#405277 - 01/17/05 12:07 AM
12 valve cummins vs. 24 valve
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HumminCummins'01
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Registered: 01/16/05
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Before I bought my 2001 Dodge Cummins, I had alot of people tell me i was wasting my money and that I should have got a 12 valve, because a 12 valve could make more power. I believe that the 24 valve is a better engine for a number of reasons, but i just wanna hear why people believe the 12 valve has potential for more power than the 24 valve. I dont hear from many people who rave about the 24 valve engine like I do, so i'd like to hear from the 12 valve guys and why their pick up would out pull mine
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2001 Dodge Cummins HO 6-Speed, 275 Injectors, Superchips MicroTuner, Afe air intake, Afe 4-inch exhaust, Boost Enhancer
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#405278 - 01/18/05 04:10 PM
Re: 12 valve cummins vs. 24 valve
[Re: HumminCummins'01]
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Diesel Dan
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Registered: 01/05/00
Posts: 1657
Loc: Mothership terminal.
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Not gonna say mine will outpull yours, don't know anything about your truck.
From what I've read the 12v head has a better valve springs available aftermarket for higher RPMs. The 24V with its small diameter springs is, so far, limited to stock springs.
I prefer less electronics, personal preference. Plus side to the electronic versions is they generally start better cold, my 12V doesn't have a cold advance circuit like my DB2 GM pumps did. 24V has a centrally located injector, another plus. IIRC, the P7100 is capable of physically flowing more fuel than the VP44 IP. More fuel, more power. There are a few pullers who are running 24V heads with a P7100 pump.
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2000 Chevy Crewcab, SRW 4x4
6.5TD, 4L80E, 4.10s
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#405279 - 01/18/05 05:54 PM
Re: 12 valve cummins vs. 24 valve
[Re: Diesel Dan]
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HumminCummins'01
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Registered: 01/16/05
Posts: 3
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My pick up has a 6-speed, bosch 275 injectors, superhchips micro tuner, boost enhancer, flowmaster 3 1/2 inch exhaust (I have the afe 4-inch exhaust, just havent put it on yet)
As far as valve springs go, the 24 valve dosnt really need any stronger springs, since the vavles are smaller. To put an exhaust brake on a 12v, you need to change the valve springs, but on the 24v the springs put on at the factory were intended for exhaust brake use, or atleast that is what i've been told.
Although the VP-44 may not flow as much fuel as the P7100, it can change ignition timing to the change of rpm and turbo boost, which gives you a broader torque band. Also, the P7100 flows more fuel, but the 24v heads flow more air. More airflow raises the volumetric efficiency, plus more fuel makes for more power. Fuel isnt everything, you need air for that fuel to burn, but again, thats just what i've been told.
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2001 Dodge Cummins HO 6-Speed, 275 Injectors, Superchips MicroTuner, Afe air intake, Afe 4-inch exhaust, Boost Enhancer
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#405281 - 01/19/05 10:14 PM
Re: 12 valve cummins vs. 24 valve
[Re: Diesel Dan]
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HumminCummins'01
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That is a good question. At the moment, I dont know exactally how much boost im pushing, because when i first bought my autometer guages, my friend who has a 12v cummins told me that i wouldnt need anything over a 35 psi guage, so thats what i bought. The 35 psi guage was good enough. . .until i installed my injectors. After I installed the injectors, the needle on my 35 psi guage went straight down, quite a ways past the 35 on my guage, so im plannin on gettin a 60 pound gague. I dont want to make any more than 38 psi until i get an hx-40.
What type of oil filter do you use? I've read a TSB that said if you use the wrong brand of filter, that it could come apart and filter material could get lodged in the piston cooling nozzles. Not sure what the material was that comes apart, but I only use fleetguard since that is cummins approved. Has anyone had a problem with clogged cooling nozzles due to filters comming apart?
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2001 Dodge Cummins HO 6-Speed, 275 Injectors, Superchips MicroTuner, Afe air intake, Afe 4-inch exhaust, Boost Enhancer
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#405282 - 06/08/06 07:28 AM
Re: 12 valve cummins vs. 24 valve
[Re: Diesel Dan]
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Ryan T Kiefer
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Registered: 06/08/06
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Interested in knowing more about guys retro fitting their 24 valve with a p7100. I have heard that its a preaty difficult process and am strongly considering doing it. I would like to run that pump for what you have menchined and because simple vegetable oil runs better on those pumps. Currently running 99.9% bioDiesel on my vp44.
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#405283 - 10/03/06 06:53 PM
Re: 12 valve cummins vs. 24 valve
[Re: HumminCummins'01]
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2000 Cummins Power
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Registered: 10/03/06
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On my farm there are two 12 Valve Cummins and two 24 Valve Cummins. I can say that in stock form the 24 Valve Cummins will annihilate a 12 Valve Cummins, but I've also seen that when properly beefed the 12 valve will hold it's own. The 24 Valve Cummins is pretty tough to beat, whatever 12 Valve is messing with it better eat it's Wheaties.
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My Truck:
2000 Ram 2500 Cummins
AFE Cold Air Intake
Super Chip
4" exhaust
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#405284 - 10/13/06 08:34 PM
Re: 12 valve cummins vs. 24 valve
[Re: 2000 Cummins Power]
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5.9Cummins
Member
Registered: 11/23/05
Posts: 68
Loc: West River, SD
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In stock form, a 98-02 24 valve has more power than a 94-98 12 valve engine. That is IN STOCK FORM! Put a fuel plate and a set of larger injectors (maybe throw in 4" exhaust and aftermarket air intake to help with the exhaust temp), and the 12 valve will be much more powerful than a 24 valve. A chipped gen-2 24 valve may be pretty powerful, but the injector pump will have a higher probability of trouble.
The reasons that people prefer the 12 valve often doesn't center around the power output. First, the VP44 pump has grenaded on many of the 24 valves out there, and is pricey to fix, of course. This is caused by the malfunctioning of the lift pump, so it could be avoided by a fuel pressure gauge, but many people did not know this before the IP went to hell. The VP44 is electronic, which is partially why fuel rate is so important. This leads to another reason that many like the 12 valve: it is mechanical, not electrically controlled.
Also, there are some 98-00 models with a "53" block casting that has had a problem with cracking. While many pickups are running with a 53 block that has not cracked, it is still a potential time bomb.
Another reason for praise of the 12 valve is the fuel mileage. Fuel mileage is influenced by many factors, but generally speaking, the old 12 valve Cummins has been more efficient than the 24 valve.
In my opinion(and many others), the 98-02 model 24 valve have been the most troublesome of the 5.9 Cummins engines in Dodge pickups. I am not saying that it is a horrid engine, its just that the other 5.9 engines are so awesome.  Luckily, the 03-present 24-valve with common rail injection has been a great engine. If only i could afford one. 
Ryan, I have heard the same about the P7100 conversion, very difficult. It would be a sweet conversion, though. BTW, hows the biodiesel working?
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My Ride: 1992 Dodge 3/4 ton CUMMINS diesel. 4X4. Pump turned up. 4" exhaust.
Fuel Saver: 1999 Chevy Lumina. 3.1 V6
Parked: 1979 GMC 3/4 ton. Ran but made horrible mileage.
Dad's Pickups: 1989 GMC and 1998 Chevy 3/4 4X4s. Both have a 350 and 5 speed.
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#405285 - 11/26/06 06:29 AM
Re: 12 valve cummins vs. 24 valve
[Re: 5.9Cummins]
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Blue3500
New Member
Registered: 10/28/05
Posts: 23
Loc: Bayji, Iraq
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I agree with much of this but may add a couple points. First off, you can get a stiffer spring for the 24 Valve as I have a set on my truck. But the valve springs will work just fine with a Jacobs Break if this is what you want or need. They will also hold up pretty well if your boosting around 60 lbs. Over that you will want to invest in a valve job. Secound, the older 12 Valve is a much more dependable engine. Much simpler than the newer engines with far less to go wrong. But todays engineers aren't happy unless they complicate things beyond most of our comprehension. Hence all the nice little sensors that tell you when something in all this computer mess they've added on is going arye, but if it's mechanical, it's back to old school mechanics. Third, if you want to make more hp/tq than the newer trucks already have, it's extremely easy. With just bolt on's you can break 600 hp, where as with the older trucks, you pretty much had to rebuild the entire topside of the engine. Finally, the fuel milage debate has and probably will go on forever. It's a pretty well know fact that the older 12V got better fuel milage, though some may tend to want to argue. In their stock forms, a 12V will always get better fuel milage than a 24V. Once you modify them however, they tend to pretty well even out.
The biggest problem I've seen with the newer engines/trucks is as mentioned; the lift pumps. It's an easy fix though. Buy and put on either a FASS or AirDog and your problems are solved. I would tend to stray away from any truck with an NV series transmission, though they are one of the best, because if anything does go wrong with it, you may have a long wait on parts as New Vision was bought out and nobody seems to be making parts for them anymore.
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04.5 Dodge 3500 DRW 4x4,FASS,Gauges,AFE Intake, Twins,125 hp Injectors,cam,fire rung head,14mm HXD studs,ATS Intercooler,ATS Arc Flow,water/methanol&propane injection,dual feed injection line,etc.
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#517528 - 06/25/07 05:12 AM
Re: 12 valve cummins vs. 24 valve
[Re: Blue3500]
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yankee
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Registered: 06/24/07
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i prefer the 24v. they have more power stock and i believe they get better milage. my 02 does around 18-22 mpg when its loaded.(around 1500 lbs of pivot parts). the only problem i ran into with it is that it caught dead pedel syndrome and had to get a new fuel pump otherwise i believe the 24v is better. im fairly sure that it is easier and cheaper to modify and plus the 12v i had didnt have an intercooler. the 24v is great for cold weather starting. on my old 12v i always had to have someone round the front squirting either into the d*mn thing. But both are great trucks
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! Can't believe the amount of slippage the converter has before lockup, around 500 rpm. 
