Forged pistons expand more than a cast piston. Therefore, when the engine is cold, there is more clearance between the piston and the bore. I am not sure how Ford has dealt with this, but it would be interesting to see.
I think you may be able to get rid of the slap with a properly placed offset pin or a very good skirt coating.

I am not saying at all that a forged piston would be a bad thing, I think it would be great. But the fact is that GM is gun shy to do this. Plus, they are so strapped for cash right now, adding any more cost into an engine is out of the question for them.

 

Exactly right!

With forged pistions you need more of a piston to cylinder wall clearance. This is due to the higher thermanl expansion rate a forged piston has than a cast (or hypereutectic) piston.

Hence 06 Z06 = cast pistons.

Besides, most people want forged so they can add nitrous with "no worries".

GM isn't about to upgrade to forged so people can "spray" thier oem warrantied car.

 

Yeah, I don't know if that is the case. Plenty of people have forged internals, and they aren't any louder than stocker's. And the piston slap in the LS1 had nothing to do with forged internals, since the LS1 doesn't have forged internals ....

 

It was never a "piston slap" issue, IMHO, it was lifter/valvetrain noise mis-diagnosed as piston slap. That seemed to be the case at my dealership at least.

 

Oh ok, yea i dont know a ton about forged pistons, just in the few cars that ive seen/heard with forged pistons they havent been any louder than any other car in my experiences with them. I agree though GM isnt quite on the up-and-up right now so i cant see them making any of their vehicles more expensive (adding more expensive engine parts) but it would be awesome to see them go that route. Also, there are tons of guys on the board who spray on their stock ls1/ls6/ls2 engines so I dont think that by adding a completely forged bottom end would open the flood gates to people spraying on their oem engines, because if they are gonna spray they are gonna spray.

 

Very true.

 

I would like to see a 4.6in bore center. 'Nuff said.

 

Back to the topic...GM could learn alot from the Germans. Take a look at the technology Mercedes is using, espeally in the AMG line. How about clean diesels? esp in the 3-4L range, perfect for most trucks and utes. . How about 75-100 HP/L like the Japanese and Europeans. Cars are getting heavier with all the near luxo gadgets and safety bits. How about a new Camaro that weighed in at 3200 lbs and had 400HP from an all aluminum 4L V6/8. Remember the folks here are an exception to the rule. For the economies of scale in engine lines, GM needs to address the concerns of the other 98%. But many of these technologies I've mentioned can make us hot rodders happy too.

--JMarsa

 

Just wondering how DOD deactivates the Valves? does it remove the lobe from the cam?

Cam lobe control's the valve so the valves will open and close in a DOD motor (especially in a single cam OHV motor like the Gen III / IV motors).

DOD controls Fuel feed from the Injector and spark... Cylinder should still do a complete cycle due to the cam. It would be induction, compression, decompression (due to no combustion), then exhaust.

So a DOD motor from GM will actually feed air into the exhaust line for the cylinders that do not have fuel and spark going on (deactivated pistons).

That increase in air flow in the exhaust line could cause the O2 sensors to read off, which if GM hasn't programed the computer correctly it would try to richen up the mix to compensate for the Lean reading the O2 sensors would give off.

Unless GM has something special going on to stop the cam from pushing the lifters which push the push rods which in turn move the rocker arms that open the valves... DOD still opens the valves.

 

DOD = 8 Hydraulically controlled lifters & 8 standard lifters.

 

Not to change the topic but did anyone else see that post with the vague specs on the corvette SS? DOHC V8 and S/ced? Is that bullshit or is that a serious post?

 

Independent throttle bodys, VVT, 11 degree valve angle heads, bigger valves, better oiling system and more cubes.

 

Oooo... ITB.

 

You guessed it. They have lifters that can be activated/deactivated.

 

A 4+ rotor rotory. Go someplace none of the other manufacturers are willing to go. (Remember the 787B, which was BANNED because it was so much better.)

 

DOHC? Heh, that doesn't sound like GM. Remember a DOHC motor is going to cost tons more. Much much harder to work on, more cramped, higher mass, takes up more space.

Pushrods define GM v8's! Personally, I like easy to work on motors. GM has put so much money and effort into pushrods why turn back now. It is traditional. If you want DOHC get a Honda or a Mustang. DOHC? Yea, but a set of cams in that bitch. Real fun. lol

I don't understand why everyone is so up-ity about DOD. It is already being used with no problems in several GM cars. O2 sensors look at ratios, don't they? What has to be reprogrammed?

 

Or how about some coates heads...


A new spherical port-type rotary valve system is incorporated with conventional reciprocating engines by replacing the traditional noisy cumbersome high pumping-loss poppet valve-train.

The operation of this new economical valve package has been proven durable (in extended dynamometer and road tests) and shown to deliver many superior engine performance features.

The only moving element in the new mechanism is one set of rotating spherical valves per cylinder mated with respective floating ports whose sealing actions are linked to the cylinder pressure variation. This creative concept has become a proven engineering reality thanks to recent advancements in design and some new material technology.

Among the beauty of the new invention is no need for costly modification in the existing manufacturing line of the present engine block. It is truly an engine technological breakthrough which offers revolutionized performance and convenience.

Absence of poppet valves and other operating accessories normally housed under the valve cover has permitted elimination of both oil lubrication and cooling water flow in the upper portion of the cylinder head. This reduces the overall engine height by as much as 20 cm from that of its conventional counter part, and maintains a clean engine.

The new, patented simple valve-train unit has minimized the area of contact for fluid flow through the gas exchange ports by making use of wide-open circular cross-sections. This significantly cuts down the pumping loss and unmatchable increases the volumetric efficiency to achieve a high torque/power-density engine.

The new dynamically balanced rotating spherical port valve eliminates entirely mechanical noise produced by current poppet-valve components. Hissing sound generated as gas flow squeaks through the narrow annulus valve opening in the conventional cylinder head is no longer audible. At the same time, the new unit cuts down, by an order of magnitude, the need for power out of the crankshaft. Normally a big parasitic power drain is required in conventional engines to drive the valve train.

Performance & Excellence

SUMMARY
Many production engine blocks mounted with Coates rotary port-valve cylinder heads have been operated in the original host vehicles to implement extensive tests. For example, one of them has successfully been driven over 150,000 miles and shows many performance advantages. Some proven engine characteristics are listed below along with the best probable reasons for the observed results.

LOW MANUFACTURING COST:
• Far fewer parts in simple valve mechanism
• Simple cylinder head
• No costly change in manufacturing line of the existing engine block
• Shorter assembly time

LOW MAINTENANCE COST:
• Simple package to produce fewer troubles
• No oil in the cylinder head to burn or leak
• No liquid lubrication in any part of the rotary valve
• No cooling water in the upper portion of the split cylinder head

LOW NOISE:
• Absence of noisy reciprocating valve train smooths intake
• gas flows and no valve bounce

LOW PARASITIC POWER CONSUMPTION:
• Low pumping loss in gas exchange process
• Low power required for rotary valve operation

HIGH EFFICIENCY ENGINE:
• High critical compression ratio - No hot exhaust valve
• Low parasitic power consumption
• Low pumping loss

HIGH VOLUMETRIC EFFICIENCY:
• Fully opened circular valve ports
• Low-temperature intake port
• No back flow of residual gas
• No need for valve overlap

FLEXIBILITY OF GAS MOTION CONTROL:
• Near zero tradeoff problem between gas motions and volumetric efficiency
• Fully opened circular cross-sectional port|
• Staggered variable valve openings

HIGH TORQUE/POWER-DENSITY ENGINE:
• High volumetric efficiency
• Fewer parts in the engine and simple cylinder head
• High thermal efficiency
• High engine speed-dynamically stable rotating valve with no valve floating problem

HIGH EFFICIENCY IN PART-LOAD OPERATIONS:
Low pumping work
• Use less than 10% power to operate the poppet valve mechanism

LOW KNOCK TENDENCY:
• No high-temperature wall, e.g. exhaust poppet valve
• Low filling work to the intake charge

LOW POLLUTANT EMISSIONS POTENTIAL:
• No oil burned in the valve ports
• Absence of valve overlap
• Low-temperature cylinder head wall
• High exhaust gas temperature

CLEAN ENGINE BLOCK AND COMPARTMENT:
• No oil leakage from the valve cover
• No coolant leakage from the cylinder head/gasket
• No need for valve cover ventilation

FLEXIBILITY OF AUTO-BODY STYLING:
• Low overall height- Absence of valve cover
• No water jacket in upper portion of the cylinder head
• Compact and clean engine package


-Sly

 

The Coates Spherical Rotary Valve Engine is the most advanced in the world, with the most positive valving system ever built. The breathing capabilities of the system are almost double that of a poppet valve. For instance: a static test of a five-litre poppet valve engine on an airflow machine produced a reading of 133 cubic feet per minute (CFM) with valve fully opened. The five-litre Coates Spherical Rotary Valve Engine on the same machine, however, produced a reading of 319 CFMs fully opened; a colossal advantage in airflow comparison. A five-litre poppet vavle engine tested on a dynomometer under the same loads and conditions at 5500 produced 480 BHP and 454 foot pounds of torque. The maximum RPMs on the poppet valve engine were 5700 RPMs; the Spherical Rotary Valve Engine in comparison reached 14,850 RPM's, The Coates Spherical Rotary Valve comprises two spherical rotary valves assembled on two separate shafts - one for inlet and one for exhaust. They rotate on ceramic carbon bearing with no oil lubrication, the spheres do not make contact with any part of the housing. The seals are a floating type and are also made of a ceramic material. They have two piston rings and are floating in a small cylinder-type chamber, they are activated by the compression and the combustion strokes of the engine which allows 100 percent sealing effectiveness, when compressed.

 

GM has done pushrod V8 but its also done some mighty fine DOHC engines! the "Red top" 2.0 ltr four was outstanding! you can get 300bhp out of one N/A. that 150bhp per Ltr!!!! so they do know how to do it and can make it work! also they have done some nice V6's.

Chris.

 

where could we get info on said redtop.