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Old 12-04-2009, 07:49 PM
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Woody,

Truck diesels have used 4 valve heads commerically since the 70's (maybe earlier), I agree there are many meritts to 4 valve as you explained.

I want to look back in time diesel wise regarding N/A truck diesels such as the early Macks 2 valve heads, early Cummins 2 valve heads, hell look at the NA B & C series all 2 valve heads designed for low rpm torque in dozers and backhoes.

Let's look at the Lambos they race in offshore, they are 2 valve engines made for industrial equipment that had 4 valve heads out on for better breathing ast high rpms to get more HP but the tractors remained 2 valve, low rpm torque.

I want you to also think about something else, N/A gas engine compression ratio 9:1, N/A diesel is 16:1 and have seen higher. Even with that the 4 valves lacked bottom end.

Don't get me wrong, 4 valve heads far superior to two valves for overall HP. I just think in a boat as a N/A engine you will find that there is no torque there - BUT I've been wrong as well!
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Old 12-04-2009, 08:07 PM
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On there site it says 534 lbs of TQ at 3000 rpm. That seems to be a lot of TQ for a naturally aspirated 350ci @3k

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Old 12-04-2009, 08:18 PM
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Quote:
Originally Posted by HabanaJoe View Post
My 2 cents about the 4 valve heads on NA engines, again from experience with diesels and gas many years ago so somewhat by today's electronic age.

None the less the principles of how an engines breathes have remained the same.

PS - I'm negative not Ray - LOL!

Now the 4 valves although able to breathe better at high RPM will not and I say that without hesitation work well at the lower RPM's needed to get a boat on plane with ease because the engine will not make good horsepower at those low RPM's.

Think about this, the best torque low rpm engines (NA's only) have very small valve area, this is because without good piston speed the cronologic time an intake valve is off it's seat is to long and the negative pressure in the cylinder will drop to almost nothing, can't suck in enough air in time.

The smaller valves offset that making a smaller hole that increases the air velocity and not volume so the suction time into the cylinder is longer. Don't forget there is a time period when the piston is going upward and the intake valve is still open, without velocity the piston pushes the air back out (to a certain point). Velocity allows the cylinder to keep filling.

With the 4 valves there is almost no air velocity at low speed, think of any import car with 4 valve heads - no ability to launch off the line even in drag racing without lots of RPM's.

Now take those same heads and put postive air pressure with them like a "blower" and you have a great power package for a boat.

Think diesel for a minute and all the advancements in postive air boost that have been made in the Dodge, Ford & Chevy to be able to build a higher Hp engine yet still have bottom-end pulling - variable turbos, multi turbos, variable timing, etc all things to compensate for the 4 valve heads having no air flow at the bottom end range.

I say this as having fought this for years, think about the load on a boat, everyone has some variation of semi or surface periecing props to go the speeds you go - the biggest problem is when the boat goes slow the prop is all wet - that is why for years the foreign engines don't make good boat engines. They can't over come the fact that their multivalve heads can't work well at low rpm's
We have a nice easy fix for that low torque number at low speed!

But honestly, Ford's been doing this for years with the 4.6 and 5.4 motors, some are NA'd and others our SC'd. The NA's do quite well at low speed torque but they do best at high rpm.

Our manifold bolts right to these, so does our 2 different intercoolers, as well as our 3.3, 4.0, 4.5, 5.0 and 8.3 liter superchargers!

Thanks,
Dustin
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Old 12-04-2009, 08:23 PM
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Haven't they been making these heads for quite a few years .If not this company ,one with a similar name .Old brains forget
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Old 12-04-2009, 08:35 PM
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Coool!!!!!! I stopped by Russell's shop (ARAO Engineering) the other day and saw this. I asked him about marine applications and it hasn't been his target market. I hadn't seen him in over 25 years.....he's always doing something tricky!
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Old 12-04-2009, 11:18 PM
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Been discussed many times on LS1Tech.com. They had potential, but were very very expensive ($10K), had a proven competitor in ET Canted Valve heads and I don't think they ever came to fruition.

Last edited by aTX427; 12-04-2009 at 11:43 PM.
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Old 12-07-2009, 10:28 AM
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Dustin,
If you have developed manifolds that fit them does that mean you have had some "play" time with them? Please elaborate if you have. Do you have any dyno numbers for engines with these heads and your superchargers you could post from tests you have run?
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Old 12-07-2009, 12:26 PM
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Quote:
Originally Posted by woody2 View Post
Dustin,
If you have developed manifolds that fit them does that mean you have had some "play" time with them? Please elaborate if you have. Do you have any dyno numbers for engines with these heads and your superchargers you could post from tests you have run?
I don't think they have ever tested these heads but the heads use the same pattern as the L92 heads, I think. So it is the same intake they use on other LS motors.

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Old 12-07-2009, 02:09 PM
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They were called Dominion heads 10 years or so ago when I first saw these. A guy I know had them on his Vette way back.

It's still a good idea.
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Old 12-07-2009, 04:22 PM
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Weapon,
What size engine did he have in the vette? What was the low speed tq & hp like. Overall how did he like them?
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