need some serious help!!!!!!!

[murderface]

Ok what I have is a 95 k2500 3/4 ton 4x4. I have done a major engine upgrade but now im having tuning issues.

The engine: 350 bored .40 over, vortec heads, edelbrock vortec intake #2116, comp cams 12-364-4, speed pro flat top pistons, polished and ported 50mm 454 tbi w/ 55lbs injectors & 18psi fuel spring, 155lt per hour fuel pump, msd super blaster coil, super conductor wires & pro billet distrib, acdelco R44LTS plugs...tbi is from spr performance and fuel pump and chip is from harrison performance...egr has been deleted.

Heres the problem, at low rpm engime runs great but when you step on the gas its acing like its not advancing or being starved for fuel. Base timing is at 10 degreese and there are no error codes right now.

If any of you guys have any ideas whats wrong or something im over looking please, im all ears!

[jim_in_dorris]

That combo is pushing 400 hp, you have no where near enough fuel. with 55 # injectors to fuel 390 hp you need 52 psi. You will lean melt that motor if you keep running it that way. At minimum you need 90# injectors running at 20 PSI.

[murderface]

Thank you. I will call the guy today who built the tbi for me and tell him that.

[cancritter]

lm only running 14 psi with my setup..runs great...to much gas?..would bump it down to 14 and give that a try

ps...am running 55s as well

has comp been tuned?

[murderface]

So we got one saying too much and one saying not enough. I called spr performance and they agree with not enough and are swappin tbi's with a 54mm w 90# injectors @30psi

[cancritter]

just stateing what mines running at and it runs fine...this a over the counter chip?not a big fan of those types of tunes...if your gona bump pressure your gona need to tune it again...starting to suspect theres nothing wrong with present tbi set up other than to much gas and bad tune...my engines a few steps ahead of yours and am running 14psi fine...this in itself would have me thinkin and wonderin...tune must be addressed with any change in psi

am running a 50mm extreme tbi

[murderface]

No I had brian at harris performance do the chip. Its not that its getting too much fuel its not getting enough, its running really lean. I donno this is my first build like this.

[1.721afr]

A: cancritter is right your mail-order tune is not likely to be successful.

B: Sean supplys good parts, he is not in the tuning business.

C: Your 350 only needs 600CFM at 6800 RPM, will you be shifting at 7000?


You would be best served by a 46mm TB with #17084327 injectors at about 32psi, that should cover the power that engine will make and more.

It will never run right until properly tuned.

[murderface]

Ok well so far im gettin my tbi swapped for a 54mm w/90# injectors@30 psi at no charge, now to get the chip tuned correctly is gonna be the hard part it seems like. Harris performance has been highly reccomended for the chip thats whyI used him, so whats the easiest way to get it tuned properly?

[1.721afr]

The bigger tb and injectors will just be harder to tune, you don't need them, but do as you please.

I'm inclined to let you and your "highly recommended tuner" figure this one out.

[murderface]

Yeah I feel like im getting the run around with this. Im holding off on changing the tbi and Im getting an aldl cable and trying that route out. There is almost too many things that could be the issue right now. One thing I never thought of is were running open headders right now but I donno. Im no mechanic by anymeans. And I want to thank all you guys for all your imput.

[Eagle-Mark]

A starter tune is fine but unless you can record some data and get it fine tuned you'll never be right. Talk to Dave at Old School EFI, he only does these this way.

Old School EFI

[cancritter]

westers is another tuner ..both my tunes have been bang on so have no prob recomending this tuner..lots here use his tunes...if you can find someone localy that dose both dyno and tune would be best bet

http://westersgarage.eidnet.org/

[murderface]

Thank you guys so much.

[Doober]

One word: Wideband. It will give you an idea what's going on with fuel, but I'm with the others, 18psi on 55lb. injectors probably isn't giving the engine the fuel it needs. I also say the engine isn't pushing 400hp with that cam, more like 340 tops... especially since it's a flat tappet cam. It will make for a fun little driver once it's all tuned though.

[Jameslleary]

Any updates on this?
I know I'm a little late, but you may want to upgrade to a TPI fuel pump, like they did in some of the TBI 454's.

[cancritter]

just rereading and notice your running a 155 ltr/hr pump....thinking that may be to low...lm running a 190 as a basic min for my engine..wondering if you should be running a 200+ one as most here do

[murderface]

a little update, were doing some data logs and we found a few other problems that were an easy fix. for the most part were gettin it tuned, the fuel trims are still a little too lean.