Cummins 4BT & Diesel Conversions Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
I spent my lunch looking for information and I've run out of time. Are the mounting points the same for a 4bt and a 6bt? Are they dimensionally the same from the back of the engine to the mount? I have an f150 with the 300 I6 motor mounts and I want to know if I will need to modify them to get it to fit or if it will bolt in like a 4bt would.

I got a tip on a cheap 91 non-intercooled 6bt that I am going to look at tonight. I want to guage how much more fabrication I'm in for if I go this route.

Thanks
 

·
Registered
Joined
·
801 Posts
There are a lot of options for mounting the engine. Regardless you will be fabbing stuff. As far as I remember the 6 is further forward, but there are bolt holes in the block for front, forward and mid mounts.

I wouldnt trust an OBS f-150 frame with a 6bt. MAYBE if it was boxed/strengthened. I've owned many and they typically crack just behind the spring mounts on the passenger side with our michigan rust. The 250's do it too.
 

·
Registered
Joined
·
11,875 Posts
On your question about the location of the mounting point on the 4bt and 6bt blocks, they are not in the same distance from the rear of the engine. They are straddling cylinder #3 on both, but that is 1 cylinder from the rear on a 4bt and 3 from the back of the 6bt. In other words, they will be 2 cylinders farther forward on the 6bt. To put a 6bt in an F150 will require some frame reinforcement, a different front axle and suspension, and probably a different rear axle. You're looking at an 1100 lb engine which will overload any F150 suspension and has more torque that most light duty rear axles will stand. You'd probably need to convert the F150 into and F250 or F350.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #4
The motor mounts I've seen for a 4bt were mounted near the front of the engine, lined up with the first forward cylinder. This would be cylinder #3 like what you were describing on the 6bt. I wouldn't think they would cantilever most of the engine out like what you're describing.

This truck is a 1991 std. cab, short bed 4x4 that I want to get good mileage with. I have other trucks for towing duties so I'm not worried about the axles and transmission. The 6bt I'm looking at is less than 1/4 the price of 4bts I've looked at so I was hoping to make it work. Maybe even detune the 6bt to 4bt power levels, but I haven't looked into that possibility yet.

Thanks for the info. I might buy this 6bt, even if I just use it for trade on a more suitable engine.
 

·
Registered
Joined
·
11,875 Posts
The front mounting point you're talking about on the 4bt is also on the 6bt but they will be about 10-12 inches farther forward. You wouldn't want to put all that weight up front anyway. Would be too much stress on the transmission mount. You can get premade mounts for that series truck but they aren't cheap. What transmission were you planning on running? Nothing that was stock in that truck will stand up to that engine. If memory serves me right, the rear end is an 8.8. It won't live with the torque of that engine. An equal problem up front. I have seen a Bronco done with a 6bt and kept the independent front 4x4 suspension. Took some serious beefing up and I wouldn't plan on wheel bearings lasting a long time. Just a lot of weight to stick in the front of a 1/2 ton pickup.
 

·
Registered
Joined
·
41 Posts
Me and a good friend of mine about 4 years ago tried this. Listened to all that was said here and said "they were wrong we can do it" we tried. The axles didn't hold up the frame didn't like it. Bad idea. Tried two years later with a 4bt in an f150. Love it. He still drives it everyday. Sometimes ya gotta pay to play. I know that's what you don't want to hear. But take it from some one who's tried. Either buy an f 250 or a 4bt.
 
1 - 6 of 6 Posts
Top