Hey, I have a '75 duster with a 400 big block in it (non original) with smog heads and an 8.2:1 compression ratio. I would like to raise the compression ratio, possibly by swapping on a set of '67 915 magnum castings with a closed chamber design as opposed to the open chamber design of the later heads. I heard that with the lower compression pistons in the 400, however, that the combustion chamber design of these heads makes the combo prone to detonation. Would it be easier to just have the open chamber smog heads milled to decrease chamber volume? please help!
big block head question
Jun 28, 2005
8 Replies
how many miles on the engine now?
"Dodge-Him" > smog heads and an 8.2:1 compression ratio. I would like to raise the
Not sure of the mileage, I bought it from a restoration shop nearby and the previous owner had swapped in the 400.
thinking fresh rings might be good too
Possible, although I did a compression check and everything checked out
most engines like this.........if you pull the heads and replace the gaskets, and it has more than 75,000 or so, the poor thing suddenly starts using oil!
That's good to know. Thanks for the advice!
don't want you to suffer from "James bond disease" leaving a blue smoke screen lol
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required