346 Fuel injection system??

[gary griffin]

Does anybody kow of a Fuel injection conversion for the 346 Cu Inch flat head? I would assume it would be throttle body? If so is it successful??

[TJ Hopland]

TBI is usually easier for an engine that no one makes a multiport intake for.  Sometimes its not too difficult to drill and weld 'bungs' for injectors but its unlikely to be in the ideal position so you loose what you would usually gain from a multiport so you might as well make it easy and cheap and do a TBI.  All you have to do is come up with some sort of adapter flange to replace your existing carb.   Another nice thing about TBI is the fuel pressure is usually under 20lbs so you can still use regular fuel lines and clamps.  Multiport stuff is in the 30-60 range so you have to pay a lot more attention to the whole fuel system. 

I dont know what sort of carb came on those engines.  If its anything like a a 60's+2 bbl it should be pretty easy to bolt up a TBI.   By far the most common TBI systems out there were the GM trucks from 87-95.  A complete throttle body with the injectors should be under $25 from a u pick it junk yard these days.  Everything but the 454's had the same physical throttle body.  The 454's were a slightly larger bore and are not that common.  The size of the injectors is what varied depending on the model and engine.  You can in theory flash the chips in the ECU's to do a custom tune but the people that know how to do that seem to try and keep it a secret so you have to pay them to do it.   http://www.megasquirt.info/  is a good place for some reading about EFI.  Megasquirt is a ECU that can pretty much be configured to run any engine with any combination of hardware.   Its not plug and play, there is a pretty steep learning curve.  Holley still makes more or less their original 'pro jection' system.  You just turn the dials to tune it.     The megasquirt stuff is good reading even if you decide not to go that way.

Hope that gives you a place to start and some reading.   

[bcroe]

If you want something that bolts on and works, the system must be a
MAF based EFI.  Anything else will be a major tuning project after the
installation.  Another issue, will the EFI take over the spark advance
map, with features like knock detector?  good luck, Bruce Roe  CLC 14630

[Dan LeBlanc]

The only aftermarket systems I know of (Holley Commander 950, Holley Avenger, and there's a new one coming out in March from MSD) are all intended to replace a 4 barrel carb.  The 346 is a two barrel, correct?

[gary griffin]

Yes Dan it is a 2 barrel, and any adaptor would probably screw up the air flow? Thanks for the ideas everyone. I now need to go to the boards and do some calculations. I am looking to gain some economy and possibly some small gain in power and reliability. Back in the 80's my 84 Lincoln got about 15 MPG on the road and about 11 MPG around town, and when I went to a 86 Lincoln with EFI I got 26 MPG on the road and 18 MPG around town. The 86 also boasted 40 more HP. The 346 CU engine pulls in just under 5 CFM pre revolution and I need to figure out RPM's at various speeds and see what comes out. Has anybody ever done this conversion? Is there a chart showing the power curve for the 346 engine? If I did this I would make an adaptor to my stock manifold and hide it under the original air cleaner. I am going out of my way to do an authentic restoration and would keep the freshly rebuilt Carter Carb in case I ever wanted to seriously show the car? I am restoring the car to enjoy driving and economy along with reliability are always an issue.

[Dan LeBlanc]

If man built it, man can modify it.  Whether he can do it successfully is another story!

[TJ Hopland]

I apparently didnt post the link to the basic Holley system.   No computer needed for tuning. You just turn the knobs till it runs good, just like a carb.  Im not saying its the greatest thing in the whole world but its a complete kit that is pretty easy to install and get running. 

http://www.holley.com/502-20S.asp

Looks like it sells for around $1000
http://www.summitracing.com/parts/HLY-502-20S/

Its a 2bbl.  They are about the size of the secondaries on a Qjet.   They are pretty much the same as the GM ones.  Holley makes adapters to fit several different carb bases. 

http://www.holley.com/17-47.asp

[Eric DeVirgilis CLC# 8621]

Yes Dan it is a 2 barrel, and any adaptor would probably screw up the air flow? Thanks for the ideas everyone. I now need to go to the boards and do some calculations. I am looking to gain some economy and possibly some small gain in power and reliability. Back in the 80's my 84 Lincoln got about 15 MPG on the road and about 11 MPG around town, and when I went to a 86 Lincoln with EFI I got 26 MPG on the road and 18 MPG around town. The 86 also boasted 40 more HP. The 346 CU engine pulls in just under 5 CFM pre revolution and I need to figure out RPM's at various speeds and see what comes out. Has anybody ever done this conversion? Is there a chart showing the power curve for the 346 engine? If I did this I would make an adaptor to my stock manifold and hide it under the original air cleaner. I am going out of my way to do an authentic restoration and would keep the freshly rebuilt Carter Carb in case I ever wanted to seriously show the car? I am restoring the car to enjoy driving and economy along with reliability are always an issue.

Gary: There was something wrong with your '84 Lincoln if it was returning 11/15 MPG. We sold a bunch of these back in the day and none got less than 25 on the highway. One amazed customer reported 28 MPG highway on an '80 T/C. At any rate, the dramatic increases in fuel mileage on vehicles of that generation was more to do with the new overdrive transmissions with lockup torque converter. These units reduced engine RPM by a third at highway speed which is the primary contributing factor to fuel mileage; far less to do with presence of fuel injection which was primarily designed to address emissions and engine management concerns.

That said, you're going to spend a lot more $$$ tinkering about with your fuel system than you're ever going to see returned at the gas pump via increased economy- assuming any MPG gains occur at all. Secondly you're going to have to install an auxiliary fuel pump to maintain necessary pressure in the fuel lines. Thirdly, since you are taking great pains to do an authentic and correct restoration, I would strongly discourage violating the integrity of the original design as there is no reason a correct properly restored fuel system cannot fulfill its original function as intended by Cadillac engineers. Finally, there is a strong preferance for originality in the marketplace as well as on the show field.

Just a few points to consider.

[Caddy Wizard]

Another source is Affordable Fuel Injection in Michigan. I used one of their systems on a 1949 Cadillac and it worked very well.  Similar price to the Holley, but they provide an adapter to adapt the throttle body to your stock intake manifold. 


Advantages of TBI on an old engine:  better fuel economy, no more vapor lock, no more fuel smells in the garage, instant starting, etc


Disadvantages of TBI on an old engine:  non-original, needs 12v alternator (requires very consistent voltage), can be hard to make idle as low as on the stock carb, extra fuel line must be run, need to make an adapter to connect TV rod correctly, etc.

[Andrew Pullin]

Well, this has piqued my interest, since I feel like my technical skillset is better suited to figure out an EFI system rather than some wonky 70 year old carburetor.

Art, do you have any pictures of the throttle linkage setup from the car you converted? That's the only question mark in my mind, since I'm already committing to switching to 12V and a Pertronix ignition.

[gary griffin]

Thanks for the comments everyone. Both the pros and cons of such a conversion. As to value and authenticity I would never do something that hurts the future of the car. I figure I am a temporary curator for my cars and in the future someone else will have that chore. If I do  a conversion I will make up a redo kit and instructions for some future owner to peruse and possibly reconvert. I feel some oblication to preserve a car that has only 3 club registered mates. I could not make non reversable alterations but could make semi temporary ones.
The main reasons I am contempalting the conversion are reliability and possibly some economics.  Hopefully I will be able to do an update on this in the future.

[Eric DeVirgilis CLC# 8621]

On the subject of fuel mileage, the only direct comparisons I've been able to make on Cadillacs with fuel injection vs carburetion were on the 1980 Cadillac 368 4bbl and 1981 Cadillac V-8-6-4 368 L FI and on the 1977 425 FI and 425 4bbl.

There was no difference in fuel mileage in the 1977 example; In the 1981 example there was a real world 1 MPG advantage. Needless to say, the 1981's edge came from variable-displacement V-8-6-4; not FI.

Surely, any significant improvement to MPG would have been accomplished by GM's engineering team if there were any to be had from FI. Given the observations above, it is highly doubtful that any appreciable MPG gains are to be had by the conversion. It's still an old design flathead high friction engine; nothing is going to change that.

To the OP: If you wish to proceed with your plans of conversion for any of the other isssues cited above, fine. Just don't do it with the  expectation of any type of dramatic increases in MPG. It ain't gonna happen. 

[Caddy Wizard]

I was definitely getting better mileage with my fuel injected 49 than with a carb.  The change is totally reversible, as I didn't cut any hole in the firewall or elsewhere in the body.  It was a true bolt-on modification. The stock intake manifold is used, with an adapter.   The next owner can put the carb back on if desired.


To connect the linkage to the TV rod and make the transmission shift correctly, you merely have to mimic the geometry of the carb's original throttle linkage arm (same radii and angular positions for the connections with the throttle rod and the TV rod).  Here is a picture of how I did it on a 49.  Oh, and by the way, I gutted a 49 air cleaner and put it on the throttle body so it really looked like a carb.