I am new to the board and will be going through all the old posts to see what I can dig up but thought I would post the question and look for user input. I am planning a Cummins conversion in an older truck and from what I have found my two choices are a 2003 24 valve engine (complete) that will run around $6,500 with computer and accessories or a 96-98 12 valve that would run around $3,500 complete.

Either way my goal is 450 to 500 hp.

With the 24 valve I guess all I need is a chip (I know it is more than a chip) and that I could then add bigger injectors and a bigger turbo later to go even higher.

With the 12 valve I understand I would need the bigger injectors and turbo to get to 450 and even bigger stuff to go further.

And my final question is with both motors configured at comparable horsepower and torque which would get better mileage and would the difference be significant?

I expect many of my answers are in the forums and I will read to find them. I just though some users may have some advice for me and maybe someone has done a conversion and can offer some tips.

Thanks!

 

12 valve would be simpler to work on since everything is mechanical just in my opinion.

 

I agree with dieseldude..


Take those 3000 dollars you will save with that 12V cummins and BOMB THE HECK OUTTA IT.. With a 100 plate, a good turbo (edited, sorry guys i forgot) some 370 injectors, 16.5 degree timing, and a good clutch behind ur tranny you should be able to easily pass the 450 mark, oh and dont forget the GSK 3K, and hte BHAF...

Best of luck

Tx

 

Welcome to DTR ITLKICK. Good to have you with us.

Both engines will have their strong points. However, for a conversion like the one youre planning, a 12 valve may be a better option.

Once bombed, I do not know which would provide better mpgs.
The 24 valve will be tougher to get all the wiring and computers swapped over, but once completed, you can adjust the power easier.
The 12 valve will be easier to get into the conversion vehicle (less wires and computers) but once bombed, its not as adjustable on power with out some wrenching.

Id probably have to agree with the above. Save the extra $$$ and spend that on the upgrades.

Rich

 

The wiring doesn't bother me, I have done a lot of high end computer conversions in gasoline powered cars. I can't imagine it would be any harder.

What would it cost to get the 12 valve to 450 hp and what would you need? In other words if it would cost $3,000 then maybe the 24 valve is the way to go.

Thanks for all the feedback. I am really having a hard time deciding.

 

the 12 valve won't cost near as much to get to 450 hp as a 24 valve... both will require bigger turbos so that's a wash... both will require a beefy transmission or clutch so that's a wash... gonna need gauges on both, exhaust and intake on both as well....

A lot of things can be done to a 12V with tools and time... bump the timing, turn the star wheel, slide the stock fuel plate forward or install a new plate all together.

 

I guess I am surprised at all the 12 valve recomondations. The only reason I am arguing the 24 valve is to understand why people recommend the 12. I really appreciate the input.

I have been told that with the 24 valve I can do a "Chip" (I know, more than a chip - intercept cam position, MAP, fuel pressure, etc....) and get to 450/500 with the STOCK turbo and STOCK injectors. Is that not true?

I have also been told that the same chip that gets you to 450/500 will work when you go bigger turbo and bigger injectors.

I have been told that with the 12 valve you NEED bigger injectors and bigger turbo to get to anywhere over 350 HP.

Have I been misinformed?

The transmission is (hope there are not any Ford haters here) a C6 so it will be plenty strong.

Please tell me if I have been misinformed.

Thanks again!

 

I am not a Ford hater by any means and I think the C6 is one of the best transmissions made, but.... for your use one of the variations of the 727 would be my choice. It bolts up and is strong. Just so some don't get confused, you are talking about a 24 valve common rail engine not a regualr 24 valve. A 12 valve with 3500 added to it for parts is a strong engine. And much easier to install.

 

As far as milage I know 2 people that bought a new 24v Cummins and were dissapointed with the milage. Both said that they lost about 3-5 mpg even after the break-in. My personal thoughts are mechanical = GOOD , computerized=BAD Just more things to go wrong and cost you money.

 

The 24 valve I am looking at is a 2003 with 21,000 miles on it.

The 12 valve would be a 96-98 from a manual transmission truck (bigger pump stock). It would probably have 100-200k miles.

I found an adapter to let me use the C6. I like the 727 as well but my truck is 4 wheel drive and I don't want to swap everything.

I am planning on running a Gear Vendors overdrive. I have 3.5 gears and 36" tall tires.

This is the truck I am planning the swap in...

 

It appears everyone is saying the same thing you are...

If I got a used 12 valve with say 150k miles would you rebuild it? Just run it?

What mods would you do to get to the 450 hp range?

 

12 valve $3500

24 valve CR $6500

$3000 to BOMB the 12 valve PLUS an additional $xxx(x) from the cost of performance goodies you would be adding to the 24 valve to make 500hp.

tough choice, but you know what you are capable of doing and you know how much you want to spend.

either way, 500hp will make your tranny cry. remember to allow some funding for that. because of this reason, i say go with the 12 valve and use some of the difference in $ to put towards a tranny modification.


Pat

 

run it thats nothin on a 12 valve

 

Well, I am glad I asked! I am really surprised at the support for the 12 valve. I am sure all of you know way more than I do about the Cummins motor so I will have to keep that in mind.

I am really looking forward to the conversion. I think the diesel conversion will "fit" my truck. Plus it will be damned fast with that much power!

Thanks - if anyone has any more advice please feel free to let me know. If you think I am dumb for doing it let me know that too...

 

Nice choice for conversion. Make sure you register it as an antique or collector car if it's available. Here in NJ that means no more inspection and registration is a one time fee. When I did my Cummins conversion into a '75 Dodge Crewcab, I did exactly that.