Which motor to use 1970 472? Or 1976 500?

[fleetwood472]

I have a choice to get either motor and I was wondering what the horese power and torque differences are in stock form? I was wonderinc because of the difference in net and gross specs. How much of a horsepower difference is there? Also what would be the best to go with as far as a stock rebuild is concerned as far as power? One of these motors are going into a 78 Fleetwood that is going to be a daily driver so i'm not sure how drastic the difference would be in gas mileage between the low compression and high compression anyone know? Also I am swapping an EFI setup onto the motor which is from a 425 and i'm going to be using the 730 ecm out of a 91 camaro and newer electronics and high impedence injectors. My question is will the egr valve work on the 472 since it is from 70 it didnt originally use egr so is there even a port on the head? Thanks - Justin

[cj2/500]

I'd use the 500. It will be better suited for the egr and knock sensor operation. The higher compression engines tend to suffer from octane deficiency. (even with 92 octane fuel) Even though you may not detect the "ping" the knock sensor will. Will your project include spark control or are you having alot of things "edited " from the ecm? The system I'm creating is using all gm parts(including the ecm), each one available from a napa or a gm dealer to avoid lengthy breakdowns. But That's just me. By the way, do you plan to convert the mass air system to map ? I don't see that little camaro mass air meter flowing enough. The egr is fed exhaust from the crossover so either heads will work. I believe the 425 intake ports are pretty small in comparison to the 472/500. You may want to find a 500 efi intake. :?:

[fleetwood472]

The system I am using is the map setup from the 90-92 camaros they stopped using the maf setup at the end of 89. I am not using spark control I am using a distributer from a 368 that has the 7 pin HEI ignition module. The 425 EFI manifold and the 500 EFI manifold are the same manifold I believe at least thats what I have heard. How do you think the 472 will run as far as gas mileage? Will there be that noticable of a power difference between the 472 and 500? Thanks - Justin

[cj2/500]

MMMMMayyyyybeeeeeeee 30hp difference. The higher compression engines were more efficient when we had octane. Remember, the ratings were generated with a full supply of tetra-ethel lead in our fuel,hence lots of octane. How well does your wife perform when she's tired?

[~JM~]

.... How well does your wife perform when she's tired? :lol:

Hey Dave.... Check your PM's.

Thanks
~JM~