Cummins 4BT '68 F-250 4x4 swap

[averagef250]

[eggman918]

Well I drove the Beast around a bit,no drive line vibrations at any speeds so my math must have been correct . Installing a"366" spring this week.
Any ideas as to pump adjustments to get me in the ballpark for my HX35 in a #6800 truck with 3.55 and 32" tires?
Tires and registration coming the first part of Feb. I am so close that I can hardly sleep
Steve.

[averagef250]

My tuning goal is to get just enough fuel to light the turbo quickly without excess smoke. My preference is a little puff then no smoke at all once the turbo's working.

Your overall fueling- the max allowable fueling and how the pedal feels is controlled by the full load screw on the rear of the pump.

The diaphragm on the top of the pump converts the boost pressure signal into an effect on the fuel rack in the pump. This part is called the aneroid. The spring under the diaphragm controls the rate at which the ramped cylinder under the diaphragm moves. Less spring pressure, the quicker the pump adds fuel under low boost/heavy throttle situations. Think of the aneroid like the accelerator pump cam on a holley carb.

[eggman918]

Thank's again Dustin,that gives me an idea on how to proceed.
I dont want any more fuel than needed to move the Beast,mileage was the main reason for the swap in the first place.

[eggman918]

OK the spring is in the star wheel is turned up 1/4 turn and 1 turn on the full load screw.that gives good response and power,10-11 psi boost at 65 on level ground.
my egt at 65 is 950 is that too high, when I back off the throttle it drops off quickly to 650.Should I turn it down a bit or is that acceptable?

[1971ford]

NOt sure if the 4bt's are different than 6bt's as far as acceptable EGT's, i'm guessing not..
Those numbers sound fine. Seems you need to worry when the numbers are around 1100.

[KRob]

Also depends on where your egt probe is located. Is it located post or before the turbo? Before the turbo on the manifold then that should be fine as long as the specs are the same as a 6bt. If its post turbo then don't run over 900 for very long.

[eggman918]

Probe i upstream from the turbo by aprox.2".
thanks guys,I did not want to do any damage and this my first diesel

[Fordnatic]

Nice work. Wish I had your machining equipment! Looking forward to reports on driveability/mileage compared to the 390! Also appreciate all your pictures & captions.

[averagef250]

950 EGT is a little high for loafing along at 65. 10-11 PSI cruising boost is a little high too. A normal 1 ton sized truck with a 4BT and a stickshift at 65 MPH should be under 5 PSI boost. I'd expect to see 10 PSI if you were running 85 empty or towing a bunch at 65.

You're not going to hurt anything with EGT under 1200 or so, but it's something to keep an eye on and figure out why it's doing what it is.

What did your HX35 turbo come from? If you get a chance, measure the pressure drop across your intercooler (add a pressure gage before the IC).

Things that can cause higher than normal EGT-

Timing retarded
Clogged IC
Bad turbo
wrong turbo application (too big)
clogged muffler/exhaust
Bad headgasket

[eggman918]

The turbo is off a early 90's F-800 with a 6BT,I was thinking that it has the big exhaust housing but I am not sure.
The highway I am using as a test run is a bit of a grade in fact the other day I ran it up the hill about 20 miles after turning the full power screw in another turn
and it seemed to run better the last part of the grade is 6% and I was running about the same EGT/boost numbers 65 mph is a guess it could be closer to 75 tach and speedo cables are still on the list.
If it has the 16/cm housing would the 12/cm be better?
I am basically clueless at this stage of the game..just enough knowledge to be dangerous.I will add psi gauge as soon as funds allow .
Thanks again for your help/patience
One thing I forgot to mention is that I checked the valve clearance and all the exhaust valves were at .026/.028 they are now at .020 but I have not drove the truck, need a moving permit
Steve.

[eggman918]

Took a quick test run with the Wife pacing me @ 65 on the flattest piece of highway now I'm at 750/800 and 6/7 psi.
There is a 100* difference from4th to 5th gear 5th being hotter. how do I test the head gasket?

[KRob]

My experiance is with a Dodge and a 6bt Cummins so its not probably apples to apples...however the PSI for just flat running sounds about right and if traveling the exact same speed going from 4 to 5 you will probably see a little bit of a hike in the egt.

Think about it...if the engine is turning 2300RPM to go 65 and then you shift to 5 and your running 1900 at 65 the engine will have to work a little harder each rpm to do just the same amount of work. Now this may apply more to climbing a grade but just a thought. I am remembering though that 600-800 degrees was kind of the cruising temp on my truck.

But then its been 4 years since i drove my truck on a regular basis so i may be all wrong...by regular basis i mean an ocean between me and it.

Also make sure you don't have a boost leak, what the highest you've gotten your boost.

[eggman918]

max boost I'v seen was18psi pulling the 6% grade @about 65 mph.
I have found a lot of info on line about this subject but dont know what is accurate for my situation
I always expect the worse and as funds are short I have a lot of time worry about it

[eggman918]

I was under the truck today and I noticed that exhaust pipe in front of the muffler is changing color it is straw to light purple,
I am going to replace the muffler with a piece of tube and turn it out and down in front of the rear tire and see if that helps.
I was running the muffler off the bread truck to get it running,was planing to replace it anyway.