Holley model 59 running rich

[actioncat]

I have a 1936 ford flathead with a Holley 94, Model 59 on it. I emptied the tank and put 5 gallons of REC 90 (straight 90 octane gas) and about one gallon of 110 octane racing fuel. It ran fine, but when I put another 10 gallons of REC 90 in the tank it seemed to be running a little rich. I did have to put an aftermarket air filter on it (it had a stock air filer, but somewhere along the line it was lost and nobody even looked to see that without a lid, you really don't have a filter.) and with the aftermarket filter, it is very sooty. Do I need to change the jetting, idle adjustment screw? Ya'lls help is greatly appreciated.

[Bruce Lancaster]

If "aftermarket" means a small chrome dome one, first step is to give it a run without that! Many of these are very restrictive.

[ford38v8]

Aftermarket filters often are too restrictive for use on a 94. You aren't getting enough air to pass the filter. Rather than reduce the size of your jets, install the correct filter.

[dick lyons]

not to highjack, but I have a 59 carb with a k&m filter. do you think it is restrictive?

[Bruce Lancaster]

I think those are looser weave than the common paper ones. The little chrome helmets, though, are just plain too small, and if they have elements that flow adequately, they will still stop up and become chokes in a few miles.

[Blu Dice]

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So does a restrictive air filter cause the carburetor to run rich?

[ford38v8]

Originally Posted by Blu Dice

So does a restrictive air filter cause the carburetor to run rich?

That's exactly what it does.

[Bruce Lancaster]

venting affects this...a 59 has its bowl vented into air horn, giving it a bit more resistance to this choke effect than an externall vented 99, but the effect is still there.

[ford38v8]

Originally Posted by Bruce Lancaster

venting affects this...a 59 has its bowl vented into air horn, giving it a bit more resistance to this choke effect than an externall vented 99, but the effect is still there.

Yes, and it gets more complicated still, as ignition advance and power valve operation is also affected.

[39topless]

How do you know it's running rich? Did you remove a spark plug and find it covered in black carbon or are you saying the air cleaner is sooty? Also, did it run rich before you emptied tank and then ran racing fuel? Maybe you ain't hot enough (no offense) to burn that kind of fuel.

[Blu Dice]

So these little cheap $10.00 after market air cleaners that every Tom Dick and Harry sells can f%#* up your carburetor? For real??

[WestCoast]

if the spark plugs are either wet or sooty black and your tail pipe is sooty black, your running rich, I don't want to get a whole lot of guessing going on about that but it could be your floats to high, or the power valve is leaking, there, ive done it, now you will get a lot of possible causes, LOL

[Fordestes]

Lets see here now / as I remember high octane fuel tends to slow down the combustion rate as to avoid spark knock , as we once used in 10 - 12 to one compression ratio engines, why would any one waste money on racing fuel for a maybe 8:1 compression ratio engine ? when regular fuel has more b.t.u. could it be the additives in the racing fuel had a detrimental effect on the needle and seat of the carb causing a flooding situation? What did the high octane fuel have mixed in it? and no doubt I too have had nothing but problems from the cheesey off shore air filters. I would start from square one and check the needle valve for sealing and power valve for damage .

[scicala]

High octane fuel is less volatile and slows down the burn to reduce detonation as Fordestes stated. Theoretically, lower octane fuel would be better for starting an engine (especially when a cold start). It is a waste of money unless you have high compression and need it to avoid detonation.

Sal