Re building a 1990 4.0 with a friend. I have re built lots of engines but usually import 4 bangers. What are people running for gap on their 4.0's? Manual says"compression rings .010-.020" but I am used to different specs for top and 2nd ring. I was thinking bore X 0.035 for top and bore X 0.040 for 2nd.Anyway let me know your opinions.

Thanks, Brian

 

What are you running for pistons? Stock? While there is little harm done by increasing the gaps slightly, this sort of stuff I prefer go exactly by the book on. If there's a question- call the piston manufacturer instead of relying on anecdotal data that may not be right for your exact application.

 

Yup. Stock pistons

 

Then I'd stay within the stock gaps ....unless you are planning on adding nitrous or something