Unleaded fuel in a 73 deVille

[nick.stratta]

Hi guys!
What kind of fuel do you run in your early 70's Cadillacs?  I have a 73 deVille which I tend to use for long trips (80 plus mph, air on, 6 hours at a time) when I use it. Just got back from a 1100 mile round trip to France from here in Ireland. 5 three quarter tanks absolutely no issues.
However I'm worried about not having lead additive in the fuel. I just use regular pump fuel and nothing else. The car was designed for leaded fuel as you know and has no cat. I heard that Cadillac put hardened valve seats in their engines from the mid sixties on and not to worry about it. However a bad experience with hugely recessed valve seats in a '67 440 from a M*par has casued me to think again. These things were so badly worn down there was absolutely no compression in one cylinder and some of the valves were white as anything from running too hot.
Any advice on whether to use leaded fuel additives or not please?
Thanks all, Nick

["Cadillac Kid" Greg Surfas 15364]

Nick,
Unleaded fuel, besides being the only kind sold in "normal" gas stations is just fine for the '73.
Greg

[nick.stratta]

Greg,
Thanks! I see you have a '73 Coupe deVille too! Nice cars. Can't quite see which one is in your avatar. Pic is too small for me!
thanks, Nick

[paul]

unleaded gas is just fine. i have run it in all my old cars since america got stupid back in the eightys and put lots and lots of miles on them. i did run the highest octain i could find. never used a drop of  additive never had any trouble.

[Mike Josephic CLC #3877]

The 1973 engines were designed to run on unleaded fuel.  It is so stated in the owners
manual.

So as others have already pointed out -- drive it and don't worry.

Mike

[Ted in Olympia WA]

Even though Cadillac never did put in harden seats they did have lots of nickel in the cast iron.  This made them very hard and worked just great for unleaded gas.  In fact when unleaded gas became required Cadillac did nothing different to the heads, at least up to 1979 (as new as my knowledge goes with these cars).  Mopars were not of the same quality as the Cadillac.  Also with the engines that I have tore down, none of them had valve seat problems.   When you rebuild and your machinist wants to put in harden seats, just tell him no.

Also with the 1973 low compression and a proper tune, regular gas should work just fine.

Sounds like you had a very fun trip and seen a lot of county.  I would think that the 73 DeVille is very rare now and gets lots of comments.

TED

[nick.stratta]

Hi Paul, Mike, Ted. Hi Ted!

Thanks for the answers. So I won't worry. 
Yup the trip was a blast - up tight mountain passs in Wales at 65 mph, through lovely Wesh valleys and across England. Got put in pride of place on the boat by the dockers and lots of questions from other drivers. Put the V12 E-tye that was with us well in the shade. Was the motor of choice for cruising through Le Touquet and we are now honorary members of the Club Le Touquet Automobiles de Collection.
Will post pics as soon as I get them out the camera.

regards, Nick

[Guidematic]

I agree.

Starting in 1971, all engines were required to be able to run on low or unleaded fuels. This was an EPA requirement. This was the main reason for the drop in compression ratios from 1970 to 1971. Usually in the area of 2 points.

However, earlier cars should also run fine on unleaded gas, and in many cases run better. The lead tended to shorten spark plug and exhaust system life as a side effect of allowing engines to run with higher compression ratios. If you do not beat on the engine, as in racing use, pulling heavy loads and so on, there is no requirement for lead additives.

My '70 has been running on unleaded with no issues since I bought it in '93. Leaded gas was taken off the market here in '91, I believe.

Mike

[nick.stratta]

Thanks Mike, much appreciated, Nick