'90 454 TBI build.... Looking for pre-advice

[Jester1]

Ok I am starting a thread for the work truck motor rebuild. I first have a couple of questions for the more experianced (being I haven't built a motor newer than the 70's). Truck is a '90 K3500 with 145,000 miles. It has a turbo 400 with 4.10 gears and 245/75/16 tires and rims. Will be putting bigger tires on later to help with RPM in top gear.

Here are some questions that I am either confused about or just don't know the answer to. I will be also asking for advice on components to put on the motor to increase fuel mileage. Just remember this will be going back into DD status and crazy horses are not needed. Reliability and fuel econ are more important, as well as budget. I am saving that stuff for the blazer.

I also know that if I want better fuel milage to put in a smaller motor, get a new car, stay home, get a diesal (have one), blah, blah, blah...

History of the motor/truck is bone stock, 145,000 miles, spun a bearing last year. Pulling motor to fix bottom end and do a freshen up build on it. Will be staying with cast heads and such....

Need options/opinions on intake, cam, injectors, gaskets, timing chain, ignition (aftermarket?), or anything else that can help. Truck has always been great on power and tourqe with plenty to spare. I just want to hear from the brotherhood about practical solutions. I will be working out of town for a couple of weeks and this build will be spread over a couple of months in order to help with work schedule and budget.

Here is the truck. Have had it since new, no major accidents (couple dents on the bumpers), no rust anywhere, totally straight. The only trouble ever was replaced waterpump at 97,000, dizzy at 115,000 miles, spun bearing a year ago, and typical stupid heavy chevy door not aligining right (and pins and bushing won't fix, need new hinges, old pins wore all the way through and oblonged the hinge hole).

 

[dyeager535]

My opinion is that if you don't want to get into more work, don't mess with anything. Build it stock. With some tuning, even on a stock motor, you can pick up some decent mileage by tuning the prom. Talk with Eaglemark on this.

If you start changing stuff (headers, intake, cam, heads, etc) then you are really getting into the realm of REQUIRING a new chip be burnt. If you stay away from that stuff, then all that would need done is some economy mods to the PROM, and that's that.

Not that all those parts aren't good...simply that anything you change on a fuel injected motor is not going to work as good as it can, without tuning the PROM. And anything that effects fueling (and that's just about every modification you make) needs adjustment in the PROM.

My dad put a "computer friendly" mild cam in his 454, headers, and an Edelbrock dual plane intake. Those changes alone required about 20% more fuel across the board. It felt like it ran "fine" without PROM changes, but not fixing the issues could have led to far more serious problems later. And we really aren't done yet, haven't verified my fuel pressure regulator modification worked to bump up pressure.

You'll find many people say "I changed such and such and it runs fine!" but more often than not, these are people who have not bothered to hook up some tools to the vehicle to make sure it's not running lean, which they almost invariably are.

 

[Stomis]

My opinion is that if you don't want to get into more work, don't mess with anything. Build it stock. With some tuning, even on a stock motor, you can pick up some decent mileage by tuning the prom. Talk with Eaglemark on this.

If you start changing stuff (headers, intake, cam, heads, etc) then you are really getting into the realm of REQUIRING a new chip be burnt. If you stay away from that stuff, then all that would need done is some economy mods to the PROM, and that's that.

Not that all those parts aren't good...simply that anything you change on a fuel injected motor is not going to work as good as it can, without tuning the PROM. And anything that effects fueling (and that's just about every modification you make) needs adjustment in the PROM.

My dad put a "computer friendly" mild cam in his 454, headers, and an Edelbrock dual plane intake. Those changes alone required about 20% more fuel across the board. It felt like it ran "fine" without PROM changes, but not fixing the issues could have led to far more serious problems later. And we really aren't done yet, haven't verified my fuel pressure regulator modification worked to bump up pressure.

You'll find many people say "I changed such and such and it runs fine!" but more often than not, these are people who have not bothered to hook up some tools to the vehicle to make sure it's not running lean, which they almost invariably are.

I second this. TBI needs a tune with a better air cleaner and headers for christs sake

Honestly the only mileage your pulling out of that truck is to let it fart good, huff good, and remove resistance in it. A close to stock roller cam, stock ration roller rockers, intake, and exhaust will all benefit mileage but expect the needed tune.

 

[80' 427]

I am helping a buddy do a intake, cam and headers swap on a tbi 454. The cam will be a small speedpro 204/214 duration and the intake is a weiand Street warrior, and headers. It will be dynoed and tuned.

 

[dyeager535]

Doing a before/after dyno? Just curious what the before/after looks like.

Are they dyno tuning it, or actually taking it out and open road testing it? I've heard/read that dyno tuning doesn't get any of the low end/cruise stuff taken care of.

 

[Jester1]

This is why I started this as a pre advice thread. Thanks guys.

I always thought I could get and aftermarket plug and play chip for any mods I do, but I never thought about having the chip reprogramed with econ settings. I am still new to the computer controlled thing. I have a chip in my diesel that I have set to econ and have changed the tire size to make the speedo correct.... I guess I thought you could cange the facory chip out and program your own.

Anyway still considering at least intake and cam, and have been thinking about shorty headers to eliminate the heat sink that is cast exaust (farting better). Also want to get the wind in better with some cold air. Thats abiut it for the mods....

The while I am there list is just new replacement parts such as hi-volume oil pump, timing chain, minimal head work, new valves springs etc.. Make it breath better and reduce some friction. As far as exaust it came factory with 3" out the back and 2 1/2" off the flange so no need to change much there and wont change my bottom end tourqe values.

While we are talking dyno work and reprograming does anyone know what the cost average. It may be something I can look in to and see if it fits into budget. I would like to see the before and after as well '80 427, and know if there where any major issues to the computer with the work you are doing.

 

[dyeager535]

Unless there is a reason you can't run them, use long tube headers. I have yet to see a set of long tubes outperformed anywhere by short tubes, as long as they are properly sized.

You can tune these systems, but it's not a flash deal like the later PCM's.

I *think* I understand the MAP systems, but it's too bad Eaglemark hasn't chimed in. In any case, getting WOT right without getting "normal" conditions right means it could be running lean except when on the gas. A "plug and play" chip is pretty much a waste of money on these systems. (Jet, Hypertech)

I don't want to make tuning/engine mods out to be some massive problem...it CAN be, it just depends on the engine. Most people get away with it and don't see any problems.

But in the case of my Dad's 454, if he were lean at normal cruise (and he was), the ECM had enough "room" to compensate and bring it back into the 14.7:1 AFR range. BUT when towing a trailer (for instance), load increases drastically, and the ECM may run out of adjustment, meaning you are now lean with a load. Far worse than being lean with no load.

There is a fair bit more to it than that, but that's a basic, common example.

 

[Stomis]

Theres some knowledgeable guys here in the injection section but hands down the biggest TPI/TBI tuning website is thirdgen.org.

 

[80' 427]

Doing a before/after dyno? Just curious what the before/after looks like.

Are they dyno tuning it, or actually taking it out and open road testing it? I've heard/read that dyno tuning doesn't get any of the low end/cruise stuff taken care of.

No before. It is going to be a swap into a K10. Driveability can't be tuned on a dyno really. It does allow like driving a 60 under load. They will be dyno tuning it for power.

 

[black dawg]

My tbi 454 build for my burb was
stock 74 shortblock
oval port heads
performer intake
stock vortec cam with retrofit lifters.

The power increase over stock is very noticeable, especially above 3k.
It doesnt feel as strong down low (oval ports vs peanut ports??)

As far as the chip, This thing runs ok, but could really benefit from tuning.

It is too rich any time it is open loop, and lean while in closed loop. The computer is able to adjust BL to where it runs ok, but every so often at really light throttle there will be a slight lean sag. WOT is very rich.

 

[80' 427]

I think the reason it is better above 3k is that you go to WOT and it becomes richer. Low speed is off the chip, WOT is off of the fuel pressure.

 

[Jester1]

One thing that comes into play with carburators is altitude. Is the same true for a tbi? I understand that the computer counteract that through multiple engine readings, but your telling me I runs lean and black dawg is saying rich under throttle. And he is admitting to needing tune but we re at a constant 5000+ feet here and that is around town.

What part of Montana are you in black dawg?

 

[black dawg]

south of missoula. about 3500 ft.

 

[gotblazers]

I have nothing to add but just thought i'd say i'm glad to see the old girls gonna get running again. Good luck with it!

 

[Stomis]

One thing that comes into play with carburators is altitude. Is the same true for a tbi? I understand that the computer counteract that through multiple engine readings, but your telling me I runs lean and black dawg is saying rich under throttle. And he is admitting to needing tune but we re at a constant 5000+ feet here and that is around town.

What part of Montana are you in black dawg?

Shouldnt effect it. Especially since TBI is speed density.

 

[dyeager535]

I understand that the computer counteract that through multiple engine readings, but your telling me I runs lean and black dawg is saying rich under throttle.

Open loop doesn't mean just WOT. He didn't really clarify under what condition open loop, or any time it's open loop, which WOULD include WOT. Of course, WOT includes things like power enrichment (PE) which will add fuel and potentially more spark, so that skews things as well. All referenced off the volumetric efficiency(VE) on the PROM though.

On the big block setup my dad had, it went OL at idle as the O2 sensor cooled down.

It is odd that its rich during open loop, but that could be a function of the camshaft, although I assume the Vortec cam is pretty mild too.

 

[black dawg]

It is most rich right when you start it cold, smells rich, and will blow black smoke if you lightly blip the throttle. It is also an open loop idle prom, so idle is also rich. Sustained WOT is rich also, dont have a WB o2, but it smells very rich and shows over .980 on the scan tool.

Block learn had enough room that steady throttle conditions in closed loop are fine (145-150 BLM). Quick throttle transitions are good, no noticeable lean spots. It is the light throttle transition where the lean conditions are noticed, but they are very small, and usually completely gone when up to operating temp.

overall, I am pretty happy with it, 10-12mpg unloaded 10 loaded.

 

[dyeager535]

AFS-74 heated O2 sensor can help with the idle, I forgot the BBC setups were programmed open loop idle. Once changed to closed loop, and the heated O2 sensor, idle seems to clean up really well, although I will admit in my Dads setup, even open loop idle was not real bad.

Once we fixed the IAC (PO of the setup had monkeyed with the throttle stop, caused all sorts of stalling/surging issues) the truck ran very well on the surface. Without towing it would have been fine to leave as-is. We need to bump fuel pressure up more though, have run out of fueling adjustment at whatever the current fuel pressure is.

 

[Jester1]

I have nothing to add but just thought i'd say i'm glad to see the old girls gonna get running again. Good luck with it!

Hey Greg long time no chat. Have been slammed and will be for the next couple weeks but thanks for popping in. Job held up till monday so I am now looking for a travel trailer to live in for the next three weeks.

Anyway yeah, way to nice of a truck to let sit, and paid off so....

The bride says all systems go on the Blazer when the gold is rolling again. Shes worried I may work on the toy before I work on the work. Silly girls...

 

[Jester1]

First what is open loop? I am no computer guy but I am an electrician. Open loop means there is a switch in the normally open position (no power or signal passing) and what is in open loop? computer, O2, I am confused...

And just so I am not losing it. The upgrades planned intake and cam can be corrected by a reprogrammed chip or even a reprogrammed stock chip? Any ideas on cost? Has anybody actually written a check for this yet? Yes I will talk to local shops but if they tell me $1000.00 and nationally its $250.00 I am gonna drive my butt to some place else.

As far as the rest I was only thinking shortys cause of room and trying to tye them back it with the y pipe or are we talking dual exaust for the long headers?

And does the TBI have any ties to the cat? We dont need that crap here. So if you guys are talking dual I dont wanna nother cat. Do you need a second O2 or does it read both banks from the crossover pipe?