FSJ Frame Strength for a Diesel Swap

[The PIG Smith]

Someone brought up a good point on one thread, how much torque does a slightly build 401 put out? And how much does one weigh?

Excellent point.
It's for sure that a hot 401's weight does not exceed the weight of a 6BT, however the torque is another issue.
Would the torque of a hot 401 put more (or less) stress on a FSJ frame than a stock 6BT with it's massive weight?

[seamus]

Excellent point.
It's for sure that a hot 401's weight does not exceed the weight of a 6BT, however the torque is another issue.
Would the torque of a hot 401 put more (or less) stress on a FSJ frame than a stock 6BT with it's massive weight?

My first gen will weigh over 1100lbs, it will produce over 700 ft/lbs

My daily driver makes over 800 ft/bs

[jMedia]

My first gen will weigh over 1100lbs, it will produce over 700 ft/lbs

My daily driver makes over 800 ft/bs

And your frame? I'm guessing stock. Which makes me happy I wonder if the "shake" of a diesel would be a factor as well

[Mikel]

And your frame? I'm guessing stock. Which makes me happy I wonder if the "shake" of a diesel would be a factor as well

I just returned from a 300 mile in my 4BT-powered J300. I am utterly amazed at how smooth the engine is (I did raise the idle a bit).

[jMedia]

Dang jealous of that 4bt. Wish I could, stupid CA. Next rig will be pre 76 or if first diesel craps out I'll put a 4bt next

[Hubjeep]

Mikel,
what motor mounts did you use? I have the factory liquid filled mounts in my 4BT CJ and used Benz liquid filled mounts in the Waggy swap (I have yet to start it though).



-John

[710 Burner]

Someone brought up a good point on one thread, how much torque does a slightly build 401 put out? And how much does one weigh?

I think the person to ask would be Ghinmi.

[Greg Taylor]

Would you have to beef up the frame for a GM 6.2 swap. I would think the only reason a fellow would have to beef the frame up for the cummins is the higher torque. Because it would seem to me that the GM 6.2 would be a heavier engine than the 6bt but I'd bet the 6.2 does'nt produce near the torque of the 6bt. Just a thought.

Here are pics of Jim Obey's FSJ buggy with a 6.2L diesel in it. I can ask him if he reinforced the frame at all, or not (guessing not).

FWIW, there have been some pretty serious 401's built for FSJ's, pushing 400+ ft/lbs torque ... and those frames probably were not reinforced.

We even have a IFSJA member (ghinmi) who drag-races a Waggy with a built 500 HP 401 in it ... maybe he can chime in here on how much torque his 401 is making with 500 HP (probably in 550-600 ft/lb range) and if he did anything to the frame. Check it out at http://www.youtube.com/user/ghinmi#p/u/10/7vjJOTC5G3s and http://www.cardomain.com/ride/727760

[threepiece]

I'm not much involved with hi torque and HP but I am interested in this thread from a durability point of view. Is actually deforming a FSJ frame from overload the issue here or is this about developing stress related cracks? Or both?
Dan

[Mikel]

Mikel,
what motor mounts did you use? I have the factory liquid filled mounts in my 4BT CJ and used Benz liquid filled mounts in the Waggy swap (I have yet to start it though).



-John

Hello John,
I used the Lord Fluidlastic mounts that came with the Frito Lay vans, with mounts very similar to yours. Here is an old picture:

[Ghinmi]

We even have a IFSJA member (ghinmi) who drag-races a Waggy with a built 500 HP 401 in it ... maybe he can chime in here on how much torque his 401 is making with 500 HP (probably in 550-600 ft/lb range) and if he did anything to the frame.

I still haven't done any modifications to the stock frame. It probably made 550 ft-lb with the old 401 on spray right off the line. Pulled both front tires about the same height. Very little twist.

IMO the front (boxed) part of the frame is pretty strong but the rear not so much. The body is pretty rigid and helps out a lot as long as you've got good body mounts. It's kind of like a unibody/front subframe setup but with a full frame if that makes sense. So far it's worked pretty well for me up to this point. Good luck with the diesel swap!

[CJ the noisemaker]

How about a 4bt?

[Greg Taylor]

I still haven't done any modifications to the stock frame. It probably made 550 ft-lb with the old 401 on spray right off the line. Pulled both front tires about the same height. Very little twist.

Thanks for the good feedback on your experience with the hi-po 401 in there.

[mr.kowall]

in the last couple of years i drove more then 200000 km in my cummins powered cherokee chief and my brothers j20. both are daily driving cars with the stock frame and both have 6bt engines with tweaked pumps. sure, the fsj frame is not the strongest thing, but i never had probs with it. in my opinion its not necessary to upgrade the frame for a diesel conversion, if your jeep is used on-road or mild off-road.

regards from north germany

[jMedia]

in the last couple of years i drove more then 200000 km in my cummins powered cherokee chief and my brothers j20. both are daily driving cars with the stock frame and both have 6bt engines with tweaked pumps. sure, the fsj frame is not the strongest thing, but i never had probs with it. in my opinion its not necessary to upgrade the frame for a diesel conversion, if your jeep is used on-road or mild off-road.

regards from north germany

prettttyy. I like. And thank you very much for your input. And thank you Ghinmi. This thread makes me happy I believe if you were to do the cummins pigsmith, you would need a little beefing up though because you seem to be using it for a more heaby duty purpose