Max Torque Big Block

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dukeboy_318 said:
depends on your skill level. and what year 6B you start with.

I used to work for a diesel performance shop and truck pulled for several years before all the high school kids with their mommy's money ruined it.

Anyway, that 5 grand stroker in a confined environment like a motorhome is not only going to run hot, but be very hard to cool. 2nd. you can get a late 90s, I'd go 99-00 non-HP Cummins for less than 1000, in running order. Those truck are rusting out badly and you can get the whole truck usually for not much more if you look hard enough. Then you have two options, you can stay with the electronic injection pump and run something along the lines of a TST PowerMax 3 or similar tuner. a a stock 99, with the TST tuner, we saw an increase of 167 hp and 350 ft lbs at the rear wheels. putting you around 400 hp and 750 ft lbs at the tires, reliably. and stayed under the exhaust temps that wreck havoc on pistons. Add 4-5 hundred for the tuner. As for the transmissions. my pulling truck was putting 1350 ft lbs to the rear tires, in 10 years of pulling, dyno runs, drag races, somehow I never blew the transmission. Granted it was a NV4500 5 speed manual with a Southbend dual disc clutch. And guess what, they did put that very manual into a few motor homes. even school buses.

your other option would be to swap to a mechanical P7100 injection pump, then you can simply turn the power up and down with a simple screw driver.

If you source your parts right, you could do it and make more power at a more usable RPM with better fuel economy for near the same or LESS than a big block stroker. For comparison, I'm gonna have about 6500 in my darts 440 drive train, I'll only be making my 500-550 and 550-600 ft lbs. at the flywheel. Just the heads alone for a stroker BB are gonna set you back 1000-1500, cam kit- 500, stroker crank, rods and pistons 2000-3000. intake 2-3 hundred.

RB stroker: 3700 engine alone
Trans upgrade to handle that power: 1000-2000 plus converter.
Total 5-6 grand for maybe 650 hp and 700 ft lbs flywheel

Cummins, 1000-1200 is the going rate for a good used running motor
Tuner: 4-5 hundred (mechanical injection pump if you went that route would be a 1000.
NV4500/NV5600: 1000-1500.
Aftermarket injectors: 500
HX40 turbo: 500
Clutch: 900

Total for cummins swap with transmission: 5500-6000 for 650 hp and 1350 ft lbs at the rear wheels (I essentially gave you my truck's combo, it was also my daily driver and was featured in 8 lug diesel magazine years ago). Add 1500ish if you went automatic trans. (could go with an Allison swap for less). Oh and I averaged 18.6 mpg city/highway combined. a motorhome would be less but more than a big block stroker for sure.
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Where are you finding used cummins engines for that price?
 
One thing to keep in mind with a Cummins swap is weight. They’re 1100 lbs and IMO the pre 90 dodge truck platform is not properly set up to handle that weight. I had an 89 CTD that tore the LCA Mount right through the rivets. I had noticed cracking around the rivets but didn’t think enough to do anything about it. My friend with an 89 CTD had the same cracks at the LCA mounts. My fix was to buy an entire front chassis from a 91. They redesigned the front cross member and LCA mounts to be a single stamped piece.

Just a thought. 6BT is an awesome engine, but it’s also a heavy pig.
 
AndyF said:
I would agree if there was a better option than 50 year old heads. Cast iron heads are good for an application like this but it would be even better if there were brand new thick wall castings with quench. That doesn't exist so you have to use 50 year old parts which is a crap shoot. We had an engine on the dyno recently that was a full rebuild using all stock parts (number matching type of engine) and one head let go after a few pulls. That head had been fully rebuilt, pressure checked, magnafluxed, etc. and it still let go after it got a little bit of stress. So the owner had to go find another casting and pay for another head rebuild.
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IMO, The problem with the aftermarket heads for this type of application is that the ports are bigger than stock, and so are the valves.
Neither of those two things are going to be desirable for high load, low rpm situations.
The only “good” way around that is add a bunch of cubes so the proportions between the cylinder size and the port/valve size don’t get skewed too far out of whack.
Of course, the stroker kit and heads makes the motor cost about twice as much.
I’d probably risk it with some stock heads myself.
I’d look for some 516’s that didn’t have a ton of core shift.
 
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Here’s my old 89 CTD that broke
 
mbaird said:
Coincidentally someone just posted a rebuilt 6bt and 4500 trany for 5k on craigslist here.
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I don't recall seeing any high mileage used 6bt on craigslist for any less around here. You could just about buy a whole used pickup for the same asking price.
 
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