Octane Booster?

Well some of you may know my father owns a 1972 Mustang Mach 1 351 H/O this car has 11.1:1 compression and I want to keep it that way. Way back when they had leaded gas it ran on that. Now these days without adding hardend valves and valve seals it will run crappy. The best octane we have here is 93 octane. I was wondering if I added octane booster and lead additive would it be the same as the old day stuff or am I gonna have to whip out the cash for a 55 gallon drum of 101 octane?

Additives these days don't have lead. They have other ways of boosting the octane rating, but the actual tetraethyl lead is a thing of the past.

I would say your most important thing is keeping the valve seats happy, but keeping 11:1 is going to be tough. The only way to do it as-is would be to retard the timing, but then you're sabotaging the intended state of tune and you'll be down on power... so the 11:1 won't be doing any good.

You could run water/methanol injection. Its a bit of a pain since you have to keep a steady supply on hand and if you get stuck 20 miles from home with an empty methanol tank you're kinda up the creek.

The simple answer is no. The real answer is, with a light foot, methanol injection, octane boosters, and a little retard to the ignition you should be able to keep most of the benefits from the compression and still be able to drive it. Dropping compression isn't a bad thing. Going to newer (better) heads and dropping to 10:1 could actually gain you a nice chunk of power and you won't need all those other tactics.

The reason i was asking is because we have a huge lawn and we use a old 8N ford tractor to mow it. All that's needed is the lead substitute and it runs fine. Also buying the 101 octane gas that has lead in it won't work?

True, but the 8N has 6.5:1 compression and only revs to 2500 rpm. The 101 leaded you refer to... do you mean avgas? Yes, it will work, but at $5-6 a gallon it might not be worth it. You'll also have to completely rejet the carb. Avgas is lighter than gasoline and is stoichiometric at about 12:1 compared to gasoline at 14.7:1. It also only takes one narc at the airport to notify the FAA that "there was this mustang with this plate number getting leaded gas" and unfortunately its a Federal offense punishable by up to 15 years in a federal pen and fines up to $150,000. I only ever heard about one guy getting caught, but he had some enemies that tattled. I think he was fined 15,000 and slapped on the wrist.

I guess what I'm saying is, there is no easy way to do it without completely altering the state of tune of the engine. If you need 100 octane, anything you do to make it able to run on 93 more than negates the benefits of running high compression. Jumping from 10 to 11 compression alone is probably responsible for about 3%, so maybe 14 hp? Making it run on 93 would probably neuter about 40 hp out of it, so the 11:1 is actually hurting your power if you run 93.

The "right" way to do it is run the octane that it requires. If you want to run pump gas, the easiest way is a head swap for less compression. I've done it many times and was able to pick up a sizeable bit of power. Old school heads flow terribly and the chamber designs are antiques. A simple $600 swap to later (good) heads can lower the compression to 10-10.5:1 and you might pick up as much as 50 hp... or more if you spend more on the heads. Consider that versus your fuel cost per year and it might be worth it for you

Another possibility is to get an E85 carb and run ethanol. You'll take a big hit to MPG and HP, but it will be more suited to the higher compression.

By the way, do you have some pics of the 8N? Dad and I have restored one and we both love them. I'll try to dig up some pics of ours.

just a note on octane boosters, their effectiveness is quite pitiful if you read the instructions carefully. When they say X ratio will give you X points increase, what they mean by "points" is TENTHS of octane rating. In other words, if you add enough to increase 5 points, you will go from 87 octane, to 87.5 octane.

It requires a lot of booster to get any realistic octane rating

I know thats not what the question was, but it something many people don't know about boosters.....its much cheaper to just by high octane gas most of the time

lol.
add 20 bottles of super 104 to 10 gallons of gas...


i agree with curtis though.
keep you old heads of course, but then put a new set of good flowing heads on.
you will pick up more power than your 11:1 heads ever could