I think there may be some misconception extant about unleaded fuel use,
hardened valve seats,and 'pinging'.
But first of all, a well cared for 440 with 114, 000 is a long way
from needing an overhaul. Of course if a compression check shows a problem
- then it has to be taken care of.
Second, while unleaded fuel is generally lower octane fuel, it does not
mean that the hardened valve seats which are recommended (and then
only if the heads are off for machine work anyway) will have
any impact on pre-ignition.
Engines which are making pinging noises on acceleration due to pre-ignition
are telling us that they need higher octane gas and/or a good clean-out of the
combustion chamber and/or a correction (retarding) of the ignition timing.
None of this is related to unleaded gas or to hardened valve
seats. One hardens the valve seats to guard against valve seat
recession, which is occasionally seen on pre-hardened era engines which are
worked very hard with unleaded gasoline. I have never
seen a case of valve seat recession, and I have driven and rebuilt engines for
almost 50 years, the last 30 or so on unleaded gas.
Subject: Re: IML: IML DIGEST rebuilding 440 in 1968 Crown
> This thread is of considerable interest to me - I have as
yet been unable to obtain any previous maintenance records for my '68 Crown
other than the few receipts that "came with" in the glove box. The car does run
splendidly with nary a ping on 89 octane gas, though, so I suspect the engine
has been through an overhaul once in its life - mileage is now just over
114,000. I try to drive her once a week on my commute of about 75 miles
round-trip freeway miles, and she really rolls when you "turn the horses loose",
having great compression and engine braking and tons of 440 power. >
> Did the dealers do a "warranty" change to these cars when the fuel
changes took place, or was the timing such that it was strictly after market
rebuilding? Did they actuall retime or recam to obtain a lesser compression
ratio, or was it just the hardened valve seats thing I have heard about? >
> I have excellent reason to believe this car was mostly dealer
maintained, at least through the warranty period - the a/c has also been
updated, but not by the selling dealership. The abundance of OEM parts makes me
think it was only after the original owner died and the car "passed down"
to people with less appreciation for her that things began to get iffy on
maintenance. Thank goodness I got her before she slid too far in
condition! > > Say Ken, where are you and your '68 located? I have
yet to see another Imperial of any year on the road in my area, though I know
from the list that there are a few! Waiting for summer?? > > Kate
Justet Triplett > Kate's Custom Gunleather > Monroe,
Washington > Proudly a member of NRA > and owner of "Lucille" 1968
Imperial Crown 4-door HT > > >Date: Thu, 04 Dec 2003 09:20:22
-0800 > >From: Ken & Tracie > <Subject: IML: Compression
Ratio & Rebuilding > >Reply-To: mailing-list@xxxxxxxxxxxxxxxx >
>Hello All, > > >I would appreciate your opinions, thoughts
and experiences with rebuilding a >late 1960s 440 for use with today's
gasoline. > > >I plan to go with the necessary modifications to
accommodate unleaded gasoline. >But what about the compression ratio? Will
the currently available 91 octane >"premium" grade work in a '68 or '69
440 rebuilt to stock specifications? Or >should I have my machinist take the
steps required to drop the compression >ratio to 9:1? I know about the tricks
such as retarding the timing or using a >water injection system. But I also
know that some older engines can be modified >with different distributor
advance curves and/or cam shafts with different lift >and duration specs to
allow older engines to retain their original performance >
<characteristics with a lower compression ratio. > > >Thanks
in advance for any replies. > > <Ken Josephson > <'68
Crown Four Door Hardtop > > > >
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