1941 oversize pistons

[Tom M]

I've got some cylinder damage in a 1941 series 62 and It looks like I'll need to use oversize pistons. The bore is already .040" oversize so I was wondering if someone can please tell me how much larger I can go and if these larger piston sizes are commonly available. This is a new car so I'm scrambling to get the manual, the parts list and to join the club, but in the mean time I hope someone can give me an idea of what to expect.

Thanks and regards, Tom

[Otto Skorzeny]

I don't know how much you can bore a flathead  but  .050 and .060 oversize is not out of the question for other engines.

[Jim Stamper]

     There were some new .60 over pistons for sale on here recently. A month or two at most. Very reasonably priced as I recall.

                                                  Jim Stamper  CLC# 13470

[Dave Shepherd]

Try Egge for the pistons also.

[markl]

Tom,
You didn't say if it was just one or two, or all the bores that are damaged.  These engines can be sleeved, so if it is just a single bore, you might consider sleeving that bore, assuming the other bores are not excessively worn and the pistons are in good shape (no scuffing, ring lands w/in spec etc.).  You can probably come up w/ a single 0.40 over piston by placing a WTB post on this forum (Buy-Sell section).  Of course, you'd still need to take everything apart to balance the replacement piston.  Interestingly, the 37-38 shop manual only refers to oversizes up to 0.30. 

Perhaps someone else can respond w/ what the Shop manual for 41 mentions as to the range of over-sizes.

Mark Lowery, CLC#25216

[Doug Houston]

I have four '41 Cadillacs. Three are bored .030". They have Hydra-Matic transmissions on them, though this has no meaning; just sort of a coincidence. The engines were tired, and Cadillac had the .030" pistons in stock, so I used them.

The fourth one had a badly neglected engine block, and it took a .060" overbore to clean it up. It happens to have a manual transmission. All of the cars run perfectly, and the one with a manual shift has gusto like I've never known in those cars!

While it's not like me to do any overkill on things like piston fits, the 4 dr.convertible happens to have needed the big overbore. The other cars with the .030" overbore go like the blazes as it is, and I'm mighty happy with all of them.

It's not all bad to clean up a rusty block with a few thousands over size. You'll probably never do it more than once, anyway.

[Tom Martinez]

Thanks to everyone who responded, since there are at least 2 bad cylinders, I think I'm going to go through the whole engine. My research indicates that up to +.080 on the bore is acceptable but it looks like +.060 will clean them up. (unfortunately the + .060 set for sale mentioned above are NLA) The car had very good power and was running quite well except for the hot running so after I bore bigger, dust off the deck and spank the heads I'll have a hot rod on my hands. After putting over 1k miles on this car, I now understand why the 41 Cadillac is so well regarded, the brakes, gearing, suspension and steering are well matched and make for a great driving highway and city car.