: 500ci questions

08-02-04, 06:38 PM
Ive found a 1975 Eldorado, and Im pretty sure it is a 500ci. The emission tag on top of the grill says 500 on it, but I will probably go back and check the numbers on the block tomorrow now that I have found this site with all the info.

1. Is $250 a good price for the complete motor with all accessories, assuming it runs? What about if it doesn't run, is it still a good price?

2. I have searched and cannot find the answer to this: What is necessary to get the 1975 model 500's back up to '70&'71 power ratings? I know the compression ratio is part of it. Is all of that gained in the piston, or is there a difference in rod length and head design too?

Thanks in advance,

lux hauler
08-02-04, 07:59 PM
I've heard that there were some differences in cams from year to year. Don't know it to be a fact though. The heads and pistons were different too. 1968-1973 had a closed chamber (76cc) heads. 1974-1976 had open chamber 120cc heads (some say the 552 casting heads were 126cc's). Compression was dropped too. If the engine in the Eldo is original, it's a 500. All Eldo's from 1970-1976 had 500's from the factory. It wouldn't take much, really, to take the engine back to 1970 specs. $250 is about right for a core.....if it runs, it's a bonus. Personally, I consider just about any motor a core if I don't hear it run.

barge master
08-02-04, 09:03 PM
I had a discussion with Al at MTS about this one time, and he claims that a cam change and the neccesary valve spring upgrades will wake the low-comp 500s up to the power levels of the old stuff. Of course, the intake change and all that are pretty much a must to really make it count. That seems to be the greatest hinderance to power that is an external bolt on.The Caddys greatest advantage is the ability to get huge power without big money or changes to the engine.

08-03-04, 12:09 AM
There's honestly not too big of a differance between a 70 500 and a later low compression 500. About 20-25hp in reality, no matter what the ratings were. An Edelbrock manifold or mild cam will make up for that.