Mild TBI buildups please........

[cst70rocket]

I'm about to start an '87 TBI 355 build, and haven't done one before. I need to know just what you can get away with and it run well on a "chipped" computer. The PO said it had a crane cam that was comp. compatible, but it had to be small, no performance at all lol. So, if anyones got any info, let me know please.
Kirk

Oh yea, what all would be needed to be done for that tbi to run on a small block 400?

[Captkaos]

The big deal with TBI and cams is that the ECM uses a manifold absolute pressure (MAP) sensor and needs manifold vacuum that is within stock parameters so it will run properly. I would say that 360hp is about the max for a Stock TBI, but it will require some chip mods.

http://4wheeloffroad.com/howto/60118/

[Tx Firefighter]

In my 93 truck, I built a decent 355, but not a real powerhouse.

Edelbrock TBI intake, Edelbrock TBI cam, and full Edelbrock tubular exhaust from engine to rear bumper with a high flow converter. Stock heads and 350 throttle body. Stock type dished pistons for 8 point something to one compression ratio.

I used a stock PROM that my buddy at the dealership ordered for me. He found that the Mexican market trucks used a different PROM, with a supposedly hotter program. I needed a chip anyway, and they were all the same price, so we used it.

The truck ran real good and still got about 18 miles per gallon in a 93 extended cab 2WD, short bed with 3.42 rear gears and 4L60E auto trans. No driveability issues at all, and it passed Texas emission test.

[Russell]

I just put a fairly warmed up 355 into my 89 half ton.

Again, not a real powerhouse, but it has flat top pistons, mild cam of some sort (noticeable idle), stock intake, and throttle body, with stock TBI heads on top of it. Engine originally came out of a 73 Nova, and was rebuilt recently. It prefers to run on 89 octane, so its got a reasonably high compression ratio.

I put a stock 350 prom in it, and while it gets you down the road, it is far from running "well"

Anything below 1800 rpm (basically the range of the first VE table in the prom) is extremely rich, computer runs full enleanment in an attempt to correct it, but doesn't have enough adjustment room to correct the rich condition.

In open loop, the truck barely runs, stumbles bad, and puts black clouds outta the tailpipes, rich enough to make your eyes water if you walk behind the truck. Once it hits closed loop, it has enough adjustment ability to make it run a bit better, but it is still rich enough to give it a rough idle, with the occasional miss-fire.

Above 1800 RPM, the truck runs well, bit on the rich side, but far from excessive, until about 4500 RPM, where it starts to run a bit lean.

My vac at an idle is low too, only about 16 inches of mercury.

I just put the order in for a couple of chips, and a programmer, I am fairly confident that within the first two chips, I'll have the truck running twice as well. As it stands, it needs less fuel in the lower VE table range, more in the upper VE range. Also need to set it to idle higher, 500 rpm is too bumpy for it to be happy. Setting it at 750 - 800 rpm would be just about perfect.

After that, its just a matter of tweaking everything till the engine runs the best it can, then its time to sell it and do the same thing all over again with my 80's TPI, lol

[b454rat]

I built a 406 for my old truck that wan't really too radical. Typical rebuild, 30 over, turn crank/rods, but I used 5.7" rods, KB pistons, SpeedPro rings. I used Comp Cams Xtrme Energy 268, with basically stock but new lifters. Stock/rebuilt heads, stock intake, TBI, computer. Can't remember the headers I used, but they were shorty that went into a 3" y-pipe. I never had an engine light come on, no idle probs (sounded awesome at idle), didn't water your eyes, no black smoke. No probs whatsoever. Just touching the throttle from a dead stop would pull hard, more pedal, more pull. Would pull to about 4500, never had a tach, so can't be 100% on that. It was jsut an all around awesome motor. I regretted selling the truck, but got tired of doing body work. And it needed a trans. Something about 235k on a stock trans and a healthy motor....

[Warrens69GMC]

Hey rocket, heres some things to consider.
THE most important thing for the tbi motors is the heads. In all reality the 193's or equivalant casting heads is fine for a basic rebuild or a tow truck. They are swirl port and can be usefull if the swirl is cut out.
If you are looking for more peformance consider aftermarket heads. The gm manifolds for the tbi's have the canted center intake bolts. You can get aftermarket manifolds if you don't want to modify the center bolt holes to accept later model manifolds.
Gm used very basic cams for the TBI's usually(@.50, 180*or 181*) and even the "vortec" cam is only (@.050 191*) on the intake side. Gm has the 350 "ramjet" cam out into production (@.050, 194*intake , 204 exhaust)
and it is available cheap enough. If you want something bigger take the hint from gm from the TPI cars:some of the 350's had up to (@.050, 206*)on the intake. It is reasonably accepted that 210* is the easiest way to improve power while remaning a FI cam. However might require a chip change.
Also pick up the book "tpi and tbi peformance "
heres one of the books-
http://www.amazon.com/gp/product/188...lance&n=283155
gary

[Warrens69GMC]

After thinking it over, you can run a larger cam. You have to run a larger LSA (lobe seperation angle) for the cam to smooth the vacuum signal. If you run too large of cam, you would need to have the smaller vacuum signal programmed into the chip.
gary

[cst70rocket]

Thanks guys for all the help, the deal fell thru, so....... I'm in the market for something to build!
Kirk