Basic TBI mod success

[Rusty Nail]

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[Catbox]

I have often wondered if there were any hope for more power from the TBI engine in my 1995 Suburban.
I always figured that I would simply just yard the whole thing out and replace it all with something more efficient.
Or sell the whole damn thing...

 

[bucket]

Do the spacers make much of a difference on the 454? I've been thinking about what Im going to do with mine and I think the simplest option to make some decent power from mine will be to ditch the TBI and go carb - I'd like to go injected, but the setups I like are just a little out of my price range at the moment

I can't say, as I've never owned a 454 TBI truck. But on 350's, 305's and even a 4.3 S-10, the spacer seemed to help in the upper RPM range.

To anyone with a TBI engine in fair condition, you don't have to drive a slug. I can't say it enough times here, advance the timing!!! The factory spec of 0° downright sucks. Then improve the intake and bolt in a decent set of longtube headers with decent exhaust. All of that combined will make a good improvement without investing too much.

Beyond that, it gets expensive because the heads and cam can't support any more.

 

[68post]

The heads really are not the restriction , it's the tiny 166* cam (and any part of the original factory exhaust), but you cannot use much more cam with the original computer.

The factory BBC TBI manifold adapter will let you use a regular 4 bbl manifold and not waste money on an exclusive TBI intake.

 

[Jppr26]

So seeing as my sbc 350 is all stock on my 87 v20 4 speed 4x4. I am planning to do exhaust and looking at heads, and possibly cam, and chip. I'm new to the GM 350 world and dont wanna break the bank or get crazy with it for my first time, kinda like sex no S&M full rebuilds just some foreplay to start, I'll get there

For starters can anyone ID this head cast, I cant find anything.

 

[Jppr26]

Cant seem to load a pic

 

[Rusty Nail]

The number is underneath the valve cover and you'll have to break that seal to find out. Valve cover gaskets are plenty cheap though.

 

[Overland Suburban]

I can't say, as I've never owned a 454 TBI truck. But on 350's, 305's and even a 4.3 S-10, the spacer seemed to help in the upper RPM range.

To anyone with a TBI engine in fair condition, you don't have to drive a slug. I can't say it enough times here, advance the timing!!! The factory spec of 0° downright sucks. Then improve the intake and bolt in a decent set of longtube headers with decent exhaust. All of that combined will make a good improvement without investing too much.

Beyond that, it gets expensive because the heads and cam can't support any more.

Makes a lot of sense! I'm going to just bump the timing up on my stock TBI engine and when I'm ready to spend any real dollars it's all going to go to something that isn't piece modded together.

As far as the TBI mod goes I have to wonder if most of the power gain didn't result from the rebuild of the unit rather than the actual mod.


Tracy

 

[Jppr26]

I need to replace the valve cover gaskets any way maybe I'll get some time this weekend to look in them

 

[Rusty Nail]

It's a 8 digit number? Nestled in between some rockers...not hard to determine.
I bet money you have #193s though. Very standard fare 87-95?
All kinds of great info regarding found in the links I posted.

 

[4WDKC]

To anyone with a TBI engine in fair condition, you don't have to drive a slug. I can't say it enough times here, advance the timing!!! The factory spec of 0° downright sucks. Then improve the intake and bolt in a decent set of longtube headers with decent exhaust. All of that combined will make a good improvement without investing too much.

Beyond that, it gets expensive because the heads and cam can't support any more.

I believe this is true on the later model tbi and the cars with roller cam engines but, the early model truck tbi engines are boat anchors and why gm changed the cam. The one in my truck was stock down to the paper air filter and smog pump, it reacted fine and moved the truck best it could with 342s and 33s but above 3k it just revved it never pulled any better. I advanced the timing and nothing made it better. IT wasn't until I found this that it made sense to me and why it was flat above 3k

4. The cam in the TBI engine is just plain AWFUL. Specs on Stock TBI cam is .050″ tappet lift (intake/exhaust) is 165/175; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is .382/.402. I got those specs right off the Jegs website selling the new GM replacement TBI crate engines.

then look that up here 350/8 = 43.75 CID per cylinder and you can see how terrible that cam really is.

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IMHO unless you are going to change the heads and cam I wouldn't waste any money on performance parts as you see they arent going to help that much with that cam. Save your money for heads and cam or ls swap.

 

[bucket]

I believe this is true on the later model tbi and the cars with roller cam engines but, the early model truck tbi engines are boat anchors and why gm changed the cam. The one in my truck was stock down to the paper air filter and smog pump, it reacted fine and moved the truck best it could with 342s and 33s but above 3k it just revved it never pulled any better. I advanced the timing and nothing made it better. IT wasn't until I found this that it made sense to me and why it was flat above 3k



then look that up here 350/8 = 43.75 CID per cylinder and you can see how terrible that cam really is.

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IMHO unless you are going to change the heads and cam I wouldn't waste any money on performance parts as you see they arent going to help that much with that cam. Save your money for heads and cam or ls swap.

Mine have mostly been early models, '88-'91 with no roller cams. They have all responded just as well as my '92 Camaro with roller cam.

Intake mods are very cheap. Timing is literally free. The exhaust is usually falling off with cracked manifolds due to age, so spending money on the exhaust often has to be done anyway when you buy one.

It's worth doing a little tinkering on them, because it goes a long way. It's not much work to get improved power, mpg and driveability.

 

[Jppr26]

Just pulled a valve cover has the 191 heads

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[jake wells]

watch out on the early throttle body's specially the 454 units they are bad about eating the throttle shaft bushings.

 

[68post]

Just pulled a valve cover has the 191 heads

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Swirl port heads, same as '193 heads. More torque off idle than any other heads GM made ('193 & '191 - same). Less ignition advance needed than any other head also, because of the swirl vane creating so much mixture motion.