Re: IML: Unleaded gas effects

[RandalPark@xxxxxxx]

Sorry that this happened to you Dick, but it is a good lesson for all of us. I am an advocate for "going the whole nine yards" when doing a valve job, hardened valve seats and all, but only when it is already going to be done. So far, I have not recommended that the heads be reconditioned in this way until the apparent need for work arises, or the process was going to be done anyway. It is interesting that this car was only run 16,000 miles before requiring more work. I may have to rethink my philosophy on this.

Paul W.

In an email dated Thu, 17 11 2005 2:30:54 am GMT, "Dick Benjamin" <dickb@xxxxxxxxx> writes:

>I have been an advocate of ignoring the supposed bad consequences of using
>unleaded gas in our older cars - as most of you probably know, those cars
>built before 1974 were not designed to be run on unleaded gas.
>
>There are a lot of scary stories propagated by the automotive press and the
>people who sell the "104+" and other supposed lead substitutes to "protect"
>your car from the dreaded effects of running on unleaded gasoline, which is
>all that has been easily available in most of the country since about 1984
>or so.
>
>One comment I have made on this mailing list and other places is that one
>doesn't need to be concerned at all about this "problem" unless one is in
>the habit of blasting across the desert in 100+ temperatures at 80 MPH+,
>with a full load on (the car!). 
>
>The problem is described as damage to the valve seats, usually called "valve
>recession" in which the valves have been pounded into the seat so vigorously
>that the seat metal is displaced or burned off, leaving an eroded valve seat
>- ultimately resulting in the need for a "valve job" sooner than the usual
>100,000 miles or so. ?The symptoms of this damage are the same as any other
>valve problem, leaking valves showing up as compression loss. ?
>
>This problem comes to all cars sooner or later, but running on unleaded gas
>was supposed to hasten the day when you have to pull the heads off the
>engine and send them off to your friendly local machine shop for a "valve
>grind" (we're talking about overhead valve type engines here - flatheads
>have the same problem and solution, but the machine shop needs the block
>instead of the head to fix the problem.)
>
>
>The above is to serve as background for the following: ?I am preparing my
>gold 1968 for sale on eBay - I've just finished my (nearly identical) 67 and
>I plan to keep it, and sell the 68. ?I've noticed that lately, when driving
>the 68 with the AC on (which it usually is, with 100+ temperatures the norm
>here in the high desert), that when idling at a traffic light, there is a
>perceptible vibration from the engine - a sort of roughness to the idle
>which is definitely not Imperial-like! ?I did not want to sell the car in
>this condition, as that would not be an accurate representation of what
>these cars should be like to drive, and the car is otherwise quite nice. ? 
>
>Accordingly, I followed my own advice and ran a compression check on it. ?Lo
>and behold, I had two cylinders that were down on compression - #2 was at 60
>PSI, and #5 was at #118. ?The other 6 were all at 150 plus/minus a few %.
>(we're at high altitude here, so these numbers are about 10% low for you
>flatlanders.) 
>
>Since I had done the engine when I got the car in 1989, about 16,000 miles
>ago, I was surprised at this result, and immediately pulled the heads off
>for inspection. ?
>
>Guess what, folks: ?I've got valve recession! ?In spades, I've got valve
>recession! ?#2 and # 5 were both visibly down in their seats, and the others
>were headed the same way. ?
>
>So, I took out the book I keep on each of my cars and reviewed the usage
>this car has been subjected to in the 16 years I've owned it. ?Almost all
>the usage of this car has been in summer (read 110F plus) family trips
>across the western deserts, from Palm Springs to Death Valley, Salt Lake
>City, and Boise Idaho (all places where we have family gatherings). ?The car
>has always been our favorite long distance travel car, especially if we had
>a full load of people and luggage, which we usually did on these trips.
>Also, since usually the family was asleep during most of the trip, I just
>set the ATC on 68 degrees and the Auto-Pilot on 80 or 85, and let'er rip -
>for hours and hours on end. Since these cars run very cool, and get
>reasonable gas mileage even at these speeds (we averaged 17+ on these trips
>- I've got the data to prove it!) I didn't give a second thought to what gas
>I was using or to "valve recession". ?
>
>OK, now I get to pay the piper! ? 
>
>So, to make a long story only slightly longer, I am now putting in hardened
>valve seats for the 68, for the first time in my history - after rebuilding
>about 30 engines over the years and pooh-poohing the need for this, I see
>the consequences of my past actions. ?
>
>I still feel that considering the way most of us in the hobby drive our
>cars, and the environmental conditions most of you deal with, the addition
>of hard seats is not worthwhile, but from this point on, when I think a car
>is going to be driven HARD in hot weather, at high speeds with a heavy load,
>I'm going to start recommending that hard seats be installed when ever the
>heads are pulled for service.
>
>So, to those who I might have mislead (no pun intended), I humbly apologize.
>Sorry about that.
>
>Dick Benjamin 
>
>
>
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