need help/advice/ideas!!!!!

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flatbed24v

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I drive a dodge and have not kept up with the dmax aftermarket. I have mad respect for the dmax!!! My girlfriend has a 2001 dmax and when I get her a dodge she says I can have her truck to play with. So here is what I will have to work with. 2001 chevy dmax/allison 2500 2x4 single cab long wheel base with manual windows and all and only has 62,000 miles on it. I would think this could be a great drag truck, but don't know anything about modding a dmax. What are the weak points of this motor? How high can you take the hp up to, with and without "the bottle"? What are good combos for this truck? Any ideas or thoughts? Thanks!!!
 
flatbed24v said:
I drive a dodge and have not kept up with the dmax aftermarket. I have mad respect for the dmax!!! My girlfriend has a 2001 dmax and when I get her a dodge she says I can have her truck to play with. So here is what I will have to work with. 2001 chevy dmax/allison 2500 2x4 single cab long wheel base with manual windows and all and only has 62,000 miles on it. I would think this could be a great drag truck, but don't know anything about modding a dmax. What are the weak points of this motor? How high can you take the hp up to, with and without "the bottle"? What are good combos for this truck? Any ideas or thoughts? Thanks!!!
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Motor wise they say the stock rods are good up to 500rwhp. Some have handled more, some have handled less. Before you worry about that you will need to rework the allison. I personally like suncoast but to each his own. For tuning I would suggest EFI Live. That'd be a good start.
 
My rods to enjoy 600hp every time I drive it. Some have seen 700hp but I am sure they are not long for this world. Injectors are the LB7's issue from the factory. You can make 500hp pretty easy if you have a tranny and a good tunner or EFI Live. I made 492hp with a PPE Hot+2 .E.T. I wouldn't trade my LB7 for anything.
 
Boost valve-but keep it under 32psi with the stock charger.
tranny rated for 500HP I have an SCIII
lift pump
Tune up to 500rwhp (No bottle needed)
Done!

Over 500rwhp and your looking at engine internals.
Under 330rwhp and the tranny should last awhile.
 
EFI live and something for the tranny. that should hold you over for a while.
 
thanks for the responce guys, so rods and injectors are weak spots. I understand the rods, but what are the issues with injectors? I knew a tranny would need to be upgraded to hold power as well with a lift pump to feed it. The stock turbo will cool and support 500hp? If wanting over 500hp what internals need to be upgraded besides rods?
 
The seals on the injectors are known to go bad and cause fuel to enter the crankcase and mix with the oil. I ran the PPE programmer with out a lift pump for a wile. It did fine on the 350hp tune (492hp at the wheels) untill you got to about 90mph and then it would fall on it's face. Never had a problem on the dyno with out a lift pump. Factory turbo can go to about 550rwhp but you are really over speeding it and risk major problems. Rods and pistons would be a good start to a motor build if you went that far. The LB7 pistons were the strongest of all the duramax factory pistons. You are less likely to crack and LB7 piston but you could still burn a hole in them if you tuned it to hot. I have been told that you are just as likely to spit out a head gasket in an LB7 as you are to hurt a piston. Head studs would also be another good idea for your build.
 
when you say the injectors are a bad design with no fix, does that include the after market injectors? Are the normal and hot egt's gunna be the same as my dodge? 1100-1300 ok but much higher for a duration will be bad? What size is the stock turbo?
 
I don't believe there are any aftermarket injectors. I think you can only get your stock injectors worked on. At least that's all I know about. I ran about 1600 degrees max with my PPE on level 10 before I had water/meth and a little bigger turbo. Add a 8,000 pound trailer and I could bury a 2000 degree pyro gauge. Not sure on the size of a stock turbo.
 
First thing is to do a VIN check and see what's been done to the truck. It is almost a given that the injectors either have or will go bad. They were warranted to 200K or some number of years which I can't rememeber but know the 2001's no longer qualify. You can easily ck your injectors with either EFI live or a TECH 2.

As far as building a drag truck, how far do you want to go? I currently own two of these WT single cab model bare bones trucks. The 02 GMC is about ready for the track with a full built motor and a duraflite transmission. That a full Billet Dodge tranny with a duramax adaptor and stand alone controller. They have proven to hold up much better than an Allison under big power.

If you want to start with a stock motor and just add to it, you need first to build your transmission. Suncoast or ATS both make good ones. You'll need a good after market TC as well. I'd contact Mike L at Inglewood Transmissions, he can advise you. I run Obviously you need a good intake and exhaust. There are several good tuners, but if you want to get serious you need to invest and learn EFI Live.

Traction is going to be a mayor issue with a 2 wheel drive, I've never had one so other than the obvious you need input from guys who race them.

You will need a good lift pump as you get toward the higher hp, many good choices there. Logging your engine with efi live or a tech 2 to check rail pressure will tell the tail there. Anything below about 22,000 psi is too low for performance IMO. You will need to get more air, an after market turbo will help you make more power. I'm a big fan of twins, but there are single chargers that will work well too.

To go farther than that you'll need to start beefing up the engine. Rods, aftermarket pistons, head studs, reworked heads, cam, keyed crank, about endless here, Steve at TTS or Guy at SoCal diesel would be great help. This is also where you add twin CP's and big injectors, I did twin CP's and injectors on a stock LB7 and bent all 8 rods.

There is a limit to what an Allison will take, built or not. It appears to be in the 750 hp range. You will have to refreshen it annually if it lives a full year. Obviously if you get it under 11.5 you will need a roll bar as well. Good luck.
 
thanks for the input!!!! This doesn't have to be a daily drive, I will still have my dodge for that. So I was gunna go all out!!! I am going to tub out the bed and stuff fat slicks in there with a four link to hold it together. Looks like I can get bigger injectors, but will the problem be fixed with them? I like twins as well!!!!! Rods and head work with studs. Built dodge tranny and efi. With all of this done what should I expect on hp and et? How hard is efi to operate? Like I said this will be a toy, so no limit on what I am willing to do.
 
Samdweezel05 said:
The LB7 pistons were the strongest of all the duramax factory pistons. You are less likely to crack and LB7 piston but you could still burn a hole in them if you tuned it to hot. I have been told that you are just as likely to spit out a head gasket in an LB7 as you are to hurt a piston.
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LB7's and LLY's have the same exact pistons. Same exact shortblock as a whole. ;)

Head gaskets are not an issue on duramax's and putting head studs on an otherwise stock engine is a waste of money.

In my own experience you will crack pistons WAY before you break rods and blow head gaskets.

Keep it under 550-575rwhp and you will be fine with the rods on an 01-05 dmax. 06+ rods will take 650rwhp reliably. EGT's under high load are what cracks pistons.

Piston cooling is the duramax's Achilles heal IMO. We need to increase or redesign the piston cooling system if we want these stock pistons to survive under the high EGT's and abuse we put them through. The cummins guys have mass on their side; the pistons are much bigger and therefore can absorb a lot more heat and shed heat effectively while still remaining "stable" and not cracking.

ben
 
flatbed24v said:
when you say the injectors are a bad design with no fix, does that include the after market injectors? Are the normal and hot egt's gunna be the same as my dodge? 1100-1300 ok but much higher for a duration will be bad? What size is the stock turbo?
Click to expand...

the duramax is rated to withstand 1375* constantly. Short stints above that are ok, but not for more than 20 seconds or so.

On any performance build I would do:

cut stock pistons
head studs
main studs
aftermarket rods (crower, carillo, howards, R&R)
balanced

stock cranks are plenty strong. After doing the above, you can do ported heads, aftermarket cam, etc...
 
I did not know that the LLY's had the same pistons Ben. Interesting. I have just always heard of guys cutting LB7 pistons because they were stronger. Not to hyjack the thread but what causes a piston to crack? Is it heat, high CP or both. With all the talk about rods and pistons and a built motor I figured head studs were worth a mention.
 
Samdweezel05 said:
Not to hyjack the thread but what causes a piston to crack? Is it heat, high CP or both. .
Click to expand...

that my friend is the 500 million dollar question....

people can speculate what they want, but the fact is no one really knows (and has a sure-fire proven fix) what actually cracks duramax pistons.

ben
 
if it really is gonna become a balls to the wall affair, when you dive into that rear end/4-link setup... chop that dude off at the cab, tube frame the rear with the 4-link setup and run a short bed.


the other guys have covered the power aspects nicely...
 
I like that idea ^^^^^^^ I will cut weight where I can. My girl friend's dad bought this truck new so I know all that it's been threw and it has not been to the shop for anything.
 
While you are at it, upgrade that oil pump with one from SoCal diesel. TTS has some cast after markert pistons made by Mahle you might want to look at. I going to try a set in my 06 LBZ that I going to build for a play truck. Can't sell it going to build and keep it.
 
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