Cadillac Owners Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Okay so I recently purchased a square body chevy with a caddy 500 that needs some work, and I plan on swapping out my 500 with a 350 bb that is currently being rebuilt.

My question is what would be the better engine to invest in? Should money go into the 350, or should money go into the 500?
 

·
Registered
02 Eldorado ESC, true 2.5" duals, 18X10's & 275/40ZR18's, 14" rotors, C5 Vette brakes
Joined
·
254 Posts
You've already got an upgraded engine in the vehicle. There were many reasons for that swap, like:
Two times the torque

Same MPG with more torque (or better MPG if the right cam and fuel injection was used.)

Better reliability with more torque

Only 35 lbs. (heavier if it has an aluminum intake.) With more torque

Cheapest way to get 600-650 lbs. of torque below 4,000 RPMs.

If you want to revert to a wimpy gas guzzler by comparison, I'll gladly take the 500 off of your hands for free.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #7
You've already got an upgraded engine in the vehicle. There were many reasons for that swap, like:
Two times the torque

Same MPG with more torque (or better MPG if the right cam and fuel injection was used.)

Better reliability with more torque

Only 35 lbs. (heavier if it has an aluminum intake.) With more torque

Cheapest way to get 600-650 lbs. of torque below 4,000 RPMs.

If you want to revert to a wimpy gas guzzler by comparison, I'll gladly take the 500 off of your hands for free.
Wait, I dont understand, what engine are you listing with all of these benefits? I already have the 500 in my truck.
 

·
Registered
Joined
·
10 Posts
If you are indeed getting 6 mpg, per your Name suggests, I would start investigating what is causing the poor gas mileage. A properly tuned up 500 powered 2wd truck should be able to achieve 12-15 mpg empty with the right rear gearing at 60 mph. This is better than the stock 350 that the truck came with. Your mpg while towing with a 500 will be 30-45% better than the stock 350 it came with, and much better than a 454 BB.
To find out what is causing the 6 mpg:
1) Look for drivetrain power drag, bearings, dragging brakes, low tranny fluid, etc. Whatever is dragging or binding in the drivetrain will get pretty hot and be easy to find.
2) Check for a proper operating distributor, wrongly installed wires, points, no vacuum advance, check the voltage to the points, or HEI to see if it is in spec, check the coil.
3) Look for a dead cylinder or a non firing cylinder
4) Worn out or improperly adjusted carburetor, choke stuck on?
5) Improperly set timing, and advance
6) Check the plugs to see what is up, are they oily? Brown, white, or a mix? Do you have a lot of blow by or blue smoke while driving?
7) Steep rear end gears (4:11 or higher) will cause excessive gas consumption in a 500 on the highway. The 500 likes to run at 1,500 - 2,500 rpm in order to get the best gas mileage.
8) Mismatched tires and wrong air pressure and poor front end alignment can really reduce mpg.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
67,921 Posts

·
Registered
1980 FBC
Joined
·
969 Posts
Most gearheads can't agree on what makes an engine a bigblock verses a smallblock but nobody refers to a chevy 350 as a bigblock.
And screw spellcheck too. Its smallblock not small-block. No nerd language Nazis allowed.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
67,921 Posts
You need to do some Google work on magazine articles for Chevrolet "big block" and "small block". Try Car Craft and Hot Rod for starters.


At least they were two words back in '63 + when I was building them ............... and I still build the 454 big block marine conversions ........
 

·
Registered
1980 FBC
Joined
·
969 Posts
You need to do some Google work on magazine articles for Chevrolet "big block" and "small block". Try Car Craft and Hot Rod for starters.


At least they were two words back in '63 + when I was building them ............... and I still build the 454 big block marine conversions ........
Yep the space between the words is OK fine. Not going to use a hyphen.

Find an article that lists rules for multiple brands of engines defining small block verses big block.

There are no such lists. Only some Chevycentric stuff.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #14
If you are indeed getting 6 mpg, per your Name suggests, I would start investigating what is causing the poor gas mileage. A properly tuned up 500 powered 2wd truck should be able to achieve 12-15 mpg empty with the right rear gearing at 60 mph. This is better than the stock 350 that the truck came with. Your mpg while towing with a 500 will be 30-45% better than the stock 350 it came with, and much better than a 454 BB.
To find out what is causing the 6 mpg:
1) Look for drivetrain power drag, bearings, dragging brakes, low tranny fluid, etc. Whatever is dragging or binding in the drivetrain will get pretty hot and be easy to find.
2) Check for a proper operating distributor, wrongly installed wires, points, no vacuum advance, check the voltage to the points, or HEI to see if it is in spec, check the coil.
3) Look for a dead cylinder or a non firing cylinder
4) Worn out or improperly adjusted carburetor, choke stuck on?
5) Improperly set timing, and advance
6) Check the plugs to see what is up, are they oily? Brown, white, or a mix? Do you have a lot of blow by or blue smoke while driving?
7) Steep rear end gears (4:11 or higher) will cause excessive gas consumption in a 500 on the highway. The 500 likes to run at 1,500 - 2,500 rpm in order to get the best gas mileage.
8) Mismatched tires and wrong air pressure and poor front end alignment can really reduce mpg.
Turned out I have a dead cylinder, I'm taking the engine out and rebuilding it now.
 

·
Registered
Joined
·
10 Posts
If they touch your heads, all you need is a standard valve & seat grind and a head resurface. Don't let them talk you into replacing the valve seats with hardened seats. It is really almost never required on Cad heads unless there was valve seat damage like from a bent valve. They are very hard Ni-Iron and not chevy heads.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #16
If they touch your heads, all you need is a standard valve & seat grind and a head resurface. Don't let them talk you into replacing the valve seats with hardened seats. It is really almost never required on Cad heads unless there was valve seat damage like from a bent valve. They are very hard Ni-Iron and not chevy heads.
Well I'm planning on doing a full rebuild myself. I don't know how many miles the engine has on it but I can guess atleast 150k
 

·
Registered
Joined
·
10 Posts
When you said you have a dead cylinder, did you trace it to the piston and rings?
Or is it from the head gasket or valves?

If you put a threaded air fitting (or rubber tipped) in through the spark plug hole and add compressed air with the piston at TDC, then listen. Where does the air come out?
If the air is hissing out the:
Crankcase (oil cap) = piston rings or possibly cracked cylinder or scored cylinder. Need a rebuild
Intake manifold (carb) = intake valve damaged or not seating, or possibly cracked head. Need to rebuild or replace head.
exhaust pipe = exhaust valve damaged or not seating, or possibly cracked head. Need to rebuild or replace head.
bubbles in radiator coolant = head gasket or cracked head. Resurface & rebuild or replace head if cracked.
multiple places = cracked or warped head, two bad valves, or piston is not at TDC

You might be lucky and only need head work or a new head gasket.
 
1 - 18 of 18 Posts
Top