The Stovebolt Site Forums The Shop Area The HiPo Shop Frame concerns with Cummins Diesel Swap - 47 1.5T

Hi guys, I'm going to be putting a 6BT cummins with Mercedes G56 6-speed in it.... I'm planning to be turning about 500hp and 1000 lb-ft of torque. My question is this, what will I need to do to the frame of my 47 1.5 ton to take the power?

I'm going to run a 4-link air ride system in the rear for rear suspension. I will have a 10 foot flat bed sat on the frame rails and u-bolted down. This bed will probably have 6" C channel runners with square tube stock cross-members on it that will double as air tanks.... Then will have expanded metal welded to the top of the cross members......

I plan to do towing with this rig, and the occasional truck pull once a month through the summer months... So I WILL be putting down this power regularly. I'm thinking boxing the frame, but I'm concerned about the legality of welding the frame? Plus, I shudder at the thought of boxing because of that all-encompassing fear of RUST living here in the north...... I like the idea I've heard of cutting oval cutouts in the boxing plates.....

What do you guys think.....

Assuming you have a 161" wheelbase frame? Then it's the same as the 2 ton frame and I think is plenty stout in stock form. at least to me they look a fair amount more substantial than the dodge truck frame that came with the Cummins...

Not sure I like the idea of making 6"x? rectangular tube into air tanks. Most all air tanks you'll find are round for a reason.. that's the shape they want to be.
I expect you'll have plenty of room for air tanks under the bed and above the frame.
Also look at some of the air tanks on semi trailers, they can mount between frame rails left to right, and are pretty cheap to get new.

I would not box the frame, both for your reasons and the risk of cracking because it's to stiff and or poor transitions leaving places for cracks to start. It's also difficult to run brake lines and wires and such.

Grigg

That's the info I was after. Good. Will save me a mountain of work.

Also, I'm not going to use 6" tube for air tanks.... I was thinking of using 1-1/4" square tube as the cross-supports and double them as air tanks.... I may just use 1" steel pipe.....

I know I can get tanks and all that, but I'm trying to cut weight were I can.....

Definitely don't use anything other than a round shape for a pressure vessel. The stresses are pretty impressive, even at a relatively low pressure. I'd suggest 3" pipe if you're planning to go that route, as the cross-sectional area of a pipe increases by a factor of six as the diameter doubles. You'll restrict your volume too much by using 1" pipe, and when you use enough of it to get the volume you want, it will weigh more than a piece of 3". Welded schedule 40 pipe will hold all the pressure you need.
Jerry

just buy a tank. They are cheep.

A stock air tank is 14 gauge.. Schedule 40 is what I made cannons out of.

to get 500hp from the 6B, you will be dumping lots of fuel and boost. If your running a 12V, then the engine will be a bit tempermental and not like light loads. Either way, your looking at a good-sized CAC.

The stock 2T frame will be fine. Its much more stout than the 1T Dodge truck frames.

The frame will twist a bit if you plan on pulling, however let it. If you try to keep it rigid, your cross-member joints will fail (especially if you welded a cross-member in place).

Yah, lots of fuel and lots of boost.. Probably a twins setup......

I plan to use a large air/water intercooler. I'll run ice water for pulling, and have a good sized radiator for cooling the water when towing......

I do disagree on the tempermental part.... Lots of guys running 12v cummins with P pumps at the 500 hp mark.....

Ok, I'm set now... Just gonna leave the poor frame be! I'm gonna get the cab off this winter, clean the frame up and paint the whole thing with POR15 and then topcoat with their hardnose paints....... Also get my new axles and get the air ride built... Then I at least can roll the project around instead of having to drag it with a 100hp tractor!

Im not saying you cant get there with the P pump. Its just that I've not seen them idle well without nearly wet-stacking which made them nearly useless in daily driving.

Either way, good choice of a diesel.

Well, there's two ways to get power on these engines... The easy way and the expensive way..... The easy way is the route most pullers take, which, like you point out, can cause rough idling, and rich running (excessive smoke) when under all conditions.. This is normally done by maxing out the pump controls and putting hogged-out injectors in along with a large (but laggy) turbo to create the boost needed.......

The expensive route is to modify the pump, put a set of fast-spooling but efficient twin turbos on, put in some hi-flow edm'd injectors or similar in, and then tune the heck out of it. Modified cam isn't out of the question, and port & polish doesn't hurt either.. If done this way, you can have 500 hp that idles like stock and will tow reliably all day long, and will pull with the best of em......

I still like my 4-valves and electronic controls.

That's fine..... My best friend has a 24V and loves it.... I for one like a simple 12V myself.. To each their own.