Chevy 366: Thoughts on Throttle Body Injection

[paddywagon]

I have a Gillig-bodied '67 Chevrolet chassis with a 366 motor. It's fitting with a Holley 4150. I am not looking for power gains, just good drivability with minimal fussing. What intrigues me about throttle body injection (TBI) is good performance in all weather conditions and potentially less tuning and maintenance than a carburetor. Plus, a rev limit can be programed in which is nice for these industrial engines.



Can anyone here shed some light and share any experience with converting to TBI?

[peteg59]

Not sure if TBI was ever an option on the 366?, and it would be difficult to convert a stock 4 barrel intake to a TBI 2 barrel with an "adapter", with all of the required sensors, along with a computer.


Holley does make a fuel injection setup for the GM big block, but it is not cheap!

That's about the only way I know of to get the modern fuel delivery on a vintage engine.

You could always go full bore and drop in an LS style engine with all of the latest and greatest injection tech.
Then, your choices in fuel delivery, performance tuning, etc., would all be within your control...

[BeNimble]

I converted my 1959 Case 530 backhoe to TBI, gotta be the only one in the world.
I used a Prius throttle so it could be controlled electronically to maintain rpm under different loads, the injector was from a Geo Metro TBI, matched about 50hp in the backhoe.

You can get by with very little in the way of sensors. The early toyota EFI in my 89 Tercel was very basic. Water temp, Throttle position, Intake vacuum, o2 sensor. I was going to put a Speeduino on the 2.5 V6 in my MX-3, but sold it before that project was done and it seems to work fine with the 1.8 V6 computer, which is most full throttle anyway.
But that is a really cheap and simple way to DIY a solution. The old GM computers can be hacked into fairly easily as I understand, never done it myself, but you could probably adapt an older TBI from a bigger V8 from the early 90's without even hacking into one.

[JamesKS]

FiTech is a well known name for aftermarket EFI. They are typically simple, minimal tuning and most kits are around $1k.

[CHEESE_WAGON]

Hardly worth the effort IMO... Yes, there are cold-weather benefits, but that's what mixture / idle screws and choke plates are for... Most folks that aren't used to carburetors don't understand that most need at least 2-3 pumps of the accelerator before starting with the choke closed or near closed, or one last good hard shove of the accelerator to the floor to set electric choke before most carb'd gassers will even try to start below about 35-40.

Even on an Olds Cutlass I had with a brand-new replacement Q-jet, that car would flat refuse to start without at least 3-4 pumps of the accelerator, cold weather or not. Pump the accelerator 3-4 times and it fired on the first try. I suspect OP has carb or tuning issues, I really would recommend exploring replacement or rebuild options before going to all the trouble to convert to TBI...


You might be able to adapt a late-model factory GM system, the 454 (7.4L) used it from around 1992-2000 or possibly later. These used the tach signal to control the injector pulses, but they used a 2-injector setup. A 366 doesn't need as much air and is similarly limited RPM wise, so I suppose it could work - GM's factory TBI systems were fairly low pressure, not much more than a carburetor.

I've heard that a later 427/454 HEI dizzy's innards can be swapped from the tall deck's housing and shaft assembly to convert to HEI, that's basically the heartbeat of such a system, so who knows. I still say some troubleshooting is in order to see if the carb is out of whack.

[Jolly Roger bus 223]

Originally Posted by JamesKS

FiTech is a well known name for aftermarket EFI. They are typically simple, minimal tuning and most kits are around $1k.

yes FiTECH is an option and self tuning.
the one i researched for my old ford 460 with no computer. IT was 900,came with everything except the bungs to weld in the exhaust for the 02 sensor but would have had to buy an second sensor and wiring because i have true dual exhaust and it needs to read both sides to keep each bank happy or mixed but mine dont mix.
also self tuning.
i decided to find and rebuild a holley 750 for a total of 300 and a distributor upgrade which was simple enough. and havent thought twice about it.
am happy with my decisions because if i have fuel problems its simple enough to pop the hood a figure the issue out within a few minutes with minimum tools.
no guessing if it was a sensor or a burnt wire or anything like that just straight forward fuel fire or compression.
i will rebuild something old school before ever trying to add a computer to it.
well my personal stuff anyway.
a dizzy upgrade is always a step in the right direction if you have the old points distributor.
my upgrade was to the ford since its a ford DURASPARK 2 and a high voltage coil.
good luck

[Ronnie]

Old school TBI for sure but I have used holley's older Pro jection units with success. I did have one on my bus but at this point there is little support for it and I needed a new o2 sensor and they are not available for this unit.



However from a drivability standpoint great starts and cold weather performance. I have a carb on my bus now and it works well but miss the drivability when the engine is cold. It is still good but not as good as the tbi and not worry free, one must pay attention to the choke if a manual choke.


I had converted several old trucks about 20 years ago to this system and liked it. The Fitech, and holley's newer systems out perform it greatly and are easy to adapt to your engine, and what I would recommend. These will go directly in place of the 4150 no mods needed to the manifold.

[Ronnie]

Speaking of dizzy... an electronic one is a must. So much better then the old points one. You should be able to get a GM hei unit for your engine. Check with Daves unified industries (D.U.I.) Check for firewall clearance though. I tend to forget GM sticks them on the back of the engine instead of front like International. I had to clearance the thermostat housing for it on mine.

[Ronnie]

CadillacKid Knows this stuff like no other best he chimes in.

[s2mikon]

Count me in the carb group. Very simple, can be fixed on the side of the road with minimal tools. The biggest problem with medium duty gas engines is vapor lock due to RFG and E-10. If you mount an electric fuel pump at the tank most of that can be stopped. On my fleet of International gas rigs I dumped the holley carbs for autolite (I know Ford) 2 and 4 barrels with manual chokes. I got better driveability, better starting and less fuel leaks. It really is a very good carburetor. Simple and effective. Most have brass floats that are impervious to E-10 fuel. That motor should have had a velocity governor mounted between the manifold and the carburetor as factory equipped. If not use a tach. On cold mornings I start the fuel pump let it fill the bowl pull the choke give it 3-4 pumps and crank it. It starts. Salvage yards are your friend. A ford with a 390 v8 would have your donor carburetor with jetting very close for your 366. Convert it to manual choke and you are ready to go. This bus should be exempt from smog check? The other thing to think about, medium duty gas trucks should not run lean. This is a problem for most tbi feedback systems. It will always try to go to 14.7. This will be good coming down I-5 from Redding but not going up. This was what the power valve in the carburetor did for you when under a load.

[s2mikon]

And with all the money you save you can buy gas and drive!

[Ronnie]

Originally Posted by s2mikon

Count me in the carb group. Very simple, can be fixed on the side of the road with minimal tools. The biggest problem with medium duty gas engines is vapor lock due to RFG and E-10. If you mount an electric fuel pump at the tank most of that can be stopped. On my fleet of International gas rigs I dumped the holley carbs for autolite (I know Ford) 2 and 4 barrels with manual chokes. I got better driveability, better starting and less fuel leaks. It really is a very good carburetor. Simple and effective. Most have brass floats that are impervious to E-10 fuel. That motor should have had a velocity governor mounted between the manifold and the carburetor as factory equipped. If not use a tach. On cold mornings I start the fuel pump let it fill the bowl pull the choke give it 3-4 pumps and crank it. It starts. Salvage yards are your friend. A ford with a 390 v8 would have your donor carburetor with jetting very close for your 366. Convert it to manual choke and you are ready to go. This bus should be exempt from smog check? The other thing to think about, medium duty gas trucks should not run lean. This is a problem for most tbi feedback systems. It will always try to go to 14.7. This will be good coming down I-5 from Redding but not going up. This was what the power valve in the carburetor did for you when under a load.

An aftermarket TBI system will have power (valve) settings that are adjustable. Even my old pro jection units have that, and I could set the fuel mixture as needed for power. The transition from light throttle cruise to moderate power was not the best but newer systems have that much better. Mine would go lean just for a moment.



Yes cruise will normally try to be 14.7. I do think that is even tunable on the newer aftermarket systems

[Ronnie]

The old GM computers can be hacked into fairly easily as I understand, never done it myself, but you could probably adapt an older TBI from a bigger V8 from the early 90's without even hacking into one.[/QUOTE]


Hamilton fuel injection does this with new parts and sells a turnkey system

[Jolly Roger bus 223]

Originally Posted by s2mikon

And with all the money you save you can buy gas and drive!

yes.
with all the ethanol mess i ran a new hard line copper from front to back.
couldnt keep a off the shelf cam pump working so a blocker went in and an electric pump went in.
if you have old stuff and only want old stuff parts?
they dont make the old school stuff compatible with the ethanol mess ?
my old truck went to electric pump and hard pipe with fuel injection hose?
regular fuel hose isnt compatible with ethanol but the people at the parts counter only give what you ask for.
love your purpose

[CHEESE_WAGON]

Originally Posted by Ronnie

Speaking of dizzy... an electronic one is a must. So much better then the old points one. You should be able to get a GM hei unit for your engine. Check with Daves unified industries (D.U.I.) Check for firewall clearance though. I tend to forget GM sticks them on the back of the engine instead of front like International. I had to clearance the thermostat housing for it on mine.

Not likely on this engine. I won't say impossible, but there are very few parts sources at all for these tall-deck 366/427s, and about the only interchangables are the heads, I believe. The intake is wider, the distributor shaft is longer, the rods are longer, everything is different.

If DUI or Mallory made anything ready-built for this engine, I'd be VERY surprised -- it's been out of production over 25 years and if my sources are correct, they weren't actually intended for vehicular use originally. You just don't see them anymore, so I doubt anyone makes much, if anything in the way of upgrades for them. Too many far more popular GM engines out there that offer more benefits from such upgrades. It is possible, however, as I've mentioned, to cannibalize a short-deck 427/454 unit for its HEI system to retrofit a tall-deck housing with the more modern bits.

Interestingly, the tall-deck big-block was essentially an industrial engine that found double-duty in trucks, similar to how the Detroit 6.2 came to be used in vehicles -- it, too, started life as an industrial application for pumps, generators, etc. Story goes that the military repowered one of their trucks with an engine from a dead generator they could no longer get parts to repair, and the powers that be asked GM to factory build them under contract. That is how GM came to use it in its civilian light-duty trucks.

EDIT: I tentatively retract my previous statement about the dizzy. Some interchange information is showing that a 1990 366 did have TBI, for starters. Also, Advance shows that a 1993 3500HD 7.4L and the 1990 C60 6.0L have the same part number for dizzy. Interesting, because I seem to remember reading somewhere that the tall deck made for a longer dizzy shaft, therefore not interchangeable.

[magnakansas]

two advantages I can think of..

1)cold start/running

2) high altitude mixture control


I think the late model stuff had throttle body injection... There is a school bus near for sale for $800 because it "needs a computer" so says the ad. I think it is a 1990 c60 bluebird.... but I really dont remember.

IF this is correct, then you could get some/all of the parts you need from salvage, or maybe even new. After market systems may work too.

hope this helps

william

[s2mikon]

And I might add gear drive cams so the distributor gears are not interchangeable. These were very good motors for truck use. They did not like to be over wound or the valve train would come apart. There was a time when medium duty gas engines were the norm. Ford super duty 331/361/391 international 345/392 gm 366/427 and dodge 413 and then there were the ford and international 500+ cu in v8 engines. Worked on em all many years ago. The rumble of the big medium duty v8's was something to behold. Most were used for local P+D and vocational trucks and of course school buses.

[CHEESE_WAGON]

It's not that it's not doable or readily available -- it just ain't cheap...

https://www.fuelairspark.com/ez-efir...ttle-body.html

The only other alternative is to find a late-model with a factory setup and swap it. GM used TBI on the 366 in 1990, but not the 427, which was also still in production. Not sure of the cost/aggravation benefit there, as yours was not wired for an ECM. Also, you'll need an inline or in-tank fuel pump to maintain proper pressure, which could mean replacing the fuel tank.

GM started using TBI widely in 1987 and on some models as late as 2000, if memory serves. Any C50/C60/C70/Kodiak or GMC equivalent in that year model range should have it. But I wonder if a system from a 454 is more or less the same, likely much easier to find.

[s2mikon]

And if I remember right, the last 366 motors were chain drive cams. This would mean the cams will turn backwards. Double check because it's been decades since I had one apart. A lot of money for a little gain.

[paddywagon]

Many good points from both sides. I was originally under the impression that any TBI kit that replaces a 4bbl carb would work on this engine but it seems to be more involved than that. I'll keep looking into it though.



For now, I rebuilt the Holley 4150 carb that was on it which needs to be dialed in. There's a lot of debate out there on Holley vs Edelbrock and frankly it seems just about as conclusive as the Chevy vs Ford debate, so for the time being I'll stick with what I've got.


As to distributors, according to this website, TradeCraftSpecialties:

The distributor mounting pad is standard height, which means that a longer distributor is NOT necessary when using the factory manifold. All standard GM HEI and points distributors will fit these engines (although camshaft gear or oil pump drive shaft modifications may be necessary).

HEI sounds like a good future upgrade but electronic ignition is definitely on the books. I threw a new set of points in just to get it drivable for the time being. By the way, that website has been an excellent resource for this engine.