'77 Bronco 4bt Conversion

[blazinchuck]

The little 3.9L 4bt is tagged at a whopping 105hp @ 2,500RPM... and 260 lbs/ft of torque @ 1,700RPM.

Hope to some day take it to around 180hp and 400 ftlbs of torque. I plan to stay with the Bosch VE pump but will change out the turbo or modify the current turbo for increased rotor speeds (boost pressure).

It won't be able to take on those Ford engines in a race...but it should provide low rpm torque.

you might be surprised at how fast they can be...I give a lot folks a run for the money in my 6000lb truck it's got a #5 fueling plate 240hp/600tqmokin:

[High Pressure]

you will like that 3200 c'mon...I know I do!!!!


so when we meeting in person???? I'll be in the bronco tomorrow!!Chuck

ps...numbers in the who's who

Chuck,

Hope to have it on the road again for some shake down drives this weekend. Here's my final shake down drive list...

1) Install new radiator (might receive it today)

2) Correct the exhaust pipe "banging" problem!

3) Need a license plate!

I can wait on the Winters gated floor shifter for the C4 & the front driveshaft! I have been working almost 2 years for this weekend...

Chris

[johnpaulgolf]

Chuck,

Hope to have it on the road again for some shake down drives this weekend. Here's my final shake down drive list...

1) Install new radiator (might receive it today)

2) Correct the exhaust pipe "banging" problem!

3) Need a license plate!

I can wait on the Winters gated floor shifter for the C4 & the front driveshaft! I have been working almost 2 years for this weekend...

Chris

That is so awesome Chris...Maybe I can make it up this weekend...Like I said would love to see it in person

[High Pressure]

I took a half day of vacation today....to work on the list...

1) Install new radiator -Done

2) Correct the exhaust pipe "banging" problem! Installed new bracket hanger and ground some additional clearance around the transmission cross member brackets ..Much improved... still think more can be done..

3) Need a license plate - Done

Drove it about 6 miles today before the rain started and filled the main tank up with diesel. The tires seem to be balanced well.

Had to adjust the idle up a bit... not sure what RPM... still need to get a tach.. In park & neutral... it was fine... but as soon as I put in reverse or 1st..it would "shake" but after the idle was turned up things were much improved. We shall see..need to think more about this issue... Any ideas?

But I do have a new problem.. my 12SI alternator is not charging.. it was old and came with the engine.. plan to take it off and have it checked.. I assume a parts store can test a 12SI?

Chuck - I might be ready to make a drive to pickup some hats & shirts!

[johnpaulgolf]

Sweet that is so cool...I will not be able to make it this weekend...but will be up there soon...

As far as the alt. is concerned these guys in Dallas TX are awesome and the price is right... http://superpageshosting.com/4alterstart...tuid=10013 call them and ask to speak to Bobby.

[High Pressure]

As far as the alt. is concerned these guys in Dallas TX are awesome and the price is right... http://superpageshosting.com/4alterstart...tuid=10013 call them and ask to speak to Bobby.

JP - thanks for the alternator source... not sure what the current 12SI output amperage is that I have.. suspect 60 -80 amps... I wonder if I should upgrade to a higher amperage output.. in fact... I wonder if the Fan motor I just installed killed it!!! Maybe I should go with a 100-120 amp output 12SI??? I really want to stick with that model or one that has the same frame/housing dimensions for the brackets.. I had to make a special bracket for a 12SI during the conversion when I added the Ford Powerstroke vacuum pump...

Chris

[broncomania]

Finally got some BFG KM2 35x12.5x17 mounted to 17" rockcrawlers.... The Bronc is close to hitting on the roof when I drive it into the garage!

i want to ride in that. you built one sweet ride. :beer:

[High Pressure]

i want to ride in that. you built one sweet ride. :beer:

If you enjoy riding on "wash board" roads this is the ride for you! Been working to improve a major "SHAKE" issue that the 4bts are famous for...

The whole project is a one of a kind.. others have installed 4bts into Broncos but all motor mounts, transmissions, exhaust are different. The major "SHAKE" issue happens when I place the C4 in Reverse or 1st gear at idle with the brakes applied. As soon, as the brakes are released and the accelerator is pressed the shake is decreased significantly but other resonance types occur at various speeds that are amplified through the exhaust.

Here's what I have done so far...

~Idle~
Adjusted idle speed up/down numerous times... but I'm flying blind since I don't have a tach connected yet... received a Tach this week and hope to have it hooked up in a few days.

~Exhaust~
I believe that I'm on my 3rd exhaust hanger installation configurtion... each change has improved the sitution significantly....no banging at this time...just various speed related resonance types. Next step - install a 3" dia x 8" length of braided flex exhaust in the down pipe from the turbo. Hope this will decouple some of the resonance issues.

~Fuel Pump Timing Advance~
I've been thinking about this one for some time.. and after I discussed the problem with Chuck last Sunday (yes... the "Head Potentate" does know his diesels) I got of my butt and made the special wrench to advance the fuel pump timing. Most people adjust the timing a 1/16 of an inch above the timing mark to help with the issue. I found my fuel pump timing to be about a 1/32 below the timing mark!!! So, I adjusted it about 1/32 above the mark for a total change of 1/16 advance.. This made a signifcant improvement.. it has almost removed the difference in vibration from idle Park and idle 1st gear..

~Adjusted Revese/Low C4 Band~
I intitially thought this had some effect to improving the issue but not sure now...

Other than the vibration issue.. I'm pleased with the torque and highway speed.. but really need to get some fuel mileage readings.. especially at $4.50 per gallon for diesel!!!

[High Pressure]

Well... Monday I was able to work on the bronc again. I pulled the exhaust and changed the down pipe to incorporate the flex pipe and added another bracket support. It seems to have helped with the 50+mph exhaust resonance. In addition, the 12SI alternator had failed. So, I replaced it with a 120amp CS130 1 wire that I purchased from RRRAYYY2 on Classic Broncos. Currently the exhange rates with Canada are less than 1% difference at this time. Had to swap out my old pulley and use shaft spacer that was on the 12SI to position the 8 rib pulley in the correct position. All is fine now... charging at 15Volts at idle. Hope to finally wire the tach on Weds evening.

[broncomania]

glad to hear its coming together 4 ya.