I got my hands on a 239 flathead this weekend and I'm not sure if I should have the block machined or not. The guy I bought it from tore the top half (heads, intake, ect.) apart and everything looks okay minus some snapped off bolts in the block. Is there any reason to get the block bored out? It has some corrosion in the water passages but other than that there's nothing visibly wrong with it. Should a rebuild do okay? This isn't going to be a hot rod. I just want a stock build on it.

 

Take the bare block to a qualified shop that does Flathead work. Have them check the block to see what needs to be done. Or you can purchase a Bore Gauge, a pair of Calipers, and check it yourself. The bores can have a certain amount of taper before they have to be bored. Or in my case I have water damage in one cylinder that will cause my Merc block to be Bored.

 

What's the allowable amount of taper? I have access to the measuring equipment (micrometers, hole gauges).

 

According to my book 0.002 is the bore limit.
Check out these sites;

Techno Source for the 1932 thru 1953 Flathead Ford
Ford Flathead Specifications

 

Thanks for the help. I'm going to try to tear the engine apart in the next couple of weeks and get it hot tanked. The block is in good shape. There is some corrosion in the water jackets but its not too bad. I have some broke bolts to get out of it. I've been hitting with some PB blaster for the past few days, several times a day. The po tried to drill out one of the bolts and messed it up a bit. I'll need to put some kind of insert in it. This is my first full engine build so I'm pretty stoked!