[Donkey8012]

I have been running regular-grade gas in my Ecto, and I have been getting a significant ammount of after-fire and it has even back-fired a few times. Now, because of a massive back-fire the other day, I have to replace my exhaust pipe and muffler. I have very little experience with cars this old (1967 Bonneville with a 400ci engine) so I am clueless as to how to fix this.

For those of you with older-model cars, what grade of gas should I be using? Is it even a gas problem at all? If I start using premium, will it fix this? I know that gas regulations were alot different when this car came off the line. Any help would definitely be appreciated.

[Boomerjinks]

Zach Helm has a 70s Cadillac and it MUST take 93 to run properly.

I would never have guessed that an older car would need a higher octane, but that might be your problem.

[Chace]

I've owned 8 hearses and every one ran like crap on regular gas you wanna use 93 and if possible without ethanol added as the ethanol is hard on older gaskets

[69428scj]

94 was the lowest grade leaded gasoline available back when our cars were new. So you will need to run 93 at a minimum. Be prepared to rebuild your fuel pump so that the unleaded gasoline won't eat through the gasket inside. You can find modern rebuild kits on ebay, I just bought one for my 59.

[Donkey8012]

I actually already replaced the fuel pump, but thanks for the heads-up. Would adding octane booster to the fuel be ok to do? I only ask because it has 89 in it right now.

[69428scj]

You'll be fine for the rest of this tank, but from here on out it's only the good stuff for your car...Octane booster is a farce and waste of money.

[Donkey8012]

Here's what the back-fire did to my muffler:

[Mxlplx]

I ran a lead additive through my 59's with every tank full.
Just pick it up from your local Auto Zone or car parts store.
The UN leaded gasoline will eventually cause havoc on the old engines, unless you specifically rebuild them to run with Unleaded.

[Mr. D.]

I actually already replaced the fuel pump, but thanks for the heads-up. Would adding octane booster to the fuel be ok to do? I only ask because it has 89 in it right now.

Speaking as a 10 year mechanic, I can tell you YES go get a bottle of Octane boost for this current tank. Then use 93 from here on out.

You'll be fine for the rest of this tank, but from here on out it's only the good stuff for your car...Octane booster is a farce and waste of money.

That's a negative.

Here is how gas companies work. The gas you get at, lets say Wal-mart, is the same gas as, let say, Citgo. The only difference is the additives. You ever notice when you go to the cheap places, like Wal-mart, there is a box on the pump asking if you want to add the additives? And if you say yes it brings the price up close to what you would pay at the none cheap place.

Now this is the same thing done to octane ratings. ALL gas that is delivered to the gas companies is low grade. They then add octane (boost) to their tanks to bring the level up. So you putting 83 in your tank, then adding octane boost is the same as putting 93 in your tank.

So adding the boost will help for the current tank of low grade he has.

I also recommend buying a bottle and keeping in the trunk or some place in the car in case your ever out and can only get low grade for some crazy reason. Then you have the boost on hand.


Good luck.

[AJ Quick]

Yeah.. BUT..

If you knew about Octane boosters, they only knock your octane up a half an octane at the most.

89 octane will become 89.5 octane.. if you are lucky.

Octane really only helps prevent your car from knocking (or pre-detonating). Modern cars have computers that adjust if knocking occurs.. obviously a hearse does not. If its not knocking, I wouldn't worry about it. But I would look at the lead additive to give your car what it was meant to run on.

[Donkey8012]

AJ, that's almost exactly what I was told by an ASE certified mechanic. Good call. In any case, I've been running 93 in it since October and it hasn't given me anymore problems. Its a little expensive, but considering how much money I already have in it I would be retarded not to spring for it.

[Mr. D.]

Yeah.. BUT..

If you knew about Octane boosters, they only knock your octane up a half an octane at the most.

89 octane will become 89.5 octane.. if you are lucky.

Octane really only helps prevent your car from knocking (or pre-detonating). Modern cars have computers that adjust if knocking occurs.. obviously a hearse does not. If its not knocking, I wouldn't worry about it. But I would look at the lead additive to give your car what it was meant to run on.

That is only the cheap octane boost. Get the good stuff and it will boost you up to a 93.

AJ, that's almost exactly what I was told by an ASE certified mechanic. Good call. In any case, I've been running 93 in it since October and it hasn't given me anymore problems. Its a little expensive, but considering how much money I already have in it I would be retarded not to spring for it.

Then he needs to go back to class and get re certified.

I am an ASE certified Automotive TECHNICIAN. I have been certified for 10 years but have been working on cars since I was old enough to pick up a wrench. What I have told you above is correct.



But take the information as you wish. It's your car.


Good Luck.

[drjameshouse]

I am an ASE certified Automotive TECHNICIAN.

So are some parts store employees, and I have yet to meet one that could do anything but look things up in the computer. And if you are working on a one off project you are screwed.

Are you an actual mechanic for a living? Or just certified? I am not trying to discredit you, just curious since I have some questions. I have an old car that requires 93 octane or it will knock like crazy. I have even tried backing off the timing but I lose way more power than its worth. I had tried some octane boost when it started knocking even with a tank of 93 and it didn't help. I assume I got a bad tank of gas. So what brand or kind of boost is "the good kind"? Or what do you look for on the bottle? I now live in a town that the nearest town is at least 20 miles to get 93 so in order to fill up I burn almost 6 gallons to/from. It would be nice to have an alternative.

[Garvin Ghostbuster]

Like stated above 89 to 90 is the best your gonna get.Theirs to much casing head add to all gas like Murphy's,CItgo and so on sell.

[Mr. D.]

I am an ASE certified Automotive TECHNICIAN.

So are some parts store employees, and I have yet to meet one that could do anything but look things up in the computer. And if you are working on a one off project you are screwed.

Parts store employees may be ASE but they are not TECHNICIANS.

Are you an actual mechanic for a living? Or just certified?

Up until last year, I had been working in shops since 2001. My specialty is Honda's.

I am not trying to discredit you, just curious since I have some questions. I have an old car that requires 93 octane or it will knock like crazy. I have even tried backing off the timing but I lose way more power than its worth. I had tried some octane boost when it started knocking even with a tank of 93 and it didn't help. I assume I got a bad tank of gas. So what brand or kind of boost is "the good kind"? Or what do you look for on the bottle? I now live in a town that the nearest town is at least 20 miles to get 93 so in order to fill up I burn almost 6 gallons to/from. It would be nice to have an alternative.

Changing your timing in not the best route, as you have learned.

A bad knock can be caused by many things. On older cars it is good idea to use high octane with lead additive. That's what they were built to run on.

Not sure if the cost would out way the drive for you.

I am not sure of the brand, but my boss used to get this stuff delivered and MAN it put a kick in your pants. We put it in older cars he worked on. I will drive by and see what it is and if it's available to the public.

[AJ Quick]

I stand by what I said.

You can't increase your octane with the stuff you buy at the auto part store. Yes additives may be added at the pump, but you aren't going to be able to buy that kind of additive. And if you do.. you're gonna spend more money then draining your tank and filling back up with higher octane gas would cost.

The really strong stuff that you may be referring to is designed to treat a barrel of gasoline, and its for race teams... and the like. Its meant to make 95+ Octane race fuel.

[69428scj]

Look Mr. D, I'm glad you're an ASE certified tech with specialty on Hondas. While I am not ASE certified, I have 3 close friends that are so I understand your knowledge base. I will tell you that I have been wrenching on CARBURETED cars for over 20 years, been involved in drag racing and all other sorts of old car activities. When I speak, I speak from a position of authority on older cars. I can tell you that running octane booster in my old cars has not increased performance at all, and based on my fellow rodders experience, Donkey would be wasting money on the octane booster. Buy the higher grade pump gas, ditch the lead additive and find a fuel pump rebuild kit made for unleaded gas like I did on my '59 and all will be well. I will not say another word on this topic because I have seen your propensity to be confrontational so I will go ahead and say we will just agree to disagree and be done with it.

[Mr. D.]

Look Mr. D, I'm glad you're an ASE certified tech with specialty on Hondas. While I am not ASE certified, I have 3 close friends that are so I understand your knowledge base. I will tell you that I have been wrenching on CARBURETED cars for over 20 years, been involved in drag racing and all other sorts of old car activities. When I speak, I speak from a position of authority on older cars. I can tell you that running octane booster in my old cars has not increased performance at all, and based on my fellow rodders experience, Donkey would be wasting money on the octane booster. Buy the higher grade pump gas, ditch the lead additive and find a fuel pump rebuild kit made for unleaded gas like I did on my '59 and all will be well. I will not say another word on this topic because I have seen your propensity to be confrontational so I will go ahead and say we will just agree to disagree and be done with it.

Yeah. Better he save his money to buy a new motor later after it craps out on him from running low grade fuel.

[AJ Quick]

He is gonna need to buy a new motor from running one tank of 89 octane gas back in October?

[Mr. D.]

He is gonna need to buy a new motor from running one tank of 89 octane gas back in October?

Did I say that? No. But if he had continued to run low grade with no boost...



69428scj wrote that "Octane booster is a farce and waste of money." That's not true.

Octane boost DOES help with performance, and DOES help a knocking motor, and DOES help if you put low grade fuel in a car needing higher grade. These are PROVEN FACTS. You can accept them or not, but they are still facts.

That was the point of my reply.

Donkey already said this was back in Oct and he has since changed to 93 octane. Problem solved.

Have a nice day.

[Donkey8012]

For what it's worth, I DID try octane boost before I switched to 93. First I tried STP, then Berryman's. I tried each on a full tank of regular-grade gas. Neither of them did a damn thing. The motor still backfired like crazy. There was even one instance where I thought I had blown out my BRAND NEW muffler. That was when I, at the urging of my wife, decided that it was 93 from then on. It wanted to after-fire some with the first tank of 93, but has ran fine since.

[69428scj]

The proof is in the pudding...I rest my case. Also, unless he threw a rod or dropped a valve, he would need a few replacement parts i.e. carb, fuel pump...not a brand new engine.

[Interceptor9C1]

Aside from using premium, your back when cars got tune-ups every 10,000 miles. Whens the last time the plugs were changed and points checked? An electronic ignition upgrade may be a worth while investment if you dont want to deal with points ever again and improve reliability.

[wm6929]

Aside from using premium, your back when cars got tune-ups every 10,000 miles. Whens the last time the plugs were changed and points checked? An electronic ignition upgrade may be a worth while investment if you dont want to deal with points ever again and improve reliability.

x2

Something, in the back of my mind, was saying "Check the points on the distributor, or timing its self," while reading this thread.