Thread: 1990 chey pick up 4x4

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new here ya'll.
I have a problem with my truck hope you can help with.
Like i said it is a 90 chevy 4x4, we built a new motor for it which runs great, it is a .30 over 350 roller motor with vortec heads, mild cam (power comes in about 1500 rpm) headers, we used a duel plane perfomer intake with a TBI adaptor plate to retain the TBI fuel sysytem, and a turbo 400 trans, it has a new fuel pump and filter also, timing is set perfect.
The problem I am having is from a dead stop it will not take off with out stumbling you must feather the gas pedal until about 1100- 1200 rpms then she kicks in and runs great, any heilp would be appreaited.
Thanks all

camshaft probably is not computer friendly/ will probably need a new chip

It sounds to me like your new engine breathes better than stock, and you're short of fuel in the transition from idle to the load point, and may be running lean at power. Like Matt167 says, if you're running the stock ECM you're probably going to have to get it tweaked, ideally with a dyno run and wide range O2 sensor to know what the fuel is doing across your load range.

I think I would check the tps adjustment that is the accelerator pump of an efi sys. then check the base gasket they are notorious for failing.......ted

with the TBI you can not run a big cam you must have good idle a round 500 rpm and good VAC if not if may idle like a top fuel digger .from all i know and i have talk to many the MAP just can not work right with much of any size cam over stock cam. i did the same build over a year ago for a 350 roller with vortec heads. i seen guys try to use the TPI 350 cam and that would not work right. so i had Erson grind a roller cam i built some 4.3 TBI s they just will not take any cam .i do not know of any one that can trick the map and make computer work good

Try this link:

www.TBICHIPS.com

Get in touch with them and I think they could help you.

cams he listed are small so they can work with you engine look at the list he has. if you have your numbers of your cam see how they match up .if yours is bigger then whats listed a chip s just is not going to work . thats from a GM trouble shooter thats played with them . if you get a chip and you can trick the MAP please let me know how it works i seen alot try.... good luck

Pat-not to be indifferent,but Davide Vizard,Lingerfelter performance,Edelbrock,Holley,Accel,all have built roller hyro cam'ed over 500" lift engines on a mod'ed TBI.

ok ? it the 500 lift thats is not going to get you a trouble . you still have to trick the map ?? .you can bolt a carb on it to . all i am saying is the STOCK TBI will not take a big cam you know were the lc and 050 numbers .he ask whats wrong i said it will not take much cam . a chip may not help if the cam is way off. yep and i built TBI roller cam. ERSON cam ground a custom roller for me on this build .on the vin code letter on some of the TBI in trucks that need to idle at a very low idle like under 600 rpm from what i have been told there not much help with them .so i was not going to ram heads with Erson cam and some other guys i ask . so he better know what he has. i know a guy that pick up a crate tpi engine for his truck good deal ... i rebuilt his old engine as the tpi cam would not work. very poor idle blowing black smoke out the pipes. the TBI it self can work but how much after market parts is he going to need to make it work?? any way he go,s i still like to know how it works. i know what your telling me .all i saying is i done TBI.s the guys i built engines for did not want to buy after market parts so i used smaller cams that work

OK Pat.Lets see what he posts for the cam numbers.

you can convert to 86 till92 corvette maf sys but you have to change almost everything like the computer wiring harness and ad the mas airflow sensor and there are some co. that still make air density sys but they have drivability problems.....ted

There are some "TBI" cams and " Computer " cams available. but the dururations are what are special. however they will still need a chip program, and there still very mild...

a good example of what happens if you use the wrong... friend of mine in my high school autoshop class, swapped in a newly re ringed/ bearingd Vortech 350 into a '95 K1500 short bed step side.. He put on the TBI heads to avoid getting a new intake, and even tho I warned him about the cam choice. he put in a " Performance 3000 " camshaft.. it's a camshaft that Napa marks as OEM compatible for many carb'd 350 powered vehicles, I don't remember the dururation but it's 112" LSA I think. .442" lift IIRC.... truck sounded awsome.. problem tho, was it ran massivly rich and flooded/ destroyed 2 cats. and it would not spin the tires. just bogged down.. I don't know what he ever did with the truck..

Originally Posted by Matt167

There are some "TBI" cams and " Computer " cams available. but the dururations are what are special. however they will still need a chip program, and there still very mild...

a good example of what happens if you use the wrong... friend of mine in my high school autoshop class, swapped in a newly re ringed/ bearingd Vortech 350 into a '95 K1500 short bed step side.. He put on the TBI heads to avoid getting a new intake, and even tho I warned him about the cam choice. he put in a " Performance 3000 " camshaft.. it's a camshaft that Napa marks as OEM compatible for many carb'd 350 powered vehicles, I don't remember the dururation but it's 112" LSA I think. .442" lift IIRC.... truck sounded awsome.. problem tho, was it ran massivly rich and flooded/ destroyed 2 cats. and it would not spin the tires. just bogged down.. I don't know what he ever did with the truck..

well yes that what i said tpi cam will not work and many other will not i knew that on my last 350 build for my customer had a cam ground with one of ersons very small master with not alot of dur the 112 will not hurt its the dur and small lsa .i knew guys that used the hotter GM cams that plane would not work .... .i know abit about this as the cams were made in baycity GM and some how they were getting in some TBI engines and did not work very well. the MAP will not take the cam know if any one can tell me i am all ears i built my 4.3 bore it deck it did some bowl work to the heads back angled the ex valves used zz3 spring 1.6 harland rollers rocker .1 ich spacer .K&N fillter with edlebrock headers with stock roller cam just more lift with using the 1.6 at the time there was hotter marine cams but i knew guys were stuffing bigger cams in the TBI engines and just could not get them to run .i did put a chip in my 4.3 it ran good with it but the chip went bad. i put the stock chip back in. it ran about as good .it ran vey good for a 4.3 tbi

Originally Posted by pat mccarthy

well yes that what i said tpi cam will not work and many other will not i knew that on my last 350 build for my customer had a cam ground with one of ersons very small master with not alot of dur the 112 will not hurt its the dur and small lsa .i knew guys that used the hotter GM cams that plane would not work .... .i know abit about this as the cams were made in baycity GM and some how they were getting in some TBI engines and did not work very well. the MAP will not take the cam know if any one can tell me i am all ears i built my 4.3 bore it deck it did some bowl work to the heads back angled the ex valves used zz3 spring 1.6 harland rollers rocker .1 ich spacer .K&N fillter with edlebrock headers with stock roller cam just more lift with using the 1.6 at the time there was hotter marine cams but i knew guys were stuffing bigger cams in the TBI engines and just could not get them to run .i did put a chip in my 4.3 it ran good with it but the chip went bad. i put the stock chip back in. it ran about as good .it ran vey good for a 4.3 tbi

Pat,I would think you know about these already.Next time you do up a 4.3,might want to do this:

http://www.speedomotive.com/ps-502-8...crank-kit.aspx

I am coming up with a MAP answer for ya.

Still the O/P hasn't listed his cam numbers yet.So i am guessing what his issue is still.

Originally Posted by 1gary

Pat,I would think you know about these already.Next time you do up a 4.3,might want to do this:

http://www.speedomotive.com/ps-502-8...crank-kit.aspx

I am coming up with a MAP answer for ya.

Still the O/P hasn't listed his cam numbers yet.So i am guessing what his issue is still.

i did my 4.3 back in 2000. there were 90 cranks made back then but $$$$