at 4800 RPM, and used 10.8:1 static compression to achieve that.

The 2002 Chevrolet LS6 engine is made in Tonawanda and other places, displaces two fewer cubes (346), only 10.5:1 static, has only two valves per cylinder, three fewer camshafts to spin up, revs faster, and makes an official 405HP at 6000RPM in the 2002 'Y' car, and a flat 400 ft/lb torque at 4800.

Still thinking about extra camshafts and valves, are we?

If you're still confused, go to the track next summer on a top-fuel weekend, buy a pit pass, and see how many four-valve heads are running on those 3,000HP, 5-second BBCs and Brodix engines. I'll wait for your report....

Eddie had it right back in 1952, when some cultures were scraping Mitsubishis off the ocean floor for the scrap aluminum. Two valves, one cam, and a sheot-load of cubic inches. Fifty years later, the theory still kicks anything else squarely in the slats. It's just that we now have to scrape Mitsubishis off our grilles, and these don't have wings.