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V8 Dakotas
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graphiteRT
R/T
 
6/28/2003
12:10:20
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 Subject: RE: 5.9 or 4.7
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Duner/Notch, I don't think it's as much a HP issue as it is a boost issue. Duner, you've seen those pistons and that skinny ass top ring land. You had to replace a few, did you not? That's just not meant for boost. Guess what, the 5.7L has the same skinny ass setup. It's different for you guys because you know what you're doing and pay attention. That average bozo out there just wants to buy a truck and stand on the gas with little regard if it starts rattling for some reason. The motors have very little tolerance for detonation, N/A or boosted. Boosted just puts you flirting with that area more often.
If you're talking factory effort, nobody in their right mind would be using that piston in a boosted motor because the service comebacks alone for broken pistons would have em lined up down the street and around the corner. On a boosted effort the emissions issue starts from scratch, so you can use a different piston, add your boost, tweak your controller and still keep the EPA happy. Guarantee you if a boosted 4.7 or 5.7 effort does ever leave the factory, it will probably have forged pistons with a completely different ring land config.
Bob
'01 Graphite CC R/T, MP headers, Magnaflow muffler into 'Cuda style exhaust, M1 2bbl, ported 2.02 R/T heads, custom grind cam, Crower SS rockers, Paxton Novi2000, Boyd's 20s w/Dunlop SP9000s, Featured in April '03 Sport Truck, Viper 4 wheel discs
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Duner
Dodge Dakota
JOIN HERE
6/28/2003
14:29:53
|  No Problem.........
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I've exchanged emails with DCXer on a number of issues - and the pistons weren't the real concern. The testing that they put the engines thru was basically beating them to death to see what went first. How we use the engines has virtually nothing to do with how these engines were pushed to failure. Unless we could use our engines at WOT and full power for hours on end (which we can't do), then we don't really have anything to worry about. Now maybe if we put them into a generator set or an aircraft and demanded the full power all the time.... then we'd have some problems.
All is well in the 4.7 camp.
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R/TBlues
Dodge Dakota
JOIN HERE
6/28/2003
15:24:18
| RE: 5.9 or 4.7
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The small land for the top ring sounds pretty serious to me. It sounds like something that needs to be addressed when installing a supercharger. Aftermarket pistons have to match the originals in weight or you have to get everything rebalanced. That means disassembling the entire engine. I've ran into this problem with several Japanese engines. Especialy Mitsubisi motors. They like to break the land on the bottom ring just above the wrist pin cut outs. I guess Dodge has hired some of Mitsu engineers to design their engines.
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graphiteRT
R/T
6/28/2003
16:15:27
| RE: 5.9 or 4.7
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Message:
It's my understanding the ring land config is emissions related, though I don't know all the parameters the design had to meet.
Bob
'01 Graphite CC R/T, MP headers, Magnaflow muffler into 'Cuda style exhaust, M1 2bbl, ported 2.02 R/T heads, custom grind cam, Crower SS rockers, Paxton Novi2000, Boyd's 20s w/Dunlop SP9000s, Featured in April '03 Sport Truck, Viper 4 wheel discs
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R/TBlues
Dodge Dakota
JOIN HERE
6/29/2003
22:51:50
| RE: 5.9 or 4.7
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Yes, I'm sure it is emissions related. I'm not sure exactly how it works, but I know from my experience with Jap-Crap engines the basic design. If you remove the bottom compression ring there are probably some very small holes that go from the inside of the piston to the back side (small diameter) of the bottom compression ring. Some how, this design prevents oil from getting past the upper compression ring and therefore lowers the emissions. It also allows a lower tension oil scraper and a smaller cross section upper compression ring to be ran. I have literally broken the skirt, bottom ring land, and upper compression ring on the same cylinder and have no oil consumption. From what I understand, the small holes behind the bottom compression ring alow the vacuum inside the block and the pressure induced by the compression stroke to push the oil away from the rings. You get more blow-by this way, but you have less oil getting burned inside the combustion chamber. The PCV valve has to work overtime to evacuate the blow by. All the engines I've seen with this type of piston design also have excess carbon build up inside the valve covers and the oil filler neck tube. This would answer the guys question on an earlier post concerning the carbon build up on the bottom of his oil filler cap. I've never had a 4.7L apart to see the pistons, but I would be willing to bet they closely resemble the Japanese piston designs I've seen in all or most of the mid 80's through mid 90's. They will not burn oil, but they are junk! Throw them away and get some real pistons! Mobil 1 is a must in engines with these piston designs to keep carbon build-up down.
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Duner
Dodge Dakota
JOIN HERE
6/29/2003
23:48:22
| No Holes
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Nope. There are no gas relief holes in the stock pistons. The top ring is very close to the top of the piston to reduce the amount of unburned gasses to make the engine more emissions friendly.
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