I may have found my 500. It's from a 70 ElDorado, thus it has 10:1 compression. Think I can run it on 87 octane gas? I'm confident I could run it on premium, but being a cheap bastard, I'd like to run it on 87.

Nope. It'll probably take, at least, 92 octane to run right.

Spend a few pennies more and give that big ole 500 the juice she deserves.

Yeah....... Most places its 10c more, 20c at worst..... So your looking at an extra 2-4 on a 20 gallon fill up...... Pretty insignificant for 500cid of pure muscle.....

Well it probably doesn't matter anyway, because it turns out that I can't get this engine.

You could run the 500 on 87, but it wouldn't love you as much. I could run mine on 87 too, but I love her so much that I put in 91 :bouncy: Don't neglect your pimp mobile. At least give her premium (or the one in the middle) not the lowest grade.

My 472 gets really cranky with the cheap stuff. It even dieseled once on me! So every time at the pump, 27 gallons of premium (@ $2-something....ouch!)

And your 472 should be 10.5:1 compression. Hmm I'm pretty sure I could get away with running mid grade on 10:1, partly because I'm at 5200' asl. If that doesn't cut it, I'll pay the extra..

Right now, my 425 is running like total crap. It will die if I floor it, and occasionally at idle. The damn high pressure power steering line is leaking from the pump connection again, too. So I'm pretty pissed at my car right now.. It had been sitting mostly for the past 3 years, so could old gas be the problem or at least part of the problem?

how's that carb doing of your fw?

If it's not old gas, it's either the fuel pump or the carb. I have to figure out if I want to just try a swap now or try to keep the 425 alive for a while longer.

Why didn't you take the old gas out of the tank before running it again? To test the fuel pump, take disconnect the fuel line that's going into the carb (the line that's coming out of the fuel filter. Have a friend try to crank it over and see how much gas is coming out. If it's barily any, you need a new fuel pump. It should be shooting out at a good speed.

I didn't take the old gas out because it drove fine when I test drove it, and when I drove it to my house. I'll take it out again later today and see how she does.

So far, I've put in no less than 12 hours of work on that motherf--cking power steering hose. It's just one hose. I took the old one off after an hour, then I put the new one on twice and it leaked still after another 8 hours, and then I tried with teflon plumbing tape which didn't help for another 3 hours. Then I took the new hose back and exchanged it for another one, put it on in 10 minutes, and spilled fluid all down the side of the pump. So now I'm waiting to see if it still leaks, if it does I'm through with it and I'll take it to a shop. I'll edit this in a while when I check to see if it really leaks..

The 425 seemed to run much better tonight. It still lags seriously when I floor it, but it didn't die. I'm going to try to put in a new speedometer cable tomorrow, and I'll try to test the fuel pump and check the filter.

Edit: It's still leaking, I think I'll try taking it off and putting it back on one more time, then I'll just take it to a shop.

Buy a new fuel filter. I'm sure, if the car has been sitting, it's pulled stuff out of the tank and clogged the filter. Get some good gas in it too.

yeah dude those fuel filters are like $3 at autozone.

Took me all day, but I just fixed the power steering leak. That totals about 20 man hours of work, 15 mine and 5 my dads. And 3 hoses. And 3 quarts of fluid. I'll check the filter before I drive up to the parts store tomorrow and replace it if needed. I also need to replace the speedometer cable, get it washed and get the engine compartment steam cleaned, get the car washed, and put some Armor-All on the top to try to save the remaining vinyl.

Spend a few pennies more and give that big ole 500 the juice she deserves.:yeah: :drinker

I can't think of an engine that would need premium (91+) more than a 30 year old, 500ci with 10:1 compression. I'm take a wild guess that you'd lose about 15% power with 87 octane and I don't think it would be good for the engine.

Took me all day, but I just fixed the power steering leak. That totals about 20 man hours of work, 15 mine and 5 my dads. And 3 hoses. And 3 quarts of fluid.

...The price you pay for being able to steer a 5000lb car with your pinky...

As far as gas goes i have never put anything in there cept for 93. I want to put some race fuel in, 97 or 100 maybe...they sell it at the delta sonics 3 somthin a gallon. Im curious! Ill just burnout all the way home.

Do the fuel pumps on 70's caddies go bad often? Mine is dogging on me if I floor it, and I have tried 2 different carbs to make sure it wasn't the carb. I'm going to try a new filter just for the hell of it, like you said it's $3 at autozone. Also, I am running low octane fuel (87) right now. I have yet to spend the extra couple dollars at the pump for the premium stuff. What kind of difference will I see if my 472 runs 8.25:1 stock compression?

As for the power steering, I had all sorts of problems with mine a while back. First I had to replace a gasket in the steering box; then the pressure hose running from the box to the pump; then the pump itself; then the pulley when the belt kept snapping. I know what you went through.. many hours covered head-to-toe in steering fluid can get to you. Everything is fixed now though, no leaks and effortless steering make everything worth it :)

Do the fuel pumps on 70's caddies go bad often? Mine is dogging on me if I floor it, and I have tried 2 different carbs to make sure it wasn't the carb. I'm going to try a new filter just for the hell of it, like you said it's $3 at autozone. Also, I am running low octane fuel (87) right now. I have yet to spend the extra couple dollars at the pump for the premium stuff. What kind of difference will I see if my 472 runs 8.25:1 stock compression?

I generally replace the mechanical fuel pump on any new car I get as preventative maintenance. You should also replace the rubber lines at the pump and tank at the same time. If you suspect the fuel pump you can buy a fuel pressure gauge, hook it up and lay it on the windshield while you drive around and recreate the condition to see if your fuel pressure is bottoming out. Thats the only way to know if fuel pressure is the issue. There is also a sock filter in the fuel tank that gets clogged from sediment in the tank.

You won't see an increase in performance by running super unleaded in your engine. Super unleaded doesn't have any more energy than regular unleaded it is just more resistant to preignition so a higher compression engine won't knock or ping.

Interesting note:

The only real difference between 87 and 92 octane fuel is the length of time it takes for an charge to burn in the cylinder. The 87 is a much faster, hotter burning fuel and is more prone to spontaneous combustion(knocking, pinging and dieseling).

In theory, if you could find a more efficient way to take away the heat at the cylinders, you could run whatever grade of gas you wanted to. Normally, with the Ethylene Glycol/water mixture that we put into our engines to handle the cooling needs, there is a thin vapor barrier that forms around the cylinder where it is in contact that actually inhibits cooling to such an extent that even under the best of conditions, you get a less than stellar heat transfer ratio.

My cousin runs a smallblock chevy(383) in Los Angelos all year round. His engine is currently set up at 11.5 compression and he runs it on pump gas. When we were talking about this last year, I had to ask him how he kept the engine cool in the LA traffic.

His answer, and he swears by it is http://www.evanscooling.com/main25.htm.

I will be running this in my truck when I get it on the road next week. I haul lots of heavy stuff at low speed and cooling is always an issue.

Hope this helps.
Ogier

If it just takes a big gasp when you floor it, as opposed to spitting and chugging, you might need to adjust the tension on the little spring that keeps the secondary air doors from opening too soon. The tension starts to relax over the years and the air doors open so fast the engine just falls on it's face when you mash it. Q-jets get a bad rap for this, and it's only a simple adjustment.

I've posted this before in other threads and I know it sounds silly but if your motor is "dogging" during acceleration pull your dist. cap and see if your vacuum advance is working properly. Here's an easy way to check. After removing the dist. cap find the vac hose that runs from the dist. to the carb. Disconnect at carb. Place that end in your mouth and begin drawing air through the line. You should begin to see the points plate shift or turn in the distributor. If you keep sucking and sucking and nothing happens then your vacuum advance is shot. $8.00 part at the parts store and can make a world of difference.

I've posted this before in other threads and I know it sounds silly but if your motor is "dogging" during acceleration pull your dist. cap and see if your vacuum advance is working properly. Here's an easy way to check. After removing the dist. cap find the vac hose that runs from the dist. to the carb. Disconnect at carb. Place that end in your mouth and begin drawing air through the line. You should begin to see the points plate shift or turn in the distributor. If you keep sucking and sucking and nothing happens then your vacuum advance is shot. $8.00 part at the parts store and can make a world of difference. If it wasn't 2am right now, I'd go try that now. I'll try it in the morning before work... thanks a lot for the tip :) I wonder if that could be why it sounds like thunder is coming from my tailpipe when I let off the gas..