so my 89 will only do about 67 mph with my foot jammed to to the floor. there is no more play in the throttle cable. that got me to 2 up from 65. the truck belonged to a storage place that used it to tow gooseneck trailers. Is this the result of possibly some low rear end gears(i'll see if i can find the tag) or maybe a governer?

i would prefer not to turn up the pump as i do not want to spend the money on a pyro.

any ideas?

 

Check to see if you're hitting the high idle stop on the injection pump, if so, back it off a few turns to give you more throttle.

Advance the IP timing 1/8th inch.

Check for clogged fuel filter or bad lift pump.

Turn up the full fuel screw a turn or two.

Read in the sticky about the BHAF, fuel pin, etc.

Get a pyro, a tach and a boost gauge. It's the only way to tell what's going on with the motor.

 

3200 RPM spring.

 

x2 on the spring

 

More info would be helpful, too.

What transmission?

What rear end ratio?

What size tires?

Any smoke?

 

How many rpm's would be helpful, it have a tach ?
I wonder as it was used commercially if maybe it got governed or de-tuned in some fashion.
That be much nicer than it being sick

 

welcome to the club i get about 72 wot with the spring 4.56 gears and a th 400 with 37's the thing rips but sounds like the world is gonna end at high r's!!!!

 

Check the throttle linkage yet? Mine did the same, and that was the 1st thing I did. fixed her right up... Just last week i realized there was an inch of play in the cable. Tighten that linkage up and see. nothing to lose.

 

From the MPH he listed sounds like a 727 truck. That would mean 3:08 gears. His throttle linkage is not set right.

Over the years I have seen many 3:08 geared truck owners complain about a low top speed. Most have been badly adjusted throttle linkage. If his is adjusted properly he should top out around 82 to 88 MPH against the factory 2450 RPM governors.

Mine defuels at 88 MPH in 3rd and I still have one gear left in the auto.

 

Open the hood and watch the throttle lever on the injection pump as you slowly push the accelerator pedal. If you're able to push the pedal part way down before the lever starts to move, that's your problem and you need to shorten up the linkage at the IP. Also, check to see if the pedal keeps moving but the throttle lever stops. If that's the case, you need to adjust the high idle limit screw. There's an anti-tamper cap you'll have to remove and 2 small jam nuts you'll have to loosen to adjust it.

 

thanks for the input. i am getting all the action out of the lever. maybe i'll give that high idle screw a lil tinker.

 

Another thing to try ; If you're not using an additive (Standyne, Diesel Kleen, etc.) it might be that you have very dirty injectors. Try dumping a bottle of something in your tank. I like Power Service Diesel Kleen plus Cetane. I was pleased with how quickly I saw an improvement.

 

I have a standard with 4.11 rearend and my top speed before any mods was 92 mph with the getrag tranny

 

Mine was about 75mph foot to the floor, 31 inch tall tires (2wd) 727 auto, 3.07 gears. With the 3200 spring now I can do 90-95mph

 

My 91.5 with 3.54 gears, stock tires & 3200 rpm spring easily runs 80 in 3rd . . .