6.9 Swap is Done! - Where's the Power?

[FlySAR]

I finally finished the 86 Rebuilt 6.9 swap to my 87; power/gas mileage is terrible.

The 86' donor truck was standard cab, manual transmission, non-turbo. I could tow a car hauler at 55 no problem & plenty of power (for me) going uphill; maintained 55 empty no trouble.

I put the motor in my 87' F350, crew cab, 4x4, w/ auto trans (C6).

I've driven it a little over 2,000 miles and average about 10 mpg, terrible yes, but what is worse I can't tow anything of significant weight more than 30-35 mph up a grade; I'm getting passed by everyone. Even empty I'm lucky to maintain to 40 up a hill.

My 87' truck is heavier than the 86' donor truck but I can't believe the lack of performance.

Was that the factory, out the door performance, of this rig configured like mine, how did they sell them?

Could I have possibly missed something on the swap that is robbing power? Manual to Auto Transmission swap - IP, Timing, etc.

I would like to figure this problem out before I go to the expense of having someone install my ATS Turbo off my previous motor.

I know I should install the turbo & my problems will be solved, but there has to be something wrong w/ the non-turbo set-up. I cannot believe this is the best I can do w/ a non-turbo 6.9 - As always, any ideas would be appreciated.

Thanks,
Del

 

[84TD]

How did you time it?

I am not sure about diesels since I have never rebuilt one, but when ever I do a high compression, high performance race motor it takes a bit to seat the rings and put out proper power.

 

[Freight_Train]

You may have bumped the IP when pulling the engine or maybe crimped a line by accident.Also,the auto will change things a lot.Especially the C6.The TC doesn't lock up so basically it is "slipping" constantly where when you dump the clutch there is NO slipage or lost rotational speeds.

 

[Freight_Train]

oh yea,did you reset the Vaccumn hicky and kick down rod on the pump?Your trans might me shifting too early bogging down the engine if the TPS is not set just right.

 

[85hauler]

I can tell you there is a BIG difference between a 4/5 speed and c-6. My c-6 truck tows slow and won't get more than 12.4 mpg. My other trucks run circles around it.

 

[FlySAR]

I may have bumped the IP in the swap, the adjustment screw wire is still in place - would I have to make adjustments for a manual-to-auto swap? If it's running rich I assume I'd lack power. I read that IP adjustments are tricky & you need the proper measurement tools, Is there a shade tree mechanic option - sounds, rpms, etc.

Before I removed my auto kick-down assembly from my old throttle body I made several measurements & then installed it on the new throttle body in the same place.

Any other ideas?

Del

 

[Russ]

throttle body

If you went from a turbo to a non turbo, then tossed in an auto tranny, you will deffinatly be on the other side of power department. But No power and lots of smoke usually meets retarted timing.

 

[Mr_Roboto]

Was the IP removed during the swap? If so most likely it is not timed properly. Each IP must be timed to each individual motor.

 

[Petri317]

Also,the auto will change things a lot.Especially the C6.The TC doesn't lock up so basically it is "slipping" constantly where when you dump the clutch there is NO slipage or lost rotational speeds.

I will second that!! My friend has a 1986 F350 4x4 NA with a C6, and I have a F250 with the 4 speed. I can run circles around his truck, and his truck tops out at 60 or so normally. Granted, I have 4.10's and he has 3.55's, that C6 sure seems to rob power.

 

[FordGuy100]

If it's running rich I assume I'd lack power.

Del

Thats gasser thinking, in a diesel more fuel = more power.

 

[Diesel JD]

Yeah more fuel is more power if you have all the air you need to burn it. Now the shade of the smoke would be significant as well...black smoke= unburnt fuel, and the timing is either spot on or slightly advanced. Blue/black, hazy smoke/gray smoke means retarded timing or EXTREMELY advanced timing, or some issue with the fuel system. How old is the fuel system you have? I think I agree with these other guys it probably is timing if that pump was removed. With a healthy C6, 6.9 diesel non turbo and 4.10 you ought to be able to walk right up hills in drive with the cruise on at around 60 and get 12-15mpg. Curious, why did you go with a C6 instead of your former T19? I have some inclination to go the other way. C6 is tough, hard to kill and properly set up it can pull real well, but it seems its a power hog and even higher RPM than the T19.

 

[FlySAR]

Yeah more fuel is more power if you have all the air you need to burn it. Now the shade of the smoke would be significant as well...black smoke= unburnt fuel, and the timing is either spot on or slightly advanced. Blue/black, hazy smoke/gray smoke means retarded timing or EXTREMELY advanced timing, or some issue with the fuel system. How old is the fuel system you have? I think I agree with these other guys it probably is timing if that pump was removed. With a healthy C6, 6.9 diesel non turbo and 4.10 you ought to be able to walk right up hills in drive with the cruise on at around 60 and get 12-15mpg. Curious, why did you go with a C6 instead of your former T19? I have some inclination to go the other way. C6 is tough, hard to kill and properly set up it can pull real well, but it seems its a power hog and even higher RPM than the T19.

I believe the Smoke is Blue/Black; I'm going to have my son drive it and I'll follow - better than looking in the side mirrors.

Pump was not removed or adjusted and had about 80,000 (replaced when motor was rebuilt) or so the previous owner said - he only had the truck for a couple of months.

C6 was in my F350 originally & while I would like to have a manual transmission, preferably a 5 spd, my ability/time to make the auto-to-manual swap was not possible.

"with healthy motor/C6 ..." That's what I was thinking regarding my ability to climb/cruise & I want to get to the bottom of this issue first.

Could it be a poorly operating torque converter - are they a work or fail component?

Thanks,
Del

 

[FordGuy100]

Pump was not removed or adjusted and had about 80,000 (replaced when motor was rebuilt) or so the previous owner said - he only had the truck for a couple of months.


Thanks,
Del

Well that might be your problem right there. Our IP's only last on average to about 100,000 miles, sometimes less, sometimes more. Your lack of power might just be from your pump being worn out/going out.