GMC 270 rebore

[Conn]

We took head off of CCW engine, and it appeaars to be a lower hour engine. However moisture has caused deep pits in the three and four cylinder bores, almost like cavitation pits I've seen on the outside of diesel engine sleeves. Questions: How much can you bore a 270 engine? Might take .060. Are pistons available? Has anyone ever dry sleeved one of these engines? The other pistons and bores look good on the engine. The CCKW has a 302 engine in it that is stuck and is even more moisture damaged. Also is it common for the bolts (on the ends of the exhaust manifold) to break off, both engine seem to be that way. Finally, the the 302 engine has a double barrel carberator, is that accurate for late CCKW engines?
It's a lot, and any information is very much apperciated! Thanks a million!
Gordon and Michael Conn

[pfarber]

My 270 has a rebuild plate that says .060 over.. and still has the WWII issue domes pistons. So it can be done.... but finding .060 over domes pistons way be the hard parts.

[John V Cliche]

Hi Conn ,
If you can't find NOS pistons and rings. EGGE machine can make them to your specs they've made parts for me in the past. You can find a number for them in Hemmings.
Hope this helps.
John

[oldreliable9_47]

specs say .060 over is limit. Stick with the 270

[pfarber]

If I ever need to rebuild the engine I would have little choice in my situation.

From what I hear the later 270 block would have had different sized intake/exhaust ports that the 40s era 270.

[dr deuce]

Later 270's have bigger INTAKE ports, manifold and carb I believe. Ex is the same.

Later 270's have flat pistons and a head to match along with a different tightening sequence --- Be careful......