91 Suburban V2500 - Tow/Weekend Rig - Build Thread

[dhcomp]

hm, interesting. Although, truthfully, lining up the line is the toughest part of getting it connected. Making it longer, when really it needs to be lengthened and lifted up, would only help so much. Just be careful, and take your time, and its possible.

Just don't make me take it off and reinstall anytime soon

 

[AJMBLAZER]

Hahaha, true.

Although I seem to remember on my newer body style '92 the fuel line came up RIGHT AGAINST the body at the firewall and there was JUST enough room to tweak it so you could screw the line on. We did it once and then several years later when we took it off to work on the engine I ended up buying a new fuel line because it had bent and started to leak as soon as we disconnected it.

 

[shady]

when i did my tbi spacer i just unbolted the tbi held it flat and lifted straight up. the lines bent the way they wanted and the tbi sort of floated an inch above the intake. then the spacer just slid right in. you could do that, then unhook to clean/rebuild/mod. should make reassembliy easier

 

[dhcomp]

when i did my tbi spacer i just unbolted the tbi held it flat and lifted straight up. the lines bent the way they wanted and the tbi sort of floated an inch above the intake. then the spacer just slid right in. you could do that, then unhook to clean/rebuild/mod. should make reassembliy easier

Didn't do this before i removed the TBI, but i like your suggestion. Then all you have to do is tweak for the gauge adapter length. God I love the internet

The biggest conflict i had, which i didn't' realize, was that the return line was hooked on the vac line port at the back of the manifold. Moved/bent a lot easier once i unhooked it from below this port.

 

[dhcomp]

The time to swap axles is close!

Picked up a 79 10 bolt/14ff setup, 4.10's, open rear.

Old 14ff style backing plates not compatible with my ebrake, and want a gov lock rear.

Picking up an 85 3/4 ton 14FF with 4.10's and gov lock this weekend.

Just ordered Ruff Stuff cover, U bolts.

The $$$ is adding up quickly, but i'm almost ready to do the swap to 4.10's!!!

Need to pickup a U joint, and hope the brake lines on one axle are salvageable.

Stoked. Look for progress over thanksgiving weekend.

 

[y5mgisi]

Very nice man! I think the 4.10s are going to work out really good for you.

 

[RollinKaos]

Sweet man! This is on the radar for me soon as well.

 

[dhcomp]

Very nice man! I think the 4.10s are going to work out really good for you.

Nervous to be making only one "step" change in gears, but should do the trick. Dont' think i could do 4.56's with the amount of highway driving i do.

 

[AJMBLAZER]

4.56's would be too deep for your 33's. Be great for towing though.

 

[dhcomp]

On a side note, i've been commuting in the beast for the last week, and have put some miles on it since the CFM tech upgrades.

Overall, not overly impressed. May be able to feel a slight difference, but really, doesn't seem to run much better.

Going to yank the flapper out of the pre-heat pipe thing on the air cleaner tonight.

Do you guys recommend turning up the fuel pressure higher?

 

[cuervo]

On a side note, i've been commuting in the beast for the last week, and have put some miles on it since the CFM tech upgrades.

Overall, not overly impressed. May be able to feel a slight difference, but really, doesn't seem to run much better.

Going to yank the flapper out of the pre-heat pipe thing on the air cleaner tonight.

Do you guys recommend turning up the fuel pressure higher?

I think you should do some data logging before you make changes to fuel or VE tables.

On your gearing: I'm running 4:56s on 35s and run right around 2200 at 65/70 mph.

 

[dhcomp]

I think you should do some data logging before you make changes to fuel or VE tables.

On your gearing: I'm running 4:56s on 35s and run right around 2200 at 65/70 mph.

Change fuel tables? I'm just going to turn up the adj. regulator

No electronic work here.


35's and 4.56's sounds about right.

I'm closer to 2k at 65 right now, which, is sorta bogging the motor. Its way happier running at 80 with 3.73's and 33's.....

 

[cuervo]

Change fuel tables? I'm just going to turn up the adj. regulator

No electronic work here.


35's and 4.56's sounds about right.

I'm closer to 2k at 65 right now, which, is sorta bogging the motor. Its way happier running at 80 with 3.73's and 33's.....

Without data logging adding more fuel/pressure may just be a waste of your dough. You know the butt dyno is not going to tell you that much and if you just end up making it run rich you wont like it.

 

[dhcomp]

Without data logging adding more fuel/pressure may just be a waste of your dough. You know the butt dyno is not going to tell you that much and if you just end up making it run rich you wont like it.

Fair enough. I can turn it up some, and see what happens. I can always dial it back down, takes about 2 min.

The consensus around here seems to be that a solid 13 PSI with the adj. regulator is a lot better than the unknown 10-13 from the factory regulator.

 

[Deuling]

Sweet burb

 

[TommyM]

Won't adjusting the fuel pressure make no difference in closed loop, because the injector pulse timing is controlled based on O2 readings? So if the pressure is higher, won't the computer just reduce the injector's open cycle time to compensate?

It should, though, make a difference on open-loop (cold engine) when it's running off the tables with no O2 feedback, right?

Tommy

 

[dhcomp]

Won't adjusting the fuel pressure make no difference in closed loop, because the injector pulse timing is controlled based on O2 readings? So if the pressure is higher, won't the computer just reduce the injector's open cycle time to compensate?

It should, though, make a difference on open-loop (cold engine) when it's running off the tables with no O2 feedback, right?

Tommy

I don't know enough about this, but my hunch is that the O2 sensor readings aren't' detailed enough to really change the injector pulse.

Really, I didn't question it much. A lot of guys on here i trust had good feedback on the adj. setup, so I added it.

 

[Big Ray]

doing all that work and not tuning is just silly, IMO...

It's worth the effort, just hi tech tuning. If you're not comfortable doing it, there should be plenty of shops in CA to take it to. Have it dyno tuned.

 

[dhcomp]

doing all that work and not tuning is just silly, IMO...

It's worth the effort, just hi tech tuning. If you're not comfortable doing it, there should be plenty of shops in CA to take it to. Have it dyno tuned.

You are saying get a wideband O2, and get a custom chip burned?

That may be next. Was under the impression i'd get some decent gains from what i did, but maybe not . Whatever i do, i need to stay driveable, and reliable

 

[cdoggwsu]

I don't know enough about this, but my hunch is that the O2 sensor readings aren't' detailed enough to really change the injector pulse.

Really, I didn't question it much. A lot of guys on here i trust had good feedback on the adj. setup, so I added it.

From what I understand that's correct - since the stock O2 sensor is essentially only dealing in rich, lean or stoich condition and not a true AFR there's not a lot the ECU can or will do to compensate.

Even then, if the info from CFM tech is to be believed it sounds like a lot of times the factory FPR is running so low that these engines can spend a lot of time in a borderline lean condition as it is. In that case you're actually making the the ECU less inclined to try to compensate.

On a side note, i've been commuting in the beast for the last week, and have put some miles on it since the CFM tech upgrades.

Overall, not overly impressed. May be able to feel a slight difference, but really, doesn't seem to run much better.

Going to yank the flapper out of the pre-heat pipe thing on the air cleaner tonight.

Do you guys recommend turning up the fuel pressure higher?

Was under the impression i'd get some decent gains from what i did, but maybe not . Whatever i do, i need to stay driveable, and reliable

Did you ever end up turning up the fuel pressure? You mentioned before you were running at 13psi; CFM Tech recommends 14-14.5 when "slightly modded" which includes all the stuff you installed. At 13psi you may still be running a little lean. When I do these mods my expectation is to be running 14 minimum. I think you'll see some decent gains after a little tweaking and tuning - if not in butt dyno power for sure in driveability.