Difference b/twn SCPI and MPI ????

[Busted Knuckles]

I've got a 96 Tahoe 4dr. with a heavily used 190k. on the 5.7 .
Pulling over a 2 ton load off road up a 30* slope with no worries . The mileage has dropped drastically (18-19mpg.(after the add-ons below) is now down to 12/14mpg.) I pulled the engine not long after I got the Tahoe March 09' and installed new oil pump , single row roller timing set , gaskets and a major sludge flush . I've got a Fram Washable air filter,MSD. Hot Coil ,MSD 40-50ohm/ft. wires, Bosch Plat +2plugs , alll new O2 sensors , Magna Flow 2 into 1 (2.5"/3") 3.42/Tru-Trac , Good Year Rangler Authority 10 ply tires (run at 75psi.) . The mileage took a crap after the tires . But I noticed this winter at around 0*- -10*f. I heard piston slap for about 2-3 min after start up . At start up , oil pressure is 45-50 psi. ; after it's warm it idles around 25-30psi and on the road runs 45-50 psi. not bad for 190k. .
I've been hearing bad exhaust leaks lately , I found out Tuesday that the Cat. Converter was split away from the rear flange so a Magnaflow S/Steel is on it's way .
I'm considering upgrading the Inj. Spider from the OEM SCPI to the MFI system . Is there any noticeable gains as far as mileage or performance ?
What else am I missing , Cam ? Something mild coming in around 1500-1800
Thanks ,
Steve


http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=290462830517+&viewitem=

 

[SunlitComet]

At age 15 and 190,000 miles change it before it starts to fail real bad like mine did before I bought it. It had two cylinder misfires and looked to wash down the same two cylinders. After it was done it purred like my cats.

 

[Busted Knuckles]

I see your 96' has the MFI Conversion . Any Gains in mileage / performance ?
How about the PCM any changes to it needed ?

 

[19Yukon97]

Im also about to do this swap. should have done it when i had the upper intake manifold taken apart.... but neways. I heard and saw on some websites that the upgrade gives you gains of maybe 1-2 mpgss. Overall teh motor should run better.

 

[SunlitComet]

Part is a direct replacement it just looks and operates different. No pcm change needed but if you had codes before you started the change wipe them out before you start the engine the first time with just the ignition on. That way the truck gets a clean trouble free startup and see if anything new crops up. I have not even put 5 gallons in my tank yet since doing the upgrade been doing alot of stuff to it and am a week (if I can get $300 in the next two days) away from being able to get it back on the road. It may be a few more weeks.Once I do I will mate my laptop to the truck again and do a 60 mile highway run. and let my software do some math for me and report back here.

---------- Post added at 02:34 PM ---------- Previous post was at 02:30 PM ----------

It did get rid of a big misfire on multiple cylinders and got me a smog cert. When I bought it I was afraid I was going to have to tear out the cylinder heads because a shop said the the compression in the same two cylinders were at 140psi. Not sure how true it is yet.

 

[Busted Knuckles]

Good luck on the "Mother Run"..........
140 psi.???? Carbon Build-up ? Can you try Sea Foam . An old trick on "carbed" engines was to slowly pour some ATF. down the bores with the engine at about 2500rpm.+ . Great Smoke show , kinda like a James Bond Smoke Screen . It'll bust up the carbon , and piss off the neighbors too , overall ,,,, a great time !!!!!!!!!!!!!!! .
I have no way other than disconnecting the battery to wipe codes (if that will even work?) . I don't have a check engine light on or any real driveability probs. other than the sucked up gas mileage (pun intended), and the light miss .I'm waiting for a buddy to buy my 454/400 then I'll have the "clams" to shell out for the spider , hopefully next week get it ordered and get the gaskets etc. next month . Besides mileage how are the overall power gains?
I just put a Magnaflow front exhaust on it last week (OEM "Cat-Box" on the right bank ripped away from the flange) damn near $400.00 right there . If it one thing it's another , right ? I guess our rigs will never "really" be done . And if they do get "done" we sell em' and start over , NO WORRIES,,,, Just another case for "Divorce Court" !

 

[SunlitComet]

140 from carbon build up? Really? Those two were adjacent to each other. They also said the other six were about 170-172. Thoughts now?

Thought about sea-foaming but this truck is my ticket to getting back to work after two years. If something goes wrong I am screwed. Unless there is a definitive answer that it can do no harm and only good I am going to have to say no.Besides I don't have a HD cam to record it.

Killing the battery will do the same.

Power gains? It better obviously better. but have not timed a 0-60 time yet. It is much better than A 2005 ford escape with a v6 and mine is much heavier. There is a dyno shop locally so when I have a cheese(I love Dairy) bill I want to get it checked with three pulls before I start doing engine performance add-on's.