1970 Cadillac Valve Knocking

[Houston747]

Hello guys it’s me again,

For those of you who know I have a 1970 Cadillac Coupe Deville, I have owned the car for about a year now. The car has only 19,000 original miles and ever since I drove it for the first time there was a slight valve knocking sound. Fast forward a few months when the weather where I live got a bit hotter the car started valve knocking like crazy, the sound can be clearly heard. The radiator on the car was not wide at all, I am suspecting it was a two row and it was an aftermarket one and I also had the original one on the car. I was also told that the distributor needs to be changed. What I recently just did was: I installed a new four row aluminum radiator, a new HEI distributor, new spark plugs, and new spark plug wires. So I took the car out for a spin in even hotter weather and after that it was also valve knocking just as bad as before. I don’t think there is an issue with the engine as when I took out the old spark plugs they came out dry and clean and the car has only 19,000 miles. Also I wanted to ask you guys about one thing, I had two electric fans drilled to the radiator but they would not fit as there was not enough space, do you guys know a way I can install them without doing major modifications to the car? I was also wondering if the car running at 230 degrees during 107 degree weather with a four row radiator is normal. I would really appreciate the help with these questions, as I am not sure what to do, whether remove the thermostat or do something completely different, also if the HEI distributor needs timing what timing would you guys suggest? As it is now on 18 degrees top dead center and still valve knocking. Let me know what you think. Thanks

[Dave Shepherd]

What do you mean the valves are knocking, no such thing.  Do you mean preignition, detonation?  Where or what is 18 degrees timing, total advance, btdc, atdc?  Do you have a fan shroud on the radiator?

[Houston747]

I think another name for it is spark knock, whenever I accelerate it makes a really loud sound. The mechanic tuned the distributor to 18 degrees to top dead center. About the radiator, I have a shroud where you can put the fans on, but the radiator itself barely fit. Any suggestions?

[hornetball]

Any suggestions?

1.  Fire your "mechanic."
2.  Use premium gasoline.
3.  Buy a Field Service Manual.
4.  Flush cooling system -- Thermocure (made by the Evaporust folks) has done wonders for me.
5.  Work on getting your car back to the way GM built it.  OEM radiator.  OEM fan.  OEM shroud.

I don't have a 1970 FSM, but according to this, you should be timed at 5 degrees BTDC.  http://www.teufert.net/caddy/caddy.pdf.

[35-709]

As has very recently been discussed here, 230 degrees (especially in 107 degree weather) is not abnormal for the 501 series engines (472/500/425), they were designed to run hot and are at their most efficient when doing so.  Timing should be set to 5 degrees BTDC with the vacuum advance disconnected and the vacuum hose plugged, but the '71 and '73 shop manuals call for 8 degrees and that should be fine.  If you are really at 18 degrees BTDC with the vacuum advance disconnected, your timing is wayyy too far advanced.   

[76eldo]

As has very recently been discussed here, 230 degrees (especially in 107 degree weather) is not abnormal for the 501 series engines (472/500/425), they were designed to run hot and are at their most efficient when doing so.  Timing should be set to 5 degrees BTDC with the vacuum advance disconnected and the vacuum hose plugged, but the '71 and '73 shop manuals call for 8 degrees and that should be fine.  If you are really at 18 degrees BTDC with the vacuum advance disconnected, your timing is wayyy too far advanced.   

Absolute 100 percent great advice.  It's your car and do what you want but you are killing the value of the car by changing stuff like this.  Let me add buy a cheap IR thermometer and see what the temps actually are running.  You may have a lot of carbon buildup on the valves.  A top engine cleaner may help.  If the noise is pinging then back off the timing a bit but you also need to see what temperature the car is running at.  Take readings at the upper hose, thermostat housing, lower rad hose with the IR thermometer.

[Jeff Rosansky CLC #28373]

Respectfully asking-- May I ask the reasons for the modifications? Was it to get better performance or was it to solve other problems?
You also need to really figure out what the sound is. If not then you will just be chasing your tail.
There is really no way to diagnose this with the mods made. If you still have the distributor put it back in, time it correctly and see what happens. Just to be clear, I'm not saying you can't do what you want with your car. I am saying you need to see if it will run correctly as designed. That way you will know if the mods you make are the cause of the problem.  These are pretty robust engines but even with 19k it won't last long with the timing that far advanced.
As for the cooling, that also can't be addressed until you get the timing addressed because the timing will throw the temps off.
Just fyi, the standard fan does just fine. Be sure the electric one can move as much air as the original.
However if there is anything that you take away from these posts, please dont drive it long or push it hard if the timing really is that far advanced.
Good luck,
Jeff

[35-709]

   OK, since no one seems to believe me ---

I for one have installed and then removed temperature guages on my 72 Eldo and later my '76 coupe de Ville because in spite of acknowledging that the temperatures are as designed, I have a hard time watching a gage with 220-240 degrees on it. That is where these motors run efficiently and as designed.
Greg Surfas

Will also add that if the timing is really as far off as the OP has indicated, then bringing it back to a proper setting might help bring the temp. down some. 

The car came from the factory with more than ample equipment, radiator, cooling fan, etc. to cool it in almost any condition a Cadillac owner would find him or herself in.  All of these heroic measures --- extra fans, huge radiators, different thermostats, yadda, yadda, do nothing but mask a problem (which in this case isn't really a problem but a normal operating temp at 107 degrees) and should be totally unnecessary unless maybe one is going to pull a trailer. 

[TJ Hopland]

Another note is after about 1990 the number of cores or rows in radiators doesn't really mean what it used to.   Even in the copper cores there was an evolution in the design that increased their efficiency.  Once you get to aluminum all bets are off.  I just put a 1 row in a 1 ton truck.  That one row is at least 2" wide. It looks more like its for AC than coolant.

In the 90's when copper started to get more expensive and then for sure in the last 20 years the few people that were making replacements in copper really cheated as much as they could to save money so they didn't cool as well as what you replaced.   To get a good one you had to go to a good shop that knew the good suppliers.

Aluminum for some reason there are a lot of people making them that don't apparently know anything about engineering especially the fabricated looking all aluminum ones.   I just helped a guy with a muscle car by throwing away the $400 super duper radiator and throwing in a $99 plastic one from the parts store.   I'm no engineer but that fancy one looked like junk to me.   I actually paid for the parts store one because it didn't believe me that that was the problem.  I suggested he get one from US radiator but had to prove that just because it was expensive doesn't mean its good.   

[cadillacmike68]

Correct timing for these cars up through 1970 is Engine in drive, Climate control OFF, vacuum advance disconnected and plugged, idle screes 1 & 1/2 turns Out after a 20 RPM lean drop each side idle (in drive) 600 RPM, Dwell 30 deg, Timing 5 deg BTDC.

It's a progressive sequence.