1968 C10 DD, project "New Tricks"

[K85 Octane]

Truck did great except I really need to get that intake out of the engine bay. I was seeing temps between 145-160 while driving home. That sucks. I also don't like the trans temp being as hot as it is, just cruising at around 200-215. It will run 215 for long periods of time and I can tell by the way it shifts it's at that temp. I want to pull the lines off the radiator. The engine likes to run ~200 and the way this crossflow radiator works it seems to expose the trans fluid to the hot side more so the cold side. Talking with ChrisP, I'm thinking about running a long heatsink style cooler on the frame rail. It's out of harms way and seems like an easy fix.

 

[K85 Octane]

Last update/ concern.

This truck likes to run. OMG does it like to run. I can get on the highway and not notice I'm doing 80 by the time I'm merging with traffic. Accelerating from 60-80 is simple. Going from 70-80 takes very very little throttle input. It cruises doing 70 @ 2k rpm and is so happy doing it.

Here's the BUT and kick in the nuts.
This truck can't seem to go over 90. It can be at 80mph and the amount of effort needed to get to 90 is greater than it took to get to 80. (if that makes any sense) Like someone put a parachute on me @ 81mph. I don't know what it is. My old v6 S10 would get above 100, maybe 115 as I disabled the governor. I don't know if it's wind drag (crazy) or what.

 

[Chevy305]

Good to hear that you've got most of the quirks worked out.

 

[ashman]

This truck can't seem to go over 90. It can be at 80mph and the amount of effort needed to get to 90 is greater than it took to get to 80. (if that makes any sense) Like someone put a parachute on me @ 81mph. I don't know what it is. My old v6 S10 would get above 100, maybe 115 as I disabled the governor. I don't know if it's wind drag (crazy) or what.

It might be wind drag. Obviously with my suspension I'm not trying to do 90+, but at higher speeds, if there is much of a headwind at all I can really feel it. I'm way undergeared for my tire size so I always assumed that was the problem, but yeah, I've felt the same thing. Having the aerodynamics of a brick might be the real culprit.

 

[campfire]

It might be wind drag. Obviously with my suspension I'm not trying to do 90+, but at higher speeds, if there is much of a headwind at all I can really feel it. I'm way undergeared for my tire size so I always assumed that was the problem, but yeah, I've felt the same thing. Having the aerodynamics of a brick might be the real culprit.

Ding, ding, ding. "V squared" is a ruthless master.

 

[ekajkrats]

There are videos of suburbans with the 5.3l hitting the limiter at 100mph, I think your truck being lighter (assumption) and definitely lower would be able to do that no problem.

 

[F.S.F.W]

I really don't know anything about these motors but isn't there a sensor in the engine that need to read mph? If so is there a chance it's reading high and governing out? Like I said I don't have a clue how they work I just thought I remembered hearing something like this?

 

[K85 Octane]

My speedometer actually gets its info from the ECM, so what I see is correct. And through the initial setup and programming for tire size and gears, the speed is spot on. I believe all governors were removed, except I think redline shift is now 6k. I wonder if the higher intake temps could cause an issue, but really the engine is taking in less air than WOT rpm. I guess I'll need to get in touch with my programmer. It just feels like it can't go faster, not like something shutting down.

Just got off the highway about 30min ago. Sucker sure has no problem between 60-80mph, up and down even in 100° outside temps. The exhaust note is so smooth and sexy

 

[NorCalKid]

60-80 acceleration always puts a smile on my face. My truck is quite a bit higher and probably a lot heavier (long bed, tool boxes and iron transmission) and it will cruise right to 100+ no problem, so I dont think you can blame it all on brick aerodynamics. You maybe on to something with intake temps?

 

[F.S.F.W]

60-80 acceleration always puts a smile on my face. My truck is quite a bit higher and probably a lot heavier (long bed, tool boxes and iron transmission) and it will cruise right to 100+ no problem, so I dont think you can blame it all on brick aerodynamics. You maybe on to something with intake temps?

I agree.

 

[sreidmx]

It should pull way past 100.. there has to be some residual speed limiter still there or some weird parameter turned on.. even if the Iat was higher than normal it'll just pull timing and add fuel possibly. It shouldn't be hitting a wall though..

 

[F.S.F.W]

Is your fuel pump weak? Might be able to hold enough pressure to get it moving but not enough to keep pulling.

 

[K85 Octane]

Well, hmmmm.
I tested the pump a while ago at idle, ran 58 steady. It's new from Boyd Welding, not sure what brand.Haven't a clue what psi while driving.

The truck will pull like a raped ape 0-80. You think going from 80-90 would take more fuel? Hmmm I gotta find a second to call.

 

[sreidmx]

There gotta be something in the pcm that's not gettin the right input causing it to do that.. being speed based makes me think your vss might be bad or off

 

[F.S.F.W]

Well, hmmmm.
I tested the pump a while ago at idle, ran 58 steady. It's new from Boyd Welding, not sure what brand.Haven't a clue what psi while driving.

The truck will pull like a raped ape 0-80. You think going from 80-90 would take more fuel? Hmmm I gotta find a second to call.

It's kind of a longshot but I was just thinking maybe its pushing the limits but still getting what it needs to cruise at 80 but once you hammer on it from there it's not?

 

[campfire]

Well, hmmmm.
I tested the pump a while ago at idle, ran 58 steady. It's new from Boyd Welding, not sure what brand.Haven't a clue what psi while driving.

The truck will pull like a raped ape 0-80. You think going from 80-90 would take more fuel? Hmmm I gotta find a second to call.

Yes, it will require more fuel. But I'd be surprised if the fuel pump abruptly hit its limit, unless the pump is oversized. It's easy enough to blame the PCM, but if you want to eliminate the fuel pump from the picture, rig up a fuel pressure gauge and see what happens on the highway. You may already have a sensor as part of the injection system (in which case your job gets even easier).

 

[78K30]

Yes, it will require more fuel. But I'd be surprised if the fuel pump abruptly hit its limit, unless the pump is oversized. It's easy enough to blame the PCM, but if you want to eliminate the fuel pump from the picture, rig up a fuel pressure gauge and see what happens on the highway. You may already have a sensor as part of the injection system (in which case your job gets even easier).

I second the adding a fuel pressure gauge and seeing what happens. Friend of mines car did it awhile back where if you drove it nicely with light to medium throttle it would behave as normal, Anything over say 3/4 throttle and it would simply fall on its face. The tired pump lacked the flow needed for higher loads.

 

[campfire]

Yes, it will require more fuel. But I'd be surprised if the fuel pump abruptly hit its limit, unless the pump is oversized. It's easy enough to blame the PCM, but if you want to eliminate the fuel pump from the picture, rig up a fuel pressure gauge and see what happens on the highway. You may already have a sensor as part of the injection system (in which case your job gets even easier).

Oops, I misspoke. I meant to say that an UNDERsized pump might fail to keep up with load, not an oversized pump.

 

[K85 Octane]

Still fixing the front sway bar. CPP frame mounts don't put the sway bar rearward enough, so I oblong the holes and extended one side. (the original slotted holes didn't do anything as the bolts were both farthest out) Doing these couple things net me about 3/4" more rearward and helped line the links up perfect.

 

[K85 Octane]

Also pulled the trans cooler lines off the radiator. Managed to mount the most heatsink cooler combo between the cab mounts on the frame. Here's hoping this helps with trans temps. I'm no longer using the radiator. I saw 225* temps during a very hot day recently, just in traffic.