Octane

If I'm not mistaken, the recommended 1972 leaded octane rating for the 351C-2V was 91, so I'm putting unleaded premium in my convertible.  Under hard acceleration, I'm still getting ping and always back off to avoid damage.

What can I add to the unleaded to reduce/stop ping?  She just had a complete physical a month ago, so timing, advance, etc. should all be factory spec.

Thanks in advance.

Welcome from Boise Idaho,

I Use a octane booster. I use "Outlaw" brand which ads several points to the octane rating.

Might be affected by how much ethanol you have in your unleaded premium too. Run the minimum you can find. Also, if your engine is standard spec it's compression should be 8.6:1 I believe so it run on regular gas back in the day so it shouldn't ping on premium now.

First thing would be to hook up a timing light and verify the timing.

From your description you seem to think it is set at factory, so I assume you are not sure where it is actually set. It's not difficult to check. From there you can begin to see how it acts with different types of gas (it will differ from brand to brand) and reported octane levels.

Nightbeacon,

Before adding any type of octane booster you should be sure that the spark knock/ pinging is not being caused by carbon deposits in the combustion chamber that can cause HOT spots and making your spark knock/pinging.

That is normally accomplished by running top end cleaner thru the engine.

Half of the top cleaner would be slowly dripped thru the carb on a warm engine while keeping the engine from stalling and the remainder would be used to stall the engine out and left to hot soak while the engine cools off.

You will make lots of smoke and the engine will be hard to re-start, but this does work for removing carbon deposits

The distributor should also be checked to see if it is over advancing, due to worn parts, both in the mechanical and vacuum advance mechanism

By adding a octane booster, you may be just covering up/ masking another problem, your engine should not need octane higher than 91 and using a higher octane than needed does nothing for your engine.

Boilermaster

I do not know if you can get non ethanol fuel where you are or not. I can get it here I think $3.25 a gallon is 90 or 91 octane. I also use the Lucas gas additive the somewhat replaces the lubrication that the lead gave to the valves. I have 351 C with cam bored .050" over with flat top pistons and 2-V heads. So I probably have a little higher than stock compression. I run 6 deg. timing at idle and never even looked at speed. I never get any ping or knock even when up over 5,000 ft. in the mountains. I do have MSD ignition.

Here is a link to someone's comments on their results and what is in the stuff. https://fuelinjectorcleanerhq.com/lucas-fuel-treatment/

I pulled my intake off to do some work and the valves all look like they were sprayed with light oil which I guess is the Lucas gas treatment. I did not have any way of checking mileage the speedo cable will not hook up on my car somehow it is couple inches too short and will not reach the cluster. 

It did have a big affect on the operating temp of the engine also did lower the temp. Car has AC also with automatic and I can drive in 95 deg. heat in stop and go and never get a temp. change on the gauge. 

So I would suggest giving it a shot I am pleased with my results. I had been driving the car for over a year before getting the additive so I know it did make a difference. 

BTW I burn about a tank of gas a week so I do drive the car more than most do. Going to fill up today.

I can still get leaded gas here 105 octane but it is very expensive would probably cost near $100 to fill up. They will not pump into a vehicle has to be picked up in container.

The after market distributor (looks like Accel dual point mech. adv. only) may have too fast of a curve in it for the OC heads and likely numerically low rear gear. Just an idea. Chuck

If I'm not mistaken, the recommended 1972 leaded octane rating for the 351C-2V was 91, so I'm putting unleaded premium in my convertible.  Under hard acceleration, I'm still getting ping and always back off to avoid damage.

What can I add to the unleaded to reduce/stop ping?  She just had a complete physical a month ago, so timing, advance, etc. should all be factory spec.

Thanks in advance.

Click to expand...

You sure it's a 72? it has a 71 power steering hose although they may have overlapped into the early 72's, I'm not sure on that I'll admit. Or did someone just put that on?

On my 71 351C 4V, I had all sorts of problem with spark knock on a fresh engine. This was solved by rebuilding the distributor to cut down on the amount of crank shaft advance and increasing the initial setting to total no more the 36 degrees mechanical plus, on mine, it has 4 degrees of vacuum advance on top. I run 14 deg. initial with 20 deg. crank  on a factory Mastercraft distributor. This solved my spark knock completely using 91 Shell non ethanol fuel. Original factory timing on mine was 6 degrees initial and 30 degrees crank for the same 36 degrees total mechanical. Increasing the initial timing, which these engines seem to like, plus the 30 degrees crank is way too much advance and spark knock ensues.

If the distributor is the problem, a DuraSpark system is hard to beat on these cars...……. and it keeps it Ford!!

Other more knowledgeable may suggest other solutions for your 2V engine.

Geoff.

Nightbeacon,

Before adding any type of octane booster you should be sure that the spark knock/ pinging is not being caused by carbon deposits in the combustion chamber that can cause HOT spots and making your spark knock/pinging.

That is normally accomplished by running top end cleaner thru the engine.

Half of the top cleaner would be slowly dripped thru the carb on a warm engine while keeping the engine from stalling and the remainder would be used to stall the engine out and left to hot soak while the engine cools off.

You will make lots of smoke and the engine will be hard to re-start, but this does work for removing carbon deposits

The distributor should also be checked to see if it is over advancing, due to worn parts, both in the mechanical and vacuum advance mechanism

By adding a octane booster, you may be just covering up/ masking another problem, your engine should not need octane higher than 91 and using a higher octane than needed does nothing for your engine.

Boilermaster

Click to expand...

Many good points to this thread! You know what they say about assuming anything however.......... you said she had a good physical and I assumed the person doing that was a qualified individual/mechanic? If so they should have put there foot into it and must of "Not" received any pinging at that time "or" they would have reported it to you. You probably filled it up since you received it back from the mechanic?. Could be as simple as water in the fuel? or lower octane on that fill?

Todays issues often happen due to poor quality gas . That is why I use octane booster. I say try the booster ( in moderation) and see if the pinging stops? if so? you may have it solved the issue?.

Maybe I missed it in the thread? How many miles are on your engine?

If not go after carbon deposits and the like.