Im going to have to play around with it more.  I set the pump shot to the winter setting.  I then returned the idle mixture screws where I had it set at which was just barely rich enough that placing my hand over the choke plates did not create a increase in RPM like it was running lean.

I power braked it a but and the engine was knocking like crazy.  I took and did half a turn again to 1 1/2 turns out and the knock pretty much went away except for a slight knock at tip in that I could barely hear.  I figured ok let me go drive it.

Hit the throttle in first gear since the transmission obviously now needs a rebuild.  Well engine lays down then picks up which in my experience has always been not enough fuel.  but where this is different is the engine shakes from knocking so I am now starting to wonder if its simply the 87 octane gas I have in there is truly not 87 octane.  but the engine knocks with any kind of load on it but yet it wasn't knocking when you would power brake it hitting the throttle which is more load than pulling the vehicle.

Going to wait till I get the transmission rebuilt first then I will play around with it more.  If I cant seem to get it to straighten out I might just call it quits and snatch the engine out and rebuild it.


1956 Ford Fairlane Town Sedan - 292 Y8 - Ford-O-Matic - 155,000 mi

Rusty, it stands to reason that since your other vehicles don't knock on 87 octane, the '56 should do just fine. You mentioned not having driven it in several years, I wasn't aware of that. It may be the fuel in the tank has started to sour or undergo what's called phase separation and go bad.

The tank was replaced but the fuel in it was down to a 1/4 tank with some stabil 360 in the tank it was a little over the protection date but I added 10 gallons of 87 octane so I am now at 3 quarts of a tank.  This was back in October when this was done with 2 oz I believe it was of stabil 360 added to the fuel.

Im tempted to pull the plug on the fuel tank and drain what I can and just go get 10 gallons of 93 and put in there and see if that makes a positive change.


1956 Ford Fairlane Town Sedan - 292 Y8 - Ford-O-Matic - 155,000 mi

Im going to drain the tank this weekend. More i think of it i suspect weak fuel is the cause.

It slipped my mind but when you start the car up on a cold fast idle it knocks and does a muffled puff sound in the exhaust like a cough.

Even warmed up i think i faintly hear it at idle as well.

I know the gas isnt old but i suspect mixing 10 gallons with some old gas with stabilizer didnt weaken the fuel. Or maybe the station is not selling true 87 octane.

Going to pull the plug and drain what i can and refill with 93 octane. No point chasing my tail trying to figure this out without starting with the fuel itself first.

1956 Ford Fairlane Town Sedan - 292 Y8 - Ford-O-Matic - 155,000 mi

As a general rule, I use premium fuel in all my carbureted vehicles simply due to the reduced ethanol content in premium versus the 85 - 89 octane grades.   Even my ’50 Ford with a Flattie gets a regular diet of premium grade gasoline.  Unless driving the vehicles regularly, I keep the gas tanks on the low side so the fuel can be constantly refreshed.  The reduced ethanol content in the premium grades of fuel by itself will increase the shelf life of the gasoline.

Lorena, Texas (South of Waco)

I fought a similar issue for some time.  My engine seemed perfect.  Brand new rebuild with Pertronix igntor, new carb, the works.  Still, the darn thing wouldn't idle consistently and I had an intermittent miss. Finally pulled the gas tank.  When I looked inside the entire bottom of the tank was covered with rust.  It was getting by my fuel filter and clogging up the carb.  I put in a new gas tank and the car runs perfectly. No more miss, lots more power and no more headaches.  $150 well spent.

Since the discussion is about gasoline octane, back in 1961 I bought a 1958 Tbird convertible that had an FE 352 HIPO engine.
This had factory 10.5 compression and a solid cam. I was in Little Rock Ark and you could buy SUNOCO  ( AMACO )unleaded premium
gasoline that had 104 octane. It cost $0.35 per gallon when regular was $0.27 per gallon.
The Tbird refused to run on anything less than 104 with out the timing being retarded.
That was a really great period of American IRON and a lot of fun. Pete

Those old HiPo FE motors had tiny combustion chambers.  I had a 406 6V Galaxie and I had to run high test with a can of lead additive.  I'm pretty sure it wouldn't run on today's gas.

With this engine not being apart before I run that lead additive did my research and got the Redline stuff as it didn't have bad reviews like the others causing valves to hang up.

Anyways that's why I run a full tank cause its one bottle to a tank and I hate the thought of wasting a whole bottle on just 5 gallons of gas.  The Stabil 360 that is no problem that I have the big bottle that has the oz marks to add the right amount.  Not the same with the stabil.

I think I am going to just pull the plug and swap the fuel over to 93.  Price is more but I will pay more to eliminate this spark knock.  If I can get it eliminated then I might be able to play with my idle jets some more to hopefully get the stumble on acceleration out.


1956 Ford Fairlane Town Sedan - 292 Y8 - Ford-O-Matic - 155,000 mi

I find that the Holley 4000 carbs (Teapots) are overly sensitive to ethanol laden gasoline and require up to a two number increase in jetting in which to compensate if using 91-93 octane fuel.  If using 85-89 octane fuel, the problem will just be worse as the lower octane fuels have a higher percentage of ethanol in the gasoline than the 91-93 octane grades.
 
The first symptom of the lean jetting in those carbs is a hesitation right off of idle and on the more worse situations, a lag in part throttle response where the engine seems sluggish or not wanting to take the fuel.  The increase in primary jetting fixes both of these.  I’m fortunate that I can ‘drive’ some of these engines on the engine dyno and simulate actual driving conditions.  With that information and computer generated data, the jetting is corrected before the engine goes in the vehicle.

Lorena, Texas (South of Waco)