6.7L Cummins Forum

herro, im new and have comitted to buidling a good 6.7 I am considering II's twins but dont really like the idear of keeping a stock turbo in the eqaution. A big single will lag but is the stock turbo really capable of hitting the 650hp mark? Tht is my goal, i dont want a drag truck just something i can pass vettes with on the highway Also a question on nozzles... can stock injectors and fuel rail lines support the 650hp mark? or do i need to change all that? Nice to meet you all and this site is really helpfull, all the best AJ

First of all, welcome a board !

Well if you want to change things out, then twins is the way to go. Stock turbo has to go in the process. You are going to need a modded CP3 pump, new lift pump, injectors, exhaust system, DPF delete setup w/programmer, and more. Depending on the horsepower levels, head bolts, gaskets, and possibly connecting rods will need replacing. Twins will push a good amount of boost that blow gaskets and pistons.

Now with all that in mind, depending on your truck, a 9,000 lbs plus truck is not something you want to got speeding by other speeding vehicles. It not built for handling and short stopping like a some cars. It is one thing to race/pull on a track that is straight, it is something else on a freeway with obstacles (IE, other cars and trucks). Its built for heavy load moving. You can cause some serious injury to the people around when you loose control. Its not a case of if you do, its a case of when you do.

So what state are you in ? Just want to make sure I so I choose a different route

Hope that helps somewhat.

Cheers.

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Twin is better than a big single. You can keep the HE351 turbo as the secondary, put a S475 under it, pretty easy. How big of nozzles you thinking about? 100HP sized, there will be codes from the low rail pressure. some guys put a fuel rail shim on the rail. The best set-ups for twins use an external wastegate. A large external gate will flow tons of exhaust, and you will not get the drive pressure issues, aka head gaskets.

I like the idea of twins as well but it seems complicated. I read in my diesel power mag where a guy with a 2009 mega cab had a shop install a holset turbo from a 15.0L 565hp cummins engine (the new turbo had an exhaust brake too) along with 100hp injectors, upgraded lift pump, head studs, a programmer with an mp8 , everything deleted and made 675 rwhp with the stock cp3. A rail pressure gauge showed 25000psi at wot, but he knew he was living on the edge with the stocker. His next upgrade was a modded cp3 with hopes of hitting 700rwhp. I have read articles featuring 5.9 and 6.7 cummins making insane hp with stock bottom ends and were driven daily. I will look into this type of set up in a few years but for now I'm pretty content with the 440+hp my cummins is putting out. Keep us informed with your progress, good luck.

I would guess that it was a HE451VGT turbo, you have to watch what you buy, as a 15L 565HP cummins would have a large turbine disk and turbine housing, which equals super laggy on a 6.7L truck. I can't remember but I think its a 68mm inducer. I never done that swap. I'm going to try a GT3788R and a S366 turbo (no exhaust brake) for starts. Then build a set of twins. I'm really not liking the HE351VGT (stock turbo) on my 2010 truck. The only good part about it is the exhaust brake.

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-brand spanky new white 02 sport QC, SB, 3/4 4X4 DDP stg 3 sticks, GT3782R
-soon to nuke down, black 2010 3500 Laramie CCSB, H&S Blackmaxx, DPF & EGR delete
-grey 02 Laramie LB, 3/4 4X4, edge comp, 95 fass

The truck actually made 658hp and according to the article worked great and the owner pulled sleds from time to time. It looked pretty good but I'll keep what I have until the warranty is over. I know I've seen twin kits that keep the stock 351 and they advertise 600+ hp. Let us know how it goes.