The Stovebolt Site Forums The Shop Area Engine Shop GMC 270 Piston Clearance

Interesting to see the 1958 piston to bore clearance data from crenwelge above.

I did a search through a post WWII 1947 GMC Truck Shop Manual and a 1955 GMC Truck Manual. Below are pictures from each of those showing a slightly different piston skirt to cylinder wall clearance.

Seems like they tightened up the clearance a bit after WWII and then loosened that up just a tad after these years.

I guess a question I would ask is are the replacement pistons WWII period age for your 270 or are they later replacements that might have a little less expansion due to changes to the metals used? Later pistons that may not expand as much may allow for closer tolerances. You may have to test the expansion theory on the new pistons to confirm it is accurate or not.