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Holley 750 carb adjustment

First of all, I will order a stroboscope to check the ignition timing myself and get another vacuum gauge as well.
Just to confirm the timing settings to see if they are up to specs for this engine.
Distributor is with mechanical advance only, don't know the current setting.
What would be a good starting point regarding initial timing with how much advance?
12 deg initial and a 24 deg mechanical advance, so total 36 deg @ 2500 rpm and up?

Distributor and cables are new, less then 500 miles driven with them.

I did read some more threads where people describe exactly the same issue i am stuck with.
People replaced all fuel hoses, pumps, pick ups etc. but they also did not manage to get rid of the problem.
I am also starting to believe it is not the fuel causing the issue here, but rather ignition or air supply.
Doesn't a blocked air filter cause more vacuum in the carb which causes more fuel to be drawn in the engine and maybe causes the engine to nose dive at higher rpm due to air/fuel mixture is miles off and will not detonate properly?
 
NEW does not equate with GOOD. Check the resistance for yourself with a multi-meter. Air filter problems are possible. Easy to check. Take it off and go for a short drive... As far as your timing settings, the MSD RTR stock mechanical advance settings are easily found on their site. If the distributor has 24* at 2500 RPM, then 12* initial should work fine as starting point.
These problems are all solvable through careful diagnosing, checking and persistence.

BTW, I just tested a NEW Stant 180* Superstat. It didn't start opening until it hit 195* (a digital and an analog thermometer).
 
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True regarding being new but doesn't have to be good.
I will check resistance on the spark plug wires to be sure there is no issue.

The shop where i bought the car installed and set the MSD kit up for me, i don't know if they went with the standard setup or changed something, i was there a few days ago to speak with the mechanic but he is on holidays at the moment so i don't want to disturb him.

I did clean the air filter some time ago and re-oiled it as per K&N instructions so it should be clean.
It's a 14" x 3" round filter element which should be able to provide plenty air flow without too much restriction.

I am in the process of ordering some new spark plugs, NGK XR5/3332 (1 step hotter plug then i have at the moment) and a new fuel pump, Carter M6903, 120 gph (max 6 - 7.5 psi), some extra fuel filters and a holley rebuild kit @ Summit.
That will take at least a week to receive, but in the meantime i will wait for my stroboscope and vacuum gauge to receive first and play with that.
I will also get some new fuel hose and replace the lot as a preventive measure.

Edit: Another option that makes me wonder, as the 12 Volt supply for the coil comes directly off the battery through a relay could the wire diameter be too small causing a big voltage drop on the coil end of the wire?
As at higher rpm's i guess it will pull a lot of power and i remember reading 10 Volts is too low and will cause problems on the spark end of the ignition.
I might go and replace the wire for a bigger gauge size, believe the relay is good for 30 amps.
 
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I have never seen a relay being used in the coil circuit. If you go to MSD's site and check out their installation diagram, you should follow it exactly. When folks start improvising is when problems arise, especially with MSD's products. Again, easy to check.
 
Well, it's not really an improvised connection, the relay is in the +12 Volt supply to the coil.
I am pretty sure a lot of others done a similar setup like mine.
It is a much more direct and reliable power source compared to getting it from the ignition key, through old bulkhead connectors etc. etc. and takes the load from the original wiring.
The original 12 Volt supply to the coil is activating the relay, which in turn connect direct battery power to the coil, but now i am thinking the wire might not be enough to provide the juice it needs at high rpm's.
Only one thing makes me doubt now, is that the original ignition wire runs through the original ballast resistor to keep the relay activated.
If that signal is "lost" because the resistor the relay deactivates and shuts down the power to the coil.
Think i will try and bypass the resistor and see if that makes a difference?
 
Well, it's not really an improvised connection, the relay is in the +12 Volt supply to the coil.
I am pretty sure a lot of others done a similar setup like mine.
It is a much more direct and reliable power source compared to getting it from the ignition key, through old bulkhead connectors etc. etc. and takes the load from the original wiring.
The original 12 Volt supply to the coil is activating the relay, which in turn connect direct battery power to the coil, but now i am thinking the wire might not be enough to provide the juice it needs at high rpm's.
Only one thing makes me doubt now, is that the original ignition wire runs through the original ballast resistor to keep the relay activated.
If that signal is "lost" because the resistor the relay deactivates and shuts down the power to the coil.
Think i will try and bypass the resistor and see if that makes a difference?

Since MSD requires the removal of the ballast resistor so that you get full voltage to the system, you may be on to something. I'd be interested to know if anyone else uses a relay in their coil lead...
BTW, my MSD leads to the coil are 18 gauge.
 
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It is getting full voltage on the coil, but the signal to operate the relay is going through the ballast resistor.
If that voltage drops too far i think it might lose the signal to maintain the relay and kill the 12 Volt supply to the ignition.

The supply wire for the coil would be 0.50mm2 kabel, dunno what size that would be in gauges?
 
I would use a pure 12v signal to operate relay switching, you might be dropping the relay out after the resistor drops the voltage like its supposed to.
 
.5mm*- 22 ga. Too small.
1.0=16ga.
1.5=14ga
2.5=12ga
 
I will rewire it to by-pass the ballast resistor, i left it as is because i installed a complete new engine wire harness and did not want to cut it up to **** again.
This way i will get a continues 12 Volt without any equipment in between and install a 14 gauge wire to the coil to prevent obstructions.
 
A relay could very well work but you need to make sure of main power source && proper voltage to the kicker wire to relay & a good ground is always important.
 
Ground is ok for the relay, but i am not really sure what that ballast resistor does under higher loads.
If i understood correctly, the ballast resistor only "works" during low rpm, due to heat it is causing a restriction reducing power to the coil when it is not needed at full load.
Next week i will find some time again and correct these things and report back if it sorted the issues.
 
Actually, the ballast resistor cuts voltage ANY time current comes through it. Not RPM or temperature dependent. That's why Mopar used two leads; one for cranking with full voltage and one for running with reduced voltage.
 
Day late, dollar short. Back to all the crap in your fuel filter, for just a moment.
I'm betting it's from your tank filter, broken up from age, helped by the gas. Hope you got your fuel system cleaned out.
 
I just ordered a new fuel suction line for in the tank, new hoses, and a new Carter fuel pump.
Once received i will pull the fuel suction line, as you said it might be the suction strainer that fell apart.

For now i was unable to order new fuel filters as they were out of stock and will delay my order.
I will pull the filter anyway to replace the rubber hoses and clean again and see how much is inside.
Next time i will order something i will add them.

I also invested in a stroboscope and a new vacuum gauge and check/adjust ignition timing.
I also ordered a rebuild kit for the Holley carb to clean and re-seal it and reinstall and do some proper adjustments.
 
Time will tell, on mine. New tank, but I rebuilt the sending/pick-up unit.
It was mentioned to me, with the after-market junk, junk gas...suggested leaving the pick-up filter off! That's what I did. Chance the gas would eat it up, anyway.
Have two can fuel filters, for the two carbs.
 
I think i will follow up on your idea and leave the strainer off the pick-up unit.
I have the original filter and an additional K&N inline filter so there will never be any debris ending up in the carb.
With some spare filters i can always replace them from time to time. (i need the ones with the vapor line so i am kinda stuck to OEM filter)
 
So that means un-filtered gas goes thru your fuel pump? I don't know if there could be a down side to that......................MO
 
No, Fuel passes through the standard filter, through the fuel pump and on the way to the carb there is another in-line filter as back-up.
 
So that means un-filtered gas goes thru your fuel pump? I don't know if there could be a down side to that......................MO
Yeah, your right, Cornpatch. Un-filtered to the pump. Understand your thoughts. But, considering the way some parts are made these days, including those filters, plus the parts eating gas...
Maybe lesser of two evils. Complete fuel system new, except the sender.

A local well-known engine shop, is the one, who suggested it to me.
 
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