'68 Deville 472 - 0 degrees timing?
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500, 472, 425, 368 Discussion, '68 Deville 472 - 0 degrees timing? in Cadillac Engine Technical Discussion; Just bought a '68 Deville convertible. 71k miles. This thing is cherry, I mean as new condition. Everything is bone ...
  1. #1
    pnut is offline Cadillac Owners Member
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    '68 Deville 472 - 0 degrees timing?

    Just bought a '68 Deville convertible. 71k miles. This thing is cherry, I mean as new condition. Everything is bone stock. Anyhow, to my question:

    Previous owner says he set the timing to 0 degrees since these engines were meant to run on 110 octane gas. I was wondering what the opinions here were? What timing should be at idle and if at that setting it runs without pinging under load running 93 octane only. I DO notice it has sluggish performance, even for it's size, and some hesitation off idle.

    I have not touched the timing yet, but would set it at idle using a timing light on plug #1, with vacuum removed and plugged.




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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: '68 Deville 472 - 0 degrees timing?

    Very Nice.
    The sluggish performance is due to the late timing. The late timing is a solution to the lack of high octane fuel. If you use an octane booster in your fuel you can reset your timing to specs and your performance should improve. If you use an octane enhancer, you will have to experiment with timing settings and the ratio of the mix to achieve ideal settings Read the label, refill your tank at a set gauge reading ( 1/4 tank - 1/2 tank ) and add the perscribed amount of octane boost. You can go to a fuel supplier or local drag strip and buy 55 gal. drums of racing fuel. You may be able to buy avgas at the local airport, at least you used to be able to.
    There are other solutions from replacing clyinder heads / pistons to the use of water / alcohol injection.

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    pnut is offline Cadillac Owners Member
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    Re: '68 Deville 472 - 0 degrees timing?

    Thank you for the complete answer. I plan on not running any octane booster, getting race fuel, or any of those other solutions. I don't care much about the lack of performance, I am more interested in lazy cruising and keeping things safe and original as possible. Heads do have hardened seats.

    - If I keep it at zero, will it hurt anything other than my performance? I don't want to do any damage.

    - How much timing should I be able to put in assuming I only run 93? I am thinking not much more than 0 since the factory spec is 5 degrees I believe.

    - What do you or others run for timing on 93 octane?

  5. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: '68 Deville 472 - 0 degrees timing?

    What is the (advertised) compression ratio ?? (Octane boosters add only a point or so to the fuel octane rating: 91 to 91.1 or so - read the fine print - and they also add radically to the cost of a tank of fuel. I love the stuff because it really helps the shop profit margin. (I personally would NEVER run it in my engines.)

    If it is 10.5 or 11:1, then you can set initial timing at 6 degrees BTDC and use 91/93. Drive carefully, loading the engine as you get used to the new "feel". Listen for spark knock or ping, especially going up hills or during an occasional aggressive acceleration. If no ping is noted, advance the initial timing another degree. Keep this up until you notice a ping, then retard the spark a degree or so.

    Call the guys at Pertronix - they make some incredible distributors and trigger modules for these cars, and they know ignition systems. I run their equipment in all of my marine Olds 455 conversions with great success. I'll bet they can work out a perfect timing setup for your car.

  6. #5
    pnut is offline Cadillac Owners Member
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    Re: '68 Deville 472 - 0 degrees timing?

    Quote Originally Posted by submariner409 View Post
    What is the (advertised) compression ratio ?? (Octane boosters add only a point or so to the fuel octane rating: 91 to 91.1 or so - read the fine print - and they also add radically to the cost of a tank of fuel. I love the stuff because it really helps the shop profit margin. (I personally would NEVER run it in my engines.)

    If it is 10.5 or 11:1, then you can set initial timing at 6 degrees BTDC and use 91/93. Drive carefully, loading the engine as you get used to the new "feel". Listen for spark knock or ping, especially going up hills or during an occasional aggressive acceleration. If no ping is noted, advance the initial timing another degree. Keep this up until you notice a ping, then retard the spark a degree or so.

    Call the guys at Pertronix - they make some incredible distributors and trigger modules for these cars, and they know ignition systems. I run their equipment in all of my marine Olds 455 conversions with great success. I'll bet they can work out a perfect timing setup for your car.
    I guess that goes back to my original. Assuming I run 93 octane, and do not want to switch to Pertronix, and has original compression (10.5 to 1 I think but hopefully someone here can chime in), wondering what others run for timing. I have done the trial and error before and interested in what others have ended up with. If most people end up with 2-3 degrees, or are they able to run more.

    Thanks.

  7. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: '68 Deville 472 - 0 degrees timing?

    I'm running 10:1 in an Olds 455 marine engine which makes 430 hp at 4,200 rpm. It uses 89 octane. Initial timing, vacuum disconnected, is 8 degrees BTDC at 600 rpm idle. My vacuum can is set for 12 degrees additional, so the engine idles with about 20 degrees advance. As load and speed comes up, the vacuum drops off, bringing in a little retard, BUT mechanical (24 degrees) comes in and peaks out at 3,600, so with decreasing vacuum and increasing mechanical I wind up with a WOT advance of 32 degrees at 4,500. I never said to switch to Pertronix - but they have a lot of helpful info. Why the timing was set to 0 (TDC) is a mystery - unless the car has a rudimentary EGR, it is messed up, and the previous owner assumed that, to stop a part-throttle ping, he needed to retard timing.

    Find Doug Roe's HP book on Rochester carburetors. There's quite a chapter on timing and vacuum curves.

    I believe your initial information of "110 octane" was a bit optimistic and rosy.

    Go up to my photo albums in the blue bar and take a look at some Olds engine work.

  8. #7
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: '68 Deville 472 - 0 degrees timing?

    Every engine has different timing requirements. Those late 70's 425's have about 20 degrees of initial timing. Going from 5 btdc to 0 isn't that much of a move. It sounds bad to a late 70's guy but it really isn't that far off. I would just experiment with different timing and see how you like it. It's been a long time since I drove my old '70 Deville with the high comp 472 but it made good power without pinging. I hope your vacuum advance is working; that could make it feel sluggish if it isn't.

    By the way that car is GORGEOUS!

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    Re: '68 Deville 472 - 0 degrees timing?

    This may sound crazy, but I was running regular 87 gas in my '69, which is the same engine as yours (10.5 compression, 5* timing stock). My timing was set at the normal 5* BTDC. I switched to a DUI HEI distributor and changed the timing to about 10* - 12*, still running regular gas, changed spark plug gap to .060, following the directions from DUI. YMMV, I am no expert, but in my opinion the car was running great.

    Now, in my '72, different story. I started off running 87 gas, but I started having some dieseling issues, so I switched to 93 octane and the dieseling stopped instantly. Stock timing for '72 is 8*, compression ration 8.5. I admit I haven't checked the timing on it since I bought the car. Does anyone think it's odd that the 87 gas ran fine in the '69, HEI or not? Once I rebuild the carbonator and get timing, points, dwell, etc adjusted on the '72, I was planning on going back to 87 to see if it was OK. Is that a bad idea?

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    Brother_B's Avatar
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    Re: '68 Deville 472 - 0 degrees timing?

    I was looking up something else in my FSM, and came across the Fuel Requirements paragraph, this is pretty good stuff: In my '69 FSM, which should be equivalent to your '68, it says "The 1969 Cadillac is designed to operate efficiently on "premium" grade fuels commonly sold in the US and Canada. Use of fuel that is too low in anti-knock quality will result in "spark knock". Since the anti-knock quality of all premium grade gasolines is not the same, and factors such as terrain and air temperature affect operating efficiency, some knocking may result under unusual circumstances even though the proper grade of fuel is used. On cars to be used in foreign countries, there is a possibility that the best available fuels are so low in anti-knock quality that it may be necessary to lower the compression ratio of the engine. This is accomplished by installing low compression pistons... if persistent knocking is encountered, even with low compression pistons and the best fuel available, it may be necessary to retard spark timing. Engine fuel requirements are reduced by approximately one octane number for each 2-1/2 degrees that spark timing is retarded from the normal 5 degree setting. Do not retard beyond top dead center." So the previous owner of your car may have had it about right. My '72 FSM, reads similar, except for this part: "For 1972, all Cadillac engines have been designed to operate efficiently, and with lower exhaust emissions, on low lead gasoline. If low lead gasoline is not available, any leaded regular grade gasoline with a Research Octane Number of 91 or higher may be used." According to wikipedia, a Research Octane Number of 91 would correspond to today's 87 gas, except of course today's gas is unleaded.

    Hope that helps. For me, it clouds the issue, since my '69 runs fine on 87 and the '72 needs hi-test, for now...

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    drmenard is offline Cadillac Owners Enthusiast
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    Re: '68 Deville 472 - 0 degrees timing?

    The book says that motor has 10.5 to 1 compession , but it really has 10 to 1..It can be adjusted to run great on 93 octane... Before I would do any adjusting I would take off the distrubtor cap and rotor and check the springs and weights.. Make sure the weights are not rusted stuck or a broken spring.. Next I would set it by the book... If it don't start hard when hot or any pinging, I would go up or down to get it right..

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    buick73 is offline Cadillac Owners Member
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    Re: '68 Deville 472 - 0 degrees timing?

    I drive a 1973 Buick (timing spec = 4* BTDC). For the past 20 years, it ran on 93 Unleaded. Recently, I've been able to find lead additive at www[dot]kemcooil[dot]com/products.php?cId=4 (This is the original compound used to make ethyl fluid and leaded gasoline before the phaseout).
    There are instructions on the back of the bottle for treatment rates vs octane increase. Lead increases octane by numbers, not points (93-94-95 etc, not 93-93.1-93.2 etc). Unless, you've had a catalytic converter installed, the best way to advance your timing without knocking/pinging is with lead. I've advanced from 4* to 12* BTDC without any knocking even under summer weather and acceleration up hill. Even if you have hardened seals, lead will lubricate the insides of the engine, reducing friction, and prolonging life. You may need spark plugs a little sooner, but the longer life of the car will be worth it. Beautiful car, good luck!

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    Don East is offline Cadillac Owners Member
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    Re: '68 Deville 472 - 0 degrees timing?

    What a sweet Caddy!

    Quote Originally Posted by pnut View Post
    Just bought a '68 Deville convertible. 71k miles. This thing is cherry, I mean as new condition. Everything is bone stock. Anyhow, to my question:

    Previous owner says he set the timing to 0 degrees since these engines were meant to run on 110 octane gas. I was wondering what the opinions here were? What timing should be at idle and if at that setting it runs without pinging under load running 93 octane only. I DO notice it has sluggish performance, even for it's size, and some hesitation off idle.

    I have not touched the timing yet, but would set it at idle using a timing light on plug #1, with vacuum removed and plugged.




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    Cadman63 is offline Cadillac Owners Member
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    Re: '68 Deville 472 - 0 degrees timing?

    Hello, just joined and saw your post. I own a very similar car, slightly different shade of blue. How did your timing situation work out. Do you still own this car? I have owned mine for almost 10 years. It only has 54k original miles. I have enjoyed driving it as often as I can when weather permits. Never had any problems till now. I am finally having to face the timing chain and gear replacement. From what I have read this is about the only thing that happens to these cars after 40+ years, due to the timing chain gears being plastic coated. Apparently this was done to make them run quieter.

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    The Ape Man's Avatar
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    Re: '68 Deville 472 - 0 degrees timing?

    Late to the party too. what a nice car!

    Octane ratings are not calculated the same way as when these cars were new. New numbers cannot be directly compared.

    A 10:1 or 10.5:1 engine should be able to run fine on today's premium fuel without pinging.

    Sluggish off idle performance on these engines is often the result of carbon buildup on the intake valve stems. Top engine cleaners or transmission fluid can work wonders fixing this. Small vacuum leaks or a weak accelerator pump circuit can also contribute to hesitation. The TDC tuning itself shouldn't make this engine a dog. Later EGR/HEI engines are completely different in terms of spark advance and cannot be directly compared to anything before 1971.

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