At some point I am looking at swapping a 4bt into my 91 f150. Going to swap in the 8 valve mechanical, not the 16 valve electronic. The torque output is roughly the same as my 300 currently is. They are both right around 265 ft lbs. I also have the m5r2 transmission and since it's 4x4 I would like to keep it that way.

I have a source for the 4bt with the ford bellhop sing adapter already installed. From what I am told it is the small block bolt pattern. The engines already have a T19 mounted to them, so I am trying to find out for sure if the more will mount right up or not.

Also, if the m5r2 will mount up, I have been reading that I may need a more durable clutch if I want to get some very mild torque gains from the 4bt. What clutch should I look at? There isn't much as far as aftermarket for the 300 efi, let alone the m5r2 as far as I know.

Also, would like to know how much torque someone has put through an m5r2. Mine is in great shape. Synchro's are still good, and ended up towing almost 12,000 lbs for about 1800 miles with the truck, trailer and cargo combined. So I have no doubts mine is in good shape. Never had an issue with it. But while I have it out is there anything I can do internally on the transmission to strengthen it to give me some wiggle room as far as torque handling in case I want to do a little more with the 4bt.

Thanks for any input. I hear alot of people say the m5r2 is garbage, but I have had an awesome time with mine. Don't need to burn through the gears, it's a truck, not a sports car. Just want to do truck stuff, some occasional heavy towing and mostly just offroading and driving it daily.

 

Did some more research on my own, and if I can find the engine with the ford trans already mounted, or at least with the adapter already mounted, my M5R2 will bolt right up just fine.

Further questions though, since most everything on my truck seems to be controlled by vacuum, is there a way to modify the heater controls to work off of a cable instead of vacuum? Or will it just be easier to get an electronic vacuum pump to handle the heater operation?

And as for the brakes, I am most likely going to use the GM hydroboost system since I am already familiar with it from being in the military and working on HMMWV's. However, I am pretty sure my truck has rear ABS. Does anyone know if the ABS controller is standalone, or is it part of the EEC-IV computer?

 

ABS is standalone. It's not really feasible to convert the heater to cable control. If you're gonna run a vacuum pump for the heater controls, you might as well just keep the vacuum booster too.

I believe the 6.9, 7.3 IDI and 7.3 powerstroke trucks came with mechanical vacuum pumps you might want to look into.

 

Jut use a Dodge vacuum pump and P/S pump and make your life A LOT easier.

Also, WHY would you go with the 4bt. you will be loosing about 50hp

 

I will lose horsepower, but I will still have the same amount of torque, and with a truck, I care more about torque than horsepower anyways. Also can't argue with the economy of a diesel that runs properly versus a gas engine. It won't pay for itself, but in the long run it will be easier to maintain seeing as I won't have to worry about the electronic crap with the efi 4.9.

As far as the mechanical vacuum pump, how would that work? Is it driven by a gear or a belt similar to the air pump on the 4.9?

And honestly as far as the hydroboost/brakes go, I trust a hydraulic system more than I trust vacuum as they seem like they would potentially be able to apply more braking pressure. But idk. I'm also open to the Dodge setup seeing as the 4bt is so similar to the 5.9 that I'm sure quite a few items from a Dodge cummins should be able to be easily adapted to the 4bt.

 

The PowerStroke and IDI engines use a belt-driven vacuum pump, the older Cummins 5.9 Dodge trucks use a combination gear-drive power-steering and vacuum pump that will bolt into a 4BT.

As far as trusting hydroboost more than a vacuum booster? Hyroboost is far more complex. The vacuum booster is extremely simple in comparison.

Both systems will easily and readily lock the brakes completely up. If you didn't need vacuum at all, I'd say go with the hydroboost, but since you need vacuum for the HVAC stuff, you might as well keep the vacuum booster.

 

Good to know. I will have to do some looking at the Dodge side of things, I'm assuming you are referring to the ones that came with the 12 valve 5.9?

Most all of my experience with diesels are the 6.2/6.5 from GM, and the Cat C7, as well as some of the Detroit and even a Cummins V8 from way back in the day. Haven't gotten to mess with a 5.9 too much or even any of the IDI/powerstroke.

 

Yes, anything that will work on the 5.9 cummins will work on the 3.9

 

The stock 4bt has peak tq at 16-1800 rpm. There is no way to tell whether it will hold, but the harmonics of a 4bt are also hard on parts....not just tq. If you plan on turning it up at all, which you likely will....105 hp is a complete turd regardless of tq rating, I'd keep an eye out for a different trans at the very least. You can unlock 50 hp for basically free, and even more with just a fuel pin and governor spring (assuming you find a ve engine, which something like 90% of the 4bts are). The same can be said for the p pump engines but the pump parts are a little more costly.

any small block ford clutch will work, with a worst case scenario requiring drilling a cummins flywheel to accept one.

Misewell stay vacuum, less work in the long run. If you want to go hydroboost down the road then do it after you iron out the kinks of the engine swap. I always try to do "one build at a time" unless it's a full resto or unless one build leads to, or makes easier, another.

 

A small block ZF5 would be a MUCH better choice than the Mazda M5OD