1995 4.3 Lx coil

philbullet

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What type is used internal resisted or external?
New rebuild runs great till trying to get on step at 2300 rpm, then back fire's.
My Brother is just going through the motions first and wants to make sure about the coil.We where also trying a AC 8140 with same results.
Before rebuild the old block had a China made coil on it and not sure what type except it blue with China stamped under it.
Any idea's?
 

achris

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The book spec is for the coil to have a primary resistance of 0.60 to 0.80 ohms. That means a coil WITHOUT an internal resistor....

The AC 8140 has a primary resistance of 1.4 ohms... So don't use it...

I'd be checking compressions, timing (including the advance curve), spark plugs and leads before looking at the coil...

Chris.......
 
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alldodge

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What type is used internal resisted or external?
New rebuild runs great till trying to get on step at 2300 rpm, then back fire's.
My Brother is just going through the motions first and wants to make sure about the coil.We where also trying a AC 8140 with same results.
Before rebuild the old block had a China made coil on it and not sure what type except it blue with China stamped under it.
Any idea's?

With it back firing it's not the coil. The coil should be one which "does not" use and external resistor. The resistors were used with distributers using points.

What is your engine serial number and do you know if you have a TB-4 or 5 ignition? Do you have an alpha/bravo drive or is the engine a 175 or 190HP?

Timing should be set at 8 BTDC for TB-4 and 10 BTDC for TB-5 ignition or Bravo drive. Engine must be set while engine is in base timing mode for TB-5.
For TB-5 the Pur/Wht wire (13) is connected to ground. Primary mixture screw at 1 1/4 turns out, idle at 650RPM
TB5 Wiring 1.jpg
 

achris

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..What is your engine serial number and do you know if you have a TB-4 or 5 ignition? Do you have an alpha/bravo drive or is the engine a 175 or 190HP?

Hi AD... Being 1995 4.3LX it will be 4.3 litre 'Gen II' block with TB-IV (TB-V didn't come in until mid 96 with the introduction of the Gen + block, and the engines lost the 'LX' tag, they were either L, LXH or LH), and that also means it has a 4bbl Weber, and has a propshaft HP of 180....

HTH.... ;)
 

philbullet

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Thanks Chris and ALLDODGE
IItS a TB-4 with the 262 cam not sure on horse power 220? 4 barrel carb. Gen 11 outdrive with oil reisvor.
Old block was no good so rebuilt a 4.3 vortex truck block.All is the same but the block and heads.Same wire harness and distriutor.
Iam ready to get this motor project over with.LOL
 

philbullet

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Timing was set at 8 with 650 '-700 rpms
The thing is we tried another distributor (HEI) with plug wires from his tranmission test stand, 4.3 vortex ,runs good get back fire's when trying to get on step.
 

achris

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Start looking at fuel supply. If it's a fresh rebuild all bets are off on everything. ie... Check EVERYTHING, compressions, valve timing, ignition advance, valve lash... Everything...

I assume by 'on step' you mean on plane... ('on step' is not a term used where I live)... If so, that's maximum load in the mid range, so look at the carb closer. Oh, and using non-marine parts (I assume his 'test stand' is a standard 4.3 litre engine) is not a valid check. For a start the timing curves are completely different.... (as well as being 'unsafe').

Chris..
 
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alldodge

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Hi AD... Being 1995 4.3LX it will be 4.3 litre 'Gen II' block with TB-IV (TB-V didn't come in until mid 96 with the introduction of the Gen + block, and the engines lost the 'LX' tag, they were either L, LXH or LH), and that also means it has a 4bbl Weber, and has a propshaft HP of 180....

HTH.... ;)

Thanks Chris and it does help but since I'm not as knowledgeable as your self I try to rely on the service manual (18). Hope I can remember it so not to have to ask similar questions in the future, doubt it but I'll try. Was in the process of researching the info and didn't notice you posted until after I did.

Thanks Chris and ALLDODGE
IItS a TB-4 with the 262 cam not sure on horse power 220? 4 barrel carb. Gen 11 outdrive with oil reisvor.
Old block was no good so rebuilt a 4.3 vortex truck block.All is the same but the block and heads.Same wire harness and distriutor.
Iam ready to get this motor project over with.LOL

After checking timing, put a vacuum gauge on the motor and see if your pulling in the 16 to 22 in Hg.
 

achris

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May 19, 2004
Messages
27,468
Thanks Chris and ALLDODGE
IItS a TB-4 with the 262 cam not sure on horse power 220? 4 barrel carb. Gen 11 outdrive with oil reisvor.
Old block was no good so rebuilt a 4.3 vortex truck block.All is the same but the block and heads.Same wire harness and distriutor.
Iam ready to get this motor project over with.LOL

That could be the source of the problem right there ^... The original block was a Gen II (Not to be confused with the Gen II drives :facepalm:) and you replaced it with a Gen + block (vortec)... The Gen + was never run with TB-IV, so the timing curves were never set up for that combination. It might be easier to change the TB-IV module for a TB-V (it's only the module on the side of the dissy you need to change, everything else is the same) and that way you'll have the right curve control for that block. You'll also need to mess with the secondary jetting on the carb. Again, the carb for the Gen II blocks was never used with the Gen+ blocks....

HTH,

Chris..........
 
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philbullet

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S.S num. On cover. OF289211.
He is checking somethings now.
and yes on plane.On step is a coon *** thing I guess.lol
 
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achris

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SO num. On cover. Of289211.
He is checking somethings now.
and yes on plane.On step is a coon *** thing I guess.lol

Since the block's been changed to the next generation, that effects everything else too.... The serial number now only relates to the peripheral gear....

Oh, and that serial number does gel with it being a 1995 4.3LX, TB-IV, 4bbl Weber carb Alpha engine... :)
 
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philbullet

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Iam starting to think it might be fuel supply problem.He has a gauage to hook inline but i have to get some fittings.Carburator was rebulit before we pulled it out of donor boat,so thats good.
I went try it again after changing the coil wire and i thought maybe the chock wasn't opening all the way so we wired in the open position,BUT it was actually it was worst so i put it back on trailer and unwired the chock and it still back fires but not queit as bad.
Now that being said about the chock not opening all the way,I had put a 160 thermostat in motor and it's running to cold to open chock,so i need to change to proper one.
Now keep in mined iam still intened to check on what opinions yall have provided, iam (we) just trying to start some where.
The good thing is iam in no real hurry but just need to finish with motor and move on to next things, the Bad thing is i leave for ofshore in morning,so ill be gone for 7 days.
On may way to get fittings to check fuel preasure.
 

philbullet

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Fuel preasure 7-8 lbs. Did a compression check 125 across the board,still needs break in.Did notice almost all plugs where black so removed carb. and he will check out while iam at work.May order new distributor cap,rotor ,plug wire's even though the HIE distributor did the samething.
May put the 470 back in eng. compartment.LOL
 
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