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By the time you finish re-engineering the entire fuel and intake system, there might be a little more power and a little less fuel usage - maybe as much as 10%, more likely around 5%. Injection almost always makes starts easier by getting around the biggest limitations of carburetors.
You won't see most improvements without changes to the ignition as well, so factor in an Edelbrock or MFI system that can be tweaked and re-curved.
If an older Chev 250ci truck is worth all this work, yes, it will see some improvements. I'd guess cost in the $2-3k range... assuming zero labor cost because the mechanic has fairly advanced performance engine skills; it is not going to be NAPA-parts bolt-on work.
Or a new intake, performance 2BBL carb and engine block heater could do nearly all of that for about $500, and any driveway mechanic should be able to do it.
It’s an 81 step side he personally rebuilt and painted. He loves the truck.
If you have an old engine with a carburetor can it be rebuilt for multi port fuel injection with electronic control? If it can be done how much would such a set up cost? Would this give a slight boost in factory power as well as a more reliable start on first crank? Would such a set up result in better fuel economy?
the short answer to your questions is yes. remember the old carburetted 302s? where do you think the SEFI 5.0s came from? same with the port injected chevy engines. or the fuel injected engines of any manufacturer.
the harder question to answer would be can modern fuel injected engines be back fitted with a carburettor? again the answer is yes, you just need an intake and an ignition system to deal with the carb instead of EFI. and once again that isnt as hard as it might seem.
Yes, it can be done. For a cost of about 2-5 times the value of the truck. I don't know if there's any bolt-on or easily adaptable EFI for a Chevy straight six, so it would involve machining-level adaptation and possibly custom programming.
Or he could just put a better intake and more modern carb on it for a few hundred.
Quote:
Originally Posted by Quietude
By the time you finish re-engineering the entire fuel and intake system, there might be a little more power and a little less fuel usage - maybe as much as 10%, more likely around 5%. Injection almost always makes starts easier by getting around the biggest limitations of carburetors.
You won't see most improvements without changes to the ignition as well, so factor in an Edelbrock or MFI system that can be tweaked and re-curved.
If an older Chev 250ci truck is worth all this work, yes, it will see some improvements. I'd guess cost in the $2-3k range... assuming zero labor cost because the mechanic has fairly advanced performance engine skills; it is not going to be NAPA-parts bolt-on work.
Or a new intake, performance 2BBL carb and engine block heater could do nearly all of that for about $500, and any driveway mechanic should be able to do it.
you make it seem like its a virtually impossible task, but you are wrong on this. do you really think that adding fuel injection to an 81 chevy pick up is going to cost upwards of $5000? sorry, but it can be done for around $1000, even with the inline six. and the tuning isnt as hard as you make it seem either. in fact tuning the megasquirt system is easier than tuning a set of side draft weber carbs. you want expensive? add a set of webers to any engine, and then come talk to me about expensive.
and 3), the OP asked about DPI. TBI is a kind of half-arsed in between solution, a little better than a carb at considerably more cost. A bolt-on DPI conversion for a Chevy 250 might be out there, but it's not going to be $1k and would more likely be a true "kit" in that it would involve considerable custom machining and fitting.
But yup, for a grand or so a home mechanic can put a throttle body on a Chevy six. Whoda thunk.
Would a TBI conversion work better than the carb in power, cold starts, and fuel economy?
unlikely. TBI injection managed to combine the least beneficial aspects of fuel injection and carburetion; ie, it did nothing to solve the uneven distribution of fuel in the intake runners to the intake ports. Power is still a function of engine breathing/volumetric efficiency and fuel delivery. I don't see any significant improvement in this area swapping over from a carb to TBI on this engine.
I think this project would be better resolved with a late model crate engine designed for multi-point injection; ie, sensors, fuel delivery system, cam and ignition tailored for increased efficiency. Of course, retrofit the appropriate electronics to operate the systems … but that would be a requirement for any carb to electronic FI system.
unlikely. TBI injection managed to combine the least beneficial aspects of fuel injection and carburetion; ie, it did nothing to solve the uneven distribution of fuel in the intake runners to the intake ports.
By comparison to a good carb setup, maybe - but the 1974 1BBL with some long-gone crappy smog tubing is going to be a lot more problematic than better setups. A TBI will often have been cold start performance; everything else is a bit dependent on the exact details of the setup.
Which is why I suggested a new intake and a "modern" 2BBL in good condition and tune, with a working, adjusted automatic choke. For half the cost or less, that would deliver nearly all of the advantages of a TBI conversion.
I have a 1988 Step-side Chevy, and the motor is a 350 TBI. This motor was rebuilt from the ground up in 2007, and has around 12,000 driving miles. The person I bought it from drove it 7,000 miles, and I put around 5,000
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