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Throttle body to carburetor conversion

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MahoganyJohn

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Hi all... New to this. I am in the midst of re-powering a 2000 SR Sundancer 240 with a reman 5.7 Vortec. We have purchased a Delco Voyager ignition and a 4-barrel intake. We are planning to replace the throttle body fuel injection with an Edelbrock 1409 marine carb. I would greatly appreciate any advice from similar experience. I am particularly concerned with what I need to do with the leads in the wiring harness that went to the injectors. Any other electrical system issues/gremlins? Thanks to any/all!
 
pull the harness and rep[ace it with a standard one. PM me if interested in info
no injection system means the computer and its sensors are not needed
 
You'll need a fuel pressure regular to keep from flooding the carb. Holley makes a nice one. Set it at around 5 to 6 pounds.

The 1409 carb is not drilled for a PCV valve (and you need one to keep the oil from becoming sludge). You have to drill and tap the carb for an 1/8 inch NPT barbed hose fitting. I have photos of how this is done (easy job). Let me know.

Jeff

PS: I agree with you. You can fix a balky carb with a screw driver and a hammer; not so a messed up EFI setup!
 
Fastjeff,

Interesting perspective!!


Hammer and a screwdriver.......... Never carried a hammer in any boats I worked on in the engine bay, The outdrive area yes.

But one never knows.............Maybe when the carb messes up a hammer is the answer
 
Bought my first I/O powered boat in 1964 and with the exception of about 5 years ( sail boat with 4 stroke Honda) have run and maintained an I/O powerboat every year since. I've never had carb problems that prevented me from getting home on my own (with the occasional assistance of a screwdriver and a piece of thin wire).... not so with many friends with TBI or MPI engines.
 
You all are gonna sit there at your keyboard and honestly say that carbs are better than fuel injection? come the f on.
 
o2batsea said:
You all are gonna sit there at your keyboard and honestly say that carbs are better than fuel injection? come the f on.
Click to expand...

I agree with you on an MPI. A 555 MPI.

TBI is not any more fuel efficient than a carb. The driver for the TBI is big $$$$ to replace. When they fail the carb is the best option.
 
TBI, is not good for me compared to real injection. TBI is still basically a carb. A properly tuned 4 barrel spread bore carb, like a quadrajet, is a nice deal. Talking 460 Ford's, got a few around here. RV with TBI 8 mpg at 65mph. 4 years newer port injection gets 12mpg at 65. Same gears, same weight, 1:1 top gear. My 429 SCJ with massive spread bore even gets 14mpg in my 67 Wagon.....if you drive like you should. Throttle bodies are okay when dialed in, but there's a lot more tweaking you can do with a carb, right? This is an easy conversion. Fuel pressure. I would get rid of the high pressure electric pump completely. Safer too. How many more cars are burning up these days? Seems I see a lot more melted spots on the shoulder the last 10 years, ever notice? That 5.7 block may have provisions for pump, but check to see if camshaft has a lobe.....of course, some builders don't think versatility, you know?
 
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It's a marine engine not a car, Tim. Different rules apply.
TBI uses low pressure pump, BTW. 14 psi I think is about max

I think the OP bailed out of this thread anyway so no matter
 
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An oddball advantage of a carb in a marine engine is that it does NOT start right up. (Huh? you say.) That's right. If your engine has a water leak that lets some water into a cylinder, and it hydrolocks, parts get destroyed (like pistons and rods). With a carb, you'll hear it try to lock up on the starter and (with some intelligence!) stop cranking her over.

Where fuel mileage is concerned, in a MARINE application a well-tuned carb and EFI are very close. In automotive applications--with constant throttle changes--an EFI wins hands down.

Jeff
 
o2batsea said:
It's a marine engine not a car, Tim. Different rules apply.
TBI uses low pressure pump, BTW. 14 psi I think is about max

I think the OP bailed out of this thread anyway so no matter
Click to expand...
10x on this is not a car.
Fuel pressure is different between manufactures. Some are 30psi, Some dead head at the throttle body, some have a return system to the filter.
 
I build marine 4, 6, and V8 engines, they are the same as a truck or car. Ran a machine shop for years. How many have you guys built? There are subtle differences, gentlemen.....frost plugs, camshafts, external components. TBI is NOT TRUE fuel injection, but does most certainly require at least 35 psi to operate properly. The injector nozzle shoots at 13 to 16 psi, as there is a pressure regulator and return. This pressure MUST be produced by a higher pressure mechanical pump (as in a diesel), or electric fuel pump. TBI (throttle body injection) can be classified as EFI (electronic fuel injection), but properly considered as two different forms of aspiration. TBI has fuel passing through an intake manifold, where PI, (port injection), or DI, (direct injection) has no fuel but only air, passing through the intake. Properly presented, true injection is at least 50 psi and introduced directly at each port or cylinder. It DOES NOT have to be electronic, it can be mechanical. I really don't appreciate Mr. Chris trying to present me as stupid. I haven't "BEEN THERE DONE THAT"..........NO, I....."AM HERE AND DOING IT"! When we build a marine engine it is a "cherry picked block" considering core shift and cast formulation. I also use a sonic tester to measure the consistency of cylinder wall thickness. This is also how GM will consider certain blocks that cast out better for high performance or heavy duty applications. Marine engines often have a steel crankshaft instead of nodular iron because of continuous operation in the 4000 rpm range. We often use a little more cylinder clearance as well......004 the norm, same as in High perf applications. The rule is 1 thousandth per 1 inch of bore. A 5.7 has a 4 inch bore, as does the 5 litre Ford.
Note: Right on, Jeff.
 
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Here is my sonic tester. Costs 1,200.00, you got one too?
 

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Yeah, sorry, you must mean me. Excuse me, but I was up late playing with the cats.
 
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I have built engines for years stock ,Hi-Po and race and where would you use a sonic micrometer in a engine build???(maybe a core shifted block?) My neighbor has a FAA window repair station in his garage and he use it to mic window as they have minimum thickness specs. Repairs Lear and Mitsubitse MU2 windows.
 
Pappy, excellent, I love to go fast and hear a V8 engine turning out real horsepower and torque.....old school torque, the kind that gives me a "woodie", not this 7000 rpm crap of today with a torque curve that looks like Mt. Rainier and an 8 speed transmission to keep it in that "sweet spot".....ha! I desire a crankshaft that takes 2 hands to pick up off the table.......you know what I'm talking about! Wanna have some fun, step back 50 years into my first car, 1969 Firebird 400, Canadian made Big block Chevy 402, Muncie wide ratio 4 speed, 3.55 Positraction. Yeah, its still here. Collecting dust for 44 years, brand new 1975 Goodyear Polyglass GT white letter tires on it PMD factory rally wheels 14x8". Power steering, power front disc brakes. Black vinyl top, black interior, dark marine blue metallic. This new stuff is not for me, friend.....never!
I build 350's out of 307 blocks, with minimal core shift you can go 4" on a 307 block. No more than that. Shift has to be almost dead on, sonic tester is a must. 307's are cut for the bigger stroke crankshafts/counterweights and many are 10 to 20 percent nickel cast. Traditional original 350's with 2 piece main seals are getting hard to find. Also with the 307 cranks, you have a potential 327. I have a ton of the small block stuff around here, the most bang for your buck anywhere. Even a handful of "camelbacks" around. So cheap to build a real 400 hp. Yes its fun for me, been doing this for 45 years. Very interesting about your neighbor, never even knew that the FAA uses these for acrylics, neat. Is that you, you crazy bast@#d in that boat, or did you build that "Tower"? I love that picture. I had a "dock buster" 100hp for years. Just imagine that motor in the hands of these operators today. Reminds me of the guy that picked up his lawn mower to cut the hedge. Wonder how many Johnny Walkers he had?
 
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