Building a 350 for my 92

Hello everyone.

I have been around Toyota engines my entire life and have just recently stepped into the small block Chevy world.

I have a 1992 Buick Roadmaster with the TBI 350.

I have a spare TBI 350 out of another Roadmaster that I picked up cheap. I would like to build that engine to make decent power. Here are my plans;

Heads: Vortec heads from a 96+ truck.

Fuel Pump: 155lph direct swap fuel pump.

Cam: Summit Racing 14097395

Chip/Tuning: I guess ill need a chip??

Exhaust: Headers with a free flowing 2.5" or 3" exhaust. Which headers?

Ignition: Stock truck distributor.

Air Cleaner: I was going to run the 4.9L Cadillac TBI hat with a cone filter.

Throttle Body: Do the "ULTIMATE MOD"

Fuel: Upping fuel pressure to 18psi with spring.

Intake Manifold: Edelbrock 2116 with carb-to-TBI plate.

Transmission: Corvette servo and shift kit.

If you could please take a look and critique my list of planned modifications that would be great.

Buy a decent converter and rear gears.

Sounds like someone has been doing some reading on Harris TBI Performance page. Second the gears comment. IMO its the best seat of the pants feel upgrade.

While I have no doubts that rear gears make a nice improvement, I'm quite happy with my 3.23's and posi.

I'd like to swap to the S-10 converter however.

I already have the new motor torn down to the rotating assembly. I'd like to start building it up.

You'll definitely want to do gears and a converter to make that thing feel fast. 4.10s would be nice.

You can get Summit G-9001 headers that fit pretty much drop in (just remove your frame braces). They have ceramic coated versions too.

2.5 inch exhaust will be plenty. 3" is fine, but overkill for the power that will make. Another caveat with these cars: you'll need to remove the intake and distributor (and install them) as a single unit because of the cowl. The stock B-body intake has an oval-ish hole to clear the deep cowl.

Otherwise, enjoy. Sounds like it'll be neat.

I'm sure 4.10's would wake things up but I really like the highway mpg.
Thanks for the tip about the Summit G-9001!
I'm going with 2.5" exhaust. That should be perfect.
As far as the intake and distributor goes, I shpuld be ok since I'm installing the engine as a whole.

Thanks for the help!!

Fair enough. I usually got like 20-22mpg highway or so with my 350/3.23s back in the day when I kept it to the speed limits.

Yeah my best ever is 24mpg!

You can bore the hole for the distributor out to fit the OEM distributor, and retain the ability to remove it without removing the intake manifold. I did this to fit the distributor under the cowl on my 454 swap. The 454 is much taller than the 350, and I still must remove the manifold to get the distributor out, but it fits under the cowl, and a standard distributor would not fit under the cowl. I measured the diameter of the distributor base, and the diameter of the hole, then divided the difference by two. I used that figure with a compass, or calipers, and scribed a line around the circumference of the hole. Once I had the line scribed, I used a sanding drum on a drill to open the hole to the scribed line. The hole is round, just larger to allow you to tilt the distributor to remove it.

You can get a FiTech TBI system that will out perform even the TBI from the 454. It bolts directly onto the four BBL manifold with no adapter. You may need to use a Walbro 255 fuel pump to feed it.

I would not use 18 psi for fuel pressure. You only need to size your injectors properly. If you are going to use a 2 BBL TBI, get a set of fuel lines from a 91-93 Fleetwood, it will have a Schrader port on it so you can check your fuel pressure

Make sure you have the proper adapter for the trans cable if you are using a TBI from another engine, or the FiTech units. The specs are important, and if you get them wrong, you can ruin your trans.

Finding good Vortec heads may get interesting. They are, more often than not, cracked. I have pulled  4 heads, and 3 of them are cracked. If you can not find good ones, a good aftermarket one is an option. If you pull a pair of Vortec heads, immediately take them to a machine shop, and have them checked.

Fred,

I was waiting to hear your response on this topic.

Perhaps boring out the intake manifold would be best. It would be nice to have the ability to remove the distributor if need be.

I saw the FiTech EFI system, but at $800 it is beyond my budget. I think the factory TBI unit bored out and more fuel will be more than enough to feed this engine.

I appreciate the tip about the Cadillac lines. I will add that to my list of things to hunt for at the junkyard. You suggested not running 18psi of fuel pressure, what would you recommend to run as far as fuel goes?

I actually have a set of 906 Vortec heads I already pulled from the junkyard. I have been meaning to get them down to the machine shop for a few weeks now but his hours are horrendous. I hope to be able to take them down there sometime around Easter.

One other thing, with this Edelbrock 2116 intake manifold, I will lose my EGR setup won't I?

From what I gather, I can have a chip made to not only fully support this engine, but I can have the ECU not ever actuate the EGR. Correct?

The engine will not know if the EGR system is there or not. The intake manifold description states that it does not have EGR, and probably needs a port for the vapor recovery canister and PVC valve as well. The chip may be able to eliminate the EGR. You can get a TBI that is already bored out to 52mm from a TBI 454. You must bore the adapter and or manifold to match the size of the TBI, or the air will "trip" over the ledge it creates. This creates turbulence, and severely reduces the flow into the plenum. The 52mm TBI may be too big for the HP you are creating as well. A 52mm from the 454 may have a different blade shaft, and may need your old one to replace it, so you have the proper linkage attachment points.

Approximately how much HP are you going to make? You need about 1.7 times the HP in CFM for the TBI. If you have a lot more, you are wasting it, and can actually have less power. On that note, if you have an exhaust that is too big, it will rob your low end torque. My 454 only needs a 2.5 inch pipe.

Increasing the fuel pressure does make the injectors act like larger ones, but the computer needs to know what the size and pressure are, so that it can properly meter the fuel. I do not know if the computer can compensate for the higher pressure and smaller injector.

I may have the same intake for use on an upgrade for my 92 OCC. I am going to use an L99 cam, and a 42mm TBI. With that setup and shorty headers I believe I get about 250 HP. I bought a 1 inch spacer/adapter for the TBI. The bracket for the linkage must have a spacer under it to match the one under the TBI to align the cables. Remember to reset the trans cable for the new layout. You may want to make a brace from the cable bracket to the top of the TBI adapter to stabilize the cable bracket, because of the standoff flexibility.

I got a carb hat from Spectre #98499 It flows enough for about 300-350 HP, and will fit under the hood. You must also get an aircleaner that flows enough for the HP requirements. I had a Caddy hat, on my 91, and they tend to distort, as well as they need to be reworked on the inside. They may also not flow enough for your engine needs. When I removed it, the nut had welded itself to the shaft, and was extremely difficult to get off. It requires a specifically bent threaded shaft to install. If you are still going to use the vapor recovery system, you can move the canister behind the left side of the bumper with the bracket from a 94-96 right side (mirror image location). Make an airbox and put the filter where the canister was. I put a filter on the end of the line, and disconnected the vapor recovery system on my 454, but you could still use it with the OEM computer. The lines and connector wires need to be lengthened a little. Make sure you put it far enough forward so that the canister does not hit the wheelhouse extension.

I also got the electric fans with brackets from a 93 Fleetwood, and installed them with a relay for each. They should both turn on when the engine is started, so I wired the solenoids to a red and black wire that is powered when the key is in bulb check, start and run. I ran 2 fused 12 gauge wires from the red connector block to the relays, and then to a connector that matches the one from the Cadillac. The fans are a bolt in, although I removed the hose hooks from the lower mounting bracket to clean up the installation.

If you want to run a larger alternator, you can get the alternator bracket from a 93 Fleetwood, or a 9C1. Always connect the braces to the alternator and A/C compressor brackets, because they are cast aluminum, and will crack from flexing, and vibrations. I made some custom braces from 1/2 inch stainless tubing. It took a little experimenting and bending to get them to fit, but the braces are necessary. A stud for the exhaust bolt and an extra nut will secure it on that end. I also bought some locking header bolts "Proform 66753" to keep maintenance down. You must tighten them to 28 ft.lbs. to activate the lock feature.

I probably have more hints and kinks, but need specific prodding to access them.

Yep... learned that lesson about the braces the hard way. They can and will crack.... lol

Fred,

Won't I have a check engine light on if I remove the EGR system? What is the vapor recovery canister? The charcoal canister? Doesn't the PCV plug into the TBI unit? I can't remember. If it does indeed run into the manifold, couldn't I just use a small breather filter in its place?

As far as air intake volume goes, I think the factory TBI unit bored out will be able to provide this engine with enough volume to support it.

I am hoping to be somewhere in the 270ish range for horsepower. I don't need a 9 second drag car, I just want something with a little more oomph.

As far as exhaust pipe size goes, I only want to run 2.5" piping. Will make things easier to fit under the car as well.

From what I understand, the computer should be able to handle an increase in fuel pressure without any issues.

Good call about the linkage spacer! I'll also look into how to set the throttle valve cable, and I will see about making a brace.

Good call about the Spectre intake, I'll add that to my list of mods. Why does the vapor recovery system need to be moved? This engine will physically be the same size as the old 350.

I don't plan on running electric fans, I like the simplicity and reliability of a mechanical fan.

I am planning on keeping the factory setup on the alternator, A/C and power steering. I will be deleting the air pump and related components.

PCV does plug into the TBI.

2.5" pipe is fine - you can even buy the intermediate pipes from Summit or Jegs for a 94-96 Impala in 2.5 stainelss for a good price, and you're right - it will be much easier. You'll also need to modify your transmission crossmember for the duals (or get a 94-96 car crossmember from the junkyard and bolt it in)

You can just tune the EGR out when you send the chip in for programming (or program it yourself, whichever you choose). I think that's what Fred was alluding to. If you don't tune it out, you'll have a CEL.

I have a set of 2.25 inch exhaust pipes, and they should be sufficient for 270 HP. I modified the original cross member, because it is tubular, and much lighter than a 94-96. The left pipe for the 94-95 runs close to the transmission and exits close to the drive shaft. If you modify the OEM one, you can run the pipe almost mirror image to the right pipe. If I were to do it again, I would relief the driver's side floor about a half inch for better ground and body clearance. The 94-96 cross member mounts differently than the OEM one. I bought an OEM one from the junk yard, and an 18 inch piece of another one, then welded a channel part of the section to the top of the donor piece, then cut the bottom out, and sealed the open holes with more scrap (specs on request). Make sure that the transmission is in 1st gear when installing the left pipe, because the shifter linkage is at its lowest point, and you do not want it to interfere with the pipe. You should put a heat shield along the wiring in the shifter linkage pivot as well. Headers get really hot. Another spot to put a heat shield is over the upper joint for the steering intermediate shaft. It is close to the header, and the boot will quickly deteriorate.

The vapor canister is the charcoal canister. The reason for moving it is to make room for the air cleaner, and a box to keep it dry. The conical air cleaner at the end of the hose needs a larger space in that area than the OEM type in the toaster.

Are you going to do the intake bore yourself, or send it out? It is probably cheaper and easier to get a properly sized unit, and sell yours. I do not know all of the sizes available, but the 42 or up to a 45 mm should be sufficient. You do not have to modify it at those sizes. I use basically the same technique to enlarge the intake as the distributor hole, just make sure you get all of the aluminum/plastic dust out of any intake parts.

That 270hp figure is only an educated guess. For all I know, it might make 230.

As far as exhaust goes, I think 2.5" will be sufficient. Good to know about putting the trans in first gear for clearance. I will be sure to use heat shields on all the wiring and the steering shaft joint.

Is the charcoal canister necessary? If I remove it, will the vehicle throw a check engine light?

As far as the TBI unit goes, I am not planning on necessarily boring it out, but just polishing it and removing the rough edges. I would think the factory one is large enough to support the power.

The factory TBI will probably work, but it is barely big enough to supply the stock 350. If you smooth and polish it, that should give you better airflow. You should put slightly larger injectors in it, possibly the ones from a 9C1, because you need more fuel.

If you can retain the canister, it will make the upgrade easier. The fuel system maintains a small amount of pressure, and it needs that to calibrate properly. Moving the canister is easy. It may not throw a CEL, but it will affect the fuel system similar to the issues when you remove the PCV system.

I used the stock fuel pump, and the stock fuel pressure with the L99 cam, shorty headers, and 42mm TBI with 9C1 injectors.

The Vortec heads will get you a substantial increase in HP by themselves. You need to port/gasket match the heads and intake manifold. Any lip on the head side, or the manifold side of the gasket will cause the air to trip, and become turbulent. Align the gasket with the bolt holes on the manifold, and check for metal showing around the inside of the gasket. Then align the gasket on the head, and look for the same amount of metal showing around the gasket. If they are different, grind metal off of the head port to make them match, or show slightly less metal on the head side. You can gain substantial HP by keeping the flow smooth. You can even make the head port match the gasket, as long as the intake runner is smaller than the gasket. If the gasket hides any portion of the intake runner, you must cut the gasket so it is even, or shows a sliver of metal, and work the head to match. The way to guarantee it is right is to make both ports the same as the gasket...this is called a gasket match. Do this before mounting them on the engine. The heads can get you about 30 HP, and if you do not gasket match it can cost you almost as much.

Stock HP 180. Headers give you about 25 HP, the heads 30 HP, better intake manifold ??, cam HP?? torque??. Not enough fuel/air -??. The cam you are using is supposed to give more HP and torque than a stock LT1 cam. I would suspect you will be at least in the 270 HP range, unless it is starved for fuel/air. You need about 500 CFM to run the engine at 270 HP. The stock TBI is 40mm. I picked up a 42mm and was successful with it. I used a second gasket under the injector tower, but had to modify the opening for the fuel line connectors. I also have an adjustable fuel pressure regulator. The adjustable fuel pressure regulator needs the screw shortened because it can not be adjusted when the TBI is installed.

The 42mm TBI unit and 9C1 injectors sounds like the best setup. I did some searching but was only able to find the 46mm TBI and the 50mm TBI units. I could not locate a 42mm TBI unit.

I will retain the canister, sounds like the easiest way to do things.

I appreciate the heads up on matching the heads/gasket/intake manifold. I will make sure I do so!

How do you know where to set your fuel pressure to? I do not really have much, if any experience with tuning TBI.

The 46 mm unit would be a good one to use. I believe you may need that amount of airflow for the HP you are going to produce. You may be able to use it without doing all of the mods. I would still put a second gasket under the injector tower to open it up.

I used the original pressure, but if the engine tends to die at some point in the rpm range (falls on its face), you probably need more fuel. You can increase the pressure until it is strong in that range. Without specialty equipment to test it, that is the best way to determine the proper fuel pressure. The other way is to calculate the necessary amount of fuel, and adjust the pressure for the set of injectors you have to give you the flow necessary. A little extra maximum fuel flow is good. The guy at Harris Performance did some of the numbers, so check with his website, and interpolate what you need. He also suggested a stronger pump, and that makes a lot of sense. Remember to open up the adapter so that there is no ridge under the TBI.

Why not use the 454 TBI? You need programming anyways.

The 454 is too large for his output, and according to Harris Performance it will cause idle issues on a 350.

I will be sure to do some more research on Harris Performance's site, that guy, like you, is a wealth of knowledge.

Is there any way I could get away with just smoothing over the factory 350 TBI unit? I am trying to keep this as budget as possible.

You can smooth it, but I believe you will not get enough air for the engine with the stock unit no matter what you do to it.

The more I read the more I believe you are correct. A 46mm unit looks like the way to go.