[Goatracer1]

I have a 4bbl 389 that has a pinging problem even with 93 octane fuel. Do octane boosters work? If so which ones work best. Is there a better cost effective fix? I can't see spending a ton of money on an engine that sees little use. The engine was supposed to have been rebuilt before I bought the car and it looks it. If it was over bored or the heads were planed I can see why I might be having trouble. I

[Joe's Garage]

We've had several engines that needed a little more than we could buy at the pump, so we would mix five gallons of VP MS100 into a full tank of gas.

Pinging gone!

Of course, we've also had a couple of 12:1 455s that wanted straight 100, so we obliged.

[Sirrotica]

My experience was bad with octane booster, it cost me a fresh race engine back in 1977. I then changed the heads for the fuel available at the time, and solved the problem after rebuilding the engine again $$$$, expensive lesson learned the hard way.

My recommendation would be a set of heads to drop the compression, or mix race gas with your premium fuel if you're only doing minimal driving with the car. Detonation in the older premium fuel Pontiacs will break the pistons in a hurry, especially the older cast pistons. been there done that too.

You're correct, the overbore, and skimming the heads only makes your problem worse. The regular fuel 2 bbl heads for a 389 would probably get you in the ball park to drop the compression without replacing pistons. If you still have the original camshaft in the car a set of post 1970 smog heads from a 400 would probably work too, but you have to keep the lift low when using the post 66 heads because the valve inclination angle changed in 1967.

Those are ways to get the compression down, or mix fuel so it can tolerate what you have. You could go for dished pistons, but that is a bunch of work, and money.

Good luck in whatever avenue you choose.

[ponyakr]

I've read that Torco is one of the few boosters that actually works.

https://www.ebay.com/itm/32485835591...MAAOSwdNthfmxc

https://www.amazon.com/Torco-F500010...ews/B003TQ5QZQ

[67GTONUT]

I have used Octane Supreme in the past with good results, but they have gotten expensive - nearly $30/can with shipping

http://www.wildbillscorvette.com/octanesupreme01.htm

I have since switched to VP Octanium and works just as well, picked it up at Maple Grove from VP vendor direct for $15/can

https://vpracingfuels.com/product/octanium/?c=367&

Spoke to a few guys who have used it also, with great results, even on the dyno

[grivera]

Originally Posted by Goatracer1

I have a 4bbl 389 that has a pinging problem even with 93 octane fuel. Do octane boosters work? If so which ones work best. Is there a better cost effective fix? I can't see spending a ton of money on an engine that sees little use. The engine was supposed to have been rebuilt before I bought the car and it looks it. If it was over bored or the heads were planed I can see why I might be having trouble. I

Have you already done compression test and checked/worked timing curve to try to remedy the issue?

[Jay S]

Most all of the Race gas concentrates should work fine once you figure out what octane you need. Can pretty much tell if it will work by reading the instructions, more or less instructions say add X amount of concentrate to add Y to the octane, or there is a chart on the can to say what the blend rate is to get up to a certain octane. “Race gas concentrate” is another brand you can to add to the VP and Torco concentrates. Can order it from summit and jegs.

The boosters to run from are the ones that are vague on the octane increase. Maybe will say they add point or 2 for octane, but the instructions mostly imply the additive has great cleaning properties. Usually that is what the local parts stores carry. It is a long list, I don’t keep track of them, but when I see the words octane booster that is what I think of. Most those are just not the same as the race gas concentrates, some of the concentrates can be make some really high test octane fuels. Mixed strong enough some get up around 104+ octane, the ultra version of RGC has higher potential yet, which would be way more than what you would need for a stockish 389. The concentrates are not much different than mixing pump gas and race gas together. The cheapest mix’s that work are usually some type of 100LL Aviation gas, we usually run some blend of it, never had any issues either.

Example of RGC ultra…up to 112 octane!

https://www.amazon.com/RACE-GAS-ULTR...41745343&psc=1

[Mike Davis]

Find a local airport, buy some 100LL and throw a couple gallons in a tank full. $4.25 a gallon and problem solved.

[Lee]

Whatever happened to Eric Douthitt? I've not seen him post in over a decade. He was (is?) a engineer with fuel experience. At one time he posted a "DIY octane booster" with stuff you can get easily (xylene, acetone, etc.), and also debunked a lot of false claims on octane "boosters". Maybe search the archives, could still be some stuff saved.

[android 211]

Its been posted a gallon of Toulene purchased at Home Depot added to a tank of pump premium can be effective.

[Chris65LeMans]

Originally Posted by grivera

Have you already done compression test and checked/worked timing curve to try to remedy the issue?

X2. Too often, people skip the easy stuff and go straight to throwing money at the problem.

[napster]

This is what I use.

https://www.royalpurple.com/product/...ctane-booster/

Works well for me. I use it on my 1970 T/A. RA IV heads and did not change the valves.. This product has the lead additive I need for the valves. Compression is 9.9 and no pinging. I don't race the car and use 93 octane pump gas and this product. No problems.

[J.C.you]

Those old heads are not very efficient.....pop the heads, semi open the chambers and do 3 Singh groves in each chamber quench area

[Goatracer1]

I have done nothing to the engine (1962 389) yet except check static timing (6* BTDC). The car is a real pig on gas (less mileage than my 1964 with lowered compression 421) so I hate to do anything to make it worse. I have later heads I could put on it but I wanted to keep it looking original. And, I really don't want all the work of new heads, intake and possible cam and lifters. First I'll try some race gas mixed and then the recommended octane booster. Thanks.

[geeteeohguy]

Originally Posted by android 211

Its been posted a gallon of Toulene purchased at Home Depot added to a tank of pump premium can be effective.

It was over $30 per gallon when I checked 5 years ago and you needed about 2 gallons per tank of gas.
I've used Octane Supreme 130 and it flat works. Not for street use, As it is tetraethyl lead (which is why it works)

Torco Accelerator gets high marks by many, as well. That, or mix race gas.

[Sirrotica]

I tried the cheap easy fix, it cost me $3000 in 1977 dollars to find out the cheap easy fix (octane booster) did not live up to the promises. Each batch of fuel is different as it comes from the pump, so adding the same amount of octane boosters to each tankful isn't foolproof. At a 30% mix of boost additives adding more to the blend is fairly inconsequential. Not knowing how fuel was blended by the oil company puts you in the dark when adding more boost chemicals.

Be aware that detonation you can hear is at a pretty severe level, there is also detonation that isn't heard proceeding that audible level that is still pounding the pistons and rod bearings that will show up upon a teardown of an engine.

Since there is no easy cheap test of octane, you are pretty much on your own to get the octane where it needs to be, or lower the compression ratio. There is no warranty for self doctored fuel, but fuel that is sold to the public must meet standards and guarantee that claim of octane. If it were my car I'd buy a fuel to add to the tank that is known, rather than mixing up my own, and hoping for the best. When you have two known octane ratings, all that is required is simple math to mix the two and get what you need.

I'm not a fan of home brew fuels, because the only test they are subject to is putting them in the vehicle and run it. if you can't hear pinging, then it passes. But could still be detonation at a lesser amount that you can't hear.

Just my opinion, FWIW,......

[Kenth]

I have found the need of "octane booster" or "racing fuels" is due to poorly choosen camshafts for the present CR.
Look at original Pontiac camshafts LSA and intake valve closing point and find why these camshafts seldom if ever makes your engine ping.

[padgett]

I am finding that there is something very different about "gasoline" today and how they react to additives from the fuels of the '60s. I don't think it is the ethanol but something fundamental about "octane" and not just Research vs PON vs Motor.

Any ideas ?

[JLMounce]

I dealt with the same issue. Too much compression, wrong cam etc. On a hot day, even a full tank of 100 octane CAM racing fuel wouldn't keep it from pinging. I was fortunate enough to have that stuff a 1/4 mile down the street from me, but at 7.50 per gallon, it wasn't a cheap fill.

I tried off the shelf octane boosters on top of that and nothing worked. I ended up doing an top-end upgrade and made that money back pretty quickly.

As you start looking at cost of these things it becomes a pretty easy cost/benefit analysis. The most you drive the car, the quicker fixing it correctly becomes advantageous. That would likely be a head/cam swap more than likely. If the car is rarely if ever driven, it may make more sense to purchase the fuel it needs and store it yourself. Fill up when necessary.

If it's around your parts you can also look into converting to E85. The increased octane and intake charge cooling of the alcohol may do the trick.

[Formulas]

When faced with this situation you really have to visit alot of things,,

You have to do a compression test just to make sure something isn't largely amiss like cam timing way out or pop up pistons were used and you didn't know it or a stoker crank and so on.

Visit the timing curve make sure both advances are working properly and are not overly aggressive

Step colder on plugs until you reach the limit

Its not and everyday driver.... wont hurt to block the exhaust crossover
use a 160 stat

if the carb is stone stock it may be lean on todays fuel.

Little things add up