Ok So let me give you a brief history of my engine- 78 300, when i bought it half the smog system was gone or non functional. I tore it all out not knowing that doing that would cause detonation. New Distributor, new carter YFA, new coil, wires, plugs, cap, rotor, ICM, lifters, push rods, rockers.

My spark plugs are always clean and my compression test was fine

So... My timing is very hard to set because my balancer has slipped, if i set the timing to 10 BTDC it pings lightly at idle and very loud when you increase rpms.
I have had to set the timing by ear and with a vac gauge because i cant use a light. I move the distributor very small amounts at a time lowering it and driving it each time. once it is set to a timing that it wont tap, my acceleration is awful and i cant go over 50 mph.

I am wondering if there is anything i can do to remedy the absence of that egr system. I run 93 octane because it helps a little bit, i have tried lead additives and other octane boosters.
I am also trying to figure out how the egr system prevents detonation. All it does is proportionally introduce exhaust gas into the intake right?

any advise is welcome

 

You need to have the balancer replaced/rebuilt. Does the truck have a DURASPARK II distributor?

 

The addition of low oxygen exhaust gas reduces the oxygen in the intake system.
The diluted intake charge can be run lean without the increased combustion temperature and the lower temps also reduces NOx emissions.
Without the EGR the combustion temps increase and cause detonation.
If EGR system is eliminated you need to be able to increase the air/fuel ratio.

Concerning the balancer, are you using the timing tab on the passenger side of the timing cover or the timing marks on the driver side of the timing cover to check the ignition timing?

 

i have the duraspark 1 i think. whats the difference between duraspark 1 and 2?

 

Ok.... so would a 4 bbl intake with a large carb make any difference? on my carb no matter how much i richen it, i cant ever get the sound to change.

i am using the passenger side marks and yes i have the correct mark painted ( i know that is an issue on these 300s)

 

Also... when i replaced my distributor it looks like it may be off a tooth just by the angle of the vac advance. Could the dist being off a tooth cause my problem? or is it most likely the egr system

 

No as long as the timing is correct the distributor position doesn't matter unless you are OCD like me and would have to have is looking right.

You need to get the ignition timing issue fixed first.
Can you remove #1 spark plug and get the piston to TDC as best you can by feel and see where the timing mark is on the balancer?

 

I will have to do that tonight once im home, i have made my own mark on the damper that is at 0 TDC and set the timing approx 10 before and it still taps. i will take some pictures tonight. Seems like no matter what timing i set it to it still taps.

ok so new info... if timing is my issue and not a carb mixture issue, i may try a recurve kit.

 

The timing is fixed first even if it is a mixture issue.

 

EGR helps control detonation in a couple of ways. It slows down the combustion rate since the exhaust gas mixed with the incoming charge is inert. It lowers peak combustion temperatures, reducing NOX and making it less likely that the end gasses (unburnt fuel) will detonate. Calibration engineers increase timing somewhat to maintain some semblence of fuel economy and peppy driving feel while keeping peak temps lower. So... by deleting EGR you are left with a very agressive advance curve calibrated to take into account the slower burning exhaust-diluted charge, while at the same time promoting higher combustion chamber temperatures, making detonation more likely.

 

Did you find true TDC using a piston stop? Can make your own marks, but as mentioned the balancer really needs to be replaced. Not just for the timing marks sake, for absorbing crankshaft vibration.

You'll have to curve the distributor advance, both the mechanical weights and springs, and then the vacuum advance, one at a time. The problem with most OEM distributors is they have a very slow or lazy curve with heavy springs, and way too much fixed advance. By removing the EGR on top of that, it's all buggered now, as you've discovered. Don't change the carb or intake, have to get the ignition timing curve right first in any case.

The idle mixture screws don't factor too much on the overall air/fuel ratio, not at cruise or acceleration anyway, they will mostly affect idle and just off idle acceleration. If the idle mixture are set too rich it will tend to load up the plugs and they will foul. Don't want that either.

 

Ok so...I need a recurve kit, and a balancer.

Concerning the distributor my icm has the blue tab on the harness connection, is that what determines if it is the ds1 or 2?

Also is the recurve kit a trial and error sort of deal do the weights and springs have certain amounts they take off of the total timing.

What kit would you guys recommend?

The way I understand timing is you have initial which is set to keep certain temps in the combustion chamber at idle, mechanical curve which is set to advance the timing with rpms for best power and temps, and vacuum which is load dependant.

 

That's pretty much it. Because the OEM distributors have so much built in advance, and this is fixed, there's only so much room to play with setting the initial base timing. Usually people limit the amount of advance the distributor is capable of providing. This allows for more leeway in setting more initial or base timing without changing the total amount of timing. Changing to lighter spring or two, or bending the arm they attach, allows for the timing to come in earlier in the RPM range.

All this experimenting is done with the vacuum advance disconnected and plugged. The goal is always to get about as much advance as it will stand just short of ping or engine knock, and as early in the RPM range as it will stand, for best power and fuel economy.

Here's one description from Timing Tips Ford Distributors :

Condition A
If the distributor's mechanical advance provides 30 degrees of crank advance, and you set the initial lead to 5 degrees, your engine will have 35 degrees of total advance at high rpm. Low rpm performance will be poor, but high rpm power will be good.

Condition B
If the distributor's mechanical advance provides 30 degrees of crank advance, and you set the initial lead to 15 degrees, your engine will have 45 degrees of total advance at high rpm. Low rpm performance will be good, but the thing will ping like crazy, and you'll break something eventually.

Condition C
If the distributor's mechanical advance provides 20 degrees of crank advance, and you set the initial lead to 15 degrees, your engine will have 35 degrees of total advance at high rpm. Low rpm performance will be good, and high rpm power will be good, and the thing won't ping. This is what we want to provide for the engine!

 

Well that makes perfect sense. I will be getting a damper this week hopefully, what kit should I order? Is there one special for that distributer or are they all the same as long as they have a wide variety of springs?

Thank you guys very much for the info. I will follow up with results. And most likey more questions with it

 

Is the tapping sound there when you idle or rev the engine in neutral with the truck standing still?