Converting 502 to a carb need help
10-29-2017, 01:51 PM
#11
Registered
If you use a DUI dizzy, it has a tach connection.
if you use a Pertronix, you will connect your tach wire
to the neg terminal on the coil. If you use an ignition box, there will be a tach connection on there.
you can also use your merc EFI distributor if you swap out the ignition module for Delco Voyager module.
Jeff
if you use a Pertronix, you will connect your tach wire
to the neg terminal on the coil. If you use an ignition box, there will be a tach connection on there.
you can also use your merc EFI distributor if you swap out the ignition module for Delco Voyager module.
Jeff
10-29-2017, 05:36 PM
#12
I did this with a 94 454 mag , was able to use the old harness just went thru and removed efi connections . The fuel pump runs with the org. pump wire and I used a dui dist. ..... I recall making up wire for the alt. to battery , mines mounted low on port side. Its been over ten years ago so not fresh but still have the boat
10-29-2017, 06:50 PM
#13
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Thread Starter
Midwest, did you see any gain and performance when switching to the carb. Hallj. Maybe I will use my original distributor two questions do I need to change out the gear with the melonized gear I looked at it closely I don't see any wear but I was only running that camshaft ZZ502/502 for about a year also what is the part number of the ignition module I should run. I have been reading the form quite a bit and I saw a guy ran a D1965 but it only gave him about half the advance he needed should I just buy a module from an HP 500 . Without the MEFI one running the show have I lost Revlimid her protection. And. Is this something I should be concerned about or not worry about it
10-29-2017, 07:39 PM
#14
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I think you should switch the gear just to be safe.
this Delco pn should be correct, D1965A.
it looks like it should give you a nominal 20 degrees advance.
I am not sure if it has a rev limiter.
https://bpi.ebasicpower.com/downloads/BPIESTGMV8instructions.pdf
the HP 500 is a completely different distributor and module. Thunderbolt V.
Jeff
this Delco pn should be correct, D1965A.
it looks like it should give you a nominal 20 degrees advance.
I am not sure if it has a rev limiter.
https://bpi.ebasicpower.com/downloads/BPIESTGMV8instructions.pdf
the HP 500 is a completely different distributor and module. Thunderbolt V.
Jeff
10-29-2017, 07:45 PM
#15
Registered
Yet another option, let the MEFI system run the ignition. You don't spend a dime, and works way better than a "dumb" distributor.
Jeff
Jeff
Last edited by hallj; 10-29-2017 at 07:48 PM.
10-29-2017, 09:33 PM
#16
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Thread Starter
Hallj, yeah I'd really didn't think about that, then I would keep my rev limiter using my computer which was raised to 5400 a couple years ago by Mark at I think Precision in Louisiana. I would just let the carb do the fuel metering and I was going to keep the old wire harness as I was thinking I'll just cut off the wires that I don't need leave the grounds. Correct me if I'm wrong but if I keep my computer and original wire harness and hook up my knock sensor with that computer retard timing to stop detonation or did it used to increase fuel flow. I also think that the idle was controlled by the computer, Will this make it hard to tune the idle with the carburetor?
10-29-2017, 09:35 PM
#17
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Thread Starter
does anybody know where I can get a melonized distributor gear and how was it removed and the new one installed it looks like there's a roll pan to drive out
10-29-2017, 10:13 PM
#18
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You can use the DUI distributor.
you could also use the Merc distributor with a Daytona sensors ignition box for more tuning parameters.
you will need a melonized gear for the GM cam.
From the GM ZZ 502 install manual,
"Distributor Gear
[img]file:///page2image16072[/img]
A melonized distributor gear must be used in these 502/502 engine assemblies. The deluxe 502/502 engine assembly comes with a melonized distributor gear. For the base 502/502 engine assembly you must install an HEI distributor, part number 93440806, with melonized gear or install a melonized gear on your distributor. Use part number 10456413 gear for 31/64” diameter distributor shafts or use part number 10493532 gear for 27/64” diameter distributor shafts. "
Jeff
you could also use the Merc distributor with a Daytona sensors ignition box for more tuning parameters.
you will need a melonized gear for the GM cam.
From the GM ZZ 502 install manual,
"Distributor Gear
[img]file:///page2image16072[/img]
A melonized distributor gear must be used in these 502/502 engine assemblies. The deluxe 502/502 engine assembly comes with a melonized distributor gear. For the base 502/502 engine assembly you must install an HEI distributor, part number 93440806, with melonized gear or install a melonized gear on your distributor. Use part number 10456413 gear for 31/64” diameter distributor shafts or use part number 10493532 gear for 27/64” diameter distributor shafts. "
Jeff
the ECU would retard timing to control knock so that will still work fine.
keeping the MEFI will also compensate timing for coolant and air temp so keep those sensors hooked up.
you will also want to keep your map sensor hooked up too.
It won't control the idle with the carb so get rid of the IAC motor.
I don't think you will need the TPS either. Not sure if you will need to keep hooked up to avoid any fault codes.
just keep it Ty Wraped to the harness or use a resistor to simulate it.
maybe BUP will see this and comment.
Jeff
10-29-2017, 10:44 PM
#20
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Thread Starter
Thanks Jeff for all the words of wisdom sorry I had to ask again about where to find the gear I remember reading that post but I've read so much lately I didn't remember that it was actually in my post. Now you got me thinking this might not be so easy with some of the other sensors like the idle air control and TPS not hooked up it might affect how it runs the ignition .I will definitely have to do some research on this so if anybody out there has any ideas on the specifics of this kind of modification please dievulge any information.
