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500 Cubic Inch Cadillacs... Who gottem?

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XHitman396

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Broken Arrow, Oklahoma
Hi all. Haven't been here in over a decade after my beloved 87 K5 and I parted ways, but I've fallen into something else I need some input in. There's a good chance someone here can help.

74 El Dorado overheated once and all hell broke loose (oil pressure dropped, overheating, loss of power until stall, coolant everywhere). Ever since then, the engine starts and purrs like a kitten, BUT, the oil pressure slowly drops as the engine warms until it drops below 5 psi - the death zone. Did I fry my main/cam bearings?

For the uninitiated, the car has no gauges but speed (no oil pressure, engine temp - nothing, only lights that come on AFTER things hit the fan). I put a manual gauge on the block, which is how I know it's dropping.

Am I looking at a rebuild? Anyone here have any interest in answering a pile of questions of the engine, rebuilding it, necessary machining? They seem to be a bit cantankerous, but I don't have a great source for info, despite checking all the Cadillac forums I could find.

I recall a few guys ran 500s in their trucks on here. Anybody know if they're still around?

Cheers!
 
Lots of info here, best hp caddy shop in the world! They got it all for the old Caddys

cad500parts.com

Home of CAD 500 - CAD Company Parts

Home of CAD 500 - Cad Company specializes in engine parts and accessories for Cadillac 500, 472, and 425 engines.
cad500parts.com cad500parts.com
 
Is it losing coolant?

Did anyone add an oil cooler to it? The hoses tend to fall apart on the inside and clog shit.

If it has some valvetrain noise, the nylon crap sometimes falls off the timing set and ends up in the pan. After everything gets flowing good and warm, the shit gets stuck in the pickup screen and starves the pump for oil. You can kind of hillbilly check it by putting it at TDC and pulling the distributor cap and seeing how much the crank moves before the rotor does. Should be like 2 degrees tops.

If the oil pressure drops as it is running, and no other symptoms, I'd consider throwing a new oil pump on it, especially if it still has the original aluminum one on it. I think Melling still makes pumps, but Melling stuff sucks ass (and I work by Melling) so I would consider buying one that has been reworked by someone else if you don't want to go through it first.

There is a plunger on the back of the pump held in place with an allen plug. This bugger will get stuck sometimes and/or the spring may get sleepy. If you wanted to just pull the pump and check it, that'd be worth doing, but the aluminum pumps don't last forever. You can bump up the pressure before bypass by stacking a couple washers between the spring and the allen plug.

You can also try running some 5w40 diesel or some quality 10w40 gasser oil in it.
 
76zimmer said:
Lots of info here, best hp caddy shop in the world! They got it all for the old Caddys

cad500parts.com

Home of CAD 500 - CAD Company Parts

Home of CAD 500 - Cad Company specializes in engine parts and accessories for Cadillac 500, 472, and 425 engines.
cad500parts.com cad500parts.com
Click to expand...
Have you used these guys or know someone that has? I'm curious as to their technical credibility and not just parts (they do have an excellent parts selection). I like to know from someone 'in the know' if I'm talking to the real deal or a parts salesman. It DOES seem to be the most complete Caddy site I've found, though.

CyberSniper said:
Is it losing coolant?

Did anyone add an oil cooler to it? The hoses tend to fall apart on the inside and clog shit.

If it has some valvetrain noise, the nylon crap sometimes falls off the timing set and ends up in the pan. After everything gets flowing good and warm, the shit gets stuck in the pickup screen and starves the pump for oil. You can kind of hillbilly check it by putting it at TDC and pulling the distributor cap and seeing how much the crank moves before the rotor does. Should be like 2 degrees tops.

If the oil pressure drops as it is running, and no other symptoms, I'd consider throwing a new oil pump on it, especially if it still has the original aluminum one on it. I think Melling still makes pumps, but Melling stuff sucks ass (and I work by Melling) so I would consider buying one that has been reworked by someone else if you don't want to go through it first.

There is a plunger on the back of the pump held in place with an allen plug. This bugger will get stuck sometimes and/or the spring may get sleepy. If you wanted to just pull the pump and check it, that'd be worth doing, but the aluminum pumps don't last forever. You can bump up the pressure before bypass by stacking a couple washers between the spring and the allen plug.

You can also try running some 5w40 diesel or some quality 10w40 gasser oil in it.
Click to expand...

No coolant loss. No coolant in oil. Decent compression. A little valve noise at startup until they get re-lubed from the settled oil. I did swap the oil pump using one from cad500parts.com. Probably same as Mellings. It performed identically to before the swap - there was also no noticeable damage to the original. No added oil cooler that I saw (but I'll check again). I flushed the initial oil (it looked AWFUL), put in synthetic, changed that after letting it run a bit, and now has AmsOil in the highest viscosity the shop manual recommends - nada. I'd heard about the clogged strainer, but figured it would be an issue immediately at startup with thick oil, not warm. You make a good point on it not clogging until all the nylon and junk gets agitated enough to hit the screen. I'll check this the next time I get a chance (next weekend?).

Thanks for your help, all. Keep it coming if you got it.
 
YES, @cybrfire had them rebuild his shortblock, and its been great ever since. He’s using an early version of their heads and intake for his drag car.
 
The Cad Company is about the best you're going to find. Chris is the guy that is/used to mostly respond to email. Courtney (a guy) is the one that owns it. He's worth talking to. He's a character. You can probably find parts cheaper, but they do offer them at a decent price. I ordered a bunch of crap from them (maybe $10k?). I picked Courtney's brain about which pistons to use with heads that were down to 68cc.

Since you already ordered something from them, reply to the email and tell them what the problem was and why you bought a new oil pump and what you did to try to diagnose. They might have a better idea than an idiot on the Internet like me.

There is a decent chance the main bearings are toast, but hasn't shown up yet. Is it pumping all the oil out of the pan? They like 6 quarts, by the time you get down to 4 quarts the oil doesn't return to the pan fast enough.

The oil is fed first to the passenger side gallery which serves the lifters, cam shaft, rods and mains and then it goes over the crossover passage to the drivers side gallery.. the last thing to get oil is where the oil pressure sensor is is also where the rear main and crank throw bearings wait for what is left. Behind the oil pump is another pressure port and IIRC there is another one at the top of the motor... do you have gauges you can throw in there also and maybe find where the oil pressure is getting lost?
 
Great input, guys. I'll reach out to Cad Company and investigate that nylon in the oil via distributor cap.

I haven't heard about the multiple oil ports in the block, either. I was only aware of the one on the back of the block. I'll check it all out hopefully next weekend and see what I can come up with. That would be very interesting to compare pressure losses.

I appreciate your input. Glad to see the forum is still what I remember. Cheers.
 
Cad500.jpg
 
I ran a 75 Cad 500 with the SM465 behind it. Absolutely loved it. Ran 35" tires with 3.73 gears and got 15 mpg. I had to have the crankshaft drilled for a pilot bushing. 9/16" Depth for the pilot worked. I had a radiator shop modify my radiator to mimic the Cad setup. There is a coolant outlet by the passenger side head that creates a tight fit with the firewall. A 90 degree elbow solves that. Slight modification to the firewall with a BF hammer improved distributer access. Wish I kept that truck.
 
Speaking of stupid problems, there is a shortage of places to get coolant temperature. And there isn't a good way to move water if you don't want to use the head (and I didn't). So I used brass fittings!

Cad500_Coolant.jpg
 
Just an update. Chris at Cad Company is the man. Via email he's literally provided me with 2,000 words of diagnostic gold. Thanks a ton for that recommendation.

He does say it's a bit of a tricky description, but I'll keep going down the path and fill you all in on what I come up with.

And thanks for the great pictures. That helps a lot in visualizing.

Now, to figure out how to drop the pan without removing the engine/trans...
 
XHitman396 said:
Just an update. Chris at Cad Company is the man. Via email he's literally provided me with 2,000 words of diagnostic gold. Thanks a ton for that recommendation.

He does say it's a bit of a tricky description, but I'll keep going down the path and fill you all in on what I come up with.

And thanks for the great pictures. That helps a lot in visualizing.

Now, to figure out how to drop the pan without removing the engine/trans...
Click to expand...
You can lift the engine enough to clear the pan.
Had to do that on a few vehicles including my 80's g20 van with the 6.2 diesel
 
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