Pontiac Repair: oil contamination, water bubbles, oil contamination

Question
Harold:

My son and I are in the process of restoring a 69 Pontiac GP with a 400H engine. We had the engine entirely rebuilt (so we were told).

At the last minute they changed the stock carb due to a gas leak. It now gets poor gas milage, which I suspect is related to the probelem we've noticed with the oil. The milage is something like 7-10 mpg. Long idle times distorts the actual milage bu we never went more than 175 miles on a full tank.

The engine has roughly 4,000 miles since the rebuild. The oil consistently has black particles in it. We keep changing the oil and filter and have the engine flushed, but the black spots keep coming back. They look like small bubbles on the dip stick but it's not water bubbles, it's small black spots the size of medium grind balck pepper.

What are your thoughts and suggestions.

Thank you

olins@yahoo.com

Answer
What kind of mileage did you expect to get. You are not going to get good gas mileage out of that engine in that car. First of all, you cant check mileage by how many miles you get out of a tank full. You have to fill it up and write down the miles, then drive it and when you fill it up again you have to go by how many gallons of gas it took to fill it divided by the miles driven.
About the black spots....???????
Are they gritty?