TBI, Tune, Engine Mods, Boost!

**EagleMark** · 06-21-2013

Sorry I must have missed this post?

TBI may be ancient as far as EFI is concerned, but it's still viable. Newer systems are faster but the old system still changes things on it's own and they don't auto tune, they all make adjustments from feedback and can only do so much, they can't preform miracles.. I have a truck 10 years newer that does not get any better mileage, has more power but it's a different motor! Ten years newer same scenario... HP takes fuel, weight takes HP, nothing has changed except newer designed engines. EFI is faster and more complex... I don't have any problems tuning a built TBI engine, with the old ECM so it drives like a factory truck?

Or are you talking about the new aftermarket EFI systems? Ha! Wait till you try that one... there's nothing simple about Auto Tune except the way it's advertised!

Just depends on what you really want to do with your toy? I think this is your biggest concern? All the hours your working and only have a couple days off a month. Seems like you've been through hell already and still have no toy to drive when you get home?

The 91 EFI system for 4L80E is and easy change over to your 87. Biggest hurdle is PCM plug change, add tranny wiring, remove ESC for the knock and wire it to PCM as it handles knock now. Most of your present TBI EFI system is still used. This is not a big deal. Seriously if I had the truck and parts it's a half days work. You've never done it but are capable so... maybe a day? Changing the tranny and lines, cooler is way more work!

Do you really need a 4L80E? Do you really need a lot more HP TBI motor? If so, or if it's a want to your project they go good together without a HUGE project of LS transplant! Just because others guys do it and it can be done does not mean it has to?

HTH!

**k5nutt** · 06-22-2013

The 90 Jimmy is also a back up work truck so it has to be bullet proof as it can be and since i had a 700R4 go out on me in Shreveport LA i am rather gun shy. However i am willing to try a built bow tie overdrives unit since the miles on my 90 are unknown.

More power is needed to maintain 75/80 mph on the highway with a chalet or 4 wd poptop camper. Stock tbi motor wasn't getting it. So i think i'll go with a cam swap. Basically a plus 1 from stock as the one in my old chalet worked wonders. My web site i haven't done much with in years (blazerchalet.com).

**EagleMark** · 06-22-2013

Is the motor any good in blazer? If not get a Vortec head crate motor and I'll help pick one with cam, TBI intake, headers with dual exhaust and poof! 120 more HP and torque..

700R4 do wear out like all other auto trannys but 100k miles towing, hauling weight or pushing brick walls at 80 MPH can be done. My 90 Suburban has done all this and has 150k on it with good maintenance and factory tow package cooler, also has factory oil cooler and 3:73 gears, stock tires. Emtpy I cruise at 75 MPH but only 60 with a trailer, you can feel the brick wall parachute effect real bad at 65.

A 90 Blazer is about as aerodynamic as a brick without a chalet or poptop. 70 MPH is so much easier then 80. Gearing to tires is a main concern. I have no idea what a plus 1 cam is? Like an RV cam? Forget it, you can do so much better.

**k5nutt** · 06-23-2013

Actually the Jimmy's motor is in rather good shape. I think it was changed out before i got it but i haven't heard from the old owner in quite some time as he was following my progress on transforming her to my taste. She sat in a garage in Leadville Co. most of her life. Brought out for camping/fishing trips mostly.

Once i get the extra 9k to my ex on the first i owe for back alimony and the 3k monthly she gets i'll be able to save money to start into this project. However there is going to be a 30 day delay as i am getting set out on a 17k ft. Horizontal gamma logging job which i expect to take quite some time to complete. I can only bill them when the job is done or we hit 30 days....grrr. Such is life.

I'll do a bowtie overdrives stage 2 700R4 first and get my rock sliders along with a custom rear bumper on the way. Hopefully by then i can get a hold of my friend who has the cam card for the chalet so i can see what cam we used in her. If i do that small bump up in cam specs from factory specs i could add factory vortec heads with a gm intake to match the diff head angle for the intake and go from there. Should be a pretty good package. A long block from GM anymore price wise is getting retarded from years back. I think its 1700-1800 for a 290 hp tbi engine at the low end of the spectrum as a 1/2 ton 2 bolt block....

I'll have to look as i can't remeber if the Jimmy has the factory oil cooler option. My 79 K5 did which is basically the exact same set up Except...for the length of the brackets to the cooler it self....so i do plan to add that if it doesn't have one. And i have a few cooler fans somewhere they used in the 90-91 3/4 ton burbs with big blocks for tranny coolers....getting harder to find those. Not something i need but an interesting piece gm made.

Jimmy has 4.88's with air lockers and 35" tires.

So a vortec crate from uncle gm is a better route? I would assume that block is pre drilled for the roller lifter spider? And of course the value of the vortec heads which require the GM aftermarket tbi intake. We shall see how money pans out once the dust settles from getting the ex off my back and getting thru this next job and see which way is the best route. 120 hp is a pretty good number....of course we loose approx 20 percent between the trans and the right turn at the rear diff....lol. Getting excited to make a solid runner out of her and learning this voodoo they call tuning!

I appreciate all the time you have taken to answer my questions!

DW

**EagleMark** · 06-23-2013

I suggested a Vortec crate engine because I thought your engine was toast. Since yours is good, then no.... but you don't seem to have a budget so yes! New 383 340 HP 400 ft lbs tourque for about $5000.

Or just a cam in your engine with some more fuel pressure?

4:88s and 35 is a great combo.

**k5nutt** · 06-26-2013

The engine in the retired 79 K5 is toast due to whipple. The 90 Jimmy is in really good shape. I'd like to step up slightly in cam - install adj regulater....and let you handle the chip tweaking for right now....in the future... :0) i'll probably play a bit!

Prior to Whipple destruction i had to drive the 79 with 4.88's n 35's from Gilbert Az. to LA-PA-WV-TX-AR for work....combo worked well....coulda used more ponies but we got the job done!

DW