Pre ignition gas knock

[dkclark]

1961 Catalina 2-door 389 Tri-power 4 speed Hydromatic: I get gas ping upon passing gear, not good for the pistons. I use 93 fuel, add leaded additive, octane boost. Timing is correct, if I retard it I will lose performance. Any suggestions ?

dkcphoto@swbell.net

[Stu Norman]

What type of octane boost are you using? Most of the stuff you purchase at auto supply houses is worthless. I had limited success with Outlaw brand, but I was using it at about 8 times the rate recommended on the directions and it made real strange orange deposits on my spark plugs.


I have had a lot of luck using Toluene or Xylene, both available in the paint thinner section of hardware stores, although Toluene has become harder to find in the past few years. i use it at about 1 gallon per tankful of premium. The mix works very well for my 1963 421 HO engine. I have seen recipes online that use 1 gallon of Toluene to 10 gallons of 92 octane, plus they mix in a quart of ATF.

DO NOT SPILL IT ON YOUR PAINT!

This web site discusses using Toluene in detail. Xylene can be directly substituted.

http://www.elektro.com/~audi/audi/toluene.html

[Guest]

That engine should run just fine on 94. Try Shell. Also blocking the intake heat with two 1-1/4" freeze plugs, removing the choke and running a 160 T stat will help...

[Guest]

The guest is wrong. Do not listen this ill advised advice. Running a 160 t-stat means the t-stat will remian open ALL of the time, not allowing the water enough time to sit in the radiator and cool.

Many people have this misconception of how a t-stat works. Running a 160 does not mean the engine will run at 160 degrees. This is not an opinion. This is a fact.

[engineer]

a thermostat is a temperature regulating device. For example, a 160 deg F means that the thermostat will start to open at that temp. and not sooner. So the engine has a chance to heat up before the coolant starts circulating to the radiator. Once the T-stat is open, it will remain open until the temp were to drop below 160. Water always circulates if the stat is open and the coolant is continously moving through the radiator at all times. The coolant will pass thru the radiator as the pump requires subject to pressure drop, pluggage etc. Holding it in the radiator is not what happens.

[Larry]

It has been a long time since I heard the old "hold the water in the radiator long enough to cool it" theory.

That has been a bit of an urban legend since the days of the old flathead Fords that had people putting washers and drilled botton juice cans in the radiator hoses to "hold back the water". The theory was that the dual Ford pumps drove the water through the engine so fast that it 1) didn't pick up the heat, and 2) didn't sit in the radiator long enough to loose what heat it did have.

People never seemed to grasp the idea that if water sat in the radiator longer "loosing heat" then water remained inthe eingine longer "getting even hotter". It would have been pretty much a trade off at best.

But now back to the pinging problem and the thought that it is heat related. Granted a hot engine will ping more, but that is usually when it is about red-hot. A "normally" hot engine isn't going to have an extra pinging problem.

It is a good idea to reduce the heat on the engine by blocking the heat crossover in the intake, but don't use freeze plugs (do they really fit!??!). The intake gasket kits usually have nice plates with them to use.

But, again, unless there is a moderate to severe heating problem, that is not the source of the ping. Do some experimenting with different gas. Shell is good, but so is Sunoco. Try to avoid any with ethanol in it too. This is 2008, so it might be an idea to back off the timing a degree ot two. Also check how much advance there is at acceleration; it might help to do some recurving.

I remember the good old days when my dad would set the timing by ear, back the car out of the driveway, try starting out in second gaear, and if he heard a tiny ping-- PERFECT! All set!

Any more ideas?

[Guest]

Freeze plugs are superior to those cheap gaskets. I've used them many times in the 64 down heads and so has the factory, Smokey, Royal ect ect . First you shoot my recommendation down then you ask do they fit?
That's the biggest problem with this internet, opinions instead of experience.

Back to the topic.
I would also limit the vacuum advance by 1/3. You can do that with solder. Look up Jim Hand pontiac tune up. It's all in that article.

93-94 unleaded Shell is more then adequate for a hi compression 389. Ask the bikers in your area what they like....

[Larry]

Please don't go getting snarky. I have never had a problem with the plates in the gasket sets. You are right, they sure seem flimsy, but they work.

The question of "do they fit" was simply that. I was "thinking out loud" as I couldn't visualize the openings in the intakes that I remembered being quite that round. It's been a few years since I had an intake off.

You are correct though about "opinions" on the internet-- and everywhere else. They are like "you-know-whats"... everbody has one!

However QUESTIONS-- that's a different matter. That was my question, and you answered it.. well too I might add. For that I thank you, and I'm sure others will too.

How about joining PontiacRegistry.com and sharing your Pontiac knowledge as one of our Technical Advisors? We would sure appreciate your help and knowledge as we work so hard to build a place for ALL Pontiac lovers to go. It sounds like you have much Pontiac information and many stories to share.