Leaded Fuel (Full Version)

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Leaded Fuel

  

scitrick -> Leaded Fuel (5/8/2008 6:06:15 PM)

Hello all, This is probably a dumb question but I just bought and have been restoring a 67 camaro. My question is do I have to add lead to the tank each fill up? It has the original 67 engine. thank's in advance.

        Scott

  
Gorn -> RE: Leaded Fuel (5/8/2008 6:14:18 PM)

No, 

98SS#689 -> RE: Leaded Fuel (5/8/2008 8:57:53 PM)

Depends on whether or not the heads have been rebuilt.  If they have and I believe the seats have been hardened then you can run unleaded.  If not, use the additive.  Otherwise, you'll start hearing a lot of knocking going on.  Keep in mind, you will also probably need to use an octane booster.  If you don't have the original owner's manual, try to find one.  It will tell you what is the minimum octane you should be running.  I had a 67 Mustang a few years back and had to run both in the tank.  I forgot the lead additive one time and those heads sure let me know about.

z28pete -> RE: Leaded Fuel (5/9/2008 5:16:24 PM)

If you plan to drive the car much, as part of the restoration you should have the heads rebuilt and have hardened valve seats installed. Some of those old car had compression ratios in the 11:1 ratios and needed 100 octane fuel similar to today's 94 octane, (octane was measured differently back then). You can always put in a longer duration cam with more overlap and blow off some of that compression, and cut down on the pinging.

scitrick -> RE: Leaded Fuel (5/11/2008 6:53:53 PM)

Thank you all so much for replying, I believe they are the original heads (not rebuilt). If I do 94 octane plus booster will that be ok?

SS396 -> RE: Leaded Fuel (5/15/2008 9:24:43 AM)

There are actually 2 issues which come from running an original 67 block. The 2 are different and not related, the solution back then was the in the form of lead additive, which helped on both the problems.
 
Prob #1 Pinging/knocking
This is caused be detonation of the gasoline by compressing it before you want it to (like still on the compression stroke, or before the sparkplug fires) the solution to this is by raising your octane level. Octane is the resistance to combustion due to compression. It has very little to do with the amount of power you can get from the gasoline.
 
Prob #2 hardened seats
The seats on pre-1975 heads (not all but most) were not hardened, back when they were running leaded gasoline this was not a problem, since the lead when it combusted with the gas gave off a chemical that bonded to the heads providing some cushioning from the hard valve slamming into the soft seat, it wore away a little, but built up with every combustion as well. It also chemically bonded and helped create a harder valve seat surface.
 
Back then the solution was to add lead which increased the octane - solving the knocking, and provided protection to the heads, preventing head damage.
 
Today’s solution: hardened valve seats or lead additive.
Hardened valve seats (no you cannot harden the original seat, you have to actually mill out and add a harder insert) get rid of problem number 2, but you will more than likely have to run an octane booster.
Lead additive. it will do just what it did back in the day. The difference is, back then they were running 1 ppb (1 lead molecule part per 1 billion gas molecules) in the gas, the little lead additive bottle that you can get now usually increases it to about 8ppb. so that one bottle will last you about 8 tanks. Also of note, the benefits of the lead do not wear out in the first tank you run on unleaded, it takes time to wear out, so many people run a tank of gas with a bottle of lead additive and run 3-5 tanks of regular unleaded.
 
As a side note for those that don't believe the octane related to power, the 85% ethanol that is starting to become popular has the same octane rating as regular unleaded, but you will get about a 25% drop in gas mileage.

GRIFF -> RE: Leaded Fuel (5/15/2008 10:17:31 AM)

I think you ment to say E85 has a higher octane rating but has 25% less milage. I believe E85 is rated at around 100 105 octane. E85 has the potential to make more power than regular unleaded gasoline though, it just has less energy or caloric value per gallon, but consider the octane and the fact that it is oxygenated that is where it has potential for more power in an engine built for it. I really want to try the stuff but untill we have a nearby source its not worth the effort.

SS396 -> RE: Leaded Fuel (5/15/2008 11:06:56 AM)

I live in Iowa, so needless to say the corn that makes ethanol is readily available.
We have service vans that average 19 MPG on regular gas at $3.60 a gallon.
We also have a few of the exact same vans running flex fuel, which average 16 MGP at $2.85 a gallon.
The difference is about $11 dollars in savings every 1000 miles driven. Oh, and not sending all your money to overseas oil companies...

  

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